University of Virginia Physics Department Heat Transfer A Physical Science Activity

Materials

beaker (at least 200 mL)	scrap paper massing chemicals
two 6-8oz Styrofoam cups with lids	scoop for chemicals or plastic spoon
hot plate	graduated cylinder
heat resistant gloves (or pot holders)	Celsius thermometer
marking pen	safety glasses

Procedure

1. Place 100 ml of water in the beaker and record the temperature. Place the beaker on the hot plate and heat it to boiling.
2. While the water in the beaker is heating, label the Styrofoam cups, #1 and #2.
3. Pour 25 ml of tap water into each of the cups and let the water come to room temperature. Record the temperature of each in the data table.
4. When the water in the beaker has come to a boil, remove the beaker from the heat, measure its temperature and record it in the table. Using the gloves or pot holders, carefully pour the boiling water into cup #1. Cover the cup with the lid and thermometer. Gently rotate the cup and take the temperature once it has stopped rising. Record the temperature in the table as temperature of cup #1 after mixing.
5. Pour 50 ml of tap water in the beaker and heat it to a boil. When it has come to a boil, pour it into cup #2, place the lid on the cup and find the temperature after mixing. Record the temperature in the data table .

Data Sheet - Part 1

Temperature of tap water in beaker _____________________oC Temperature of 100mL of boiling water _____________________oC Temperature of tap water in cup #1 _____________________oC Temperature of tap water in cup #2 _____________________oC Temperature of 50 mL of boiling water _____________________oC Temperature of water in cup #1 after mixing _____________________oC Temperature of water in cup #2 after mixing _____________________oC Questions: 1. What was the temperature of the water after mixing in cup #1? In cup #2?  #1_________________ #2___________________   2. What was the temperature change of the water in cup #1? In cup #2?  #1_________________ #2___________________   3. What was the temperature change of the boiling water in cup #1 after it was mixed with the tap water? In cup #2?  #1_________________ #2__________________   4. Based on the temperature increases in cups #1 and #2, which delivered more heat, 100 mL of water or 50 mL of water?     5. The water temperatures in the beakers containing the boiling water were both the same, however, they did not raise the temperatures of the both cups equally. How could you explain this?    6. After mixing boiling water with the room temperature tap water, could the final temperature ever reach the same temperature as the boiling water? Explain.     Calculations:  1. If the volume of water in each cup was 10 ml before the boiling water was added, calculate the mass of 10 ml of water and enter it in the table. (1 ml of water has a mass of 1 gram)   2. Calculate the temperature change of the water in the cup. Subtract the starting temperature of the room temperature water from the temperature after mixing. Enter the value in the table.   3. Using the formula below, calculate the amount of heat gained by the water in each cup. Enter the answers in the table. Formula: Heat gained (J) = S.H. (4.19 J/g C) x mass of water x change in temperature   Calculations Cup #1 Cup #2 Mass of water _________________ _________________ Temperature change _________________ _________________ Heat gained by water _________________ _________________

Materials

safety glasses	0.5 grams of sodium hydroxide (NaOH)
rubber gloves	balance
2 Styrofoam cups	graduated cylinder
Thermometer (Celsius)	1.0 grams of baking soda
250 mL of room temperature water. (Let tap water sit in a beaker for 1 hour to reach room temperature.)

Procedure

1. Mass out 1.0 gram of baking soda on the balance.
2. Measure out 20 mL of room temperature water and add it to one of the Styrofoam cups. Measure the temperature of the water and add it to the table below.
3. Pour the baking soda into the Styrofoam cup and quickly replace the lid and insert the thermometer. While gently swirling measure the temperature for several minutes and record the temperature in the table.
4. Record the temperature of the solution that differs most from the original temperature.
5. Repeat the procedures using 0.5 grams of sodium hydroxide.

Data Sheet - Part 2

Measurement Baking Soda NaOH Mass of solid _____________________ _____________________ Volume of water _____________________ _____________________ Temperature of water _____________________ _____________________ Temperature of solution _____________________ _____________________ Questions: 1. What does a negative temperature change indicate about the process?    2. What does the temperature change indicate about the heat gained or the heat lost?    Calculations: 1. Determine the mass of the 20 mL of water used in part #2. (1 mL of water has a mass of 1 gram.) Enter the value in the table.   2. Calculate the temperature change of the water and enter the value in the table.   3. Calculate the heat gained using the same formula as in part #1. Enter the value in the table.   Calculations Baking Soda NaOH Mass of water _____________________ _____________________ Temperature change _____________________ _____________________ Heat gained or lost _____________________ _____________________