01 Chemistry and Matter

8/4/2019 01 Chemistry and Matter

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Topic1 Topic 1: Chemistry and Matter

Table of Contents

Basic Concepts

Additional Concepts


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Chemistry is the science that investigatesand explains the structure and properties ofmatter.

Composition, Structure, and Behavior

Chemistry and Matter: Basic Concepts

Matter is the stuff thats all around you: the

metal and plastic of a telephone, the paperand ink of a book, the glass and liquid of abottle of soda, the air you breathe, and thematerials that make up your body.

A more formal definition ofmatter isanything that takes up space and has mass.

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Mass is the measure of the amount of matterthat an object contains.

Composition, Structure, and Behavior

The structure of matter refers to its

compositionwhat matter is made ofaswell as how matter is organized.

The properties of matter describe the

characteristics and behavior of matter,including the changes that matterundergoes.

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Matter that is large enough to be seen iscalled macroscopic, so all of yourobservations in chemistry, and everywhere

else, start from this perspective.

Macroscopic View of Matter

You may get hints of the actual structurefrom a macroscopic view. You must go to asubmicroscopic perspective to understandhow the hidden structure of matter influencesits behavior.

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The submicroscopic view gives you aglimpse into the world of atoms.

Submicroscopic View of Matter

It is a world so small that you cannot see it

even with the most powerful microscope,hence the term submicroscopic.

You learned in earlier science courses that

matter is made up of atoms.

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In your study of chemistry, you will use bothmacroscopic and submicroscopicperspectives.

Using Models in Chemistry

For example, sucrose and aspirin are bothcomposed of carbon, hydrogen, and oxygenatoms, but they have different behaviors andfunctions.

These differences must come about becauseof differences in the submicroscopicarrangement of their atoms.

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aspirin sucrose

Comparing the Structures of Aspirinand Sucrose

The different submicroscopic arrangements ofthe atoms in aspirin and sucrose cause thedifferences in their behavior.

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A scientific model is athinking device that helpsyou understand and

explain macroscopicobservations. Scientificmodels are built on

experimentation.

Using Models in ChemistryTopic

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A powerful way to classify matter is by itscomposition. This is the broadest type ofclassification.

Classification by Composition

A qualitative observation is one that can bemade without measurement.

When you examine an unknown piece of

stuff, you first ask, What is it made of? Sucrose is composed of the elements carbon,

hydrogen, and oxygen. This is a qualitative

expression of composition.

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After a qualitative analysis, the next questionthat you might ask is how much of each ofthe elements is present.

Classification by Composition

A quantitative observation is one that usesmeasurement.

For sucrose, the answer to that question is

that 100 g of sucrose contains 42.1 g ofcarbon, 51.4 g of oxygen, and 6.5 g ofhydrogen. This is a quantitative expression ofcomposition.

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Pure substance or a mixture?Topic

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A substance is matter,either an element or

compound, with the samefixed composition andproperties.

A sample of matter is either puremade up ofonly one kind of matteror it is a mixture of

different kinds of matter.


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A mixture is a combination of two or moresubstances in which the basic identity of eachsubstance is notchanged.

Unlike pure substances,mixtures do not havespecific compositions.

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Pure substance or a mixture?


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A physical change is a change in matter thatdoes not involve a change in the chemicalidentity of individual substances.

Examples of physical changes include:

boiling,

freezing,

melting,

evaporating,

dissolving,

and crystallizing.

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Examples of the physical properties of achunk of matter include its:

solubility,

melting point,

boiling point,

color,

density,

electrical conductivity,

and physical state (solid, liquid, or gas).

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Ch i d M B i C


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A heterogeneous mixture is one withdifferent compositions, depending uponwhere you look.

The components ofthe mixture exist asdistinct regions,often called phases.

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Ch i d M B i C


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Homogeneous mixtures are the samethroughout.

Another name for a homogeneous mixture issolution.

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Some solutions are gases. Air, for example, isa homogeneous mixture of several gases.

Some solutions are solid.

Liquid solutions do not have to be liquid orcontain water.

Ch i t d M tt B i C t


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Alloys are solidsolutions thatcontain different

metals andsometimesnonmetallicsubstances.

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When you dissolve sugar in water, sugar isthe solutethe substance being dissolved.

