S CIENCE S PONGE What do gold, aluminum, and iron have in common?

E LEMENTS, C OMPOUNDS, AND M IXTURES …O H M Y !

Substances can be identified as either an element, compound, or a mixture.

There is only one type of particle Each element of the substance contains the same type of atom throughout The particles of a pure substance are alike, no matter where they are found

An element cannot be further broken down or purified by chemical or physical means Each element has its own characteristic properties that are different from the set of properties of any other substance

Compounds Can be decomposed into simpler substances by chemical changes, always in a definite ratio Elements Cannot be decomposed into simpler substances by chemical changes

Mixtures are two or more substances that are NOT chemically combined.

Variable composition Components retain their characteristic properties May be separated into pure substances by physical methods Mixtures of different compositions may have widely different properties

Homogenous mixtures look the same throughout but can be separated by physical means (dissolution, centrifuge, gravimetric filtering, etc.). Examples: milk, yogurt

Have the same composition throughout Components are indistinguishable May or may not scatter light Examples: milk, yogurt, etc.

Heterogeneous mixtures are composed of large pieces that are easily separated by physical means (ie. density, polarity, metallic properties).

Do not have same composition throughout Components are distinguishable Examples: fruit salad, vegetable soup, etc.

A solution is a mixture that appears to be a single substance. It is composed of particles of two or more substances that are distributed evenly among each other. Examples: sugar water, salt water