9 th class CBSE

1. Fill in the blanks

(a) In a chemical reaction, the sum of the masses of the reactants and products remains

unchanged. This is called ————.

(b) A group of atoms carrying a fixed charge on them is called ————.

(c) The formula unit mass of Ca3 (PO4)2 is --------------------

(d) Formula of sodium carbonate is ———— and that of ammonium sulphate is ————.

2. Compute the difference in masses of 103 moles each of magnesium atoms and magnesium

ions.

(Mass of an electron = 9.1×10–31 kg)

3. Which has more number of atoms? 100g of N2 or 100 g of NH3

4. Compute the number of ions present in 5.85 g of sodium chloride.

5. A gold sample contains 90% of gold and the rest copper. How many atoms of gold are present

in one gram of this sample of gold?

6. What are ionic and molecular compounds? Give examples.

7. Compute the difference in masses of one mole each of aluminium atoms and one mole of its

ions. (Mass of an electron is 9.1×10–28 )

g). Which one is heavier?

8. A silver ornament of mass ‘m’ gram is polished with gold equivalent to 1% of the mass of

silver. Compute the ratio of the number of atoms of gold and silver in the ornament.

9. A sample of ethane (C2H6) gas has the same mass as 1.5 ×1020

10. What is the fraction of the mass of water due to neutrons?

11. Does the solubility of a substance change with temperature? Explain with the help of an

example.

12. Calculate the number of moles of magnesium present in a magnesium ribbon weighing 12 g.

Molar atomic mass of magnesium is 24g mol-1

13. Verify by calculating that

(a) 5 moles of CO2 and 5 moles of H2O do not have the same mass.

(b) 240 g of calcium and 240 g magnesium elements have a mole ratio of 3:5.

14. A sample of vitamic C is known to contain 2.58 ×1024 oxygen atoms. How many moles of

oxygen atoms are present in the sample?

15. The visible universe is estimated to contain 1022 stars. How many moles of stars are present

in the visible universe?

16. Compare the properties of electrons, protons and neutrons.

17. What are the limitations of J.J. Thomson’s model of the atom?

18. What are the limitations of Rutherford’s model of atom?

19. Describe Bohr’s model of atom.

20. Compare all the proposed models of an atom given in this chapter.

21.Summarize the rules for writing of distribution of electrons in various shells for the first

eighteen elements.

22. Define valency by taking examples of silicon and oxygen

23. Explain with examples (i) Atomic number, (ii) Mass number, (iii) Isotopes and (iv) Isobars.

Give any two uses of isotopes.

24. Na+ has completely filled K and L shells. Explain.

25. If bromine atom is available in the form of, say, two isotopes 7935Br (49.7%) and 81

35Br (50.3%), calculate the average atomic mass of bromine atom.

GUESS PAPER SUMMATIVE ASSESSMENT –I (2011) SCIENCE- Class – IX (Chemistry)GUESS PAPER SUMMATIVE ASSESSMENT –I (2012) Class – IX (Chemistry

Section A

1.What is dry ice ? What happens when the pressure under which it is stored is decreased to

1 atmosphere ?

2.Why is glass or chinaware packed with straw ?

3.Name the processes by which CO2 and H2O move into and out of the cell ?

4.List in tabular form any two differences between homogeneous and heterogeneous mixtures.

5. (a) Define evaporation. (b) Explain how the following factors affect the rate of evaporation of a liquid:

(i) temperature of the liquid. (ii) area of the exposed surface.

(iii) moisture in the surrounding air. (iv) Increase in wind speed.

6.(i) Name the process or the separation technique you would follow to separate : (a) Dyes in black ink (b) Butter from cream (c) Ammonium chloride and common salt (d) Iron filings and sand (ii) State the principle used in separation by centrifugation.

7. Based on the following characteristics distinguish in tabular form the behavior of true solution, suspension and colloidal solution. (a) appearance (b) visibility (c) filterability (d) Tyndall effect (e) particle size OR

(a) What is distillation ? List the two conditions essential for using this as a method of separation of components of a mixture. (b) Draw a labelled diagram of the apparatus used to separate a mixture of two miscible liquids.

8..Compare in tabular form , the properties of Solids, Liquids and Gases with respect to : (i) Shape (ii) Volume (iii) Compressibility (iv) Diffusion (v) Fluidity or Rigidity

OR ,

Account for the following : (a) For any physical state of a substance, the temperature remains constant during its change of state. (b) Water kept in an earthen pot becomes cool in summer. (c) We are able to sip hot tea from a saucer rather than from a cup.

Section B

09.If common salt is added to the unsaturated solution of water and common salt it

will

(a) become a colloid (b) become a suspension (c) start showing Tyndall effect (d) remain a true solution

10.A student was asked to mix the white of an egg with water and stir well. The student observed that

(a) a transparent solution is formed. (b) a translucent mixture is formed.

(c) egg white settles down at the bottom. (d) egg white floats on the surface.

11.The reaction of iron and sulphur to form iron sulphide takes place at :

(a) at high temperature (b) in the presence of a catalyst

(c) at moderate temperature (d) in the presence of an acid

12.Which of the following compounds when dissolved in water gives coloured solution ?

(a) barium chloride (b) sugar solution (c) sodium chloride (d) copper sulphate

13.For determining the accurate melting point of ice we should prefer

(a) ice made from distilled water (b) ice made from tap water

(c) crushed dry ice mixed with salt (d) a mixture of ice and salt

14.Mohan used a thermometer having 20 divisions between 30degC mark and 40degC mark. While determining boiling point of water using this thermometer he observed that the level of mercury becomes constant just 3 division below the 100o C mark. Mohan should record in his note book

(a) Least count=0.5degC, B.P.=97degC (b) L.C.=0.5degC, B.P.=98.5degC

(c) L.C.=1degC, B.P.=98.5degC (d) L.C.=1degC , B.P.=97degC

15.Ramu was asked to separate a mixture of common salt and ammonium chloride. Sublimation is used to separate ammonium chloride because :

(a) ammonium chloride sublimes

(b) ammonium chloride changes directly from solid to gaseous state on heating

(c) mixture contain a sublimable volatile component and a non Sublimable impurity (salt)

(d) all the above

16.Which is the correct colour sequence of iron filings, sulphur and iron sulphide ?

(a) Greyish black, yellow, black (b) Black, yellow, brown

(c) Brown, yellow, black (d) Black , yellow, greyish black

17.The colour of magnesium after rubbing with sand paper is

(a) Silvery white (b) Grey (c) Black (d) Brown

18.Common salt and sand can be separated by :

(a) Filtration (b) Crystallisation (c) Sedimentation and Decantation

(d) First dissolving in water, then by filtration and followed by crystallisation.

19.A student put five raisins each in two beakers A and B. Beaker A contained 20 mL ofdistilled water and beaker B has 20 mL of saturated sugar solution. After some time the student would observe that :

(a) raisins in beaker A were more swollen than those in beaker B.

(b) raisins in beaker B were more swollen than those in beaker A.

(c) raisins in both beakers A and B were equally swollen.

(d) raisins in beaker A did not swell up at all.

20.In the preparation of temporary mount of onion peel which of the following is not used :

(a) water (b) glycerine (c) safranin (d) alcohol

21.Arun, Deepa, Uma and Priya were asked to select a plant material which would not give blue black colour with iodine solution. Who did not select the right material ?

(a) Arun selected maize grains. (b) Deepa selected wheat grains.

(c) Uma selected ground nut seeds. (d) Priya selected potato.

22.Deepak washed a few grains of tur dal in water. The water became yellow. He then added a few drops of HCl to the same test tube, the water turned pink in colour. From the above test Deepak concluded that tur dal contains. (a) proteins (b) starch (c) turmeric (d) metanil yellow HCl

23.A student recorded the mass of dry raisins as 2.5g and the mass of raisins after soaking in water as 4 g . While performing the above experiment. The percentage of water absorbed by raisin is :

(a) 20% (b) 30% (c) 60% (d) 40%

24.The mixture of sand and water when filtered gives.

(a) pale brown solution (b) brown solution

(c) transparent solution (d) grey solution

25. When a mixture of sulphur powder and iron filings is heated.

(a) iron filings starts melting (b) sulphur sublimates leaving iron filling behind

(c) ferrous sulphide is formed. (d) sulphur melts

You might also like:

IX Chemistry Sample paper 2012

One mark each:

1. Define atomic mass unit?

2. Define Mole?

3. An atom has electronic configuration of 2, 8, 7

(1)What is the atomic number of the element?

