ca-inspire-chemistry-sampler

Ted Kinsman/Science Source

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Summary

• A mixture is a physical blend of

two or more pure substances in

any proportion.

• Solutions are homogeneous

mixtures.

• Mixtures can be separated by

physical means. Common

separation techniques include

filtration, distillation, sublima-

tion, chromatography, and

crystallization.

Demonstrate Understanding

27.

Classify

each of the following as either

a heterogeneous or a homogeneous mixture.

tap water b. air c. raisin muffin

28.

Compare

mixtures and substances.

29.

Describe

the separation technique that could be used

to separate each of the following mixtures.

two colorless liquids

b. a nondissolving solid mixed with a liquid

red and blue marbles of the same size and mass

30.

Design

a concept map that summarizes the relation-

ships among the categories of matter, elements,

mixtures, compounds, pure substances, and homoge-

neous and heterogeneous mixtures.

Crystallization

Making rock candy from a sugar

solution is an example of separating a mixture by

crystallization.

Crystallization

is a separation

technique that results in the formation of pure

solid particles of a substance from a solution

containing the dissolved substance. When the

solution contains as much dissolved substance as it

can possibly hold, the addition of even a tiny

amount more often causes the dissolved substance

to come out of solution and collect as crystals on

any available surface.

In the rock candy example, as water evaporates

from the sugar-water solution, the solution becomes

more concentrated. This is equivalent to adding

more of the dissolved substance to the solution.

As more water evaporates, the sugar forms a solid

crystal on the string, as shown in

Figure 22

Crystallization produces highly pure solids.

Figure 22

As the water evaporates from the water-

sugar solution, the sugar crystals form on the string.

Get It?

Classify

which techniques for separating

mixtures depend on phase changes and

identify

the change used by each.

Module 2 • Matter—Properties and Changes