Using Physical Properties
People use data about physical properties to solve many different types of problems. 
Physical properties are used to identify a material, to choose a material for a specific purpose, or to separate the substances in a mixture.
Using Properties to Identify Materials
The steps used to identify a material are similar to the steps used to test for purity. The first step is to decide which properties to test. The second step is to do tests on a sample of the unknown. The final step is to compare the results with the data reported for known materials.
The identification of a material can be a crucial step in solving a crime. A detective collects red paint chips from the scene of a hit-and- run accident. He asks a chemist at the crime lab to use the chips to identify the model of the missing vehicle. Because paint is a mixture of substances, the chemist can do tests that distinguish one type of red paint from another. The technician compares the data she collects to an FBI database. The database contains information about the paints used on different makes and models of cars. Once the detective knows the make and model, he uses a database of registered owners to create a list of possible suspects.
Using Properties to Choose Materials
Properties determine which materials are chosen for which uses. For example, yo wouldn't want shoelaces made from wood. Shoelaces must be flexible, that is, they must be able to bend without breaking. They must also be durable, that is, they must be able to withstand repeated use. Laces in hiking boots like those in Figure 13 are usually nylon or leather.
People don't consider just one property when choosing a material for a particular application. They look at a set of properties. For example, the How It Works box on page 49 explains how the properties of wax are used when clay molds are made for casting metal sculptures.
Figure 13 Shoelaces for hiking boots are sometimes made from leather. So are some belts and shoes. Making Generalizations What properties of leather would make it a suitable material for all three types of objects?
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