(2)Which of the following elements have same number of valence electrons

N(7), F(9), P(15), Ar(18)

4. Why are He, Ne and Ar are Inert?

5. Why are all electrons called fundamental particles of all atoms?

6. Calculate the value of moles in 17g of H2O2.[(H =1u), O =16u]

7. What is meant by Avogadro ‘s constant?

8. State Law of conservation of mass.

9. Calculate the number of molecules in 4g of methane (C=12u, H =1u)

10. What are isotopes? Give examples.

2 marks each:

11. What is the electronic configuration of Na+,if atomic No, of Na atom is 11.What is the atomic

No. and atomic mass of Na+ .

12.Which of the two would be chemically more reactive element ‘X’ of atomic No.18 or element

‘Z’ of atomic No. 16 and why?

13.What is the difference between sodium atom and sodium ion?

14.How many molecules are present in

(a) 9g of water (b) 17g of NH3 .

(H = 1u, O = 16u, N =14u)

15.Calcium and Oxygen are combined in the rates of 5:4 by mass to form calcium oxide. What

mass of oxygen gas would be required to react with 2.5g of calcium?

16.How many atoms of carbon and hydrogen are present in 3 moles of ethane

( C2 H6 ).

17.The atomic number of Aluminum is 13 and that of Chlorine is 17.How many electrons ,

protons and neutrons are present in Al3 and Cl- ions.

18.What you meant by valence electrons?

(1) Write the electronic configuration of elements potassium (19) and N (7)

(2)Write the No.of valance electrons in each of these elements?

19.An element has three valence electrons in the 3rd shell. Name the element and give its atomic

No. and state is it a metal or non-metal?

20.Calculate the mass of 6.022 x 10 23 N2 molecules. (N = 14u)

3 mark each:

21. Write the chemical formula for the following:

(1) Ammonium Carbonate.

(2)Barium Sulphate.

(3) Sodium Sulphide.

(4)Aluminium Hydroxide.

(5)Calcium Flouride.

(6)Potassium Nitrate.

22. Calculate the molecular mass of the following:

(i)(NH4)2SO4 (ii)Al2(SO4)3 (iii) Ca(HCO3)2

[ N = 14u, H =1u, S = 32u, Al = 27u, O = 16u, C = 12u ]

23.Calculate the No.of Al3+ ions present in 0.056g of Al2O3.

24.What is chemical formula? Give two information conveyed by chemical formula of a

compound.

25.Explain Rutherford’s Alpha Scattering experiment for the discovery of Nucleus. Write his

observations and conclusions.

26.The average atomic mass of a sample of an element X is 16.2u.What are the percentages of

isotopes 16X8and 18X8 in the sample.

27.(1) An ion M3+ has 10 electrons and 14 neutrons. What is the atomic number and mass

number of M.

(2) Write the electronic configuration of the following ions.

(1) Mg2+ (2) O2- (3)S2- (4) Na+ (5) N3-

28. (1) Which has more No.of atoms, 100g of Sodium or 100g of Iron

(Na =23u, Fe = 56u).

(2) Which has more No.of molecules, 4g of CH4 and 8g of H2O

[ H = 1u, O = 16u, C = 12u ]

29. (1) For the symbol, H,Dand T Calculate three subatomic particles found in each of them?

30.If Chlorine atom is available in the form of say two isotopes 17Cl35 (75%)and 17CL37(25%),

Calculate the average atomic mass of chlorine atom.

5 Mark Questions:

31. (1) Explain Bohr model of an atom?

(2)Draw the Bohr model of the following atom

(1) Sodium (11Na23)

(2) Oxygen (8O16)

(3) Calcium (20Ca40)

32.(1) Calculate the molecular mass of the following :

(1) CH3-OH (2) CuSO4.5H2O (3) Ca(HCO3)2

(2)Calculate the No.of particles in each of the following:

(1) 46g of Na atoms (Na = 23u)

(2) 8g of O2 molecules

(3)0.1 mole of carbon atoms

(4)100g of CH4

33. (1)What are the postulates of Dalton’s Atomic theory of matter?

(2)Define the following terms:

(i) Atomicity (ii) Valency (iii) Relative atomic mass (iv) Molecular mass

GUESS PAPER SUMMATIVE ASSESSMENT –I (2011) SCIENCE- Class – IX (Chemistry)GUESS PAPER SUMMATIVE ASSESSMENT –I (2012) Class – IX (Chemistry

Section A


1 atmosphere ?




5. (a) Define evaporation. (b) Explain how the following factors affect the rate of evaporation of a liquid:







OR ,


Section B

09.If common salt is added to the unsaturated solution of water and common salt it will




















(d) all the above









19.A student put five raisins each in two beakers A and B. Beaker A contained 20 mL ofdistilled water and beaker B has 20 mL of saturated sugar solution. After some time the student would observe that :











23.A student recorded the mass of dry raisins as 2.5g and the mass of raisins after

soaking in water as 4 g . While performing the above experiment. The percentage of water absorbed by raisin is :

(a) 20% (b) 30% (c) 60% (d) 40%






(c) ferrous sulphide is formed. (d) sulphur meltsSaturday, August 11, 2012

9th Chemistry : MCQ Is Matter around us pure Practical based Guess Questions

9th Chemistry : MULTIPLE CHOICE QUESTION ON PRACTICLE SKILLS

EXPERIMENT NO –2

1. Which one of the following is an example of heterogeneous mixture

a. NaCl + water b. kerosene + water

c. sugar + water d. alum + water

2. Which one of the following is a mixture of two elements

a. iron fillings + sulphur powder b. sugar + common salt

c. water +milk d. air

3. Which one is not the property of a mixture

a. heterogeneous b. variable composition

c . constant composition d. none of these

4.Correct method of separating iron fillings from sulphur powder

a. heating in china dish b. heating in boiling tube

c. heating in water d. moving magnet

5. In the formation of which one a large quantity of heat is involved

a. compound b. colloid

c. true solution d. each one

6. When a magnet is moved through of iron fillings and sulphur powder , then

http://chemistryadda.blogspot.in/2012/08/9th-chemistry-mcq-is-matter-around-us.html

http://chemistryadda.blogspot.in/2012/08/9th-chemistry-mcq-is-matter-around-us.html

a. iron fillings will cling to magnet b. black mass is produced

c. sulphur will cling to magnet d. none of these

7.When a mixture of iron fillings is heated with sulphur powder

a. nothing happens b. black mass is formed

c. yellow mass is formed d. white mass is formed

8. which one is a mixture

a. salad of fruits b. air

c. sea water d. all of the above

9. Name the process of conversion of solid to vapor

a. evaporation b. fusion

c. distillation d. sublimation

10.Which one of the following is a pure substance

a.milk b.cold drink

c .carbon d oxide d. brass

11.What is observed when iron fillings and sulphur powder is heated in a china dish

a. sulphur melts b. iron melts

c. mixture evaporates d.. yellow mass is formed

12. Mixture is always –

a. homogenous b. heterogeneous

c. homogenous or heterogeneous d. none of these

13. Compound is always –

a. homogenous b. heterogeneous

c. homogenous or heterogeneous d. none of these

14..Which of the following is a compound

a. blood b. air

c. soil d. water

15.On heating iron and sulphur in a china dish

a. mixture is formed b. compound is formed

c. both are formed d. no change

CBSE TEST PAPER Chapter : Matter in Our Surroundings

CBSE TEST PAPER Chapter : Matter in Our Surroundings

1. State whether True or False.(i) Water has no definite shape; therefore, it is not matter.(ii) Gases expand to fill the space available.

2. A substance has a definite volume, but no definite shape. State whether this substance is solid, liquid or gas.

3. Which physical state of matter is the densest?

4.What are the different factors affecting evaporation?

5.Give two reasons as to why a block of ice is considered as matter.

6. Why does matter change state?

7. It is observed that water boils at lower temperature at higher altitudes. Why?

8. If some alcohol is rubbed on the hand, the rubbed portion of the hand feels cool. Why?

9. Name the following.(i) State of matter having the maximum intermolecular space(ii) Force between particles of matter(iii) State of matter with only one free surface

10. A large crystal of potassium permanganate is kept in a glass beaker containing water. This setup is then left undisturbed for an hour. The solution undergoes a change in colour.

(i) What is this change in colour?(ii) Why does such a change take place?

