Chemistry Energy Worksheet Answer Key Energy Storage & Transfer Mechanisms 1. Indicate how most of the energy is stored in each of the objects. Energy is often stored in most of the six mechanism, but we are focusing on the one or two mechanisms that store most of the energy. The storage mechanisms are E k, E th, E g, E el, E ch, and E i. a. Water at the top of a waterfall. E k and E g b. A soccer ball rolling along the ground toward the goal. E k c. A lump of coal. E ch d. A skier standing still at the top of a hill. E g e. A roller coaster half-way down a hill. E k and E g f. A box sitting on the top shelf. E g g. A compressed spring. E el h. An ice cube. E th, and E i i. Steam entering a turbine. E th, E i and E k j. A moving turbine blade. E k k. A stretched bungee cord holding cargo in place. E el l. A hot stove top burner. E th m. A peanut butter and jelly sandwich. E ch
2. Indicate which transfer mechanism was used to transfer the energy from one object to the other object, and identify which object is gaining energy. There may be more than one mechanism involved in the transfer. The transfer mechanisms are work (W), radiation (R), and heat (Q). a. A bow shooting an arrow. Work b. A car engine moving a car up a hill. Work transfers energy from the engine to the car. c. A charcoal fire cooking hot dogs. Heat transfers energy from the fire to the hot dogs. d. A camp fire warming up campers who are seated beside the fire. Radiation transfers energy from the fire to the people. (Heat is a minor source) e. The sun warming the ocean. Radiation transfers energy from the sun to the ocean. f. A compressed spring launching a Nerf arrow. Work transfers energy from the spring to the Nerf arrow. g. The wind turning a turbine blade. Work transfers energy from the wind to the turbine blade. h. A light bulb lighting up a room. Radiation transfers energy from the light bulb to the room. i. The gas from a Bunsen burner heating a beaker of water. Heat transfers energy from the flame of the Bunsen burner to the beaker of water. (Radiation is a minor source) 3. Use column graphs to show how energy is stored in the objects, transferred between objects and how total energy is conserved. a. Ice cubes in a glass of warm water.
b. A student lifting their backpack from the floor to the top of the desk. c. The flame of a Bunsen burner bringing cold water to a boil. d. A person running up a hill. e. A person running on level ground.
Units of Energy Conversions Use conversion factors and dimensional analysis to answer these problems. 1 calorie = 4.184 joules. 4. A person uses 550 kcal of energy to run a race. Convert the energy used for the race to the following energy units: 5. Convert each of the following energy units: 6. Convert each of the following energy units: 7.
8. It takes 4184 J of energy to raise the temperature of 1.000 kg of water 1.000 C. a. How many joules does it take to raise the temperature of 1.50 kg of water 1.00 C? b. How many calories does it take to raise the temperature of 1.0 kg of water 15.5 C? Temperature Conversions 9. Complete the table below:
Specific Heat Calculations 13. Water has a specific heat of 4.184 J/g C. a. How much energy must be added to 1450 g of water to raise the temperature from 5.5 C to 29.0 C? b. How much energy is removed from 10.55 kg of water to lower the temperature from 22.5 C to 3.0 C? c. Adding 550 calories of energy raised the temperature of water from 10.0 C to 13.25 C. What was the mass of the water? 14. Iron has a specific heat of 0.45 J/g C. a. How much energy must be added to 376 g of iron to raise the temperature from 25.5 C to 429.0 C? b. Removing 9550 kcal of energy lowered the temperature of iron from 100.0 C to 73.25 C. What was the mass of the iron? c. 15. Steam has a specific heat of 1.90 J/g C. a. How much energy must be added to 125 kg of steam to raise the temperature from 105.5 C to 129.0 C? b. How much energy must be removed from 1520 g of steam to lower the temperature from 202.5 C to 100.0 C? c. 109 kj of energy was added to 2.50 kg of steam. If the steam was originally at 100.0 C what was the final temperature of the steam?
16. What is the specific heat of a substance if 525 calories of energy increases the temperature of 10.0 g of the substance 5.75 C? 17. What is the specific heat of a substance if removing 95.0 J of energy decreases the temperature of 5.0 g of the substance from 23.5 C to 18.1 C? Calorimetry Calculations 18. A chemical reaction takes place in 255 g of water. During the reaction the temperature increased from 22.8 C to 31.2 C. How much energy did the reaction transfer to the water? 19. A chemical reaction takes place in 925 g of water. During the reaction the temperature decreased from 22.8 C to 1.2 C. How much energy did the water transfer to the reaction? - 83600 J 20. A piece of metal with a mass of 105 g was heated to 100.0 C and placed in 175 g of water to cool. The water temperature increased from 22.8 C to 39.2 C. What is the specific heat of the metal? 21. A piece of metal with a mass of 15 g was heated to 80.0 C and placed in 102 g of water to cool. The water temperature increased from 22.8 C to 27.7 C. What is the specific heat of the metal? 22. Copper has a specific heat of 0.39 J/g C. If 22.3 g of copper is heated to 157 C and placed in 235 g of water that is initially at 22.9 C, what is the final temperature of the copper and water?
23. Lead has a specific heat of 0.13 J/g C. If 72.3 g of lead is heated to 122 C and placed in 151 g of water that is initially at 23.9 C, what is the final temperature of the lead and water?