1. What are the boiling points & freezing points for the 3 temperature scales?
Scale / Freezing Point / Boiling PointKelvin / 273 / 373
Celsius / 0 / 100
Fahrenheit / 32 / 212
2. You can touch the aluminum pan of a TV. dinner after it has been taken out of the oven, but you will burn your hand if you touch the food it contains. Explain in terms of the specific heat of aluminum and the water in the food. The water has a high specific meaning it heats & cools slowly, the aluminum has a low specific heat meaning it heats and cools quickly
3. When you heat a substance and the temperature rises, how much it rises depends upon its specific heat.
4. What are three ways thermal energy is transferred? Describe them. Conduction- requires contact/collision of molecules, Convection occurs in fluids (gases & liquids) warmer less dense fluid rises – cooler more dense fluid sinks, Radiation is the transfer of heat by electromagnetic waves.
5. Calculate the specific heat of a metal if 0.5 kg of the metal absorbs 9 000J of heat as it warms by 10 °C.
Q= mc(final temp. – initial temp.) 1800J/kg °C
6. Explain why materials that are good conductors of heat. Good conductors like metals have loosely held electrons in their atoms, they bump into other electrons and easily transfer energy. Insulators like air and rubber conduct heat poorly.
7. Would plastic foam, which contains pockets of air, be a good conductor or a good insulator? Insulator
8. What is the second law of thermodynamics? Heat always flows from hot to cold
9. A wooden block has a mass of 20.0 kg and a specific heat of 1 700 J/kg °C . Find the thermal energy of the block as it warms from 15° C to 25° C. 340,000J
10. The thermal energy of water in a mug increases by 12 552 J when the water is heated from 20° C to 40°C. If the specific heat of water is 4 184 J/kg °C, what is the mass of the water? 0.15kg
Substance / Specific Heat (J kg-1 K-1)Aluminum / 900
Copper / 390
Brass / 380
Silver / 230
Platinum / 130
11. If 500 J of energy were added to 1 kg of each of these samples, which would experience the LEAST temperature increase? aluminum
12. A scalpel made of surgical stainless steel is sterilized by heating in a flame and then quenching in 175 g of ethyl alcohol. The alcohol is initially room temperature, 23.7°C, warms to 38.6°C. The specific heat capacity of ethyl alcohol is 2.4 J/(g*K). Calculate the heat released by the alcohol. 6258J
Substance / Specific Heat Capacity J/Kgo CAmmonia / 4700
Ethanol / 2440
Gasoline / 2220
Water / 4186
13. A liquid has a mass of 18.39g. If 655J of heat are required to change the temperature from 32.8oC to 18.2oC, what is the identity of the liquid? 2439.5 ethanol
14. You are walking on a beach and find a mystery piece of metal. You take it back to your lab and measure its mass to be 0.5 kg. In order to heat the metal 1 degree K, you must add 115 J of heat. Identify the metal. q =mCΔT 230 silver
Substance / Specific Heat (J kg-1 K-1)Aluminum / 900
Copper / 390
Brass / 380
Silver / 230
Platinum / 130
15. Microwave ovens heat food through the process of radiation
16. Brownies cook faster in a glass baking dish because heat is transferred by radiation & conduction. In a metal baking pan heat is mainly transferred by conduction.
17. True/False Fluids are liquids only.
18. A thermos has a vacuum between two inner glass walls to prevent heat transfer by conduction & convection. Therefore the only type of heat transfer that can occur is the one that does not require a medium, which is radiation.
19. Two units of energy are Joules Calories.
20. True/False air is a good conductor.
21. Energy on Earth radiates back out into outer space.
22. What does salt do to the freezing point of water? Salt lowers the freezing point of water because it interferes with the lattice structure of solid water, the result is a liquid below the freezing point of water