II. Physical Properties physical property- any characteristic of a material that can be observed or measured without changing the composition of the substances in the material. Viscosity- The tendency of a liquid to keep from flowing High viscosity is thick like honey Low viscosity is thin and fluid like water

Conductivity- A material’s ability to allow heat to flow Materials that have a high conductivity, such as metals, are called conductors. Good conductors of heat are usually also good conductors of electricity. Malleability- the ability of a solid to be hammered without shattering it Most metals, such as gold, are malleable Solids that shatter when struck are brittle, not malleable

Hardness- One material’s ability to scratch another material if it is harder than the other material. Melting and Boiling Points- The temperature at which a material changes its physical state Melting point- The temperature at which a substance changes from solid to liquid (melts). Boiling point- The temperature at which a substance changes from liquid to gas (boils). Density- the ratio of the mass of a substance to its volume Density can be used to test the purity of a substance.

Using Physical Properties A material can be identified by its properties. Decide which properties to test. Do tests on a sample of the unknown material. Compare the results with the data reported for known materials. Properties determine which materials are chosen for which uses.

Using Physical Properties Laces in hiking boots are usually made of nylon or leather, not from wood because nylon or leather is more flexible and durable than wood

C. Using Properties to Separate Mixtures Filtration- a process that separates materials based on the size of their particles. Distillation- a process that separates the substances in a solution based on their boiling points. Sometimes all the particles in a solution are small enough to pass through a filter.

Physical change- when some of the properties of a material change, but the substances in the material remain the same. During a physical change, the size and shape of a material can change but not the composition. Melting Slicing Crushing Breaking Dissolving Bending

Recognizing Physical Changes Some but not all physical changes can be reversed. Braiding hair is a reversible change. Cutting hair cannot be reversed.

Which of the following is not a physical property? Assessment Questions Which of the following is not a physical property? density boiling point flammability Conductivity ANS: C

Which of these materials is not malleable? Assessment Questions Which of these materials is not malleable? copper aluminum glass Gold ANS: C

Assessment Questions In choosing a material for use as a wire to carry electric current, which physical property would be most important? conductivity malleability hardness boiling point ANS: A

Assessment Questions Which of these statements best describes a physical change in a pure substance? The substance changes into one or more new substances. Some of the properties of the substance change, but the material remains the same. The properties of the material do not change, and the material remains the same. The substance is separated into two or more simpler substances. ANS: B

Assessment Questions The process of filtration uses the difference in boiling points of substances to separate a mixture. True False ANS: F, distillation