Purpose: to Predict the Final Temperature of a Mixture of Cups of Water at Different

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Heat Part 1

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Purpose: To predict the final temperature of a mixture of cups of water at different temperatures.

DISCUSSION: If you mix a pail of cold water with a pail of hot water, the temperature of the mixture will be between the two initial temperatures. This lab investigates what factors are involved in changes of temperature.

1. What information would you need to predict the final temperature?

Your goal is to find out what happens when you mix equal masses of water at different temperatures. Before doing this, imagine a cup of water at 60C and a pail of water at 20C.

1. Which do you think is hotter—the cup or the pail?

2. Which do you think has more energy?

3. Which would take longer to change its temperature by 10C if left lone?

4. If you put the same amount of red-hot iron into the cup and the pail, which one
would change temperature more?

PROCEDURE:

Step 1: Read over the entire lab sheet and make a data sheet to record all the measurements that you will be asked to make. Every place the instructions say to record something that is a clue to what to add to your data sheet.

Step 2: Get three styrofoam cups. Fill one cup 3/4 full with cold water from the cold water supply. Mark the water level along the inside of the cup. Pour the cup's water into a second cup. Mark it as you did the first one. Pour the cup's water into a third cup, and mark it as before. Now all three cups have marks that show nearly equal measures.

Answer question 1. Why don't the marks show exactly equal measures?

Step 3: Empty the water from the 3rd cup. Refill it with cold water. Fill another cup to the mark with hot water. Measure and record the temperature of the cold cup. Measure and record the temperature of the hot cup.

Answer question 2. What will be the temperature if you mix the two cups of water in a larger cup?

Step 4: Pour the two cups of water into a large styrofoam cup, stir the mixture and record the temperature.

Answer question 3. If there was a difference between your prediction and your observation, what might have caused it?

Step 5: Empty all the cups. Now, fill one cup to its mark with cold water. Fill the other two cups to their marks with hot water. Measure and record their temperatures.

Step 6: Record your prediction of what the temperature will be when all three cups of water are mixed in one container.

Step 7. Pour the three cups of water into a large styrofoam cup. Stir the mixture and measure and record its temperature.

Answer question 5. How did your observation compare with your prediction?

Answer question 6. Which of the water samples (cold or hot) changed more when it became part of the mixture?

Answer question 7. Why do you think this happened?

Step 8: Empty all the cups. Fill one cup to its mark with hot water. Fill the other two cups to their marks with cold water. Measure and record their temperatures.

Step 9: Record your prediction of what the temperature will be when all three cups of water are mixed in one container?

Step 10: Pour the three cups of water into a large styrofoam cup. Stir the mixture and measure and record its temperature.

Answer question 8. How did your observation compare with your prediction?

Answer question 9. Which of the water samples (cold or hot) changed more when it became part of the mixture?

Answer question 10. Why do you think this happened?

Answer question 11. What factors affect how much heat is transferred from a hot body to a cold body?