Warm Up 9/19 1. Suppose you have a sample of an unknown mineral. Its mass is 50 g and it has a volume of 100 cm3. What is its density? 2. Copper has a density of 8.9 g/cm3. If there is a 6 cm3 sample of copper, what is its mass?

Physical Properties of Matter Can be observed using the 5 senses. Help to identify a material and determine how it can be used. Ex: appearance, texture, color, odor, melting point, boiling point, density, solubility, taste, and many others. 2

Melting and Boiling Points Both are physical properties!!! Melting Point: The temperature and pressure at which a solid becomes a liquid Boiling Point: The temperature at which a liquid becomes a gas. 3

Chemical Properties Describe how a substance will change into a new substance (react) Are not easy to observe Examples: Does the metal rust? Does this mineral react with water? Baking soda vs. sugar (mixed with vinegar) 4

Chemical Properties Reactivity is a chemical property which describes how an element or compound reacts with things like oxygen, acid or water. Flammability is another (the ability to burn). Substances all have chemical properties even though you can’t see them! 5

Physical and Chemical Properties Song http://www.youtube.com/watch?v=uJOGy0dgmUU 6

Physical Changes What the substance is made of does NOT change. Ex. If you break a piece of chalk in two, it is still chalk (chemical properties remain unchanged)

Physical Changes After a physical change, a substance might look different, but has the same atomic structure. Important to remember that all changes of state are physical changes because the identity of the substance stays the same (ex. water to ice) Dissolving is a physical change (sugar in water) because the sugar molecules do not change.

Changes in state from solid to liquid to gas are physical changes; it is still the same substance…

Physical Changes

Chemical Changes When a substance changes what it is made of by bonding with another substance. In a chemical change you might notice odor, fire, light or rusting Ex. Digestion, sour milk, baking a cake, skunk, camp fire, fireworks

Chemical Changes Form new substances that have different properties from the original properties. Ex. When you bake a cake, you start with several different ingredients, but after it is done baking all are mixed together and look very different from what you started with. Chemical changes are known as “chemical reactions.”

Chemical Changes Easy to detect (change in smell, color, fizzing, foaming, heat or light) Ex. You can see that the batter has hardened into cake, you can smell it and sometimes you can hear it being cooked.

Chemical Changes Cannot be reversed by physical changes Cannot “unbake” a cake by separating the ingredients. Some chemical changes can be reversed by other chemical changes. Ex. Water can be split into H and O using an electric current to initiate a reaction.