You might also like: Chemistry Guess Questions Banks :Matter in Our Surroundings CBSE SOLVED TEST PAPERS CLASS - IX Science (Is matter around us pure) Class–IX CHEMISTRY Chapter-2:IS MATTER AROUND US PURE CCE Class IX Chapter: Is matter around us pure : Fill In the Blanks MCQ 9th Questions on Practical Skills Experiment No.--1 Chemistry: Is Matter around us Pure

LinkWithin

Posted by J Sunil at 9:05 AM 0 comments

Email ThisBlogThis!Share to TwitterShare to Facebook

Labels: 9th Matter in Our Surroundings

Chemistry Guess Questions Banks :Matter in Our Surroundings

Chemistry Adda Class IX, Chemistry Guess Questions Banks

Chapter 1: Matter in Our Surroundings

1. What are the different states of matter? Why do matter exist in these different states? [2]

2. Why is ice at 273k is more effective in cooling than water at same temperature? [2]

3. Give reasons. a. Naphthalene balls disappear with time without leaving any residue.

4. b. We can get the smell of perfume sitting several meters away [2]

5. What is the physical state of water at a)30oC b)0oC c)100oC

6. What type of clothes should we wear in summer? [2]

7. How does the water kept in an earthen pot (matka) become cool during summer? [2]

8. Why are we able to sip hot tea or milk faster from a saucer rather than a cup? [2]

9. Why does a desert cooler cool better on a hot dry day? [2]

10. For any substance, why does the temperature remain constant during its phase change?[2]

11. What is sublimation? [2]

12. Give reasons for - [3]The smell of hot sizzling food reaches you several meters away, but to get the smell from cold food you have to go close.

13. Give reasons for : How does evaporation cause cooling? [3]

14. Explain giving an activity that the liquids differ in their relative diffusion rates [3]

15. Differentiate between evaporation & boiling. [3]

16. Give two reasons to justify.(a) Water at room temperature is a liquid(b) An iron almirah is a solid at room temperature. [3]

17. Give reasons- [3]

(A) A gas fills completely the vessel in which it is kept.

(B) A gas exerts pressure on the walls of the container.

(C) A wooden table should be called a solid.

18. What are the characteristics of the particles of matter? [3]

19. A diver is able to cut through water in a swimming pool. Which property of matter does this observation prove? [3]

20. What will happen if we put an animal cell or a plant cell into a solution of sugar or salt in water? [3]

21. Define the following terms.

Fusion, latent heat of fusion, boiling point, latent heat of vaporization and sublimation. [3]Thursday, September 20, 2012

GUESS PAPER SUMMATIVE ASSESSMENT –I (2011) SCIENCE- Class – IX (Chemistry)

GUESS PAPER SUMMATIVE ASSESSMENT –I (2012) Class – IX (Chemistry

http://chemistryadda.blogspot.in/2012/09/guess-paper-summative-assessment-i-2011_20.html

http://chemistryadda.blogspot.in/2012/09/guess-paper-summative-assessment-i-2011_20.html

Section A


1 atmosphere ?




5. (a) Define evaporation. (b) Explain how the following factors affect the rate ofevaporation of a liquid:







OR ,


Section B

09.If common salt is added to the unsaturated solution of water and common salt it will




















(d) all the above









19.A student put five raisins each in two beakers A and B. Beaker A contained 20 mL of distilled water and beaker B has 20 mL of saturated sugar solution. After some time the student would observe that :











23.A student recorded the mass of dry raisins as 2.5g and the mass of raisins after soaking in water as 4 g . While performing the above experiment. The percentage of water absorbed by raisin is :

(a) 20% (b) 30% (c) 60% (d) 40%






(c) ferrous sulphide is formed. (d) sulphur melts

Q.1. What are Canal rays?Q.2. On the basis of Thomson’s model of an atom explain

how the atom is neutral as a whole.

Q.3 Draw a sketch of Bohr’s model of an atom with three shells.

Q.4. Helium atom has atomic mass of 4u and has two protons in the nucleus. How

many neutrons does it have?

Q.5. If the K and L shells of an atom are full, then what would be the number of

electrons in the atom?

Q.6. If the number of electrons in an atom is 8 and the number of protons is also 8,

then;

(i) What would be the atomic number of the atom? (ii) What is the charge on the

atom?

Atomic Structure John Dalton-Rutherford-J.J. Thomson- Atomic Model

Atomic Structure

The word atom originally meant a smallest possible particle of matter, not further

divisible.

Democritus

1. The existence of atoms was proposed as early as in the 5th century BC by the

Greek

philosophers Leucippus and his pupil Democritus, for which they were called

atomists.

2. Democritus, develop the idea of atoms. He asked this question: If you break a

piece of matter in half, and then break it in half again, how many breaks will you

have to make before you can break it no further?

3. Democritus thought that it ended at some point, a smallest possible bit of matter.

He called these basic matter particles, atoms.

4.The word "atom" is derived from the Greek word "atomos", which means

indivisible".

John Dalton

1. Five main points of Dalton's Atomic Theory

• All matter is composed of extremely small particles called atoms.

• All atoms of a given element are identical, having the same size, mass, and

chemical

properties. Atoms of a specific element are different from those of any other

element.

• Atoms cannot be created, divided into smaller particles, or destroyed.

• Different atoms combine in simple whole-number ratios to form compounds.

• In a chemical reaction, atoms are separated, combined, or rearranged.

Weakness

1. Atoms consist of even smaller particles called electrons, protons and neutrons.

2. Atoms can be created and destroyed in the nuclear reactions such as nuclear

fusion and nuclear fission.

Atoms of the same element can have different physical properties, for example,

isotopes of hydrogen.

J.J. Thomson Plum pudding model

1. In physics, the Plum pudding model of the atom was made after the discovery of

the electron and was proposed by the discoverer of the electron, J. J. Thomson.

2. In it, the atom is envisioned as electrons surrounded by a soup of positive charge,

like plums surrounded by pudding.

3. The electrons were positioned uniformly throughout the atom.

4. Instead of a soup, the model is also said to have had a cloud of positive charge.

5. This model can be compared to a British treat called plum pudding, hence the

name. It is alsoknown as the chocolate chip cookie model.

Ernest Rutherford Gold foil experiment

The Gold foil experiment, or Geiger-Marsden experiment was an experiment done

by Hans

Geiger and Ernest Marsden in 1909, under the direction of Ernest Rutherford at the

Physical

Laboratories of the University of Manchester which led to the downfall of the plum

pudding modelof the atom.

1. They measured the deflection of alpha particles directed normally onto a sheet of

very thin gold foil.

2. Under the prevailing plum pudding model, the alpha particles should all have

been deflected by at most of a few degrees.

3. However they observed that a very small percentage of particles were deflected

through angles much larger than 90 degrees.

4. From this Rutherford concluded that the atom contained a very small positive

charge which could repel the alpha particles if they came close enough.

Rutherford Atom

1. Early in 1911 Rutherford published a revised model of the atom, known as the

Rutherford atom.

2. He concluded that

• the atom is mostly empty space,

• most of the atom's mass concentrated in a tiny center, the nucleus and electrons

being held

in orbit around it by electrostatic attraction.

• The nucleus was around 10-15 meters in diameter, in the centre of a 10-10 metre

diameter atom.

• Those alpha particles that had come into close proximity with the nucleus had

been strongly

Model: Solar System Model (Bohr’s Model)

1. Niels Bohr improved on Rutherford's atomic model.

2. Bohr model depicts the atom as a small, positively charged nucleus surrounded

by electrons in orbit - similar in structure to the solar system, but with electrostatic

forces providing attraction, rather than gravity.

3. According to Bohr’s Model

• Electrons in an atom of an element are not randomly distributed around the

atomic nucleus.

• Electrons move around the nucleus in fixed orbits.• Each orbit forms a circle and

has a fixed distance from the nucleus.

James Chadwick’s Model

In 1932, James Chadwick bombarded beryllium (Be) with alpha aprticles. He

allowed the radiation emitted by beryllium to incident on a paraffin wax. It was

found that protons were shot out form the paraffin wax. People began to look for

what was in the "beryllium radiations". 1. Chadwick discovered the presence of

neutrons in the nucleus.

2. He concluded that the nucleus contains another tiny particle known as a neutron

that has nocharge.

3. The neutron mass is almost similar to the proton mass.

4. All nuclei contain protons and neutrons, except for the hydrogen which contains

protons. only

Modern Atomic Model

1. The atomic model in the present day is based on the contributions of the above

scientists.

2. According to the modern atomic model,

(a) The central nucleus consists of protons and neutrons. It containing almost all

the mass of the atom.

(b) the nucleus of an atom is very small compared to the size of the atom

(c) the electrons are orbiting outside the nucleus in the electron shells(d) the

electrons are moving in electron shells at a very high speed and we cannot

determine theposition of the electrons at a particular time

The subatomic particles of an atom

1. Atoms are made up of tiny particles called subatomic particles.

2. An atom contains three types of subatomic particles:a. proton,b. neutron andc.

electron,

3. The proton and neutron form the nucleus at the centre of an atom.

4. The electron moves around the nucleus at a very high speed.

5. The nucleus is positively charged because of the presence of protons, which are

positivelycharged. The neutrons are neutral.

Proton number and nucleon number

Proton Number

1. The proton number (Z) represent the number of protons found in the nucleus of

an atom.

Proton number = the number of protons

2. The proton number is also known as the atomic number.

3. In an atom of neutral charge, the number of electrons also equals the atomic

number.

