Chem115 unit1

Chemistry• the study of matter

• its chemical and physical properties• the chemical and physical changes it undergoes• the energy changes that accompany those

processes

• Most changes either require energy or produce energy

• This class will focus on the changes that happen in living systems

CHEMISTRY

medical practitioners

pharmaceutical industry

forensic sciences

food science

public health

Why do you need to know chemistry?

Bunny reproduction is biology!

Chemistry overlaps with many different disciplines.

Bunny reproduction is biology!

But chemists study the hormonal changes that

tell the bunnies when to mate!

Psychologists study how mice “learn”.

But chemists study the

neurotransmitters responsible for learning!

Psychologists study how mice “learn”.

What happens when a bunnybaby crosses a road is physics.

What happens to the bunny baby’s bodyin the hot summer sun is chemistry!

MAJOR AREAS OF CHEMISTRY• Biochemistry - the study of life at the

molecular level• Organic chemistry - the study of matter

containing carbon and hydrogen • Inorganic chemistry - the study of matter

containing elements, not organic• Analytic chemistry - analyze matter to

determine identity and composition• Physical chemistry - attempts to explain the

way matter behaves

Chemistry uses the scientific method• How does something

work?• What is the “truth”

about how something works?

• Does my data support my hypothesis?

• Do I need to change my hypothesis?

Experimental methods• Experiments produce DATA & RESULTS • DATA:– Recorded observations or measurements• Mass, Time, Temp, volume, energy

• RESULTS:– Outcome of experiment– Conclusions drawn from observations– Usually several pieces of data form a result

CHEMISTRYthe study of matter

and its changes

. . . but what is matter?

Matter is “stuff ”

(anything with mass and volume)

and its changes

hammer Q-tip fear paper bag beauty

blood talent acorn air gravity

Which of these are matter?

and its changes

• Pure substance - a substance that has only one component

• Mixture - a combination of two or more pure substances in which each substance retains its own identity, not undergoing a chemical reaction

Classification of Matter

• Element - a pure substance that cannot be changed into a simpler form of matter by any chemical reaction

• Compound - a substance resulting from the combination of two or more elements in a definite, reproducible way, in a fixed ratio

• Mixture - a combination of two or more pure substances in which each substance retains its own identity

• Homogeneous - uniform composition, particles well mixed, thoroughly intermingled

• Heterogeneous – nonuniform composition, random placement

Classification of Matter• Which classes of matter are shown below?

compound Heterogeneous mixture

Homogeneous mixture

The Periodic Table of the Elements

We know that all “matter” is made up ofvery, very, very tiny spheres called atoms.

Each square in this table represents a different kind of atom.

There are over 114 different kinds of atoms.

Table organization is based on each atom’s makeup and thesimilarities of the properties of the various kinds of atoms.

We know that all “matter” is made up ofvery, very, very tiny spheres called atoms.

Each square in this table represents a different kind of atom.

We won’t discuss any of these elements in

PhysiologicalChemistry

Table is usually displayed this way.(it takes up less space)

Every kind of atom has a name and a “symbol.”

All modern symbols are based on letter abbreviations

Hydrogen (H)Oxygen (O)Iodine (I)

Every symbol startswith a capital letter.

Some symbols have two letters.

Scandium (Sc)Bismuth (Bi)Neon (Ne)

First letter is capitaland second is lower case.

Some symbols come from foreign languages.Tungsten (W) -- ‘W’ is from wolfram (German)

Sodium (Na) -- ‘Na’ is from natrium (Latin)Antimony (Sb) -- ‘Sb’ is from Stibium (Latin)

Some types of atoms are very common in air!

nitrogen, oxygen, carbon, argon, neon, helium

Some types of atoms are very common in dirt and rocks!

oxygen, silicon, aluminum, iron, calcium, sodium

Some types of atoms are very common in stars!

hydrogen, helium, carbon, oxygen, neon, magnesium

Some types of atoms are very common in human bodies!

oxygen, carbon, hydrogen, nitrogen, calcium, phosphorus

1 2 3 4 . . . . . . . . . . . . . . . . . . . . . . . . . 16 17 18

18 columns(Columns are called groups)

This is group 13.

7 rows(Rows are called periods)

1234567

This is period 4.

alkali metals(Group 1)

alkaline earth metals(Group 2)

halogens(Group 17)

noble gases or “inert” gases(Group 18)

All of the atoms in a grouphave similar properties.

http://www.an.psu.edu/rxg1/pt1999/halogens.html

Consider these three halogens:

• All smell like a swimming pool.• All produce colored vapors.

• All react rapidly with sodium to give edible salts.

• All are poisonous.

Groups in the periodic table are comprised of elements with similar properties.

http://www.an.psu.edu/rxg1/pt1999/halogens.html

Consider these three halogens:

Consider these three alkali metals:

Lithium (Li)Sodium (Na)

Potassium (K)

• All are shiny, soft solids when pure.• All melt at very low temperatures.

