To investigate three factors that affect the rate of cooling a liquid and to test these factors to see exactly how much they affect the rate of cooling water.

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Aim

The aim of this experiment is to investigate three factors that affect the rate of cooling a liquid and to test these factors to see exactly how much they affect the rate of cooling water.

Background Information

* The specific heat capacity of a substance is the heat required to produce a 1?C rise in 1kg.

* The 'thirst' of a substance for heat is measured by it's specific heat capacity (c).

* Heat is measured in joules (J).

* The formula for heat received or given out is:

* Heat received or given out = mass ? temperature change ? specific heat capacity

* The formula for the heat received by water is:

* Heat received by water (J) = power by heater (J/s) ? time heater on (s)

* The formula for the specific heat capacity is:

* Specific Heat capacity = heat received by water

mass (kg) ? temp. rise

* The formula for the rate of energy loss is:

* Rate of energy loss = U value ? surface area ? temp. difference

* The U value for a specified heat conductor is the heat energy lost per second through it per square metre when there is a temperature difference of 1?C between its surfaces.

* The rate at which an object cools, i.e. at which it's temperature falls can be shown to be proportional to its area (A) to its volume (V):

* For a cube of side l

o A1 / V1 = 6 ? l 2/ l3 = 6 / l

* Finally, when there is a temperature difference between two bodies, energy is transferred from the hotter to the colder, until they reach the same temperature. This is known as the Zerath Law of Thermodynamics.

Identifying the Variables

The variables that affect the rate of cooling liquid that I am going to investigate in this coursework are:

Insulation

Insulators are bad conductors, so instead of taking in heat like conductors, they effectively act as a barrier to stop heating from passing through. Air offers about 15,000 times as much resistance to heat flow as a good thermal conductor such as silver does, and about 30 times as much as glass. Typical insulating materials, therefore, are usually made of non-metallic materials and are filled with small air pockets. They include magnesium carbonate, cork, felt, cotton batting, rock or glass wool, and diatomaceous earth.

The Volume of Liquid

The time a liquid takes to cool is proportional to the area of it and therefore the more the volume of liquid there is, the longer it will take to cool. If there is more water, the heat transfer rate will still be the same as if there was less water. Therefore it will take longer to cool a larger amount of water and there should be quite a definite pattern.

Conductors

If the container storing the water is made of a heat conductor, the water or other liquid would cool more quickly, as heat energy is being lost all the time, transferring from the water to the container. A heat conductor is any material that offers little resistance to the flow of heat energy. The difference between a conductor and an insulator, which is a poor conductor of heat, is that insulators stop the heat from escaping, but conductors absorb the heat.
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Method

Experiment 1 - Insulation

This experiment is to investigate insulation and its affects on the rate of cooling a liquid.

Equipment

In this experiment I will use 3 glass beakers of capacity 200ml, 150ml of water, a Bunsen burner, a heatproof mat, a tripod, a thermometer that can measure between 0?C and 100?C, woollen lagging, corrugated cardboard and a stop clock. I will also use elastic bands to attach the material to the beakers.

Method

Before I start heating the water, I will attach woollen lagging to a 200ml capacity beaker ...

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