4. Hence, the proton number of an atom can also represent the number of

electrons.

Nucleon Number

1. The nucleon number (A), also called atomic mass number or mass number, is the

number ofprotons plus the number of neutrons in an atomic nucleus.

Nucleon number = Number of protons + Number of Neutrons

The nucleon number of an atom is about the same as the mass of the atom because

the mass of anelectron is very small and can be ignored.Continued>>>>>>>>>>Read more to excelIX Atomic Structure ( a fundamental particles) Discovery of Electron

9th Atomic Structure (Discovery of a fundamental particle protons)

9th Atoms and Molecules

9th Structure of Atoms

Practice paper and sample paper based On Atomic structure

Saturday, December 3, 2011

9th CBSE Science Chap 3 Atoms and Molecules Test paper





(c) The formula unit mass of Ca3 (PO4)2 is --------------------


2. Compute the difference in masses of 103 moles each of magnesium atoms and magnesium

ions.

(Mass of an electron = 9.1×10–31 kg)

3. Which has more number of atoms? 100g of N2 or 100 g of NH3

http://chemistryadda.blogspot.in/2011/12/9th-cbse-science-chap-3-atoms-and.html


http://jsuniltutorial.weebly.com/structure-of-the-atom.html

http://chemistryadda.blogspot.com/search/label/9th%20Structure%20of%20Atoms

http://chemistryadda.blogspot.com/search/label/9th%20Atoms%20and%20Molecules

http://chemistryadda.blogspot.com/2011/12/ix-atomic-structure-discovery-of.html

http://chemistryadda.blogspot.com/2011/12/ix-atomic-structure-fundamental.html

http://chemistryadda.blogspot.com/2011/12/class-ix-chemistry-notes-atomic.html


5. A gold sample contains 90% of gold and the rest copper. How many atoms of gold are present

in one gram of this sample of gold?

6. What are ionic and molecular compounds? Give examples.

7. Compute the difference in masses of one mole each of aluminium atoms and one mole of its

ions. (Mass of an electron is 9.1×10–28 )

g). Which one is heavier?



9. A sample of ethane (C2H6) gas has the same mass as 1.5 ×1020

10. What is the fraction of the mass of water due to neutrons?

11. Does the solubility of a substance change with temperature? Explain with the help of an

example.

12. Calculate the number of moles of magnesium present in a magnesium ribbon weighing 12 g.

Molar atomic mass of magnesium is 24g mol-1




14. A sample of vitamic C is known to contain 2.58 ×1024 oxygen atoms. How many moles of


15. The visible universe is estimated to contain 1022 stars. How many moles of stars are present

in the visible universe?

16. Compare the properties of electrons, protons and neutrons.

17. What are the limitations of J.J. Thomson’s model of the atom?

18. What are the limitations of Rutherford’s model of atom?

19. Describe Bohr’s model of atom.

20. Compare all the proposed models of an atom given in this chapter.

21.Summarize the rules for writing of distribution of electrons in various shells for the first

eighteen elements.

22. Define valency by taking examples of silicon and oxygen

23. Explain with examples (i) Atomic number, (ii) Mass number, (iii) Isotopes and (iv) Isobars.

Give any two uses of isotopes.

24. Na+ has completely filled K and L shells. Explain.

25. If bromine atom is available in the form of, say, two isotopes 7935Br (49.7%) and 81

35Br

(50.3%), calculate the average atomic mass of bromine atom.


Chemistry Adda: Basic concepts for the study of chemistry

Chemistry Adda : Metals And Non-metals Notes

Chemistry Adda: The Chemistry of Love

Chemistry Adda : What is cholesterol?

LinkWithin



Labels: 9th Atoms and Molecules

Thursday, November 24, 2011

atoms and molecules class 9 Solved questions For FA3

CHEMISTRY ASSIGNMENT- 1 CLASS-9 ATOMS AND MOLECULES

Q1 What are polyatomic ions? Give examples.

Q2 Write the chemical formulae of the following compounds.

(a) Magnesium chloride (b) Calcium oxide

(c) Copper nitrate (d) Aluminium chloride

Q3 Calculate the molar mass of the following substances

(a) Ethyne C2H 2

(b) Sulphur molecule S8

(c) Phophorous molecule P4

(d) Nitric acid HNO3

(e) Hydrochloric acid HCl

Q4 What is the mass of

(a) 1 mole of nitrogen atoms

(b) 4 moles of aluminium atoms

http://www.blogger.com/share-post.g?blogID=5658836504857763582&postID=3426938866891422276&target=facebook

http://www.blogger.com/share-post.g?blogID=5658836504857763582&postID=3426938866891422276&target=twitter

http://www.blogger.com/share-post.g?blogID=5658836504857763582&postID=3426938866891422276&target=blog

http://www.blogger.com/share-post.g?blogID=5658836504857763582&postID=3426938866891422276&target=email

http://chemistryadda.blogspot.in/2011/11/atoms-and-molecules-class-9-solved.html

http://chemistryadda.blogspot.in/search/label/9th%20Atoms%20and%20Molecules

http://chemistryadda.blogspot.in/2011/12/9th-cbse-science-chap-3-atoms-and.html#comment-form


http://www.linkwithin.com/learn?ref=widget

(c) 10 moles of oxygen molecules

Q5 Convert into moles

(a) 12g of oxygen gas

(b) 20g of water

(c) 22g of carbon dioxide

Q6 Write the cations and anions in the following compounds

(a) CH3COONa

(b) NaCl

(c) HNO3

(d) MgCl2

Q7 Verify by calculating that

(a) 5 moles of carbon dioxide and 5 moles of water do not have the same mass.

(b) 240g of calcium and 240g of magnesium elements have a mole ratio3:5

Q8 Compute the number of ions present in 5.85g of sodium chloride.

Q9 What are ionic and molecular compounds? Give examples.

Q10 What do you understand by the term atomicity?

Q11 Write the formulae for the following and calculate the molecular mass for each one

of them

(a) Caustic potash(b) Baking powder

(c) Lime stone

(d) Caustic soda

(e) Ethanol

(f) Common salt

Q12 Give the chemical formulae of the following compounds and compute the ratio by

mass of the combining elements in each of them

(a) Ammonia

(b) Carbon monoxide

(c) Hydrogen chloride

(d) Aluminium fluoride

(e) Magnesium sulphide

Q13 Does the solubility of the substance changes with temperature? Explain with the

help of an example.

Q14 Give the formulae of the compounds formed from the following sets of elements

(a) Calcium and fluorine

(b) Hydrogen and sulphur

(c) Nitrogen and hydrogen

(d) Carbon and chlorine

(e) Sodium and oxygen

(f) Carbon and oxygen

Q15 Wrire all the postulates of Dalton’s atomic theory.

CHEMISTRY ASSIGNMENT-2 CLASS-9 ATOMS AND MOLECULES

Q1 State law of conservation of mass.

Ans The mass can neither be created nor destroyed in a chemical reaction.

Q2 State law of constant proportion.

Ans A pure chemical compound always consists of the same elements that are combined together in

a fixed proportion by mass.

Q4 Define atomic mass unit.

Ans The mass of one twelfth (1/12) of the mass of one atom of carbon taken as 12.

Q5 What are molecules?

Ans Molecules represents a group of two or more atoms(same or different) chemically bonded to

each other and held tightly by strong attractive forces. Molecules are of two types

(a) Molecules of elements (b) Molecules of compound

Q6 What do you mean by molecular mass?

Ans The average relative mass of the molecule as compared to the mass of carbon taken as 1u.

Q7 Write the relationship between number of moles and atomic mass.

Ans Number of moles=given mass/gram atomic mass

Q8 Why are chemical reactions according to law of conservation of mass?

Ans In all chemical reactions, there is only exchange of reactants taking place when products are

formed. Since there is no loss or gain of mass,the chemical reactions are according to law of

conservation of mass.

Q9 What is basic difference between atoms and molecules?

Ans Atoms except those of noble or inert gas elements cannot exist of their own. However , all

molecules can have independent existence.

Q10 The atomic mass of an element is in fraction .What does it mean?

Ans If the atomic mass of an element is in fraction, this mean that it exists in the form of isotopes.

The atomic mass is the average atomic mass and is generally fractional.

Q11 What is the difference between the mass of molecule and molecular mass?

Ans: Mass of a molecule is that of a single molecule also known as its actual mass. But molecular

mass is the mass of Avogadro’s number of molecules.

Q12 Where do we use the words mole and mol?

Ans In the text part we use the word mole while as a unit ,we call it mol.

Q13 How many moles are present in 11.5 g of sodium?

Ans Gram atomic mass of Na =23g

11.5g of Na represents= (1mol)*(11.5g)/23.5g)=0.5 mol

Q14 Explain why the number of atoms in one mole of hydrogen gas is double the number of atoms

in one mole of helium gas?

