What factors affect the cooling of hot water in a container?

Method:

Each time the experiment is performed the insulating material will be changed, but to make it a fair test, we will keep constant:

* The beaker we used

* The volume of water we used

* The temperature of the water

* The length of the experiment

* The time we measure the each of the readings

* The same liquid we'll conduct the test with e.g. water

* The material we perform the experiment on e.g. wood.

We will use a standard glass beaker and fill it up to 200ml. The starting temperature we will use will be 80°C and we take the reading of the thermometer every 30 seconds over a 4-minute period. We will simultaneously conduct the experiment, therefore 3 results would be obtained in the same amount of time of performing one. Having three sets of results would make the results more accurate and reliable because we could see and compare them, and if one was wrong we could clearly see, also we can workout the average.

I will use the following apparatus in my experiment:

* Kettle

* Glass Beaker

* Thermometer

* Stopwatch

* Silver foil

* Cardboard

* Small bubble wrap

* Large bubble wrap

* Nylon

* Foam

* Sellotape

* Scissors

To carry out the investigation I will use the following steps:

. Cut appropriate size of the insulating material and Sellotape all the way around the sides of the beaker. Cut an extra piece to go over the top but do not situate until step 3. (Placing the material around the sides decreases the amount of radiation, on top, reduces convection, and for conduction the science room table is made out of wood. This is a good insulator of heat so you can perform on that. Putting some of the listed insulation materials under the beaker could cause the beaker to topple over, so it would be safer and wiser to just stick with the table).

2. Boil water in the kettle and then pour the water into the beaker, and fill up to 200ml. Insert Thermometer.

3. When the temperature falls to about 82°C securely fit the extra material over the top but leave room for the thermometer to stay in. (make sure you can clearly still read off the thermometer).

4. By the time you have done step 3 the temperature should have fallen to 80°C. Therefore you should now begin the experiment. Start the stopwatch.

5. Every 30 seconds record the current temperature. Do this for a total of 4 minutes.

6. With the results obtained, take off the material around the beaker and pour the water down the sink.

7. Repeat these steps until you have a performed on all of the insulating materials.

To present my results I will use a table and graph of temperature and the average end temperature. I will look at my graph and by the way the results turn out, I can tell what was the most poorest and best insulator to help write in my conclusion.

Diagram:

Thermometer

Water

200 ml

Insulating

material

(held by

Sellotape)

Wooden table

Beaker

Results:

Time taken Sec. / Temperature in °C

0 30 90 120 150 180 210 240 270

Insulation

Material

Large bubble wrap

80 80 80

79 80 79

78 79 78

78 79 77

77 78 76

76 78 75.5

75.5 77.5 75.5

75 77 75

75 76 74.5

Small bubble wrap

80 80 80

79 80 79

79 80 78

78 79 77

77 77 76

77 77 76

76 76 76

76 75 75

75 74 75

Card

80 80 80

79 79 79

77 78 79

76 77 78

75 76 77

75 75 77

74 74 76

74 73 75

73 72 74

Nylon

80 80 80

80 80 79

79 79 79

78 78 79

78 77 78

77 77 77

76 76 76

76 75 75.5

75 74 74

Foam (5cm)

80 80 80

80 80 79

80 79 79

79 79 78.5

79 78 78

78.5 77 78

78 76 77

77 76 76

77 75 76

Silver foil

80 80 80

80 79 80

80 78 79

79 77 79

78 77 78

77 76 77

77 76 77

76 75 76

75 75 75

Averages:

Insulating material

Av. end Temp. °C

Large bubble wrap

75.2

Small bubble wrap

74.7

Card

73

Nylon

74.3

Foam (5cm)

76

Silver foil

75

Insulating material

Difference from start temp to end

Large bubble wrap

4.8

Small bubble wrap

5.3

Card

7

Nylon

5.7

Foam (5cm)

4

Silver foil

5

Conclusion:

By looking at the graph and the tables you can clearly see that the foam was quite clearly the best insulator out of all those materials. This confirms my prediction; that the foam is a good insulator material compared to the other ones listed. Air did play a big part in this experiment by getting trapped in the foam and acting as the real insulator. However not far behind foam was the silver foil. This did not contain any air so how did it act as an insulator? Well the shiny-silver reflected the radiation back into the beaker rather than conducting it and passing it outwards. A good example of this is a thermo flask, and how it reduces the processes of conduction, convection and radiation quite dramatically. It prevents conduction by having a gap between two walls, one containing the actual fluid and the other holding the fluid container. This gap creates a vacuum which radiation could pass through, however a shiny-sliver coating it placed in the inside container. This reflects most of the radiation back into the fluid. Convection is prevented by the lid being air-tight closed, so no cold air can enter, also if the fluid is filled to the top inside the flask less convection is likely to happen because there is a smaller amount of normal air to cause it. The bubble wraps contained air so that's why they showed to be quite sufficient in keeping the water warm. Followed was nylon, this is a material which we wear, it keeps the object warm by the tiny little air sockets in the material but not as much air as other materials. Card was the material that decreased the most, it is quite thin, solid all the way through with no spaces for air, and it was a dull dark brown colour. If a warm object is wrapped it a dull colour it acts as a good radiator of heat and so the object cools down. Overall changing the insulating material of an object has proven to have quite an impact on its temperature.

Evaluation:

Fortunately we didn't encounter any major problems whilst conducting this experiment. Just minor ones such as it was quite hard wrapping the foam around the beaker, but we managed to overcome it with some extra Sellotape.

On the basis of this experiment I would say it is a reasonably fair test. However some slight factors could have caused a very little difference. E.g. the thermometer sticking out left little gaps. Because the material going over the top sometimes didn't go all the way around the thermometer which didn't form an tight seal, so cold air etc. could have got in and distorted a bit of the experiment. Another very small factor is that the table we conducted our tests on had tiny little divots in them in some places. This could have caused a very slight difference because in- stead of conducting out it would have radiated out.

. . . . .

conduction Divot causing radiation from

beaker instead of conduction

I believe my results are fairly accurate and reliable as I gathered three sets of results. To make them more reliable I could have performed more tests, but there simply wasn't time to. From what I can see there isn't any anomalies, which is quite fortunate really. As it shows the test was conducted well. I feel that to get the best accurate and most reliable results, it should be performed in a proper laboratory with much more precise apparatus e.g. a digital thermometer.

Other experiments I could do to check if my conclusion is right are to record the temperature fall in a thermo flask compared to a normal flask.

To extend the investigation I could choose another factor e.g. volume of water, to examine or mix the current insulating materials and see what affect it has. E.g. putting silver foil under the foam would surely keep the water very hot.