advertisement

Specific Heat You can get all the information you need about specific heats from the following web sites • http://www.engineeringtoolbox.com/specific-heat-metals-d_152.html • http://www.engineeringtoolbox.com/specific-heat-solids-d_154.html • http://www.engineeringtoolbox.com/specific-heat-fluids-d_151.html Note: you need the data from the column with the heading kJ/kg K, and don't forget that 1 kJ = 1000 J. 1. How much heat is required to heat 300 grams of water from 20 oC to 75 oC? 2. How much heat must be extracted to cool 300 grams of water from 20 oC to 0 oC? 3. If you add 20,000 J of heat to 5 kg of aluminium initially at 20 oC, what is the final temperature? 4. 200 g of water at 20 oC is mixed with 450 grams of water at 75 oC. Assuming no heat loss to the surroundings, what is the final temperature of the water? 5. 25 kJ of heat is added to 5 kg of Pyrex glass. What is the temperature change? 6. 5 kg of Pyrex glass at 90 oC is immersed in 2.5 kg of water at 25 oC. Assuming no heat loss to the surroundings, what is the final temperature of the water? 7. 300 grams of a solid is immersed in 750 grams of water. The solid initially has a temperature of 250 oC and the water initially has a temperature of 15 oC. The final common temperature is 27 o C. Assuming no heat loss to the surroundings, what is the specific heat of the solid? Latent Heat You can get all the information you need about latent heats, including the temperatures of the transitions, from the following web site • http://www.engineeringtoolbox.com/melting-boiling-temperatures-d_392.html 1. What is the energy required to melt 0.4 kg of lead? (Assume the solid lead is already at the melting temperature.) 2. What is the energy required to melt 0.4 kg of copper? (Assume the solid copper is already at the melting temperature.) 3. Repeat question 1 if the lead starts at room temperature (25 oC) 4. Repeat question 2 if the copper starts at room temperature (25 oC) 5. Starting at room temperature (25 oC), how much heat would you have to add to turn 2 kg of liquid water (the amount of water in a 2 litre bottle) into 2 kg of water vapour at 100 oC? 6. Starting at room temperature (25 oC), how much heat would you have to extract to freeze 2 kg of water (the amount of water in a 2 litre bottle) to produce 2 kg of ice at 0 oC? 7. Starting at room temperature (25 oC), how much heat would you have to extract to produce 0.15 kg of liquid nitrogen at -196 oC? (Note the boiling point in their table is incorrect. It should be -196 oC. Also, assume the specific heat of nitrogen gas is essentially the same as that of air, about 1,000 J/kg/Ka) a http://www.engineeringtoolbox.com/air-properties-d_156.html