Ans Hydrogen gas is a diatomic in nature(H2) while helium gas is monoatomic (He).As a result, the

number of atoms in one mole of hydrogen(2*NA )are expected to be double as compared to

number of atoms in one mole of helium(NA)

Q15An element Z forms an oxide with formula Z2O3. What is its valency?

Ans Valency of Z=3

Q16 The valency of an element A is 4 . Write the formula of its oxide.

Ans The formula of its oxide is A2O4 or AO2.

Q17 An element X has valency 3 while the element Y has valency 2.Write the formula of the

compound between XandY .

Ans X2Y3

Q18 What are ions?

Ans Ions are of two types (a) cations - positively charged (b) anions - negatively charged

Q19 Which postulate of Dalton’s Atomic theory is the basis of law of conservation of mass?

Ans “ Atoms can neither be created nor destroyed during a physical or a chemical change”

Q20 Write the formulae of sodium oxide and aluminium chloride

Ans Sodium oxide = Na2O Aluminium chloride =AlCl3

Q21 Find out the ratio by mass of the combining elements in the following compounds

(a) MgCO3 (b) CH3OH (c) CaCl2

Ans21 (a) MgCO3 ------ Mg :C:O = 24:12:48 = 2:1:4

(b) CH3OH ------ C : H : O =12:4:16 =3:1:4

(c) CaCl2 ----------- Ca :Cl = 40:71

Q22 Define atomicity of the molecule.

Ans Atomicity of the molecule is the number of atoms present in the molecule.

Q23 What is the atomicity of oxygen,ozone,neon and sulphur?

Ans Oxygen O2 = 2 Ozone O3 = 3 Neon Ne =1 Sulphur S8 =8

Q24 What is wrong with the statement '1 mol of hydrogen'

Ans The statement is not correct.We must always write whether hydrogen is in atomic form or

molecular form. The correct statement is : 1mole of hydrogen atoms or one mole of hydrogen

molecules .

Q25 The atomic mass of an element is in fraction. What does it mean?

Ans If the atomic mass of an element is in fraction, this mean that it exists in the form of isotopes.

The atomic mass is the average atomic mass and is generally fractional.






LinkWithin




Saturday, November 19, 2011

CBSE IX Atoms and molecules Sample Test Paper 2012PH: 9835859669 JSUNIL TUTORIAL PUNJABI COLONY GALI 01

Class – IX Subject -Science Atoms and molecules Sample Test Paper Time 1 hr M.M.35

(Section A) 10 x 1 = 10

1. The atomic radius of hydrogen atom is

a. 0.037 nm b. 0.037 x 10 -9 m c. both a &b d. none

2. Complete the following sentence : In water, the proportion of hydrogen and oxygen is ----------

by mass

a. 1:8 b. 3:4 c. 9:0 d. none

3. The actual mass of hydrogen atom

a. 1.673 x 10 -24 g b. 1.673 x 10 c.1u d. both a & b

4. The symbol of cobalt a.C.o. b. CO c. Co. d. none

5. Atomicity of noble gases is one

a. True b. false c. can’t say d none

6. The molecular mass of sulfuric acid

a. 28 u b. 108 u c. 98u d. none

7. What are the number of electron and proton in chlorine ion

a. 17p & 18 e b. 18 p & 17 e c. 17 e & 0 e d. none

8. The value of symbol ‘L’ a. 6.022 x 10 23 b. 6.022 x 10 -23 c. 0.622 x 10 23 d. none

9. What is the mass of of 0.2 moles of oxygen atoms?

a. 2.3 g b. 3.2 g c. .32 g d. none





http://chemistryadda.blogspot.in/2011/11/cbse-ix-atoms-and-molecules-sample-test_19.html


http://chemistryadda.blogspot.in/2011/11/atoms-and-molecules-class-9-solved.html#comment-form

http://chemistryadda.blogspot.in/2011/11/atoms-and-molecules-class-9-solved.html


10. Write the atomicity of CO2 gas a. 2 b. 3 c. 0 d. none

(Section B) 10 X 1 = 10

1.what is meant by saying “the atomic mass of oxygen is 16?

2. What is the significance of formula H2O?

3. Calculate the formula mass of calcium chloride and sodium carbonate

4. An element Z forms an oxide ZO3. What is the valency of Z?

5. Write the Latin names of sodium, iron, mercury and tin.

6. Define 1 u.

7. Define electro negativity of any atom.

8. Name the element represent by the following symbols Hg, Pb, Au, Ag and Sn

9. Write down the atomicity of carbon dioxide, oxygen, ozone, solid sulphur.


(Section C) 5 x 2 = 10


2. Give major draw –backs of Dalton’s atomic theory of matter.

3. Work out the formula of magnesium chloride.

4. The mass of a single atom of an element X is 2.65 x 10 -23g. What is its atomic mass? What

could this element.

5. Calculate the molar mass of the following Ethyne and nitric acid

(Section D) 2 x 2.5 = 5

6. State the law of conservation of mass. Give one example also.

7. In an experiment, 1.288 g of copper oxide was obtained from 1.03 g of copper. In another

experiment 3.672 g of copper oxide obtain from the 2.938 g of copper. Show that these figures

verify the law of constant proportion.

jsuniltutorial.weebly.com Other Educational Portals

CBSE PHYSICS| CBSE MATH STUDY | CHEMISTRY ADDA | CBSE ADDA




http://cbseadda.blogspot.com/

http://chemistryadda.blogspot.com/

http://cbsemathstudy.blogspot.com/

http://physicsadda.blogspot.com/

http://jsuniltutorial.weebly.com/



LinkWithin






LinkWithin

Posted by J Sunil at 6:21 PM 1 comments



CBSE IX Atoms and molecules Sample Test Paper 2012PH: 9835859669 JSUNIL TUTORIAL PUNJABI COLONY GALI 01

Class – IX Subject -Science Atoms and molecules Sample Test Paper

Time 1 hr M.M.35

(Section A) 10 x 1 = 10

1. The atomic radius of hydrogen atom is





http://chemistryadda.blogspot.in/2011/11/cbse-ix-atoms-and-molecules-sample-test.html


http://chemistryadda.blogspot.in/2011/11/cbse-ix-atoms-and-molecules-sample-test_19.html#comment-form

http://chemistryadda.blogspot.in/2011/11/cbse-ix-atoms-and-molecules-sample-test_19.html



a. 0.037 nm b. 0.037 x 10 -9 m c. both a &b d. none

2. Complete the following sentence : In water, the proportion of hydrogen and oxygen is ----------

by mass

a. 1:8 b. 3:4 c. 9:0 d. none

3. The actual mass of hydrogen atom

a. 1.673 x 10 -24 g b. 1.673 x 10 c.1u d. both a & b

4. The symbol of cobalt a.C.o. b. CO c. Co. d. none

5. Atomicity of noble gases is one

a. True b. false c. can’t say d none

6. The molecular mass of sulfuric acid

a. 28 u b. 108 u c. 98u d. none

7. What are the number of electron and proton in chlorine ion

a. 17p & 18 e b. 18 p & 17 e c. 17 e & 0 e d. none

8. The value of symbol ‘L’ a. 6.022 x 10 23 b. 6.022 x 10 -23 c. 0.622 x 10 23 d. none

9. What is the mass of of 0.2 moles of oxygen atoms?

a. 2.3 g b. 3.2 g c. .32 g d. none

10. Write the atomicity of CO2 gas a. 2 b. 3 c. 0 d. none

(Section B) 10 X 1 = 10

1.what is meant by saying “the atomic mass of oxygen is 16?

2. What is the significance of formula H2O?

3. Calculate the formula mass of calcium chloride and sodium carbonate

4. An element Z forms an oxide ZO3. What is the valency of Z?

5. Write the Latin names of sodium, iron, mercury and tin.

6. Define 1 u.

7. Define electro negativity of any atom.

8. Name the element represent by the following symbols Hg, Pb, Au, Ag and Sn



(Section C) 5 x 2 = 10


2. Give major draw –backs of Dalton’s atomic theory of matter.

3. Work out the formula of magnesium chloride.

4. The mass of a single atom of an element X is 2.65 x 10 -23g. What is its atomic mass? What

could this element.

5. Calculate the molar mass of the following Ethyne and nitric acid

(Section D) 2 x 2.5 = 5

6. State the law of conservation of mass. Give one example also.

7. In an experiment, 1.288 g of copper oxide was obtained from 1.03 g of copper. In another

experiment 3.672 g of copper oxide obtain from the 2.938 g of copper. Show that these figures

verify the law of constant proportion.

jsuniltutorial.weebly.com Other Educational Portals

CBSE PHYSICS| CBSE MATH STUDY | CHEMISTRY ADDA | CBSE ADDA






LinkWithin







http://cbseadda.blogspot.com/

http://chemistryadda.blogspot.com/

http://cbsemathstudy.blogspot.com/

http://physicsadda.blogspot.com/

http://jsuniltutorial.weebly.com/

LinkWithin




Thursday, October 27, 2011

9th chemistry Self-evaluation on Mole conceptSample Problem 1. Calculate the number of mole in 52 g of Helium.