Lithium mp = 181oCSodium mp = 98oCPotassium mp = 63oC

• All are shiny, soft solids when pure.• All melt at very low temperatures.• All react violently with water.

http://www.westga.edu/~chem/courses/desc.inorg/490Jan14/sld009.htm

MetalsNon-metalsMetalloids or semimetals

Hydrogen is an odd-

The Periodic Table of the ElementsMetals are . . .

• Lustrous• Malleable

• Ductile• Conductors of

electricity• Prone to losing electrons • Lower Left of periodic

The Periodic Table of the ElementsNonmetals are . . .

• Not lustrous• Not malleable

• Not ductile• Not conductors of

electricity• Often prone to gaining electrons • Upper Right of

Classification & Behavior of Matter• Properties of Matter– Physical– ChemicalWhat are some examples of properties of matter?

• States of Matter– Solid– Liquid– Gas• Gas Laws

hydrogen + oxygen water

reactants products

Chemical Properties & Change• Property - result in a change in composition

and can be observed only through a chemical reaction

• Reaction (chemical change) - a process of rearranging, removing, replacing, or adding atoms to produce new substances

Physical Properties & Change• Property - is observed without changing the

composition or identity of a substance

• Change - produces a recognizable difference in the appearance of a substance without causing any change in its composition or identity- conversion from one physical state to another- melting an ice cube

Separation by Physical PropertiesMagnetic iron is separated from other nonmagnetic

substances, such as sand. This property is used as a large-scale process in the recycling industry.

Three States of Water

(a) Solid (b) Liquid (c) Gas

Three States of Matter• gas - particles widely separated, no

definite shape or volume solid

• liquid - particles closer together, definite volume but no definite shape

• solid - particles are very close together, define shape and definite volume

Solid Liquid Gasordered

condensednot orderedcondensed

not orderednot condensed

Comparison of states of matter

Solid Properties

Solids are . . .

•Not compressible

•Organized

But solids are more complex than this!

•Don’t take the shape of their container!

All solids are considered by chemists to be either crystalline or amorphous.

Crystalline: at the atomic level, material is highly organized and has a repeating pattern of particles

Amorphous: at the atomic level, material appears randomly thrown together and no patterns are present.

All solids are considered by chemists to be either crystalline or amorphous.

Crystalline: at the atomic level, material is highly organized and has a repeating pattern of particles

Ionic Solids

Covalent Solids

Molecular SolidsMetallic Solids

Ionic SolidsMolecular Solids

http://www.btinternet.com/~digital.wallpapers/hot_air_balloon.jpg

GasesGases

Some Gaseous Odds and Ends

Gases have very low densities

N2 (s) d = 1.03 g/mL

N2 (l) d = 0.808 g/mL (78%)

N2 (g) d = 0.00125 g/mL (0.12%)

(implied by “mostly empty space”)

Gases readily expand to fill their container

(implies that gas molecules are moving rapidly)

Gases are readily compressible

(implied by “mostly empty space”)

Gases are readily compressible

(Liquids and solids are already compressed)

And they “spring” back!

(implies that gases exert “pressure”)

Gases exert “pressure” because gas molecules collide with container.

forcePressure

Usually in2 or m2

Usually “pounds” or Newtons

pounds2m

Newtons

usually abbreviated as “psi”

pounds2m

Newtons

known as a “Pascal” (Pa)

pounds2m

Newtons

Convert 34 psi to Pa.

Some Gas Problems

101,325 Pa = 14.7 psi

Papsi 000,234

325,10134

What is blood pressure?

The liquid inside your blood vessels is

compressed by the elastic nature of the

vessel walls.

Your blood pressure is usually 80 mm Hg

greater than the atmospheric pressure

What is blood pressure?

The liquid inside your blood vessels is

compressed by the elastic nature of the

vessel walls.

When your heart contracts, the pressure

goes up even more!

. . . Perhaps to 120 mm Hg greater than atmospheric!

THE GAS LAWS

http://elementy.ru/images/eltbio/boyle_robert_180.jpg

In 1662, Robert Boyle discovered an inverse relationship between the pressure exerted by a

gas and its volume.

(As long as the temp was kept the same)

gas and its volume.

Examine his data:

20 mL 1 atm = 20 mL.atm

In other words . . .

PV = constant

gas and its volume.

PV = constant

This is known as Boyle’s Law

Using Boyle’s Law

When atmospheric pressure = 14.9 psi, a sample of air has a volume of 30 mL. What will the volume of the air sample be when atmospheric pressure drops to 14.5 psi?

PV = constant

First, let’s find the constant:

14.9psi 30mL = 447 psi.mL

14.5psi V = 447 psi.mL

Now, use the constant to find the new volume:

14.9psi 30mL = 447 psi.mL

Using Boyle’s Law

mLpsi31

5.14447

V =×=

Using Boyle’s Law

We often see Boyle’s law written as P1V1 = P2V2

P1 = 14.9psi

V1 = 30mL

P2 = 14.5psi

V2 = ?