The substance that dissolves the solute, inthis case water, is the solvent.

When the solvent is water, the solution iscalled an aqueous solution.

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Many of the solutions youencounter are aqueoussolutions, for example, soda,

tea, contact-lens cleaner, andother clear cleaning liquids.

In addition, most of the

processes of life occur inaqueous solutions.

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Two Types of Substances

One type of pure substance can be brokendown into simpler substances. This type ofsubstance is called a compound.

Another type of substance cannot be brokendown into simpler substances. Such asubstance is called an element.

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All the substances of the universe are eitherelements, compounds formed from elements,or mixtures of elements and compounds.

Chemistr and Matter Basic Concepts


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Two Types of Substances

Of the known elements, only about 90 occurnaturally on Earth. The remainder aresynthesized, usually in barely detectableamounts, in high-energy nuclear experiments.

Less than half of the 90 naturally occurringelements are abundant enough to play asignificant role in the chemistry of everydaystuff.

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Organizing the Elements

The periodic table organizes elements in away that provides a wealth of chemicalinformationmuch more than is evident to

you now. It shows the chemical symbols forthe elements.

Their symbols usually correspond to their

names in Latin.

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Periodic Table of the ElementsTopic

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Compounds Are More Than One Element

A more complete definition is that acompound is a chemical combination of twoor more different elements joined together in afixed proportion with a unique set of chemicaland physicalproperties.

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More than 10 million compounds are knownand the number keeps growing.



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Compounds Are More Than One ElementTopic

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Some new compounds are discovered andisolated from natural chemical sources such asplants and colonies of bacteria and aresynthesized in laboratories for many differentuses.



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The properties of the compound are differentfrom the properties of the elements thatcompose the compound.

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silver + bromine = silver bromide



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More than 10 million compounds are knownand the number keeps growing.

New compounds are discovered and isolatedfrom natural chemical sources such as plantsand colonies of bacteria and are synthesized

in laboratories for many different uses.

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A formula is a combination of the chemicalsymbols that show what elements make up acompound and the number of atoms of eachelement.

Compound Formula

Caffeine C8H10N4O2

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Formulas provide a shorthand way ofdescribing a submicroscopic view of acompound.

You probably already use formulas like H2Oand CO2 as a way of talking about water andcarbon dioxide.

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States of Matter

Most matter on Earth exists in one of threephysical states: solid, liquid, or gas. A fourthstate of matter, called plasma, is less familiar.

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Changes in state are examples of physical

changes because there is no change in thechemical composition identity of thesubstance.

Ice can melt back to form liquid water, andsteam will condense on a cool surface toform liquid water.



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States of Matter

Some substances are described as volatile,which means that they change to a gas easilyat room temperature.

Alcohol and gasoline are more volatile thanwater.

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Density is the amount of matter (mass)contained in a unit of volume.

Styrofoam has a low density or small mass perunit of volume.



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States of Matter

Stones have a largedensity or a large massper unit of volume.

In science, the density of solids and liquids isusually measured in units of grams (mass)per milliliter (volume) or g/mL.

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Chemical Properties

Chemical properties are those that can beobserved only when there is a change in thecomposition of the substance.

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Rusting is a chemical reaction in which ironcombines with oxygen to form a newsubstance, iron oxide.

Inability to react is also a chemical property.



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Chemical Changes

chemical change, thechange of one or moresubstances into othersubstances.

A chemical property always relates to a

Another term for

chemical change ischemical reaction.

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Chemical ChangesTopic

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Click box to view movie clip.



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Chemical Changes

All matter is made of atoms, and anychemical change involves only arearrangement of the atoms. Atoms do notjust appear. Atoms do not just disappear.

This is an example of the law ofconservation of mass, which says that in achemical change, matter is neither created

nor destroyed. It would be equally correct tocall this the law of conservation of matter.

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Chemical Reactions and Energy

All chemical changes also involve some sortof energy change.

Energy is either taken in or given off as thechemical change takes place.Energy is thecapacity to do work.

Work is done whenever something is moved.

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Many reactions give off energy. For example, burning wood

is a chemical change in

which cellulose, and othersubstances in the wood,combine with oxygen fromthe air to produce mainly

carbon dioxide and water.

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Energy is also produced and released in theform of heat and light.

