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### Thermal Energy

1. How much heat does 100 g of water at 100°C lose as it cools and becomes water at 0°C? Ans: -41,800 J
2. 100 J of heat is needed to raise the temperature of an unknown mass of lead (c=130 J/kg°C) 5°C. What is the leadĺs mass? Ans: 0.154 kg
3. How much heat must be added to 124 g of brass (c=376 J/kg°C) at 12.5°C to raise its temperature to 97°C? Ans: 3939.73 J
4. 45 g of water at 4°C is added to 150 g of water at 75°C. What is the mixtureĺs equilibrium temperature? Ans: 58.6°C
5. An insulated container contains 100 g of ethyl alcohol (c=2440 J/kg°C) at 25°C. A 25 g block of iron (c=450 J/kg°C) is heated to 400°C and then added to the alcohol. What is the final temperature? Ans: 42°C
6. 250 g of copper (c=385 J/kg°C) at 100°C is placed in a cup containing 32 g of water at 20°C. What is the final temperature? Ans: 53.47°C
7. How much heat is needed to change 50 g of water at 80°C to steam at 110°C? Ans: 118,190 J
8. How much heat is removed from 60 g of steam at 100°C to change it to 60 g of water at 20°C? Ans: -155,664 J
9. How much heat is absorbed by 100 g of ice at -20°C to become water at 0°C? Ans: 37,420 J