Chapter 2: Matter and Change

CP ChemistryTHHS 2014-2015

Section 2.1 MatterObjectives

Identify the characteristics of matter and substances

Differentiate among the three states of matter

Define physical property and list several common physical properties of substances

Properties of MatterMatter

anything that has mass and takes up space.Mass

The amount of matter the object contains. Note mass ≠ weight.

Substance Pure substances contain only one kind of

matter.Question – is lemonade a substance?

Physical PropertiesPhysical Property – a quality or condition

of a substance that can be observed without changing the substance’s composition.

Examples of physical properties are color, solubility, odor, hardness, density, melting point, and boiling point.

Properties of Solids, Liquids, GasesSolid

Has a definite shape and volumeDoes not depend on the shape of its containerAlmost incompressible

LiquidParticles are in close contact but not rigidly

packedCan flow and take the shape of the container it is

inA fixed volume can take a variety of shapesAlmost incompressible

Properties of Solids, Liquids, GasesGas or vapor

“Gas” is limited to those substances who are in a gaseous state at room temperature.

“Vapor” describes the gaseous state of a substance that is a liquid or a solid at room temperature. An example is steam.

Gases take the shape of the container they are in.

Particles are spaced far apart.Gases expand without limit to fill any space,

so its volume changes with the container, unlike liquids.

Gases tend to expand when heated.

Physical ChangesA change which alters a given material

without changing its composition is called a physical changeExamples are cutting, grinding, bendingMelting a metal, melting ice, boiling

waterBoil, freeze, dissolve, melt, condense,

break, split, crack – all examples of physical changes

Section 2.2 - MixturesObjectives

Categorize a sample of matter as a substance or a mixture

Distinguish between homogeneous and heterogeneous samples of matter

Classifying MixturesA mixture is a physical blend of two or more

substances.Salad with lettuce, tomatoes, carrotsBlood – with water, cells, chemicalsEach of these mixtures can vary in

compositionHeterogeneous mixture – if you were to

sample the mixture in two different places the composition wouldn’t be the same (salad)

Homogeneous mixture – if you were to sample the mixtures in two different places, the composition would be the same (salt water)

Homogeneous mixtures are called solutions.

Phases in MixturesSystem Examples

Gas- gas Carbon dioxide and oxygen in nitrogen (air)

Liquid – gas Water vapor in air (moist air)

Gas – liquid Carbon dioxide in water (soda water)

Liquid- liquid Acetic acid in water (vinegar)

Solid – liquid Sodium chloride in water (salt water or brine)

Solid – solid Copper in silver (sterling silver, an alloy)

• Phase – any part of a system with uniform composition and properties is a phase.

• Homogeneous mixtures are one phase.• Heterogeneous mixtures are two or

more phases. • Oil and vinegar separates into two

phases

Separating MixturesSome mixtures can be separated by physical

methods.Magnet to separate iron filings from sulfur.Distillation can be used to separate pure

water from impurities.

Section 2.3 – Elements and Compounds

ObjectivesExplain the difference between an

element and a compound.Identify the chemical symbols of

common elements, and name common elements given their symbols

Elements vs. CompoundsElements are the simplest forms of matter that

can exist under normal laboratory conditions.This statement does not include the subatomic

level (protons, neutrons, etc.)Elements cannot be separated into simpler

substances by chemical means . Examples: Oxygen, carbon, nitrogen

Compounds are made when two or more elements combine chemically, like H2O or CO2 .

Compounds can be separated into simpler substances by chemical means.

CompoundsExample: Sodium chloride NaCl (table salt)

Composed of Chlorine (which is the gas Cl2 as an element) and Sodium (which is the solid Na as an element)

Anyone know why sodium (solid) is normally stored in oil?

Chemical SymbolsSome chemical symbols are easy to remember

Carbon = C, Oxygen = O, Nitrogen = NOthers are not so easy, and come from Latin or

other sourcesSodium = Na (from Natrium)Potassium = K (from Kalium)Gold = Au (from Aurum)Lead = Pb (from Plumbum)A list of more unusual symbols is on page 40

and on my website for you to review!You will need to know at least the top 4 rows of

the periodic table - name and symbol

Section 2.4 – Chemical Reactions

Objectives Differentiate between physical and

chemical changes in matterApply the law of conservation of mass

Changing reactants to productsChemical reactions - one or more

substances react and change into a new substanceExample: iron + oxygen = rust (iron oxide)

The starting substances are called reactantsThe ending substances are called productsWords that convey that a chemical change

has occurred include: burn, rot, rust, decompose, ferment, explode, corrode, etc.

Chemical PropertiesChemical properties tell you something about

the ability of a substance to undergo a chemical reaction to form new substancesRusting is a chemical property of ironRotting is a chemical property of waste organic

materialBurning is a chemical property of wood

Examples of chemical reactions

Chemical reactionsHow can you tell if a reaction has

taken place?Energy is always given off or

absorbed during a reactionChange in color or odor –

silver chromate forms when yellow sodium chromate is added to clear silver nitrate (above right)

Production of gas or solid from a liquid zinc + hydrochloric acid releases

H2 gas >>>Most chemical changes are not easily

reversed, like many physical changes are.

Conservation of Mass –Key conceptWhen you burn wood at a beach bonfire, the

reaction produces carbon dioxide gas (CO2), water vapor (H2O) and some ash.

It may seem that the amount of matter has been reduced when you look at the ash pile.

However, if you could carefully measure the mass of the reactants and the mass of the products, you would find they are the same.

This is the law of conservation of mass – mass is neither created or destroyed in a chemical reaction.

Conservation of MassLet’s say you have 32 grams of methane(CH4)

that combine with 128 grams of oxygen gas to form 88 grams of carbon dioxide and an unknown number of grams of water.

How much water is formed?

32 + 128 = 88 + x gramsSolve for xx = 32 + 128 - 88 = 72 gThis is because mass of total reactants must

equal mass of total products.