Solution. We know that, Atomic mass of He = 4u

So, its molar mass = 4 g That is, 4 g of He contains 1 mole of He.

Or, 4 g of He = 1 mole of He

Or, 1 g of He = 1/4 mole of He

So, 52 grams of Helium =1/4 x 52 mole = 13 moles

Therefore, there are 13 moles in 52 g of He

Sample Problem 2. Calculate the number of moles for 12.044 X 1023 atoms of

Helium.

Solution:

6.022 X 1023 atoms of Helium = 1 mole

1 atom of Helium =1/6.022 X 1023 mole

12.044 X 1023 atoms of Helium = [(1/6.022 X 1023) x 12.044 X 1023 ]moles

[ You may use ---- Number of moles = (given numbers of particles

/Avogadro number)]

Sample Problem 3. How many moles are there in 5 grams of calcium?

Sample Problem 4. How many moles there in 12.044 X 1023 atoms of

phosphorous?





http://chemistryadda.blogspot.in/2011/10/9th-chemistry-self-evaluation-on-mole.html


http://chemistryadda.blogspot.in/2011/11/cbse-ix-atoms-and-molecules-sample-test.html#comment-form

http://chemistryadda.blogspot.in/2011/11/cbse-ix-atoms-and-molecules-sample-test.html


Sample Problem 5. Calculate the mass of 0.5 mole of Nitrogen atoms.

Solution. We know that, Molar mass of of Nitrogen atoms 14 g

The mass of 1 mole of Nitrogen atoms = 14 g

The mass of 0.5 mole of Nitrogen atoms = 14x 0.5 g = 7 g

Alternate method,

Mass = Number of moles X Molar mass

Or, = 0.5 X 14 = 7 g

Therefore, mass of 0.5 mole of N atoms is 7 grams.

Sample Problem 6. What is the mass of 3.011 X 1023 number of Nitrogen

atoms?

Solution. We know that, Molar mass of of Nitrogen atoms 14 g

The mass of 6.022 X 1023 number of Nitrogen atoms= 14 g

The mass of 3.011 X 1023 number of Nitrogen atoms = [(14g/6.022 X 1023 )x

3.011 X 1023]g = 7 g

Sample Problem 7. Calculate the number of particles in each of the following:

(i) 0.1 mole of Carbon atoms

(ii) 46 grams of Sodium atoms.

Sample Problem 8 What is the mass of 4 moles of Aluminum atoms?

Determine the number of iron atoms in a piece of iron weighing 2.8 grams.

Sample Problem 9 If one mole of Carbon atoms weigh 12 grams, what is mass

in grams of a single atom of Carbon?

Sample Problem 10. Calculate the mass of 0.5 mole of N2 gas.

Sample Problem 11. Convert 12.044 X 1022 molecules of Sulphur dioxide into

moles?

Sample Problem 12. In which case the number of Hydrogen atoms is more- 2

mol of HCl

or 1 mol of NH3?

Sample Problem 13 . An ornament of silver contains 20 gram silver. Calculate

the moles of silver present.

Sample Problem 14. If 1 g sulphur dioxide contains x molecules, what will be

the number

of molecules in 1 g of methane?

Sample Problem 15. Calculate the number of aluminium ions present in 0.051

g of aluminium oxide.

Sample Problem 16. How many grams of neon will have the same number of

atoms as 4 g of calcium?

Sample Problem 17. Calculate the number of iron atoms in a piece of iron

weighing 2.8 grams.

Sample Problem 18. What is the mass of 3 moles of Zinc?

Sample Problem 19 : What is the ratio of molecules present in 6.6 grams of

CO2 and 3.2 grams of SO2?

Sample Problem 20. If one gram of Sulphur contains x atoms, what will be the

number of atoms in one gram of oxygen? (atomic mass of S = 32u)






LinkWithin




Tuesday, October 25, 2011

Numerical based on mole concept 9th ChemistryNumerical based on mole concept 9th Chemistry

1. Calculate the number of moles of magnesium present in a magnesium ribbon weighing 12

g. Molar atomic mass of magnesium is 24g/ mol




3. Find the ratio by mass of the combining elements in the following compounds.

(a) CaCO3 (b) MgCl2 (c) H2SO4 (d) C2H5OH (e) NH3 (f) Ca(OH)2

4. Calcium chloride when dissolved in water dissociates into its ions according to the

following equation.

CaCl2 (aq) → Ca2+ (aq) + 2Cl– (aq)

Calculate the number of ions obtained from CaCl2 when 222 g of it is dissolved in water.

5. The difference in the mass of 100 moles each of sodium atoms and sodium ions is

5.48002 g. Compute the mass of an electron.

6. Cinnabar (HgS) is a prominent ore of mercury. How many grams of mercury are present

in 225 g of pure HgS? Molar mass of Hg and S are 200.6 g /mol and 32 g/ mol respectively.

7. The mass of one steel screw is 4.11g. Find the mass of one mole of these steel screws.

Compare this value with the mass of the Earth (5.98 × 1024kg). Which one of the two is

heavier and by how many times?

8. A sample of vitamin C is known to contain 2.58 ×1024 oxygen atoms. How many moles of






http://chemistryadda.blogspot.in/2011/10/numerical-based-on-mole-concept-9th.html


http://chemistryadda.blogspot.in/2011/10/9th-chemistry-self-evaluation-on-mole.html#comment-form

http://chemistryadda.blogspot.in/2011/10/9th-chemistry-self-evaluation-on-mole.html


http://cbseadda.blogspot.com/2011/10/numerical-based-on-mole-concept-9th.html?spref=bl

9. Compute the difference in masses of 103 moles each of magnesium atoms and

magnesium ions. (Mass of an electron = 9.1×10–31 kg)


11. A gold sample contains 90% of gold and the rest copper. How many atoms of gold are

present in one gram of this sample of gold?

12. Compute the difference in masses of one mole each of aluminium atoms and one mole

of its ions. (Mass of an electron is 9.1×10–28 g). Which one is heavier?



14. A sample of ethane (C2H6) gas has the same mass as 1.5 ×1020 molecules of methane

(CH4). How many C2H6 molecules does the sample of gas contain?





(c) The formula unit mass of Ca3 (PO4)2 is ————.







LinkWithin





Wednesday, August 31, 2011

9th CBSE Science Chap 3 Atoms and Molecules Self ...9th CBSE Science Chap 3 Atoms and Molecules Self ...: 1. Fill in the blanks (a) In a chemical reaction,

the sum of the masses of the reactants and products remains unchanged. This is called —...






LinkWithin




9th Atoms and Molecules - Mole Concept and Proble...9th Atoms and Molecules - Mole Concept and Proble...: Mole Concept we can express the quantity

of a substance is expressed in terms of mole. Mole is a fundamental unit in the System Internatio...










http://cbseadda.blogspot.com/2011/08/9th-atoms-and-molecules-mole-concept_31.html?spref=bl

http://chemistryadda.blogspot.in/2011/08/9th-atoms-and-molecules-mole-concept.html


http://chemistryadda.blogspot.in/2011/08/9th-cbse-science-chap-3-atoms-and.html#comment-form



http://cbseadda.blogspot.com/2011/08/9th-cbse-science-chap-3-atoms-and.html?spref=bl



http://chemistryadda.blogspot.in/2011/10/numerical-based-on-mole-concept-9th.html#comment-form

http://chemistryadda.blogspot.in/2011/10/numerical-based-on-mole-concept-9th.html





LinkWithin

Articles you may like:

IX Atomic Structure ( a fundamental particles) Discovery of Electron

The direction of deflection indicates that the cathode rays constitute negatively charged particles.

Matter in Our Surroundings

At this temperature, after getting the heat equal to the latent heat of fusion, the solid form of

water i.e., ice starts changing into its liquid form i.e., wat...

Class 8th solved Question Combustion and Flame by ...

What is combustion? Ans: Combustion: - The chemical process in which a substance reacts with

oxygen to produce heat is called combustion.

9th chemistry Self-evaluation on Mole concept

Mass = Number of moles X Molar mass Sample Problem 9 If one mole of Carbon

atoms weigh 12 grams, what is mass in grams of a single atom o...

atoms and molecules class 9 Solved questions For F...

