Composition of Matter Chapter 17 section 1

Substances A substance is something that can not be broken down and still maintain its original characteristics/properties Elements are examples of a substance Compounds are examples of a substance

Difference Between Element and Compound Element-Combination of like atoms Element-Combination of like atoms Entire substance is made of the same type of atom Entire substance is made of the same type of atom Example-aluminum foil Example-aluminum foil Compound-A substance in which two or more atoms are combined in a fixed proportion to become stable Compound-A substance in which two or more atoms are combined in a fixed proportion to become stable Example-H 2 O Example-H 2 O

Mixtures  A material made up of 2 or more substances  Mixtures do not always combine the same proportions  Example-Saltwater  Mixtures can be separated  Example/Question-What happens when you boil salt water  As the water evaporates the salt is left behind

Types of Mixtures  There are 3 different types of mixtures 1.Homogenous mixture-contains 2 or more gaseous, liquid, or solid substances that are evenly blended –Examples –Coffee with milk and sugar (that has been dissolved) –Shows diffusion of molecules –Sugar and salt mixture that is mixed up evenly –Homogenous mixtures create a solution –Solution-particles so small that they cant be seen without the use of tools (microscope)

Types of Mixtures (continued) 2.Heterogeneous mixture-A mixture in which materials are not evenly blended –Sometimes they can be easily separated (not always) –Example-a pizza is made up of crust, sauce, cheese and pepperoni –Certain types of cereal-Raisin bran or Lucky charms –Some heterogeneous mixtures will separate over time –Heterogeneous mixtures that will settle = suspension –Example-River carrying dirt or sand

Types of Mixtures (continued) 3.Colloids-contains particles in varying proportions (heterogeneous) but particles will not settle over time –Examples–Fog (water particles suspended in air), hair gel, and some shampoos –Test for colloids using the Tyndall effect –Tyndall effect is the scattering of light as it passes through a colloid –You can see the beam because the particles in the mixture are big enough to cause the light to scatter