To investigate three factors that affect the rate of cooling a liquid and to test these factors to see exactly how much they affect the rate of cooling water.
Aim
The aim of this experiment is to investigate three factors that affect the rate of cooling a liquid and to test these factors to see exactly how much they affect the rate of cooling water.
Background Information
* The specific heat capacity of a substance is the heat required to produce a 1?C rise in 1kg.
* The 'thirst' of a substance for heat is measured by it's specific heat capacity (c).
* Heat is measured in joules (J).
* The formula for heat received or given out is:
* Heat received or given out = mass ? temperature change ? specific heat capacity
* The formula for the heat received by water is:
* Heat received by water (J) = power by heater (J/s) ? time heater on (s)
* The formula for the specific heat capacity is:
* Specific Heat capacity = heat received by water
mass (kg) ? temp. rise
* The formula for the rate of energy loss is:
* Rate of energy loss = U value ? surface area ? temp. difference
* The U value for a specified heat conductor is the heat energy lost per second through it per square metre when there is a temperature difference of 1?C between its surfaces.
* The rate at which an object cools, i.e. at which it's temperature falls can be shown to be proportional to its area (A) to its volume (V):
* For a cube of side l
o A1 / V1 = 6 ? l 2/ l3 = 6 / l
* Finally, when there is a temperature difference between two bodies, energy is transferred from the hotter to the colder, until they reach the same temperature. This is known as the Zerath Law of Thermodynamics.
Identifying the Variables
The variables that affect the rate of cooling liquid that I am going to investigate in this coursework are:
Insulation
Insulators are bad conductors, so instead of taking in heat like conductors, they effectively act as a barrier to stop heating from passing through. Air offers about 15,000 times as much resistance to heat flow as a good thermal conductor such as silver does, and about 30 times as much as glass. Typical insulating materials, therefore, are usually made of non-metallic materials and are filled with small air pockets. They include magnesium carbonate, cork, felt, cotton batting, rock or glass wool, and diatomaceous earth.
The Volume of Liquid
The time a liquid takes to cool is proportional to the area of it and therefore the more the volume of liquid there is, the longer it will take to cool. If there is more water, the heat transfer rate will still be the same as if there was less water. Therefore it will take longer to cool a larger amount of water and there should be quite a definite pattern.
Conductors
If the container storing the water is made of a heat conductor, the water or other liquid would cool more quickly, as heat energy is being lost all the time, transferring from the water to the container. A heat conductor is any material that offers little resistance to the flow of heat energy. The difference between a conductor and an insulator, which is a poor conductor of heat, is that insulators stop the heat from escaping, but conductors absorb the heat.
Method
Experiment 1 - Insulation
This experiment is to investigate insulation and its affects on the rate of cooling a liquid.
Equipment
In this experiment I will use 3 glass beakers of capacity 200ml, 150ml of water, a Bunsen burner, a heatproof mat, a tripod, a thermometer that can measure between 0?C and 100?C, woollen lagging, corrugated cardboard and a stop clock. I will also use elastic bands to attach the material to the beakers.
Method
Before I start heating the water, I will attach woollen lagging to a 200ml capacity beaker ...
This is a preview of the whole essay
Method
Experiment 1 - Insulation
This experiment is to investigate insulation and its affects on the rate of cooling a liquid.
Equipment
In this experiment I will use 3 glass beakers of capacity 200ml, 150ml of water, a Bunsen burner, a heatproof mat, a tripod, a thermometer that can measure between 0?C and 100?C, woollen lagging, corrugated cardboard and a stop clock. I will also use elastic bands to attach the material to the beakers.
Method
Before I start heating the water, I will attach woollen lagging to a 200ml capacity beaker with an elastic band and corrugated cardboard to another beaker. The last beaker will have nothing on it, to act as a comparison to the other two.
I shall then heat 150ml of water to 100?C and put 50ml of water in each beaker, starting the stop clock as I do so. Every 40 seconds from then, I will check the temperature with the thermometer and record them on my results table. I shall continue recording the results until the time reaches 12 minutes.
Experiment 2 - Volume of Liquid
This experiment is to investigate the volume of liquid and its affects on the rate of cooling a liquid.
Equipment
In this experiment I will use 3 glass beakers of capacity 200ml, 150ml of water, a Bunsen burner, a heatproof mat, a tripod, a thermometer that can measure between 0?C and 100?C and a stop clock.
Method
I shall heat 150ml of water to 100?C and put 75ml of water in the first beaker, 50ml in the second beaker and finally I shall put 25ml of water in the third beaker, starting the stop clock as I do so. Every 40 seconds from then, I will check the temperature with the thermometer and record them on my results table. I shall continue recording the results until the time reaches 12 minutes.
