Factors affecting the rate of Cooling

Equipment Used:

50cm3 beaker

Stopwatch

00cm3 beaker

Bunsen burner

250cm3 beaker

Tri-Pod

400cm3 beaker

Heat proof-mat

800cm3 beaker

Thermometer

Water

Gauze

* To keep an accurate measurement I will use the same thermometer and end the experiment when the liquid reaches 50oC.

* I will measure the time it takes from when the liquid reaches 95oC.

* To keep accurate and constant results I will ask a friend to measure the time while I measure the temperature of the liquid.

* I will keep the total volume of water at a constant 50cm3.

* I will try and keep the light as constant as possible by always have a fluorescent tube light lit above the experiment to keep visibility to a maximum.

* The stopwatch will be started as soon as the liquid reaches 95oC and when the Bunsen burner has been removed.

For this experiment I am going to change the surface area exposed to the surrounding air. I will use six different sized beakers each with a different radius in order to gather enough information to see a pattern if there is one.

Results

Experiment Number

Area of Beaker Cm2

Capacity of Beaker

Time (Minutes)

Average Time (Minutes)

____10000____

Average Time (to 1 decimal place)

3

50

8:51

8:51

8.8

2

-

23

00

6:04

6:04

0.4

2

-

47

250

0:08

0:08

6.4

2

-

55

400

9:48

9:48

7.0

2

-

65

800

9.34

9.34

7.4

2

02

800

5.32

6.40

25

2

7.47

Experiment Number

Volume

Cm3

Temperature oC

Average Temperature oC

____1000____

Average Temperature oC (1 decimal place)

50

57

57

7.5

2

-

00

64.5

64.5

5.5

2

-

50

65.5

65.5

5.3

2

-

200

71

71

4.1

2

-

250

72

72

3.9

2

-

300

73

73

3.7

2

-

350

75

75

3.3

2

-

400

76

76

3.2

2

-

Conclusion

When looking at the graph above it is quite obvious to see that the speed of the cooling decreases as the volumes is increases. It is therefore safe to make the assumption that the speed of the cooling is directly proportional to volume.

When looking at the graph above it is quite obvious to see that the speed of the cooling decreases as the surface area is decreases. It is therefore safe to say that the speed of the reaction is directly proportional to the surface area.

This graph shows the cooling curve to a greater effect. This graph shows clearly that the capacity of the beaker and the time it takes for the liquid to cool are directly proportional. It also shows that the smaller the area of the beaker the slower the cooling.

Through gathering results from the two experiments it is quite obvious to me that as the surface area increase then the cooling also increases proportionally. Therefore it is clear through my results tables and graphs that speed of cooling and surface areas are directly proportional to each other when using water. I.e. when the surface area increases the cooling time decreases and when the surface area decreases the cooling time increases. This links into what I predicted before the investigation.

Evaluation

Through the duration of my experiment I attempted to take as many precaution as possible to create a fair and accurate test within the time limit and environmental conditions provided. However my results and patterns in my graphs show that not all the tests were accurate, as some points do not fit the pattern.

One of the main problems that I encountered was estimating how much water to put into the beaker before heating; this was not easy as the water evaporated off and on several occasions we were left with not enough liquid in the beaker. To help with this problem I could have heated more than enough water and the poured the correct amount into another beaker, however, a lot of heat my have been lost in this way. A waterproof container may have also been helpful as it was have meant that no water to could be lost through evaporation.

Another factor could have been the humidity within the room on different days. This would have effected the cooling slightly but enough to make a difference. The slight humidity difference would have meant that the molecules would have had more energy and therefore speed up the cooling. A possible solution to this problem would be to have completed all experiments on the same day. This way it would be less likely for humidity levels to fluctuate too much. Another alternative may have been to use a sealed off laboratory

Finally, visibility was a problem. Light in the room and eyesight quality could have made a difference. Light in the room changed several times as the experiments were carried out on different days and therefore light would have been different. This could have been overcome lighting the lab with a certain light in order to keep the light a constant; also the same person could have been used to measure the thermometer. When considering eyesight, it is easy for mistake to be made as different people have different eye quality and perceptions of when visibility is none existent. Therefore the only way to overcome different perceptions is to use an electrical thermometer. This would overcome human error.

Overall I was pleased with how the experiments ran and how the results turned out. If I were to perform this experiment again I would attempt to use as many mechanical aids as possible so that I could exclude human error wherever possible.

Glen Baker April 07

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