2.2 Physical Properties Examples of Physical Properties A physical property is any characteristic of a material that can be observed or measured without changing the composition of the substances in the material. * A material can be identified by its physical properties. 2.2 Physical Properties Examples of Physical Properties Viscosity The tendency of a liquid to keep from flowing is called its viscosity. • Thick liquids, such as corn syrup and honey, have a high viscosity. • Thin liquids, such as vinegar and water, have a low viscosity. 2.2 Physical Properties Examples of Physical Properties Conductivity A material’s ability to allow heat to flow is called conductivity. • Materials that have a high conductivity, such as metals, are called conductors. • Good conductors of heat are usually also good conductors of electricity. 2.2 Physical Properties Examples of Physical Properties Malleability The ability of a solid to be hammered without shattering is malleability. • Most metals, such as gold, are malleable. • An ice cube or piece of glass breaks into small pieces when struck with a hammer. Solids that shatter when struck are brittle, not malleable. 2.2 Physical Properties Examples of Physical Properties Hardness One material can scratch another material if it is harder than the other material. • A kitchen knife can scratch a copper sheet because stainless steel is harder than copper. • The material used to sharpen the knife blade must be harder than stainless steel. Diamond is the hardest known material. 2.2 Physical Properties Examples of Physical Properties Melting and Boiling Points The temperature at which a material changes state is a physical property. • The temperature at which a substance changes from solid to liquid (melts) is its melting point. • The temperature at which a substance changes from liquid to gas (boils) is its boiling point. 2.2 Physical Properties Examples of Physical Properties Melting and Boiling Points Which of these substances are liquids at room temperature (20C, or 68F)? Answer: 2.2 Physical Properties Examples of Physical Properties Melting and Boiling Points Which of these substances are liquids at room temperature (20C, or 68F)? Answer: octane, water, and acetic acid 2.2 Physical Properties Examples of Physical Properties Density The ratio of the mass of a substance to its volume is its density. • Density can be used to test the purity of a substance. • Silver has a density of 10.5 g/cm3. A coin with a density of 9.9 g/cm3 is not made from silver, or it contains substances in addition to silver. 2.2 Physical Properties Using Physical Properties Using Properties to Identify Materials 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. 2.2 Physical Properties Using Properties to Separate Mixtures Filtration You can separate hot tea from loose tea leaves by pouring the mixture through a strainer. Filtration is a process that separates materials based on the size of their particles. 2.2 Physical Properties Using Properties to Separate Mixtures Distillation Sometimes all the particles in a solution are small enough to pass through a filter. Distillation is a process that separates the substances in a solution based on their boiling points. 2.2 Physical Properties Recognizing Physical Changes A physical change occurs 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. Some examples include • melting butter in a pan • crumpling a piece of paper • Changes of state (solid to liquid) 2.2 Physical Properties Assessment Questions 1. Which of the following is not a physical property? a. b. c. d. density boiling point flammability conductivity 2.2 Physical Properties Assessment Questions 1. Which of the following is not a physical property? a. b. c. d. density boiling point flammability conductivity ANS: C 2.2 Physical Properties Assessment Questions 2. Which of these materials is not malleable? a. b. c. d. copper aluminum glass gold 2.2 Physical Properties Assessment Questions 2. Which of these materials is not malleable? a. b. c. d. copper aluminum glass gold ANS: C 2.2 Physical Properties Assessment Questions 3. In choosing a material for use as a wire to carry electric current, which physical property would be most important? a. b. c. d. conductivity malleability hardness boiling point 2.2 Physical Properties Assessment Questions 3. In choosing a material for use as a wire to carry electric current, which physical property would be most important? a. b. c. d. conductivity malleability hardness boiling point ANS: A 2.2 Physical Properties Assessment Questions 4. Which of these statements best describes a physical change in a pure substance? a. The substance changes into one or more new substances. b. Some of the properties of the substance change, but the material remains the same. c. The properties of the material do not change, and the material remains the same. d. The substance is separated into two or more simpler substances. 2.2 Physical Properties Assessment Questions 4. Which of these statements best describes a physical change in a pure substance? a. The substance changes into one or more new substances. b. Some of the properties of the substance change, but the material remains the same. c. The properties of the material do not change, and the material remains the same. d. The substance is separated into two or more simpler substances. ANS: B 2.2 Physical Properties Assessment Questions 1. The process of filtration uses the difference in boiling points of substances to separate a mixture. True False 2.2 Physical Properties Assessment Questions 1. The process of filtration uses the difference in boiling points of substances to separate a mixture. True False ANS: F, distillation