Determine which materials make the best insulators and determine the factors affecting heat loss from a container.

Aim:

To determine which materials make the best insulators.
To determine the factors affecting heat loss from a container.

Fair Test:

I must make sure that the tests are fair by being very accurate when measuring the temperatures of the beakers with boiling water in them, so that I end up with results that will indicate which material is the best insulator.

In this investigation it is important that I use containers made of the same size, and same shape, with the same volume of water, at the same temperature. This is called ‘controlling the variables’, which will help me carry out the investigation as accurate as possible.

Theory:

The four main types of heat transfer are the following:

- Convection involves the movement of molecules and so it can only occur in fluids (liquids and gases), where the molecules can move within the body of the fluid. Convection currents are examples of floating and sinking. When part of a liquid or gas is made warmer than its surroundings it expands and rises because it is less dense. The air next to the icebox in a fridge is cooled and so it contracts. The cold air sinks because it is denser than the warm air below it. This movement of air is called a convection current. A dye in the form of a crystal or an ice cube can be used to see convection currents in water.

- Conduction is the main way in which energy transfers take place in solids, but it also applies to liquids and gases. Good conductors are needed to transfer the energy of the hot water in a radiator to the air outside and the energy from the heating element of a kettle into the water.

When one part of a material is hotter then another, the molecules in the hotter part have more energy than the surrounding ones. Heating a substance causes increased motion of the atoms and molecules. In a gas this means that the average speed of the atoms and molecules increases, but in a solid or a liquid it leads to increased vibration. Atoms and molecules do not exist in isolation, and they are continually interacting and swapping energy with their neighbours. The transfer of energy from energetic molecules to those with less energy is responsible for conduction.

Gases are poor at transferring energy in this way because the molecules are relatively far apart, compared to a solid or liquid. The more energetic molecules in part of a gas that has been heated travel large distances, in molecular terms, between collisions and so it takes them longer to transfer energy to other molecules.

- Radiation is when the warm water particles vibrate the water particles next to them. This will give them more energy and will make the water there warmer. The water particles at the top of the can will radiate the heat energy into the surrounding air. For heat to radiate it does not need to be in contact with matter. Heat can radiate for some thing to another body through a complete vacuum, this is how the sun heats up the earth. This process can also be called the Wave Motion.

- Evaporation is the process by which particles from a liquid form a vapour. Perfumes are designed to evaporate over a time period of several hours. The appetising smell of cooking food is due to evaporation. Evaporation is important to us when we are in a hot climate. This is because liquids need energy to evaporate, and they take this energy from their surroundings. You can feel the coding effect if you put a drop of a liquid on your skin that evaporates easily.