Search Go

http://chemistryadda.blogspot.in/2011/11/atoms-and-molecules-class-9-solved.html?dhiti=1

http://chemistryadda.blogspot.in/2011/10/9th-chemistry-self-evaluation-on-mole.html?dhiti=1

http://chemistryadda.blogspot.in/2012/08/class-8th-solved-question-combustion.html?dhiti=1

http://chemistryadda.blogspot.in/2011/05/matter-in-our-surroundings.html?dhiti=1

http://chemistryadda.blogspot.in/2011/12/ix-atomic-structure-fundamental.html?dhiti=1


http://chemistryadda.blogspot.in/2011/12/ix-atomic-structure-fundamental.html?dhiti=1

Ans Hydrogen gas is a diatomic in nature(H2) while helium gas is monoatomic (He).As a result,

the number of atoms in one mole of hydrogen(2*NA )are expected to ...

Concepts to explore:

Organic compounds

Unsaturated hydrocarbons, Organic Compounds, Carboxylic,Ketones

Chemical properties

Chemical properties,Characteristic properties,Inert, Miscible

Acid-base chemistry

Acid base theories, PH value, Acidified,Amphoteric

Thermodynamic properties

Calorific Value, Latent Heat of Fusion, Latent Heat of Vaporization,Activity

Chemical reactions

Chemical Reactions,Homogeneous, Reducing agent, Oxidized

Chemical bonding

Valence Electrons,Covalent Bonding, Shared pair, Hydrophilic

Subatomic particles

Fundamental particles,Subatomic Particles,Nucleus

Water chemistry

Hydronium ions, Water Pollution, H2O

Corrosion

Rusting, Coated,Sulphides, Corrode

Phase changes

Evaporates, Boiling water,Crystallisation, Change Of State

ednesday, July 27, 2011

Science Questions - Ponder over it?

1. Why does a rider feel a tendency to fall when the horse starts running of

stops suddenly?

Ans: This is caused by inertia. When the horse starts running, the rider, being at

http://chemistryadda.blogspot.in/2011/07/science-questions-ponder-over-it.html

















































rest, falls back. When a running horse stops suddenly, the rider being in motion has

a tendency to fall ahead.

2. Why does a person carrying a bucket full of water in his right hand bend

towards the left?

Ans: He bends towards his left so that the centre of gravity falls within the base.

This enables him to keep up balance, otherwise he may fall.

3. Why does tea cool more rapidly in a saucer than in a cup?

Ans: In a saucer evaporation takes place more rapidly than in a cup. Cooling is

caused by evaporation.

4. Ice packed in sawdust does not melt quickly. Why?

Ans: Ice packed in sawdust does not melt quickly, because sawdust being bad

conductor, it cuts the heat rays.

5. Why do you heat a metal rim before fitting it to a wheel?

Ans: By heating, the rim expands and fits easily over a slightly bigger radius than

that of the rim. On being cooled it contracts and has a firm grip on the wheel.

6. Why do wet clothes dry slowly on a rainy day?

Ans: On a rainy day the atmosphere air contains more water vapor than on a dry

day and hence evaporation is slower.

7. Why does a substance thrown up come to the ground?

Ans: Because of the gravitational force of the earth.

8. Why does moisture gather outside of a glass of cold water on a warm

day?

Ans: The temperature of the outer surface of glass of cold water is lower than that of

its surroundings. The vapor in the surrounding atmosphere gets condensed on

the outer surfaceof the water appears in the forms of tiny particles of water.

9. What happens to iron when it rusts?

Ans: It reacts with the oxygen of the air and forms iron-oxide which is the rust.

10. How would you distinguish between welding and soldering?

Ans: Welding is the joining of metals by raising the temperature of the metals to

fuse them together by melting their ends. Soldering is the joining of metals with the

help of an alloy called solder.

11. How does a ball which falls down, bounce up?

It is due to the operation of Newton’s Third Law of motion. To every action there is

equal and opposite reaction. A ball falling to the ground is slightly deformed. Due to

the elastic force of the material of which the ball is made, the ball tries to recover its

original shape. In doing so it forces the ground which pushes the ball upward due to

reaction and the ball bounces up.

12. An iron nail floats on mercury but sinks in water. Give reasons.

Ans: The specific density of iron is lower than of mercury, hence it floats on

mercury, while it is higher than that of water, and hence it sinks in water.

13. How do you convert Centigrade in to Fahrenheit?

Ans: With the help of the following formula – C/100 = F-32/180

14. It is advisable to work electric appliances when they are earthed

suitably. Why?

Ans: In case of short-circuiting, the current passes to the earth without harming the

user, if an electrical appliance is properly earthed.

15. How does a refrigerator keep food fresh?

Ans: Food is kept fresh so long as fermentation does not set in; refrigeration

prevents fermentation by providing low temperature.

16. Ice wrapped in a blanket does not melt away quickly. Why?

Ans: Blanket being bad conductor of heat prevents the outside heat from creeping

inside.

17. Why can a petrol fire not be extinguished by throwing water on it?

Ans: The heat of the petrol fire is so intense that the water thrown on it gets

evaporated and decomposed. Hence it is not effective in extinguishing the petrol

fire.

18. A train stops when the chain is pulled. Why?

Ans: When the chain is pulled, one small valve gets opened and air/atmospheric

pressure is admitted to the under side of the piston head of the brake cylinder

through pipe connection. Initially there is vacuum on both top and bottom side of the

piston head. When the air/atmospheric pressure enters the under side of the

piston head, the piston raises up due to difference of pressure and pulls the brake

rigging to which it is connected with links and levers. Thus the brakes are applied

and the train stops.

Courtesy: Articlediary.com






LinkWithin



Labels: Chemisrty Amazing Facts

Friday, July 1, 2011

Salt - The Spice of Life





http://chemistryadda.blogspot.in/2011/07/salt-spice-of-life.html

http://chemistryadda.blogspot.in/search/label/Chemisrty%20Amazing%20Facts

http://chemistryadda.blogspot.in/2011/07/science-questions-ponder-over-it.html#comment-form

http://chemistryadda.blogspot.in/2011/07/science-questions-ponder-over-it.html


Salt - The Spice of Life: For every meal there is one thing people generally reach

for before they even take a bite – the salt shaker. Salt is one of the oldest spices

used and is a key component to humans, animals, and plants.

Its flavor is unique and versatile, salt has been a staple throughout time. Enhancing

almost every dish, salt is added to breads, meats, fruits and vegetables to sauces

and desserts.

Additionally, salt aids foods in a variety of ways like:

Preservation – helps protect against microorganisms, bacteria through dehydration

and preventing growth of bacteria, which slows or prevents spoilage.

Texture Aid – in bread making, allows the dough to rise by giving helping the gluten

hold more water and carbon dioxide. In meats it improves tenderness and in cheeses

it aids in consistency of the cheese and the hardness of the rind.

Binder – in processed meats it helps retain water which reduces the loss of meat

when cooking.

Color Developer – in ham, bacon, and other processed meats it helps obtain the

desired color. It also helps create a golden crust for breads.

Fermentation Control – slows and controls the fermentation process in:

Pickling

Cheese production Sauerkraut production Summer sausage production

Read more »






LinkWithin



Labels: 10th Acids bases and salts, 10th Chemisty Term -I, Chemisrty Amazing Facts,Chemistry in

Daily Life

Why aqueous solution of sodium carbonate is basic in nature?Question: Why aqueous solution of sodium carbonate is basic in nature?

Ans: Sodium bicarbonate is an amphoteric compound. Aqueous solutions are

mildly alkalinedue to the formation of carbonic acid and hydroxide ion:

NaHCO− 3 + H2O → H2CO3 + OH−

Question: Why is an aqueous solution of ammonium chloride acidic in

nature?

A basic component is the one that produces hydroxide (OH-) ions when

dissolved in water. In aqueous solution of ammonium chloride, ammonium

ions (NH4+) first associate with H2O and form ammonia and hydroxide ions.





http://chemistryadda.blogspot.in/2011/07/why-aqueous-solution-of-sodium.html


http://chemistryadda.blogspot.in/search/label/Chemistry%20in%20Daily%20Life



http://chemistryadda.blogspot.in/search/label/10th%20Chemisty%20Term%20-I

http://chemistryadda.blogspot.in/search/label/10th%20Acids%20bases%20and%20salts

http://chemistryadda.blogspot.in/2011/07/salt-spice-of-life.html#comment-form

http://chemistryadda.blogspot.in/2011/07/salt-spice-of-life.html


http://chemistryadda.blogspot.in/2011/07/salt-spice-of-life.html#more

NH4Cl + H2O = NH4+ + HCl ( equation 1)

NH4+ + H2O = NH3 + OH- (equation 3)

Since ammonium ions produce hydroxide ions, NH4+ are considered to be

the basic components.






LinkWithin



Labels: Basic concept, Chemisrty Amazing Facts, Chemistry in Daily Life

Why are commercial samples of bleaching powder not completely soluble in water?Why are commercial samples of bleaching powder not completely soluble in

water?