Chemical reactions that give off heat energyare called exothermicreactions.

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Chemical reactions that absorb heat energy

are called endothermic reactions.



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You can tell that the decomposition of waterinto oxygen and hydrogen is an endothermicreaction because it doesnt occur unlessenergy, in the formof an electric

current, is passed

through water.

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C e st y a d atte as c Co cepts



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Photosynthesis isprobably the mostimportant endothermic

process on Earth.

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Green plants, algae, and

many kinds of bacteriacarry out photosynthesis.

Basic Assessment Questions


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Question 1

Identify each of the following as either acompound or a mixture.

A. sand

B. water

C. juice

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Answers

A. sand

B. water

C. juice

mixture

compound

mixture

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Classify each of the following as a chemicalor physical property.

Question 2

A. density

B. reactivity

C. color

D. melting point

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Answers

A. density

B. reactivity

C. color

D. melting point

physical property

chemical property

physical property

physical property

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Chemistry and Matter: Additional Concepts


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Additional Concepts



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Branches of Chemistry

Branch Area of Emphasis ExamplesOrganic

chemistry

most carbon-containing chemicals pharmaceuticals,

plastics

Inorganic

chemistry

in general, matter that does not

contain carbon

minerals, metals and

nonmetals, semi-

conductors

Physical

chemistry

the behavior and changes of matter

and the related energy changes

reaction rates,

reaction mechanisms

Analytical

chemistry

components and composition of

substances

food nutrients,

quality control

Biochemistry matter and processes of living

organisms

metabolism,

fermentation

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Scientific Methods

A scientific method is a systematic approachto answer a question or study a situation.

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It is both an organized way for scientists to doresearch and a wayfor scientists toverify the work ofother scientists.



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Scientific Methods

A typical scientific method includes:

making observations,

forming a hypothesis, performing an experiment,

and arriving at a conclusion.

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T iChemistry and Matter: Additional Concepts


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Scientific Methods

Often, a scientist will begin with qualitativedatainformation that describes color, odor,shape, or some other physical characteristicthat relates to the five senses.

Chemists also use numerical quantitativedata.

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A hypothesis is a possible explanation for

what has been observed. An experiment is a set of controlledobservations that test a hypothesis.



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Scientific Methods

The variable that ischanged in an experimentis called the independentvariable.

The variable that youwatch to see how itchanges as a result of your

changes to the independentvariable is called thedependent variable.

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Scientific Methods

Many experiments also include a control,which is a standard for comparison.

A conclusion is a judgment based on the data

obtained in the experiment.

If data support a hypothesis, the hypothesis istentatively affirmed. Hypotheses are never

proven; they are always subject to additionalresearch.

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Scientific Methods

Over time, data from many experiments canbe used to form a visual, verbal, and/ormathematical explanationcalled amodelof the phenomenon being studied.

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A theory is an explanation that has beensupported by many experiments.

Theories are always subject to newexperimental data and are modified to includenew data.



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Scientific Methods

A scientific lawdescribes a relationshipin nature that is

supported by manyexperiments and forwhich no exception hasbeen found.

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Scientific Research

Pure research is done to gain knowledge forthe sake of knowledge itself.

Applied research is undertaken to solve aspecific problem.

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Additional Assessment QuestionsT i


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Identify the dependent variable and the

independent variable in the following

experiments.

Question 1Topic

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T iAdditional Assessment Questions


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A student tests the ability of a given chemicalto dissolve in water at three different

temperatures.

independent variable: temperature;

dependent variable: ability to dissolve in water

Answer 1a

Question 1aTopic

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TopicAdditional Assessment Questions


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A farmer compares how his crops grow withand without phosphorous fertilizers.

independent variable: presence of phosphorous

fertilizer;dependent variable: crop growth

Answer 1b

Question 1bTopic

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Classify each kind of research as either pureor applied.

Question 2Topic

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A scientist studies plants in a rain forest insearch of chemicals that might be used to treat

AIDS.

applied

Answer 2a

Question 2aTopic

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A researcher studies the effects of hormoneson the brain of a worm.

pure

Answer 2b

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A researcher tries to develop cleaner burningfuels to help reduce air pollution.

applied

Answer 2c

Question 2cTopic

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01 Chemistry and Matter