Cooling Rate Lab Report (3)

Tiffany Kung P2 12/19/11

Determining the Cooling Rate of Hot Water Based on Volume The problem of this experiment is that two children were disagreeing about cooling rates of hot chocolate. One child said that a half cup of hot chocolate would cool faster than a full cup of hot chocolate. The other child said that a full cup of hot chocolate would cool at the same rate as the half cup of hot chocolate. This experiment was to determine if a cup with less hot water would cool faster than a cup with more water (ex. 50 mL and 100 mL). The temperature of the hot water was measured with thermometers. The cooling rate of hot water depends on how fast each mL of hot water loses heat. It also depends on how the hot water is exposed to its surroundings. Since the water loses heat through its surface, the more the surface is exposed, the faster it will cool. In this case, heat will be lost through the surface of the cup. If there is a cup half full of hot water and a full cup of hot water, the full cup of hot water will cool more slowly. In this experiment, three cups of different volumes of hot water will be tested. The fourth cup of room temperature water, the control, will also be measured in temperature to compare with the three cups. The control is the factor that stays the same in the experiment. If there is less volume in a cup of hot water, then it will cool much faster than a cup with more hot water because it has less volume. Materials needed in this experiment included four paper cups, a graduated cylinder, hot water, room temperature water, a stop watch, a large styrofoam cup, and four thermometers. Three of the four cups were filled with hot water, while the fourth cup was filled with room temperature water. The large styrofoam cup was used to pour the hot water into the graduated cylinder. cylinder. The amounts of hot water were measured measured with a graduated cylinder consisting of 50 mL, 100 mL, and 200 mL of water for the three cups. After the different amounts of hot water and room temperature water were poured, the four thermometers were put into each cup. The stop watch was used to time each time interval of three minutes up to 30 minutes to record data. The experiment was conducted in the science room (portable six) at 9:50 a.m., 12/13/11. Figure 1 shows how the experiment is performed. Over time, the cooling temperature changes moderately (Figure 2).

Figure 1 shows how to conduct the experiment using the following materials mentioned above.

Tiffany Kung P2 12/19/11

Temperature-Time Measurements Time (mins)

Volume (mL) 50

100

200

Control

0

45

52

54

22

3

42

47

50

22

6

38

45

48

22

9

36

42

46

22

12

34

41

45

22

15

33

39

43

22

18

31

37

42

22

21

30

36

41

22

24

29

35

40

22

27

28

33

39

22

30

27

32

38

22

Table 1 displays the data recorded after three minute intervals over thirty minutes.

Temperature-Time Measurements 60

    ) 50    C    °     (    e    r 40    u    t    a    r    e    p    m30    e    T

Volume (mL) 50 100 200

20

  Control

10

0 0

10

20

30

40

Time (mins.)

Figure 2 displays the results of the cooling temperature over thirty minutes with three minute intervals.

Tiffany Kung P2 12/19/11

The problem of this experiment is that two children were disagreeing about cooling rates of hot chocolate. One child said that a half cup of hot chocolate would cool faster than a full cup of hot chocolate. The other child said that a full cup of hot chocolate would cool at the same rate as the half cup of hot chocolate. If there is less volume in a cup of hot water, then it will cool much faster than a cup with more hot water because it has less volume. The hypothesis was not substantiated by the data because each of the measurements cooled at around the same rate. The cup with 50 mL of hot water cooled at about the same rate as the cup with 100 mL of hot water and the cup with 200 mL of hot water. At three minutes, the temperature dropped three degrees Celsius (fifty mL), five degrees Celsius ( 100 mL), and four degrees Celsius (200 mL). Then at six minutes it dropped four degrees Celsius (50 mL), two degrees Celsius (100 mL), and two degrees (200 mL). As you can see, the cooling rate  between the three cups of hot water drop at about the same rate. This evidence means that with less hot water, it doesn’t cool much faster than cups with more hot water. The hypothesis is incorrect. Suggestions for the improvement of this experiment are: performing multiple trials instead of just one, using hot chocolate (original liquid), and recording the data as close to the three minute intervals as possible. Another suggestion to better improve the experiment is using a digital titrator (accurate volume measurements [mL]). This experiment was invalid. This experiment was invalid because multiple tasks were not performed. Some tasks that were not performed were performing more than one trial and making no errors that would affect the results. In order for this experiment to be valid, multiple trials could have been done. Also, there may have been many errors. One error is the measurements of hot water were most likely not exactly 50 mL, 100 mL, and 200 mL. Another error is not recording data as soon as possible. Lastly, a digital titrator could have been used to make this experiment valid. Future experiments that might clarify areas of doubt will help the hypothesis would  be the suggestions made above. It would help because one trial is not enough data to support the hypothesis. Multiple records of cooling rates would back up the hypothesis more. With only one trial, the records could be very inaccurate. Future trials could consist of using better methods to better conduct the experiment. Using a digital titrator and recording at the exact time (or as close to the exact time) are better methods to collect information. In this experiment, the temperature may have been more or less than the actual temperature. This can affect the data because the temperature drops could be different. Also, recording at the closest time possible could affect the temperature drop. If the data was recorded too late, then the temperature could have dropped more than what it would have been at the three minute interval.

Literature Cited 

Bloomfield, L. A. (n.d.). Question 1431. Retrieved from http://www.howeverythingworks.org/page1.php?QNum=1431