Chapter 15

Classification of Matter

Sec. 1 Composition of MatterAll materials are either made of pure

substances or mixtures.

Substance—an element or compound, definite composition

Element—a substance with atoms that are all alike Ex. Carbon (C) & Magnesium (Mg) You can find them on the periodic table!!

Compound—a substance that contains 2 or more elements combined chemically. Ex. Table salt (NaCl) & Hydrogen peroxide (H2O2)

MixturesMixture—a material made of 2 or more substances that can be separated physically.

There are 2 types of mixtures: heterogeneous and homogeneous.

Heterogeneous Mixture—different materials can be distinguished easily. Ex. Pizza, salad, chocolate chip cookies (mmm)

Homogeneous Mixture—substances are blended evenly throughout. Ex. Pop, vinegar A homogeneous mixture is also called a solution.

Colloids & SuspensionsColloid—a type of mixture that never

settles. Ex. Paint & fog

A colloid is not the same as a solution Colloids often appear foggy If you shine a light on a colloid, you can see

the light reflected from the colloid.

Suspension—a heterogeneous mixture containing a liquid in which visible particles settle. Ex. Mud in a pond & river deltas

How to Classify Matter

Element

Substance

Compound

Matter

Heterogeneous

Mixture

Homogeneous or solution

ON PERIODIC TABLE

EX. WATER= H20

*SUSPENSION

*COLLOID

Sec. 2: Properties of MatterPhysical Properties—any characteristic of a material that you observe without changing its substances. Ex. Color, shape, size, melting & boiling point

Some physical properties describe behavior. Magnetism, conduct electricity, viscosity,

dissolving.

You can separate mixtures using physical properties. Size, color, magnetism, boiling point, etc.

Physical Changes

Physical change—a change in size, shape, or state of matter (solid, liquid, gas) The identity of the substance doesn’t change. Ex. Freezing, ripping, folding, dissolving.

Chemical Properties

Chemical Property—a characteristic of a substance that tells if it can undergo a certain chemical change. Ex. Flammability, reaction to light

Chemical Changes

Chemical Change—a change of 1 substance to another.

Ex. Rotten eggs, rust, burning.

Detecting Chemical Changes: Odor, heat, light, sound, release gas (bubbles)

Separating Substances: Ex. Cleaning tarnished silver, purifying metals. A chemical change will change the substances, so it

cannot be used to separate a mixture.

WeatheringWeathering is how Earth’s surface changes.

Weathering is a result of both physical & chemical changes.

Physical: ice wedging (ice in cracks expands & breaks the rocks), & streams cut through softer rock.

Chemical: limestone dissolves in acidic ground water (canyons & caves are formed this way)

Caves are formed through chemical weathering.

Ice wedging or the freeze/thaw cycle breaks rocks into pieces

Conservation of MassLaw of Conservation of Mass—the mass of all substances before a chemical or physical change equals the mass of all substances after the change.

In other words: mass is neither created nor destroyed during any chemical or physical change.