Chapter 2Matter & Change

Describing MatterMatter• Anything that takes up space and has mass• A pure substance or as a matter of

substances• Properties used to describe matter can be

classified as extensive or intensive1. Extensive Property• Depends on the amount of matter in a sample2. Intensive Property• Depends on the type of matter in a sample

(i.e. hardness)

Extensive Propertyi. Mass• A measure of the amount of matter the

object contains

ii. Volume• A measure of the space occupied by the

object

States of Matter• Three states of matter are: solid, liquid, and gas.

Solid

• Matter that has definite shape and volume• Particles are tightly

packed together (not easily compressed)

Liquid• Matter that flows, has

a fixed volume, and takes the shape of its container

• Particles are packed less tightly than in a solid (not easily compressed)

Gas (Vapor)• matter that has no

definite shape or volume

• It takes the shape of its container and can be compressed

• Particles in a gas are spaced far apart (easily compressed)

Sample ExerciseWhat is the physical

state of each of the following at room temperature?

• Gold• Gasoline• Helium

Physical Changes

• The shape of a sample changes, but the composition stays the same

• Boil, freeze, melt, condense, break, split, grind, cut, and crush.

• Physical changes can be reversible or irreversible

Section Assessment• In what way are liquids and gases alike?• In what way are liquids and solids different?• Is the freezing of mercury (Hg) a reversible or

irreversible physical change?

Classifying Mixtures• Consists of a physical blend of two or

more substances• Can be classified as heterogeneous

mixtures or as homogenous mixtures

1. Heterogeneous mixture

• not uniform in composition

• Ex: salad, stew

2.Homogeneous mixture

• A complete uniform composition

• Ex: iced tea, lemonade

• Also called a solution

Separating Mixtures

• Differences in physical properties can be used to separate mixtures

Distillation• A liquid is boiled to produce a vapor that

is then condensed into a liquid• This process separates liquids by their

boiling points (and impurities)

Filtration

• Separates a solid from the liquid in a heterogeneous mixture

Distillation

• A liquid is boiled to produce a vapor that is then condensed into a liquid

• This process separates liquids by their boiling points (and impurities)

FermentationPlums Mashed Plums

Distiller

Plum Mash Poured into Distiller Top View

Distiller Set Ablaze

Moonshine

3. Chromatography – a technique that is used to physically separate the components of a mixture based on the tendency of each component to travel or

be drawn across the surface of another material

Section Assessment

Classify each of the following as a homogenous or heterogeneous mixture

• Food coloring• Ice cubes in liquid water• Mouthwash• Mashed, unpeeled potatoes

Section assessment• When would you use filtration to separate a

mixture?• When would you use distillation to separate a

mixture?

Elements• Simplest forms of

matter• Cannot be broken

down• Building blocks for all

other substances• Ex: Periodic Table of

Elements

Sodium (Na) Natrium

Chlorine (Cl)

Compounds• Contains two or more

different elements chemically combined in a fixed proportion

• Can be broken down into elements, by a chemical change

• Ex: water, sodium chloride

Sodium Chloride (Table Salt)

Distinguishing Substances and Mixtures

Beryl - Be3Al2(SiO3)6

• Substance – if the composition of the material is fixed (elements, and compounds)

Mixture

Various Granite

• If the composition of a material may vary

Practice Problems• Liquid A and Liquid B are clear liquids. They are

placed in open containers and allowed to evaporate. When evaporation is complete, there is a white solid in container B, but no solid in container A. From these results, what can you infer about the two liquids?

Practice Problems• A clear liquid in an open container is allowed to

evaporate. After three days, a solid is left in the container. Was the clear liquid an element, a compound, or a mixture? How do you know?

Symbols and Formulas• Chemists use chemical symbols to represent

elements, and chemical formulas to represent compounds.

Chemical Symbol• Each element is represented by a one or two

letters• The first letter is always capitalized• When a second letter is used, it is lowercase• Chemical formulas are used to represent

compounds: CO2

Section Assessment•Write the chemical symbol for each elemento Leado Oxygeno Silvero Sodiumo Hydrogeno Aluminum

Section assessment•Name the chemical elements represented by the following symbolso Co Cao Ko Auo Feo Cu

Chemical Change• Change that produces matter with a different

composition than the original matter• Usually involves burning, rotting, decomposing,

fermenting, exploding, rusting, corroding.• Ex: milk spoils, electrolysis of water

Chemical ReactionsChemical Property• The ability of a substance to undergo a specific

chemical change• During a chemical change, the composition of

matter always changes• A substance that is present at the start of the

reaction is a reactant• A substance produced in the reaction is a product

Recognizing Chemical Changes

Possible clues to a chemical change include:• A transfer of energy• A change in color• The production of a gas• The formation of a precipitatePrecipitate (ppt)• A solid that forms and settles out of a

liquid mixture, and is usually indicated by a color change

A transfer of energy

A change in color (precipitate)

The production of a gas

Conservation of Mass• During any chemical reaction, the mass of the

products is always equal to the mass of the reactants

• Mass is conserved• Mass is neither created nor destroyed

Section Assessment•Classify the following changes as physical or chemical changeso Water boilso Salt dissolves in watero Milk turns souro A metal rusts

Section Assessment• Hydrogen and oxygen react chemically to form

water. How much water would form if 4.8 grams of hydrogen reacted with 38.4 grams of oxygen?

2H2 + O2 2H2O

Section Assessment• When ammonium nitrate (NH4NO3) explodes, the

products are nitrogen, oxygen, and water. When 40 grams if ammonia nitrate explode 14 grams of nitrogen and 8 grams of oxygen form. How many grams of water form?

NH4NO3 N2 + O2 + H2O

Key Concepts - Properties of Matter

• Properties used to describe matter can be classified as extensive or intensive

• Every sample of a given substance has identical intensive properties because every sample has the same composition

• Three states of matter are solid, liquid, and gas• Physical changes can be classified as reversible or

irreversible

Key Concepts - Mixtures

• Mixtures can be classified as heterogeneous mixtures or as homogeneous mixtures, based on the distribution of their components

• Difference in physical properties can be used to separate mixtures

Key Concepts – Elements and Compounds

• Compounds can be broken down into simpler substances by chemical means, but elements cannot

• If the composition of a material is fixed, the material is a substance. If the composition may vary, the material is a mixture

• Chemists use chemical symbols to represent elements, and chemical formulas to represent compounds

Key Concepts – Chemical Reactions

• During a chemical change, the composition of matter always changes

• Four possible clues to chemical change include a transfer of energy, a change in color, the production of a gas, or the formation of a precipitate

• During any chemical reaction, the mass of the products is always equal to the mass of the reactants