Chapter 2Section 1

Describing Matter

Properties used to describe matter can be

classified as extensive or intensive

Extensive property - depends on the amount of matter in a sample.

Ex. Mass and Volume

Intensive property - depends on the type of matter in a sample, not the amount

Ex. hardness or type of material

Identifying Substances

A substance is matter that has a uniform composition.

copper, aluminum, or silver

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

When comparing two substances you need to examine the properties of that substance.

Identify 3 differences between copper and

gold

Identifying Substances

A physical property is a quality or condition of a substance that can be observed or measured without changing the composition of the substance.

Examples include:

Hardness

Color

Conductivity

Malleability

Melting Point

Boiling Point

States of Matter

There are 3 states of matter

1. Solid

definite shape and volume

not easily compressed

particles are very tightly packed

2. Liquid

definite volume

take the shape of the container

particles are close together but not rigid

not easily compressed

States of Matter

States of matter cont.

3. Gas

take the shape of the container

easily compressed

can expand to fill any container

Vapor describes a gaseous state of a substance that is generally a liquid or solid at room temperature

Physical Changes

During a physical change some

properties of a material change but the

composition of the material does not

Physical changes can be classified as

reversible or irreversible

Ex. Boiling, freezing, melting, condensing, cutting, breaking, or crushing.

Section 2 NotesMixtures

Classifying Mixtures

A mixture is a physical blend of two or more components

Ex. Air, vegetable soup, pop

Two categories:

Heterogeneous Mixtures - the composition is not uniform throughout

Every sample will have a different composition

Ex. ?

Classifying Mixtures

Homogeneous Mixtures -composition is uniform throughout

AKA – solution

Most solutions are liquids, but some are gases (air) or solids (stainless steel)

Homogeneous mixtures contain a single phase

Any part of a sample with the same composition and properties

Heterogeneous mixtures often have more then one phase.

Ex. How many different phases would oil and water have?

Separating Mixtures

Mixtures can be easy or difficult to separate

Therefore, we can use the differences in physical properties to separate mixtures

Ex. Oil and Vinegar

1st method, pour off the oil layer

2nd method, cool the mixture until the oil layer solidifies

Each method takes advantage of the difference in physical properties of the oil and vinegar

Separating Mixtures

Filtration - process that separates a liquid from a solid in a heterogeneous mixture

Filter has holes that can be very tiny or very large, depending on the material.

Ex. ?

Distillation - separates water from a liquid mixture

Mixture is boiled to produce a vapor that then condenses into a liquid

The solid substances in the mixture boil at a higher temperatures then water therefore the water will turn to vapor first and allow it to separate

Section 3Elements and Compounds

Distinguishing Elements and Compounds

Element- the simplest form of matter that has a unique set of properties

Ex. Hydrogen, Carbon, Polonium, Zinc

Compound- substance that contains more then one element

Ex. Glucose (C6H12O6), Salt (NaCl), baking soda (NaHCO3)

The proportion of elements in the same compound is fixed

Breaking Down Compounds

Compounds can only be broken down chemically, not physically

A chemical change is a change that produces matter with a different composition then the original matter

Chemical changes include:

burning a material - glucose

sending electricity through the material - water

Properties of Compounds

Properties of compounds are very different then the element that make them up.

Sodium is a gray metal. Chlorine is a pale yellow-green poisonous gas.

When combined they form a white crystal called ?

Distinguishing Substances and Mixtures

If the composition of a material is

fixed, the material is a substance

If the composition of a material can vary, the material is a mixture

Symbols and Formulas

Each element is represented by a one

or two letter chemical symbol

The First letter is always capitalized

The Second letter is always lowercase

Ex. Hydrogen – H Copper – Cu

Symbols are based off of chemical name.

Either the English form or the Latin name.

Examples of each?

Section 4Chemical Reactions

Chemical Changes

The ability of any substance to undergo a change is a chemical propertyEx. Rust is a chemical property of Iron

Chemical properties can only be observed when a substance undergoes a chemical change.

During a chemical reaction, one or more substances (called ?) will change into one or more new substances (called ?)

Reactants Products

Recognizing a Chemical Change

Possible clues to chemical change include:

1. A transfer of energy – true of all chemical changes

Ex. When natural gas reacts with oxygen energy is given off in the form of heat and light and transferred to the food you are cooking

2. The production of a gas

Ex. Bathroom cleaners often form bubbles when reacting with soap scum

Are bubbles forming always a sign of a chemical change?

No: Water boiling causes bubbles to form but no chemical change is occurring

Recognizing a Chemical Change

Possible clues cont.

3. A change in color

4. The formation of a precipitate

A precipitate is a solid that forms and settles out of a liquid mixture

The only way to know for sure is a

chemical change has taken place is to test

the composition of the sample before and

after the change.

Conservation of Mass

The law of conservation of mass states that in any physical change or chemical reaction, mass is conserved

Mass of the products = mass of the reactants.

When wood burns it forms ash, water vapor and carbon dioxide.

The mass of the wood = the mass of the ash, water vapor and carbon dioxide