Physical Science 8th grade (1).pdf

# 23 what happens to the electrical energy used to turn

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23. What happens to the electrical energy used to turn on the lights in your home? a. It is used up. b. It is destroyed. c. It is converted to light and heat energy. 24. Do power plants create electrical energy from empty space? 25. When energy transformations occur in a system, the total amount of energy in the system: a. increases. b. decreases. c. stays the same.

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C HAPTER 3: K EY C ONCEPTS IN P HYSICAL S CIENCE 71 C HAPTER 3 K EY C ONCEPTS IN P HYSICAL S CIENCE Problems Section 3.1 1. Kyela has a mass of 45 kg. What is her mass in grams? 2. An average baseball has a mass of 150 grams. What is its mass in kilograms? 3. What is the mass in grams of a 0.454 kilogram soccer ball? 4. Which graph best represents the relative energy of the atoms of substances in the solid, liquid, and gas phases? A B C Section 3.2 5. For each of the following examples, which has more thermal energy? a. 1 kg of water at 50°C or 2 kg of water at 50°C b. 1 kg of ice at 0°C or 1 kg of water at 5°C c. 1 kg of water at 5°C or 1 kg of steam at 105°C 6. Which of the following will have the highest temperature when 1,000 joules of energy are added to it? Assume each starts at the same temperature. a. 1 kg of water (specific heat = 4184 J/kg°C) b. 1 kg of wood (specific heat = 2500 J/kg°C) c. 1 kg of glass (specific heat = 800 J/kg°C) 7. How much heat in joules would you need to raise the temperature of 1 kg of water by 2°C? 8. If a single light bulb uses 100 joules of energy every second, how many Calories of energy are used each second if there are 4,184 joules in one Calorie? 9. A very bright light bulb uses 150 joules of energy every second. An average fast-food burger contains 350 Calories of energy. If the energy of the burger could be converted to electricity without any energy loss, how long would the energy from the burger light the bulb? 10. One pancake contains about 80 Calories of energy. One Calorie contains 4,184 joules. What is the amount of energy in joules in one pancake? 11. A pizza restaurant advertises that their brick oven cooks their pizza at 800°F. What is this temperature in degrees Celsius? 12. Earth’s core is estimated to be 7,000°C. What is this in degrees Fahrenheit? 13. Which temperature scale, Fahrenheit or Celsius, has the greatest change in temperature for one degree? 14. Describe the energy transformations or conversions for each of the diagrams below: 3
THIS AT HOME Properties of Matter Chapter 4 Density and Buoyancy Chapter 5 States of Matter Can you make an egg float? Place an egg in a glass that is half full of fresh water. The egg will sink because it is denser than the water. Now mix about 8 to 10 teaspoons of salt into the fresh water. Place the egg in the saltwater mixture. Can you explain the result? Can you figure out how to make the egg sink halfway into a glass of water and then stop before hitting the bottom?

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