What affects the rate of heat transfer through - Sample Essay
Conduction- of heat mainly happens in solids i. e. metals. Conduction of heat is the process where vibrating particles pass on their extra vibrations of energy to neighbouring particles. Heat is carried through the metal by freely moving electrons; they diffuse from the hotter region to the colder region through the metal. Making all metals bad insulators but a good conductor of electricity (good conductors of heat are good conductors of electricity) because of the motion of free electrons. Conduction will take place in this experiment because there is a metal can used to reduce this I will use different types of materials.
> Convection- of heat occurs only in liquids and gases. Gases and liquids are usually free to move (much more than a solid) and that allows them to transfer heat by convection which is much more process than conduction (convection simply can’t happen I solids because particles can’t move). Convection happens when energetic particles move from the hotter region to the colder region- and take their heat energy with them. When the more energetic particles (hotter particles) get somewhere colder they then transfer their energy by their usual process of collisions, which warms up the surroundings.
In order to stop convection in this experiment I will put a lid over the can to stop it. This is why I will use two different types of materials in each test, one of he materials will be the lid and the other will be the material which will be covered around the can to limit conduction and radiation. So as the particles rise the hotter particles will bounce off the lid and remain in the can to keep the water warm or at the optimum temperature 500c. > Radiation- this is the transfer of heat from a hot object in the form of waves.
Heat radiation can also be called infrared radiation, and it consists purely of electromagnetic waves of a certain frequency. It’s just below visible light in the electromagnetic spectrum. Heat radiation is different from the other two methods of heat transfer in quite a few ways. It travels in straight lines at the speed of light. It travels through vacuums. This is the only way that heat can reach use from the sun. Its behaviour is strongly dependent on the surface colour and texture. This definitely isn’t so for conduction.
Generally dull rough surfaces absorb more heat than bright polished shiny surfaces, and bright polished shiny surface, and bright surfaces reflect more energy than dull surfaces. Dark matt surfaces absorb heat radiation falling on them much more strongly than bright glossy surfaces such as gloss white or silver. In order to limit radiation I will use dull black surfaces, a white wool material and shiny silver foil. I think that the white wool material will keep the heat energy inside the can therefore it will stay hottest longest and because of the internal air spaces within the wool.
Aim My aim is to find the best insulator at keeping water at 500c, which will be the optimum temperature. I will make this possible by using two different types of materials having different colours and properties in each test; altogether I will do three tests. Each test will be done three times to ensure that I get the best results possible. Prediction I predict that by using different materials (insulators) wrapped around an Aluminium can. I will be able to see different rates of heat loss by the materials.
I predict that the most successful at sustaining heat will be the non-metals. I predict that as time increases the temperature will decrease. I predict that the plastic lid and the wool around the metal can would be the best insulator because plastic is a commonly used material for insulating household utensils. I predict that the shiny surface of the plastic will decrease radiation by reflecting heat back allowing it to slow down heat loss. I predict that the wool would also help to decrease radiation by because of the internal air spaces, which will trap the heat.
I predict that the second best insulator at keeping heat in would be the foil and white lid because the shiny white surface will decrease radiation by reflecting heat back allowing it to slow down heat loss. The worst insulator would be the cardboard and black lid because the structure of the cardboard is quite spaced out so them spaces will cause the heat escape quite easily. Apparatus required carrying out experiment o Measuring cylinder o Water (at 500c) o Stop watch o Thermometer o Metal can Materials o Plastic lid and Wool.