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Prediction I predict that whenever there is a temperature difference , ehat energy will be transferred by conduction, convection or radiation fro the hotter to the cooler place. This increases the internal enrgy , which is the sum of the kinetic energy and the molecular potential energy of each molecule in an object, of the cooler atoms raising the temperature , and dreases the energy of the hotter atoms , lowering theirs. It continues until the temperature is the same across the region. Conductivity or thermal conductivity is a measure of how good a conductor a material is.
The rate of heat energy transfer through an object depends on the conductivity of the material and the temperature gradient. Temperature = t2 -t Gradient X t1, t2+ temps at point 1 and 2 X=distance This is the temperature change with distance along the material . The higher the conductivity and the steeper the gradient, the faster the energy transfer. Heat transfer to polystyrene cup Convection is a way in which heat energy is transferred in liquids and gases. If a liquid or a gas is heated it expands, becomes less dense and rises. Cooler, denser liquid or gas then sinks to take its place.
Thus convection current is set up. Coastal breezes used to explain convection currents We use leslies cube in my preliminary work to measure radiation, radiation is a way in which heat energy is transferred from a hotter to a cooler place without the medium, ehich is any substance through which a physical effect is transmitted. This can occur through a vacuum unlike the other two forms of heat transfer. Leslies cube is used to compare powers of radiation We did our own test with the Leslie cube in class here are our results. Start of experiment Heat lost during experiment.
Matt black 92 degrees 34 degrees 68 degrees 26 degrees Shiny black 92 degrees 32 degrees 68 degrees 23 degrees Shiny white 92 degrees 29 degrees 68 degrees 19 degrees These results sow that the side, which retains the most heat radiation energy, is the shiny white side and then the shiny black and then the matt black. This is why we will be using a shiny white polystyrene cup for the actual and preliminary work. Factors which affect different types of heat flow are, with radiation and conduction the type of material it is trying to transfer its heat energy to.
This is because they all have different atom arrangements which affects how well they are able to conduct heat energy, e. g. Metal conduct heat better than stone does. Convection can be affected by what types of material it is convecting through . e. g. Oil would convect differently with water. Different gases would also be differenyt and affect the rate of convection. To help make the table clearer and to finalise the actual test I decided to do some preliminary testing which would help me to understand things like if the cup I am using would work better with or without a lid.
Equipment used Polstyrene cup,thermometer, card board lid ( second test only ),kettle , stop watch and measuring cylinder. I measured out 100cm cubed of water , made sure that the thermometer was at the correct temperature therefore making sure that the water was. I used a polystyrene cup with out a lid on in my first test and with a lid on in my second, this was to see if I would get better results with or without it. These are the rwaults which I gained. Heat energy lost Heat energy lost With out lid With out lid With lid With lid 70 degrees and above 25. 5 degrees.
Average 21. 33 degrees 18. 0 degrees Average 18. 0 degrees 16. 0 degrees 18. 5 degrees 22. 5 degrees 17. 5 degrees 50 degrees and above 8. 0 degrees Average 17. 25 degrees 10. 0 degrees Average 10. 5 degrees 10 degrees 10. 0 degrees 16. 5 degrees 11 degrees 30 degrees and above 8. 0 degrees Average 7. 33 degrees 5. 5 degrees Average 5. 5 degrees 11. 0 degrees 5. 0 degrees 3. 0 degrees 6. 0 degrees From this chart you can see that without the cardboard lid the results atre very random and this means that the heat is able to fluctuate greatly as you can tell from my results.
I have therefore decided to have a lid on the cup as the results with the lid on seem a lot more constant and the heat isn’t allowed to fluctuate as much. I suspect that I will find that heat energy will be lost mostly conductivity and convection rather than radiation as I have tried to reduce the effects of this to as little as possible . For my acual test I will change the integers at which heat is lost from e. g. instead of going 70 degrees and above to 50 degrees and above I will try to have exactly 70 degrees and exactly 65degrees, I will then be able to draw more accurate results from this.