Chapter 7 Study Guide s2

Chapter 7 Study Guide 7-1 Elements- simplest type of pure substance; can not be broken down Metals- left of stairstep; shiny and good conductors of heat/electricity Nonmetals- right of stairstep; dull and poor conductors of heat/electricity Metalloids- on the stairstep; has properties of both metal and nonmetals

7-2 Compound- 2 or more elements chemically combined; pure substance; ex. Water H2O A compound has different properties from the individual elements that make it up. Compounds have a definite mass ratio. Example H2O 2:1 ratio Compounds can be broken down by chemical changes. *Example- electrolysis of water Properties of Water: 1) cohesion- holds molecules of singe material together; “sticks together” 2) adhesion- hold two different substance together; “sticks to other things” 3) ”universal solvent”- most substances will dissolve in water 4) Polar- one end of molecule is positive and one end is negative 5) High specific heat- water heats up slowly ex. Pool water is cool in summer 6) Buoyant force- “upward force” of water; related to floating and sinking

7-3 Mixture- two or more substances not chemically combined. Mixtures can be separated by physical means. 1) distillation- based on boiling point 2) magnet- based on magnetism 3) centrifuge- based on density Substances in a mixture do not have to be a definite ratio. Substances in a mixture keep their own identity (ex. Raisin Bran Cereal) Mixtures can be solids, liquids, or gases. (air is a mixture of gases)

Solution- special type of mixture in which particles are evenly distributed or dissolved; 1) solute- substance that is being dissolved (sugar) 2) solvent- substance in which the solute is dissolved (water) Alloy- solid solution of metal and nonmetal or metal and metal; ex. Brass is an alloy of copper and zinc dissolved together. Concentration of solution- 1) Concentrated- solution contains a large amount of solute 2) Dilute- solution contains a small amount of solute

Solubility- amount of solute that can be dissolved in the solvent How can you make a substance dissolve faster? 1)increase temp. 2)crushing the solute 3) stirring the solution