Unit 8 - Energy Vocab

Transcription

1 UNIT 8 - ENERGY - PRACTICE PACKET Name Per Unit 8 - Energy Vocab Use the context clues from the statements listed with the term to write a definition for each of the following vocabulary terms. You may not use your chemistry book or notes. You should be in groups of 2 or three. The vocabulary terms are in bold. 1. Energy People, as well as, animals use food for energy to maintain their daily lives. Machines use electrical energy and convert that electrical energy into mechanical energy. As living beings are deprived of energy, their systems began to slow and eventually cease. Shivering is caused by a lack of warmth, which can be a result of the lack of sufficient energy. 2. Potential energy The skier at the top of a run that is not moving has potential energy. Eating more calories than your body needs builds potential energy in your body. A rock held out over a cliff has potential energy. 3. Kinetic energy The same skier as in example two has kinetic energy when the skier is skiing in the middle of the run. Working out converts potential energy stored in your body into kinetic energy. 4. Law of Conservation of Energy 5. Work Use what you learned about the Conservation of Mass and apply the same principle here. Climbing Pikes Peak on foot requires a trail that winds around the mountain, which is a lot of work. Climbing Pikes Peak by walking directly up the mountain requires less work than winding on a trail because the distance is less than if you wind around. Both of the previous examples require some force to accomplish work. 6. State Function Climbing Pikes Peak on foot requires you to do a lot of work, whereas climbing Pikes Peak on a direct trail does not require you to do as much work. Although there are different amounts of work involved, the state function for both are the same. Adding 1+2+4=7 and adding 4+1+2=7 is a state function. Multiplying 2 x 3 x 5= 30 or multiplying 3 x 5 x 2 =30 is a state function. 4 2=2 and 2 4= 2 is not a state function. Dividing 6/3 =2 and 3/6= 0.5 are not state functions. 7. Temperature A thermometer placed in a cup of fast moving H 2 O molecules will have a higher value than a thermometer placed in a cup of slow moving H 2 O molecules.

2 8. Heat A thermometer placed in a gym during a basketball game will have a higher value than a thermometer placed in the same gym with the same amount of people taking a nap. An ice cube placed in hot coffee with a lid will eventually be at the same temperature as the coffee due to heat. In a sealed insulated container, hot coffee poured into another cup of hot coffee, at exactly the same temperature, does not have heat. 9. System Reactants and products of a chemical reaction and nothing else. The players in a sports event and nothing else. 10. Surroundings A beaker, lab bench, experimenter, room, building, sky that is around reactants and products in a beaker. All the fans, the stadium, parking lot, state, country, sky that is around the players in a sports event. 11. Exothermic Striking a match releases energy. In a hot pack, chemicals are mixed together and release energy. This energy is felt as heat. 12. Endothermic Sunlight strikes a plant. The plant absorbs the energy from the sunlight. Photosynthesis is an endothermic process.

3 Endothermic or Exothermic Name 1. Define exothermic- 2. Define endothermic- 3. Draw an energy diagram for an endothermic reaction 4. Draw an energy diagram for an exothermic reaction Process System Exo Endo Explanation An ice cube melts after being left out on the table. Cooking an egg in a frying pan. Burning a match. The human body uses the energy provided from food digestion. Morning dew forming on grass and plants. Dynamite explodes in the destruction of a building. Making ice cubes. A puddle of water evaporates. Plants making sugar through photosynthesis Nuclear fission Converting frost to water vapor. Freezing water

4 SPECIFIC HEAT INTRO NAME Given the formula q = msδt and the following units for each: m = grams (g) s = ΔT = C q = J (J=joules which is a measure of energy (heat)) Solve for the following: J (g C) 1. Solve for mass Convert to units 2. Solve for heat Convert to units 3. Solve for specific heat Convert to units 4. Solve for the change in temperature Convert to units Use the above formulas to answer the following: 1. A metal has a specific heat capacity of 0.34 J/g C. If you have 10.2g of the metal at a temperature of 25 C and you raise the temperature of the metal to 35 C, calculate the heat absorbed by the metal. OVER

5 g of Cu has a specific heat of.16j/g C. If the final temperature of the metal is 48 C, calculate the starting temperature of the copper. The heat absorbed by the metal is 62J. 3. A piece of plastic with a mass of 91 is heated to 28 C from 18 C, the heat gained by the plastic is 125J. Calculate the specific heat of the plastic. 4. Calculate the change in temperature if 125g Al gains 300J of heat. The specific heat of Al is 0.45J/g C.

6 SPECIFIC HEAT PROBLEMS Name Block

7 Chemistry Warm UP PRE QUIZ 1. A 40g sample of lead was placed in a bomb calorimeter that had 54.9g water in it. The lead had an initial temperature of 108 C and a final temperature of 30 C. Calculate the change in temperature of the water. Specific heat of lead = 0.39J/g C 2. A cheeto was burned under a can of water. The following data was obtained: Mass of water in can 100g Initial temperature of the water 21 C Final temperature of the water 24 C Mass of the cheeto unburned 2.6g Final mass of the cheeto 1.4g a. Calculate the heat absorbed by the water. b. How much heat was given o ff by the Cheeto? c. How many calories (lower case c ) were given off by the Cheeto?

8 d. Convert science calories given off by the Cheeto to kcal (Calories). e. How many Calories per gram is in the Cheeto? f. If the package states that there are 10.5 Calories in 30g. Calculate the percent error. accepted experimental/accepted x 100