Experiment 3 - Conductors
This experiment is to investigate conduction and its affects on the rate of cooling a liquid.
Equipment
In this experiment I will use 3 beakers of capacity 200ml made of glass, copper and aluminium, 150ml of water, a Bunsen burner, a heatproof mat, a tripod, a thermometer that can measure between 0?C and 100?C and a stop clock.
Method
I shall heat 150ml of water to 100?C and put 50ml of water in each of the three different material beakers of 200ml capacity. One of the beakers shall be made of glass, one shall be made from aluminium and one shall be made from copper. Every 40 seconds from then, I will check the temperature with the thermometer and record them on my results table. I shall continue recording the results until the time reaches 12 minutes.
Fair Test
Experiment 1 - In the first experiment I shall use the same water source for all the beakers and have the water at the same temperature when I start the stop clock. I shall use the same thermometer for all the beakers and I shall record all the beakers temperatures until they reach the same temperature. Finally I shall use the same material beakers for all of the different types of insulation and they will be all the same size and on the same material mat when cooling.
Experiment 2 - In the second experiment I shall use the same water source for all the beakers and have the water at the same temperature when I start the stop clock. I shall use the same thermometer for all the beakers and I shall record all the beakers temperatures until they reach the same temperature. Finally I shall use the same material beakers and they will be all the same size and on the same material mat when cooling.
Experiment 3 - In the third experiment I shall use the same water source for all the beakers and have the water at the same temperature when I start the stop clock. I shall use the same thermometer for all the beakers and I shall record all the beakers temperatures until they reach the same temperature. Finally I shall use the same size beakers, despite the fact that they are all different materials.
Prediction
Experiment 1 - I think that in the first experiment the beaker with no insulation will cool the quickest, then the corrugated card and finally the woollen lagging. I think this because in the beaker with no insulation, there is nothing except the glass of the beaker, stopping the heat from escaping, but with the woollen lagging and the card there is a barrier making it harder for the heat to escape.
Experiment 2 - I think that in the second experiment the beaker with the least amount of water in it will cool the fastest and the beaker with the most water will cool the slowest. I think this because the energy is constantly being transferred from the water, being lost, so if there is less water this process can occur more quickly.
Experiment 3 - I think that in the third experiment the good conductors, like aluminium and copper will cool more quickly than the bad conductor, glass. I think this because if the material of the beaker is made of a good conductor, the heat energy will be lost more quickly by being released into it, but if the material is an insulator, it will stop the heat from being lost from the beaker.
Results Tables
Experiment 1
No Insulation
Corrugated Card
Woollen Lagging
0 seconds
40 seconds
80 seconds
20 seconds
60 seconds
200 seconds
240 seconds
280 seconds
320 seconds
360 seconds
400 seconds
440 seconds
480 seconds
520 seconds
560 seconds
600 seconds
640 seconds
680 seconds
720 seconds
Experiment 2
75ml of water
50ml of water
25 ml of water
0 seconds
40 seconds
80 seconds
20 seconds
60 seconds
200 seconds
240 seconds
280 seconds
320 seconds
360 seconds
400 seconds
440 seconds
480 seconds
520 seconds
560 seconds
600 seconds
640 seconds
680 seconds
720 seconds
Experiment 3
Glass Beaker
Aluminium Beaker
Copper Beaker
0 seconds
40 seconds
80 seconds
20 seconds
60 seconds
200 seconds
240 seconds
280 seconds
320 seconds
360 seconds
400 seconds
440 seconds
480 seconds
520 seconds
560 seconds
600 seconds
640 seconds
680 seconds
720 seconds
Results
Experiment 1
No Insulation
Corrugated Card
Woollen Lagging
0 seconds
99?C
99?C
99?C
40 seconds
91?C
92?C
93?C
80 seconds
86?C
88?C
89?C
20 seconds
83?C
85?C
87?C
60 seconds
79?C
80?C
83?C
200 seconds
76?C
76?C
82?C
240 seconds
73?C
75?C
80?C
280 seconds
71?C
73?C
78?C
320 seconds
70?C
72?C
77?C
360 seconds
67?C
71?C
76?C
400 seconds
66?C
70?C
75?C
440 seconds
63?C
68?C
73?C
480 seconds
62?C
66?C
71?C
520 seconds
60?C
65?C
71?C
560 seconds
59?C
64?C
70?C
600 seconds
58?C
62?C
69?C
640 seconds
56?C
61?C
68?C
680 seconds
55?C
60?C
67?C
720 seconds
54?C
59?C
65?C
Experiment 2
75ml of water
50ml of water
25 ml of water
0 seconds
99?C
99?C
98?C
40 seconds
93?C
91?C
88?C
80 seconds
90?C
86?C
84?C
20 seconds
85?C
83?C
