Physical Properties Chapter 2 Section 2

Physical Properties Physical Property – any characteristic of a material that can be observed or measured without changing the composition of the substances in the materials. Viscosity Conductivity Malleability Hardness Melting point Boiling point Density

Viscosity Resistance to flowing The greater the viscosity = slower the liquid moves Thin liquids have low viscosity Water Vinegar Thick liquids have high viscosity Honey Corn Syrup

Viscosity Viscosity usually decreases when it is heated Why is viscosity important?

Conductivity A material’s ability to allow heat to flow Materials with high conductivity such as metals are called conductors If a material is a good conductor of heat it is usually a good conductor of electricity

Malleability The ability of a solid to be hammered without shattering . Most metals are malleable.

Hardness Compare the hardness of two materials by seeing which material can scratch the other. Diamond is the hardest known material.

Melting and Boiling Points Melting point: the temperature at which a substance changes from solid to liquid Boiling point: the temperature at which a substance boils Water MP= 0°C Water BP = 100°C

Density Density can be used to test the purity of a substance Ratio of the mass of a substance to its volume Equation for density D = M/V

Using Physical Properties Physical properties are used to: Identify a material Choose a material for a specific purpose To separate the substances in a mixture

Separation Methods Filtration – the 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

Recognizing Physical Changes Physical change – occurs when some of the properties of a material change but the substances in the material stay the same Some physical changes can be reversed others cannot be reversed Examples of physical changes Melting butter in a pan Crumpling paper Slicing a tomato Braiding hair Peeling an orange

Reviewing Concepts List 5 examples of physical properties Describe 3 uses of physical properties Name two procedures that are used to separate mixtures When you describe a liquid as thick, are you saying that it has high or low viscosity? Explain why sharpening a pencil is a physical change. What allows a mixture to be separated by distillation?

Chemical Properties Chapter 2 Section 3

Chemical Property Any ability to produce a change in the composition of matter. Can be observed only when the substances in a sample of matter are changing into different substances. Examples: Flammability Reactivity

Flammability A material’s ability to burn in the presence of oxygen. Sometimes flammability is a desirable property (gasoline, firewood) Other times flammability is not desirable (fabrics for pajamas)

Reactivity How readily a substance combines chemically with other substances Examples Oxygen – high reactivity Nitrogen – low reactivity

Chemical Change Occurs when a substance reacts and forms one or more new substances Three common types of evidence for a chemical change: Change in color Production of a gas Formation of a precipitate

Change in Color Examples: Leaves changing color in the fall Ripening of a banana peel Silver bracelet exposed to air darkens Match that burns turns black Copper changing when exposed to moist air (patina)

Change in Color A new copper roof has a reddish color An old copper roof has a greenish color

Production of a Gas Carbon dioxide gas forms when vinegar is mixed with baking soda Baking powder in a cake causes a cake to rise Baking soda and acids react when wet, cake bakes, bubbles of CO2 expand, cake rises

Formation of a Precipitate Precipitate – any solid that forms and separates from a liquid mixture Example: curds in cottage cheese – form when an acid is added to milk

Is a Change Chemical or Physical? Are different substances present after the change takes place? NO – change is PHYSICAL YES – change is CHEMICAL When matter undergoes a chemical change the composition of matter changes. When matter undergoes a physical change the composition of matter remains the same.

Reviewing Concepts List three common types of evidence for a chemical change. How do chemical changes differ from physical changes? Gold and platinum are often used to make jewelry. What can you infer about the reactivity of these elements? A piece of butter melts and then burns in a hot frying pan. Which of these changes is physical and which is chemical?