I am investigating the rate at which heat energy is lost and heat transfer happens when a beaker of boiling water is wrapped in different materials.

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For this piece of coursework, I am investigating the rate at which heat energy is lost and heat transfer happens when a beaker of boiling water is wrapped in different materials. These experiments involved the temperature of hot water being recorded at different times in a glass beaker.  Heat is generally transferred by conduction, convection and radiation.

Energy transfer in solids is by means of CONDUCTION.

CONDUCTION

Materials that allow thermal energy to transfer through them quickly are called CONDUCTORS. Those that do not are called INSULATORS. If one end of a conductor is heated the atoms that make up its structure start to vibrate more vigorously. As the atoms in a solid are linked together by chemical bonds the increased vibration can be passed on to other atoms. The energy of movement (kinetic energy) passes through the whole material.

Metals are particularly good conductors because their structure contains freely moving electrons, which transfer energy very rapidly. Air is a good insulator and reduces thermal transfer by conduction. As air is a gas there are no bonds between the particles and so energy can only be transferred by the particles colliding with each other. To obtain the best results the air needs to be trapped so that energy cannot be transferred by convection. Conduction cannot occur when there are no particles present, so a vacuum is a perfect insulator.

Examples of good conductors are metals such as gold, silver and copper - they will conduct heat readily.  Materials that are good thermal conductors tend to be good electrical conductors also.  Materials such as glass have much smaller heat transfer values and are poor heat conductors.

CONVECTION

Convection occurs in liquids and gases because these materials flow (which is why they are described as ‘fluids’). Convection occurs when hot fluids rise and cold fluids sink. The circulation of fluids that this causes is called a CONVECTION CURRENT. The particles in a fluid move all the time. When a fluid is heated, energy transferred to the particles causing them to move faster and further apart. This makes the heated fluid less dense than the unheated fluid. Consequently, the less dense warm fluid will rise above the denser, colder fluid. This is how the thermal energy id transferred.

If a fluid’s movement is restricted, then energy cannot be transferred. That is why many insulators, such as ceiling tiles, have trapped air pockets. Wall cavities in houses are filled with fibre to prevent air from circulating and transferring thermal energy by convection.

RADIATION

Radiation, unlike conduction and convection, does not need particles at all. Radiation can travel through a vacuum. All objects take in and give out infrared radiation all the time. Hot objects radiate more infrared than cold objects. The amount of radiation given out by an object depends on its temperature and on the object’s surface. The surface of an object also determines how good it is at absorbing infrared radiation.

In order to carry out this Physics coursework, I intend to focus on how extra layers of a material affect the rate at which heat is lost from a beaker containing water. I will repeat the experiment several times by adding an additional layer of the material to my beaker each time.

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During the investigation, I will be recording the results from my experiments in order to analyse them on completion of the practical work. I will be able to take a close look at my results and see whether or not they confirm my thoughts stated in my hypothesis. I will then be able to evaluate my performance and results and try to understand where I went wrong, if necessary.

Before carrying out the experiment, certain factors need to be taken into consideration as they can make a significant difference to the experiment.

The factors that need to be considered are:

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