81?C
60 seconds
82?C
79?C
78?C
200 seconds
78?C
76?C
75?C
240 seconds
75?C
73?C
73?C
280 seconds
72?C
71?C
70?C
320 seconds
71?C
70?C
67?C
360 seconds
70?C
67?C
66?C
400 seconds
67?C
66?C
65?C
440 seconds
66?C
63?C
64?C
480 seconds
63?C
62?C
61?C
520 seconds
62?C
60?C
59?C
560 seconds
61?C
59?C
57?C
600 seconds
60?C
58?C
55?C
640 seconds
59?C
56?C
54?C
680 seconds
58?C
55?C
52?C
720 seconds
57?C
54?C
50?C
Experiment 3
Glass Beaker
Aluminium Beaker
Copper Beaker
0 seconds
99?C
98?C
99?C
40 seconds
91?C
93?C
93?C
80 seconds
86?C
88?C
90?C
20 seconds
83?C
84?C
87?C
60 seconds
79?C
80?C
81?C
200 seconds
76?C
76?C
80?C
240 seconds
73?C
74?C
80?C
280 seconds
71?C
73?C
78?C
320 seconds
70?C
72?C
76?C
360 seconds
67?C
71?C
73?C
400 seconds
66?C
70?C
70?C
440 seconds
63?C
68?C
67?C
480 seconds
62?C
67?C
65?C
520 seconds
60?C
65?C
63?C
560 seconds
59?C
63?C
60?C
600 seconds
58?C
60?C
58?C
640 seconds
56?C
58?C
54?C
680 seconds
55?C
54?C
52?C
720 seconds
54?C
52?C
49?C
Analysis
Experiment 1
From looking at the results from experiment 1, I can see that my prediction was indeed correct. I predicted that the beaker with no insulation would cool the quickest and the woollen lagging would take the longest to cool. At the end of the twelve minutes the 'No Insulation' column had reached 54?C while the 'Woollen Lagging' column had only reached 65?C, evidently showing that when there was no insulation around the beaker, the water cooled more quickly as there was nothing to stop the heat energy from escaping from the beaker, but when the woollen lagging was used it effectively acted as a barrier to stop heating from passing through the beaker and therefore more time is needed for the water in the beaker to cool down to the same temperature as a beaker with no insulation.
Experiment 2
From looking at the results from experiment 2, I can see again that the predictions that I made were correct. I predicted that the beaker with least water in it would cool the quickest and that is what happened. The largest amount of water used, 75ml, reached 57?C by twelve minutes and the least amount of water used, 25ml, reached 50?C by the end. This shows that the less water there is a container the faster it will cool. The water can only cool at a certain speed in one condition and as all the beakers had the same conditions the heat transfer rate remained the same in all the beakers. Therefore if there is less water, then the water will cool more quickly and if there is more water it will take longer to cool.
Experiment 3
From looking at the final set of results my predictions were once again quite precise. I predicted that the bad conductor, glass, would cool the most slowly and the best conductor, copper would cool the most quickly. The water in the glass container cooled to 54?C in twelve minutes and the water in the copper container cooled to 49?C in twelve minutes. This occurred like this because when water cools in a glass beaker the glass is not a good conductor so not much heat energy is being lost through the glass, but when the beaker is made out of a good conductor like copper, then the heat is being lost quickly through the beaker and therefore the water cools more quickly.
Evaluation
I think on the whole this investigation was a successful one, but we still ran into a lot of difficulties. When I first attempted the different volumes of water I found that my original quantities of water took far too long to cool and so I had to reduce the quantities of the water as we could only observe the results in our Physics lesson. On the experiments when I tested for insulation, I did not actually make a cover for the beaker of the same material insulation and therefore the results may not be that accurate. Most of the heat was lost through the top of the beaker so that is why the end temperatures do not greatly differ.
The equipment we used to take these readings could have altered the accuracy of the experiment if they were not that accurate themselves. The equipment that I assumed to be correct were the thermometers and the water baths. The factors that also limited my experiment were time, as I could only record results in my short hour Physics lesson and could only record up to twelve minutes to allow enough time for each of the experiments. Other factors may have also interfered with the experiments like different room temperatures for the different experiments and the water from the taps which may have varied in Ph slightly from experiment to experiment. These factors would not make significant changes to results, but it is worth noting them for reference.
The experiments that I carried out were as fair as I could make them with the limited resources that I was given to carry them out and any other errors in results are the results of equipment inaccuracy.
Daniel Sheedy 4RM