Because it is essentially chlorinated CaO, which is insoluble. It releases

chlorine on adding to water. Stable bleaching powder has about 37%





http://chemistryadda.blogspot.in/2011/07/why-are-commercial-samples-of-bleaching.html




http://chemistryadda.blogspot.in/search/label/Basic%20concept

http://chemistryadda.blogspot.in/2011/07/why-aqueous-solution-of-sodium.html#comment-form



available chlorine when fresh.

Why aqueous solution of sodium carbonate is basic in nature?






LinkWithin



Labels: Basic concept, Chemisrty Amazing Facts, Chemistry in Daily Life

Saturday, May 28, 2011

cbse Chemisrty Amazing Facts





http://chemistryadda.blogspot.in/2011/05/cbse-chemisrty-amazing-facts.html



http://chemistryadda.blogspot.in/search/label/Basic%20concept

http://chemistryadda.blogspot.in/2011/07/why-are-commercial-samples-of-bleaching.html#comment-form



Hydrogen is the first element on the periodic table. It has an atomic number of 1. It is

highly flammable and

is the most common element found in our universe. Morehydrogen facts.

Liquid nitrogen boils at 77 kelvin (−196 °C, −321 °F). More nitrogen facts.

Around 1% of the sun’s mass is oxygen. More oxygen facts.

Helium is lighter than the air around us so it floats, that's why it is perfect for

the balloons you get at parties. More helium facts.

Carbon comes in a number of different forms (allotropes), these include diamond,

graphite and impure forms such as coal. More carbon facts, diamond facts, and coal

facts.

Although it is still debated, it is largely recognized that the word 'chemistry' comes from

an Egyptian word meaning 'earth'.

The use of various forms of chemistry is believed to go back as long ago as the

Ancient Egyptians. By 1000 BC civilizations were using more complex forms of

chemistry such as using plants for medicine, extracting metal from ores, fermenting

wine and making cosmetics.

Things invisible to the human eye can often be seen under UV light, which comes in

handy for both scientists and detectives.

Humans breathe out carbon dioxide (CO2). Using energy from sunlight, plantsconvert

carbon dioxide into food during a process called photosynthesis.

Chemical reactions occur all the time, including through everyday activities such as

cooking. Try adding an acid such as vinegar to a base such as baking soda and see

what happens!

Above 4 °C, water expands when heated and contracts when cooled. But between 4

°C and 0 °C it does the opposite, contracting when heated and expanding when

cooled. Stronger hydrogen and oxygen bonds are formed as the water crystallizes into

ice. By the time it's frozen it takes up around 9% more space.

Often formed under intense pressure over time, a crystal is made up of molecules or

atoms that are repeated in a three dimensional repeating pattern. Quartz is a well

known example of a crystal.

Athletes at the Olympic Games have to be careful how much coffee they drink. The

caffeine in coffee is a banned substance because it can enhance performance. One or

two cups are fine but they can go over the limit with more than five. (update - as of

2004 caffeine has been taken back off the WADA banned list but its use will be closely

monitored to prevent future abuse by athletes.)

Hydrogen Facts

The chemical symbol of hydrogen is H. It is an element with atomic number 1, this

means that 1 proton is found in the nucleus of hydrogen.

Hydrogen is the lightest, simplest and most commonly found chemical element in the

Universe, making up around 75% of its elemental mass.

Hydrogen is found in large amounts in giant gas planets and stars, it plays a key role

in powering stars through fusion reactions.

Hydrogen is one of two important elements found in water (H2O). Each molecule of

water is made up of two hydrogen atoms bonded to one oxygen atom.

In 1766, during an acid metal reaction, Henry Cavendish first formally recognized

hydrogen. In 1781 he also found that hydrogen produces water when burned. While

Cavendish is usually given credit for the discovery of hydrogen as an element, it had

been produced by earlier scientists who were unaware of hydrogen as a unique

chemical element.

It wasn’t until a few years later (1783) that hydrogen was given its name. The word

hydrogen comes from the Greek word hydro (meaning water) and genes (meaning

creator).

Hydrogen gas has the molecular formula H2. At room temperature and under standard

pressure conditions, hydrogen is a gas that is tasteless, odorless and colorless.

Hydrogen can exist as a liquid under high pressure and an extremely low temperature

of 20.28 kelvin (−252.87°C, −423.17 °F). Hydrogen is often stored in this way as liquid

hydrogen takes up less space than hydrogen in its normal gas form. Liquid hydrogen

is also used as a rocket fuel.

Under extreme compression hydrogen can also make a transition to a state known as

metallic hydrogen. Laboratory research into this area is ongoing as scientists continue

efforts to produce metallic hydrogen at low temperature and static compression

Nitrogen Facts

Nitrogen is a chemical element with the symbol N and atomic number of 7.

Under normal conditions nitrogen is a colorless, odorless and tasteless gas.

Nitrogen makes up around 78% of the air you breathe.

Nitrogen is present in all living things, including the human body and plants.

Nitrogen gas is used in food storage to keep packaged or bulk foods fresh. It is also

used in the making of electronic parts, for industrial purposes and has many other

useful applications.

Nitrogen gas is often used as an alternative to carbon dioxide for storing beer in

pressurized kegs. The smaller bubbles it produces is preferred for some types of

beer.

Titan, the largest moon of Saturn, has an atmosphere nearly entirely made of nitrogen

(over 98%). It is the only moon in our solar system known to have a dense

atmosphere.

Nitrogen is in a liquid state when at a very low temperature. Liquid nitrogen boils at 77

kelvin (−196 °C, −321 °F). It is easily transported and has many useful applications

including storing items at cold temperatures, in the field of cryogenics (how materials

behave at very low temperatures), as a computer coolant (a fluid used to prevent

overheating), removing warts and much more.

Decompression sickness (also known as the bends) involves nitrogen bubbles forming

in the bloodstream and other important areas of the body when people depressurize

too quickly from scuba diving. Similar situations can occur for astronauts and those

working in unpressurized aircraft.

Nitrous oxide (also known as laughing gas or by its chemical formula N2O) is used in

hospitals and dental clinics as an anesthetic (removing or reducing pain and general

awareness for various surgeries).

Nitrous oxide is also used in motor racing to increase the power of engine and speed

of the vehicle. When used for this purpose it is often referred to as nitrous or NOS.

Nitrous oxide is a considerable greenhouse gas and air pollutant. By weight is has

nearly 300 times more impact than carbon dioxide.

Nitroglycerin is a liquid used to create explosives such as dynamite. It is often used in

the demolition and construction industries as well as by the military.

Nitric acid (HNO3) is a strong acid often used in the production of fertilizers.

Ammonia (NH3) is another nitrogen compound commonly used in fertilizers.

Oxygen Facts

Oxygen is an element with the chemical symbol O and atomic number 8.

Oxygen is a very reactive element that easily forms compounds such as oxides.

Under standard temperature and pressure conditions two oxygen atoms join to form

dioxygen (O2), a colorless, tasteless and odorless gas.

Oxygen is essential to human life, it is found in the air we breathe and the water we

drink (H20).

Oxygen makes up around 21% of the air you breathe. It is also the most common

element in the Earth’s crust (around 47%) and the third most common element in the

Universe (but far less than hydrogen and helium, the two most common).

The large amount of oxygen on Earth is supported by the oxygen cycle which involves

the movement of oxygen between the air, living things and the Earth’s crust.

Photosynthesis (a process that converts carbon dioxide into organic compounds using

sunlight) plays a major role in this cycle.

Ozone (O3) is an allotrope (different form) of oxygen that combines three oxygen

atoms together. While ground level ozone is an air pollutant, the ozone layer in the

Earth’s upper atmosphere provides protection from the suns harmful rays by filtering

UV light.

The sun’s mass is made up of around 1% oxygen.

Between 1770 and 1780, Swedish pharmacist Carl Wilhelm Scheele, British

clergyman Joseph Priestley and French chemist Antoine Laurent Lavoisier

researched, documented and helped discover oxygen. The name oxygen was first

used by Lavoisier in 1777.

Oxygen therapy is used as a common medical treatment. You may have seen patients

on TV or in real life using an oxygen mask or nasal cannula (a plastic tube that fits

behind the ears and delivers oxygen through the nostrils).

Oxygen has a number of other practical uses such as smelting metal from ore, water

treatment, as an oxidizer for rocket fuel and a number of other industrial, chemical and

http://www.gophoto.it/view.php?i=http://www.sciencekids.co.nz/images/experiments/oxygen120.jpg

scientific applications.

Concentrated oxygen promotes fast combustion. While a spark or heat is still needed

to start a fire, having concentrated oxygen near various fuels can be very dangerou

Documents

9 th class CBSE