1. Challenge Problem If the density of an alloy of Al and Cd is 6.08g/cm 3, what is the % by mass and the % by volume of Al? The density of Al=2.70g/cm 3 and Cd=8.94g/cm 3

2. Heat and energy All matter is in constant motion. All matter is in constant motion. As temperature increases, so does the velocity of particles. As temperature increases, so does the velocity of particles.

3. The temperature of a substance is a measure of the average kinetic energy of its particles.

4. Heat Energy Energy transferred Measured in Joules or calories

5. Specific Heat Capacity (c) The heat needed to raise the temperature of 1g of a substance 1˚C. The heat needed to raise the temperature of 1g of a substance 1˚C. Water’s heat capacity is high: 4.184 Joule Water’s heat capacity is high: 4.184 Joule or 1 calorie or 1 calorie so c w = 4.184 J/g∙˚C so c w = 4.184 J/g∙˚C

6. Q = m∙c∙∆T Heat = mass ∙ specific heat∙ change gained or lost in temp Ex: How much heat is lost when a solid aluminum ingot with a mass of 4110g cools from 660.0˚C to 25˚C? ∆T = 660.0 – 25 = 635˚C ∆T = 660.0 – 25 = 635˚C Q = (4110g)(0.903J/g˚C)(635˚C)=2,360,000 J

7. Specific Heat Capacities (J/g·°C) copper0.387 air1.00 ethyl alcohol2.45 water4.18 What happens to the change in temperature of equal masses of copper and water when equal amounts of heat energy are given? m = 1.0gQ = 10.0J Copper: 10.0J = 1.0g (0.387 J/g·°C)ΔT Water: 10.0J = 1.0g (4.18 J/g·°C) ΔT ΔT = 25.8 °C ΔT =°C ΔT = 2.4°C

8. Calorimeter A device used to measure the energy given off or absorbed during a chemical or physical change. A device used to measure the energy given off or absorbed during a chemical or physical change.

9. A piece of an unknown metal with mass 23.8g is heated to 100.0˚C and dropped into 50.0 ml of water at 24.0˚C. The final temperature of the system is 32.5˚C. What is the specific heat of the metal? Metal m=23.8 g ∆T=100.0-32.5=67.5˚CWaterm=50.0g∆T=32.5-24.0=8.5˚CC=4.184J/g˚C

10. Heat gained by the water: Q=(50.0g)(4.184J/g˚C) (8.5˚C) = 1778.2 Joules = 1778.2 Joules Heat gained by water = heat lost by metal 1778.2J = (23.8 g) (c) (67.5˚C) 1778.2J = 1606.5 (c) C=1.1J/g˚C

11. Specific Gravity The ratio of a solution’s density to that of water. The ratio of a solution’s density to that of water. Density of water = 1 g/cm 3 Density of water = 1 g/cm 3 Ex.: 15ml of a solution has a mass of 18g. What is its density and specific gravity? Ex.: 15ml of a solution has a mass of 18g. What is its density and specific gravity? D= 18g/15cm 3 = 1.2g/cm 3 D= 18g/15cm 3 = 1.2g/cm 3 S.G. = 1.2 g/cm 3 = 1.2 S.G. = 1.2 g/cm 3 = 1.2 1.0 g/cm 3 1.0 g/cm 3