Convection functions because heated fluids rise and cooled fluids fall, (due to their lower density). A heated fluid will rise to the top, exude heat away and then fall to be re-heated, and this will continue. Convection is the transfer of heat by the movement of heated parts in a liquid or gas. It is also the circulatory activity that occurs in a fluid which is at a varying temperature, caused by the disparity of the density of fluid at different temperatures and the exploit of gravity.
The flow of heat by conduction occurs via collisions between atoms and molecules in the substance and the subsequent transfer of kinetic energy.
Conduction is the transfer of heat through a substance by molecular action or from one substance by being in contact with another, a hot substance and a cold substance. In Conduction the heat is passed on by vibration in a solid. Metals are better conductors than non-metals. This is because the heat is carried by free electrons that can carry the energy around the metal and give it to other electrons and ions.
Radiation is energy that is radiated or transmitted in the form of rays or waves or particles. Hot objects emit mainly Infrared radiation, which can pass through a vacuum, i.e. no medium is needed for its transfer. How much radiation is given out or taken in by an object depends on its surface.
A conductor is a material which allows an electrical current to transfer through it easily. Good conductors are usually metals. The antonym of a conductor is an insulator; an insulator is a material which allows electrical currents to transfer through it easily, i.e. non metals.
Heat is a form of energy that is transferred by a difference in temperature.
Temperature is a measure of the heat content of the atmosphere. The molecular motion of a substance creates energy, which can be measured in terms of the heat it generates.
METHOD
Gather all equipment.
Place the cotton wool round the whole outer edge of the copper can and attach it carefully with an elastic band.
Carefully boil the water in the kettle.
Carefully pour the required amount (40ml) into the measuring cylinder.
With the required amount of water fill the copper can covered completely in cotton wool.
Place the thermometer in the boiled water and then instantly start the stopwatch.
Record the temperature of the boiled water within the can after every 10 seconds for 100 seconds.
Now repeat this method for the two remaining materials.
PREDICTION
I predicted that Cotton Wool will be the best insulator of heat. I choose cotton wool because cotton wool is a warm thick material used to make clothes and other thermal gear. Another reason for choosing Cotton Wool would be that the actual material seems to be thick and the fibres look and feel compact. This would keep the heat compressed within the copper can, allow no eat to escape.
A FAIR TEST
To insure accurate and reliable results:
- Read the water from the meniscus.
- Always be extremely careful whilst pouring water.
- The starting temperature of the water should be the same for each material.
- Place thermometer in the same position for each copper can and material experiment.
- Try not to move the thermometer while the experiment is taking place. This could effect the temperature.
RESULTS
CONCLUSION
From these results we can gather that the most efficient insulator of heat out of the three materials chosen is Cotton Wool. This is what we had expected and predicted as a group.
To make our experiment accurate and to ensure a fair test we carried out the experiment twice on each material. We used the same starting volume and temperature of water in each experiment for each material, on each of the six tests carried out.
The Cotton Wool was always at a higher temperature than the Aluminium Foil and the Bubble Wrap throughout the whole experiment. This concludes that cotton wool is the best insulator of heat out of the three materials.
Evaluation
I (we) have made the investigation a fair test because we used the same volume of water for each material; we also made sure the starting temperature for each material was the same. Another thing we did to make the experiment fair was to test each material twice, to congregate an average temperature every 10 seconds. We could have made this experiment more accurate by testing each material more times. This would give us a more dependable average of result for each material. A additional modification we could have made to our experiment is we could have wrapped each copper can with more care to cover the whole of the tin. This would also insure that the minimum amount of heat could escape. This would then give us a more precise and reliable reading for that material. With reference to the new improvements we could have made the best insulator of heat between these three materials: Cotton Wool, Bubble Wrap and Aluminium Foil may have changed.
