1 Classifying Matter Pure Substance or Mixture?

2 Matter  Matter is anything that: a) has mass, and b) takes up space  Mass = a measure of the amount of “stuff” (or material) the object contains (don’t confuse this with weight, a measure of gravity)  Volume = a measure of the space occupied by the object

3 Pure Substance   Matter that has a definite composition Substances are either: a) elements, or b) compounds

4 Elements  Simplest kind of matter  Cannot be broken down any simpler and still have properties of that element! –all one kind of atom.  Examples – From the periodic table –Helium (He), Iron (Fe), Oxygen (O 2 )

5 Compounds  A substance that is made from the atoms of 2 or more different elements that are chemically bonded.  They can be broken down only by chemical methods –when broken down, the pieces have completely different properties than the original compound. –Example – Water, H 2 O  H 2 + O 2 (Compound)  ( elements) (Compound)  ( elements)

6 silver + bromine = silver bromide A compound has different properties than the elements that make it up have by themselves.

7 Mixtures  A physical blend of two or more different substances  Basic identity of each substance is not changed  Can be homogenous or heterogeneous

8 1)Heterogeneous – the mixture is not uniform in composition.  Differences between substances can clearly be seen with the naked eye Examples - Chocolate chip cookie, oil and water, sand and water.Examples - Chocolate chip cookie, oil and water, sand and water.

9 1)Homogeneous – Mixture that has a uniform composition.  Different substances cannot be seen with the naked eye. Kool-aid, air, salt waterKool-aid, air, salt water  Every part keeps it’s own properties.  Homogenous mixtures are also called solutions.

10 Compound vs. Mixture CompoundMixture Made of one kind of material Made of more than one kind of material Made by a chemical change Made by a physical change Definite composition Variable composition

11 Classification of Matter

12 Physical vs. Chemical Change  Physical change will change the visible appearance, without changing the composition of the material. –Boil, melt, freeze, cut, bend, split, crack, dissolving, crystallizing –Is boiled water still water? –Any phase change is a physical change!  Usually is reversible

13 Solid Liquid Gas Melt Evaporate Condense Freeze Physical Changes!!!!

14 Chemical Change A change in which one or more substances are converted into different substances. Also known as a chemical reaction A new form of matter with different properties is formed.A new form of matter with different properties is formed. Examples - Rusting, burning, decompose

15 Recognizing Chemical Changes 1)Energy is absorbed or released (temperature changes hotter or colder) 2)Color changes that are unexpected. 3)Gas production (bubbling, fizzing, or odor change; smoke) 4)formation of a precipitate - a solid that separates from solution (won’t dissolve) 5)Irreversibility - not easily reversed But, there are examples of these that are not chemical – boiling water bubbles, etc.