Materials that prevent heat loss are called insulators. They can prevent three different types of heat loss;
Conduction of heat occurs mainly in solids. This process is where vibrating particles pass their extra vibration energy to neighbouring particles.
Convection of heat only occurs in liquids and gasses. Convection occurs when the more energetic particles move from the hotter region to the cooler region taking their energy with them.
“Radiation of heat is sometimes referred to as infer-red radiation” (taken from school text book). Heat radiation can travel through a vacuum. This process is different from the other two; it travels in straight lines and at the speed of light. This is the only way heat can reach us from the sun. Heat radiation travels through transparent matter like air, glass, and water. No particles are involved in this process; it is the transfer of heat energy purely by waves.
In this investigation I will be looking at conduction of heat through glass beakers. I aim to investigate what type of material is the best insulator of the glass beaker. After the experiment I intend to conclude which material is the better insulator, what affects its efficiency and why others didn’t perform as well?
To investigate this I will conduct an experiment. To conduct the experiment I will need the following set of equipment;
* Beaker x 5
* Digital stop watch x 5
* Pure water 200ml x 5 ( 1l )
* Black paper
* Bubble wrap
* Silver backed card
* Thermometer x 5
There are small samples of each material/insulator below.
I will boil some water using a kettle. I will then pour the hot water into a beaker; from here I must move fast before the temperature falls below my starting point. The beaker will be wrapped in one of the selected materials, supported by elastic bands. I will record the temperature of the water over a 20 minute period. I will take the temperature every 60 seconds.
I will do this for each of the above materials recording my results in a table as I conduct my investigation. I have chosen to do all the experiments at the same time due to lack of time. Once I have completed this method for all the materials, I will then conduct the method using no material. This will enable me to observe the effect on the rate of heat conduction on an un-insulated source.
Throughout conducting my investigation I will take a number of precautions to ensure my experiments fair. I will ensure that the water starts at the same temperature of 78c. I will use 200ml of pure water in all the beakers because different amounts of water will largely affect the cooling rate making the experiment inaccurate. Although the materials might be different in thickness, as you can see and feel on the previous page, it is important that they cover the same surface area i.e. one layer covering the whole side of the beaker.
I will also take a number of safety precautions whilst conducting the investigation. I will ensure the kettle is used safely throughout the experiment, and hot water is transferred securely. I will have to take into consideration that basic rules may be broken and pupils around me may run. This means that I will have extra careful that no-one bumps into me as it could be very harmful to others and me. In addition, if any spillage does occur I will have to clean it up as soon as possible and make others aware of it. I will be cautious when handling the beakers when the hot water is present.
My hypothesis based on the fact that the following will affect the efficiency of the material as an insulator,
The lighter the material in colour the better insulator it will be. I predict this because light colours are poor radiators, therefore they will reflect the heat back into the beaker if the lighter colour is on the inside.
The darker materials will absorb the heat and release it the other side so is a bad insulator and will cause rapid heat loss.
The thickness and density of the material will also have a significant impact on the materials efficiency. Air is a very poor conductor, so materials with lots of large air pockets will be good insulators i.e. the bubble wrap. For the material to have lots of air pockets it has to be less dense and quite thick. The air trapped in the pockets will also trap heat that has moved with particles. These factors will help to reduce heat loss.
From the above information I have been led to believe that a poor insulator will be thin, dark in colour with small if any air pockets, allowing heat convection and conduction which will increase heat loss rapidly. When first exploring this experiment I felt that the silver backed card would be the best insulator, but because of the evidence I have deduced I predict that the bubble wrap and polystryrene will be the better insulators.
From my results I can deduce that the rate of heat loss decreases is decreased dramatically by all insulating materials. This trend was ex[ected. All the results are very close but they clearly show that the best insulator from the selection of materials is the bubble wrap.
These results do not match my prediction entirely because I did predict that the polystyrene would be best aswell. But I can understand that it is more compact and has few air sockets to trap the heat. However it still does match my hypothesis because I predicted that the bubble wrap, which had the biggest air pockets, would insulate well. This means that the primary factor in preventing heat loss is stopping convection currents and trapping warm air. To my surprise the black card was seriously ineffecient.
The result marked in red in the polystyrene column at 15 minutes was the only anomalous result I could find. This may have been because of human error.
scatter graph on the next page.
In evaluating my experiment and the overall investigation I felt I achieved my aim and my results enabled me to clearly conclude from the experiment. In correlation to my method i feel that I completed the experiments clearly, safely, and with small difficulty and feel that it satisfied my aim. As far as I can see all my results are highly accurate and only one was anomalous.
If I conducted the experiment again I would use a wider variety of materials and take each experiment at a time. I would also increase the amount of times I did the experiment for each material to gain an average. I would do this because then I would be able to gain more accurate and reliable results. I would extend my experiment further by making sure that I investigated further into anomalous results and maybe trying to find a cooling rate or point of each insulation.
Overall I think my investigation was successful as it achieved the requirments of the set task and aim. It gained reliable results and clearly showed a trend.