In this investigation I am going to survey the factors that affect heat loss from a beaker filled with 55ml of hot water. This will be done by using a numerous amount of materials.
Factors which affect heat loss from a beaker of hot water:
– Mass of H2O
– Size of beaker
– Temperature Difference
– Material Colour
– Air Pressure
– Relative Humidity
Forms of heat loss:
Radiation
This is the loss of energy, in this case heat energy, through the atmosphere via electromagnetic waves. (This gives it the ability to travel through a vacuum, i.e. the sun shining through space to Earth.) When this energy reaches an object it is absorbed by it. The energy absorbed causes particles in the object to vibrate, and so it heats up. The hotter an object is, the more energy it has and therefore more radiation will occur. Also the larger the surface area of an object, the more energy it will radiate. Dull coloured objects radiate more energy than shiny objects.
Convection
Convection is the expansion of particles when they are heated. When a water is heated, the particles within the substance expand and become less dense that normal.
Due to this decrease in density the particles rise through the substance, and at the surface of the water some of the particles evaporate. As more water evaporates, more and more energy is lost and so the water cools down and when evaporation occurs the object that the substance is evaporating off cools. (This is shown well when you get out the shower and you feel cold because the water is evaporating off of you). When the particles move away from the heat source or are so expanded that the particles are not passing heat from one to another, the particles cool. When they cool they compress back to their original density, which causes them to fall to the bottom of the water. As they are now tightly packed they heat is conducted from one particle to another and they heat, expand, rise, cool and so on as the cycle continues. This cycle is called convection current..
Conduction
Conduction can take place in solids, liquids and gases. When a material is heated the particles nearest to the heat gain kinetic energy. They then start to vibrate faster due to this energy and as they do they touch other particles and transfer the kinetic energy to them. This process is repeated and the energy is transferred through out the object from hot regions to cooler regions. As the water looses heat from the sides of the beaker, conduction will cool the mass of the water. Conduction will also occur through the sides of the beaker and then radiate and through the base.
Diagram/Apparatus
Method
– Collected and set up apparatus.
– Filled beaker with hot water
– Placed beaker on a table and timed for 600s whilst taking down results every 20s. These results were used as a control.
– Then filled up beaker again with hot water.
– Placed beaker carefully in large beaker
– Recorded starting temperature and then timed for 600s taking down results every 20s.
– This process was repeated 3 more times with varied materials.
Prediction
I predict that heat will be mostly lost through convection. This is because as hot water rises to the top it will evaporate and therefore heat will be given off. I believe that conduction will be second most deadly to heat loss, as heat will escape through the sides of the beaker and then escape out of the gaps of the large beaker or again through the sides. Radiation will be the least effective to heat loss, as foil will be wrapped around the beaker. This is because dull objects radiate more energy than shiny.
I think heat loss will be most effective when no foil is wrapped around the large beaker and when there is no insulation between it because then conduction and convection take their role therefore losing the most heat. Whereas I think heat loss will be least effective when there is foil wrapped around the large beaker and when there is insulation in-between. This is because convection is the only form of heat loss that can take place without struggle therefore losing the least heat.
Obtaining Evidence
The following factors will be considered when providing a fair test:
– The starting temperature is the same
– The thermometer is no touching the beaker sides
– The foil is wrapped fully round
– The same volume of water is used (55ml)
– The readings and timings should be constant
The following factors will be considered when providing a safe test:
– Standing up so if water spills we can move quickly
– No running
– Pour water carefully
– Let beaker cool down
Results
We first had to take a control so that we could compare it to the other results i.e. leaving the beaker by itself on a bench for 600s.
