1. Lesson 18 - Changing Mixtures You will investigate how adding salt affects the melting and boiling points of water. You will also investigate the melting points of three different tin alloys.

2. Lesson 18 - How do the properties of a mixture differ from the properties of the individual components of the mixture? Does adding salt change the melting point and boiling point of water? Do all metal alloys have the same melting point?

3. Lesson 18

6. Use Student Sheet 18.1, 18.2, and 18.3.

7. Lesson 18 - The properties of a mixture can be very different from the properties of the individual components that make up the mixture. Adding salt to ice lowers the melting point. The change in the melting point of a solvent is directly proportional to the amount of solute in the mixture. The boiling point of water rises when salt is added to water because solute particles interfere with the evaporation of a solvent. An alloy is a mixture that contains at least one metal.

8. Lesson 18 - (1-3) 112. alloy - solutions of solid metals 113. solder - used to join together metal materials 114. ** boiling point - temp. at which a liquid turns into a gas; depends on air pressure 115. freezing point - temp. at which liquid turns to a solid. 116. ** melting point - temp. at which a solid turns into a liquid; same temp. as freezing point.

9. Lesson 18 - (2-3) 117. ** material - substance from which something is made 118. metal - group of elements; usually hard solids; have common characteristics - shiny, good conductivity, and malleability. 119. ** mixture - two or more elements or compounds that are mixed together but are not chemically combined 120. **pure substance - either an element of a compound

10. Lesson 18 - (3-3) 121. **solubility - the amount of solute that will dissolve in a solvent at a given temp. and pressure; the ability of one substance to dissolve in another. 122. **solvent - the substance in a solution that dissolves the solute; the substance present in the larger proportion. 123. **solute - the substance that dissolves in a solvent; the substance in the smaller proportion 124. **temperature - the measurement of how hot something is