14.9psi 30mL = 14.5psi V2

V2 = 31mL

Using Boyle’s Law

In 1787, Jacques Charles discovered that the temperature and volume of a gas are

proportional

http://content.answers.com/main/content/wp/en-commons/thumb/b/b7/250px-Jacques-Charles_Dupont_de_L'Eure.jpg

proportional

ice bath at 0C

proportional

boiling water at 100C

20 mL of a gas at 0C will occupy 27.3 mL at 100C(as long as atmospheric pressure isn’t changed)

If temperature is in degrees Kelvin, we have the following:

ConstantT

This is known as Charles’ Law

We often see Charles’ law written as V1

Using Charles’ Law

A sample of steam at 100C has a volume of 240 mL.What will the new volume be if the steam is cooled to

First, let’s convert our temps to Kelvin:

100C + 273 = 373K

0C + 273 = 273K

100C + 273 = 373K

0C + 273 = 273KV1 = 240 mL

T1 = 373K

V2 = ?

T2 = 273K

V2 = 176 mL 240 mL

Combined Gas Law

• Derived from a combination of Boyle’s law and Charles’s law

• Change involving volume, pressure, and temperature simultaneously

Using the Combined Gas Law

• Calculate the volume of N2 resulting when 0.100 L of the gas is heated from 300. K to 350. K at 1.00 atm

• What do we know?– Pi = 1.00 atm Pf = 1.00 atm– Vi = 0.100 L Vf = ? L– Ti = 300. K Tf = 350. K

• Vf = ViTf / Ti this is valid as Pi = Pf

• Vf = (0.100 L)(350. K) / 300. K = 0.117 L

Many of the “most important” gases aren’t pure, but are actually

mixtures.

What is the composition of air?

780,810 N2 molecules

209,480 O2 molecules

9,340 Ar atoms

345 CO2 molecules

18 Ne atoms

5 He atoms

2 CH4 molecules

This is only true of dry, nonpolluted air.

For every 1,000,000 “air” molecules, . . .

What is the composition of air?

CO molecules NO molecules NO2 moleculesSO2 moleculesO3 molecules

In urban areas, the following pollutant molecules can be fairly abundant:

http://www.photo.net/photo/pcd0222/los-angeles-downtown-45.4.jpg

http://www5.worldisround.com/photos/5/282/505_o.jpg

Costa Rican rainforest

Consider a Rain Forest in Belize.

http://www5.worldisround.com/photos/5/282/505_o.jpg

At 86F and 95% humidity, we have:

Costa Rican rainforest

8,970 Ar atoms

330 CO2 molecules

17 Ne atoms

3 He atoms

39,810 H2O molecules

Water can be the 3rd most

abundant gas in air!

Consider a Rain Forest in Belize.

http://salegos-scar.montana.edu/images/Vostok%20Station.JPG

The amount of H2O in air is highly dependent on weather and geography.

Consider Vostok, Antarctica:

At -76F and 34% humidity, we have:

345 CO2 molecules

18 Ne atoms

4 He atoms

3 H2O molecules

9,340 Ar atoms

Consider Vostok, Antarctica:

Whether a gas is pure or a mixture, it still obeys Boyle’s law and Charles’ law

However, in a mixture of gases, the total pressure equals the sum of the pressures

due to each component

Why should you care?

Breathing air that is roughly 20% O2 means

that 80% of the molecular collisions in your lungs are useless.

Breathing 100% O2 increases the “partial

pressure” of O2

Liquid Properties

Liquids are . . .

•Not compressible

•Not organized

Viscosity

Liquids have . . .

Surface Tension

Vapor Pressure

Density

The Properties of Most Liquids Can be Rationalized

in Terms of Their Intermolecular Forces

Liquids have a surface tension (an edge effect)

Compare the attractive forces these molecules

have for their neighbors!

Liquids have a “Skin”!

Because it can hydrogen-bond, water’s skin is particularly tough!

Liquids with weak intermolecular attractive forces have less surface tension.

Water’s high surface tension causes it to “bead up” into large drops.

Liquids with weak intermolecular attractive forces have smaller drops.

Liquids have a viscosity

Which pours more easily, a jar of marbles

or a jar of gummy bears?

Which pours more easily, gummy bears or

gummy worms?

Long, flexible molecules with strong

intermolecular forces are most viscous.

Liquids have a vapor pressure

What happens when a liquid is poured into a perfectly empty container and the container is sealed?

Some of the molecules at the surface evaporate.

But the number of gas molecules only increases to a point.

Some of the gas molecules bump backinto the liquid layer, slow down, and “re-stick”.

When the number leaving the liquid equals the number re-entering the liquid, we have an “equilibrium”.

When equilibrium is reached, molecules with strong intermolecular attractive forces look like this.

When equilibrium is reached, molecules with weak intermolecular attractive forces look like this.

What is melting? What is subliming?

“Deposition” is the opposite of sublimation.

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