Time/s
Temperature/?C
0
80
20
79
40
77
60
76
80
74
100
73
120
71
140
70
160
69
180
68
200
66
220
65
240
64
260
63
280
62
300
61
320
60
340
59
360
58
380
57
400
56.5
420
56
440
55
460
54.5
480
53.5
500
53
520
52.5
540
51.5
560
51
580
50.5
600
50
Time/s
Temperature/?C
0
80
20
79
40
78
60
77.5
80
76.5
100
76
120
75.5
140
75
160
74
180
73.5
200
73
220
72.5
240
72
260
71.5
280
71
300
70.5
320
70
340
69.5
360
69
380
68.5
400
68
420
67.5
440
67.5
460
67
480
66.5
500
66
520
66
540
65.5
560
65
580
65
600
64.5
Time/s
Temperature/?C
0
80
20
78
40
77
60
76
80
74.5
100
73.5
120
72.5
140
71.5
160
71
180
70
200
69
220
68.5
240
67.5
260
67
280
66
300
65.5
320
65
340
64
360
63.5
380
63
400
62.5
420
62
440
61
460
60.5
480
60
500
60
520
59.5
540
59
560
58.5
580
58
600
57.5
Time/s
Temperature/?C
0
80
20
79.5
40
79
60
78.5
80
78
100
77.5
120
77
140
76.5
160
76
180
75.5
200
75
220
74.5
240
74
260
74
280
73.5
300
73
320
72.5
340
72
360
72
380
71.5
400
71
420
71
440
70.5
460
70
480
70
500
69.5
520
69
540
68.5
560
68.5
580
68
600
68
Time/s
Temperature/?C
0
80
20
79
40
78.5
60
78
80
77.5
100
77
120
76
140
75.5
160
75
180
74.5
200
74
220
73.5
240
73
260
72.5
280
72
300
71.5
320
71
340
70.5
360
70
380
69.5
400
69
420
68.5
440
68.5
460
68
480
67.5
500
67
520
67
540
66.5
560
66
580
65.5
600
65
Analysing Evidence and Concluding
By using the control you can compare it to the other results and you can see that by using insulation and double glazing heat loss can be prevented. The control finished ate 50?C. The heat was lost to the surroundings including the bench through conduction.
1st Experiment: Cotton Wool and Cork
Once the experiment started you could already see after 1 minute that the insulation was helping to prevent heat loss. This is because after a minute it was 77.5?C and the control after a minute was 76?C so there was a 1.5?C difference in temperature. After 10 minutes the end temperature was 64.5?C. This makes a 14.5?C difference between the control.
2nd Experiment: No cotton wool and Cork
This experiment was very slow starting and was losing lots of heat during the beginning but as time passed the heat loss reduced. The final temperature was 57.5?C after 10 minutes. This makes a 7.5?C difference between the control. This shows us that the double glazing does prevent heat loss.
3rd Experiment: Foil, Cotton Wool and Cork
This experiment had the most insulation. After 1 minute it was 78.5?C which meant it had only dropped 1.5?C. The final temperature was 68?C after 10 minutes. This gave it a huge 18?C difference between the control.
4th Experiment: Foil, No Cotton Wool and Cork
This experiment was constant and decreased in temperature at a steady rate. The final temperature was 65?C after 10 minutes. This made a 15?C difference between the control. Foil prevented heat loss dramatically.
Evaluating
Looking at all the experiments we can now determine which materials were best at preventing heat loss. Here is a table with the statistics of how much heat was lost (all these experiments had double glazing):
Cotton Wool and Cork: 15.5?C
No Cotton Wool and Cork: 22.5?C
Foil, Cotton Wool and Cork: 12?C
Foil, No Cotton Wool and Cork: 15?C
After looking at this table you can see that the most conserved single material was foil
as it prevented the most heat from going through. I no this because even when there was no cotton wool and cork it still came second in preventing heat loss. This proves that shiny objects radiate a little amount of energy. Although foil prevented the most heat loss cotton wool and cork still prevented conduction by having cotton wool between both beakers and by placing a cork underneath the beaker.
This means that foil would have a lower U-Value than the other materials because it is a better insulator.
After completing all the experiments I can say my prediction was correct. This is because the 3rd experiment finished on 68?C meaning it only lost 12?C in 10 minutes. All the other experiments had lost the more heat meaning this one had the most insulation. I also predicted that the 2nd experiment would lose the most heat. This was correct again as it had the least insulation except for double glazing which still prevented 7.5?C.
Anomalies
– We should have recorded the room temperature before and after to see if it had an effect on the results.
– Should have closed all windows to make sure that no drafts came in.
– The cork was not always up right.
Improvements
There are many ways we could have improved the experiment. Here are a few:
– Tested out more materials i.e. black card and foam.
– Made the experiment longer
– Use lid for the beaker to stop evaporation occurring
– Use more beakers
We could also repeat the experiment again but take it further and calculate U-Values which then would have enabled us to calculate heat energy lost per second using this equation:
Heat energy lost per second = U-value (W/m2�C) x area (m2) x T (�C)
