Calorimeter, and Heat transfer

Calorimeter  can be define as a method or instrument used to obtain the quantity of heat Q transferred to a body .

Heat can be produced or transferred through these two methods

1. From one body to another(conduction, convection, radiation)
2. Production of heat From other energy (Electrical, nuclear, solar).

From one body to another

Heat is said to be transferred when a body at higher temperature is in contact with a body at lower temperature through conduction, conduction or radiation. The temperature of the two body will eventually become the same if there is no external production of heat from other energy source.

When a hot water is added to another cold water  in a bucket , the hot water loses heat while the bucket and the cold water gain heat until the temperature are the same .

In general

HEAT GAIN = HEAT LOSS

Heat gain by cold substance = Heat lost by hot substance

Determination of specific heat capacity of a solid by method mixture  

In this experiment,  the followings are required to determine the specific heat capacity of a substance e.g  Iron bob

1. Calorimeter and Stirrer
2. Thermometer
3. Iron bob with known mass

Methods

The copper calorimeter with the stirrer(picture above) is weighed and the mass is noted .

Water is then added to the calorimeter up to 2/3 of the volume and then weighed, the mass is also noted.

The initial temperature of the cold water is noted

The iron bob is heated in hot water and quickly transferred to the calorimeter and stired until the temperature of the mixure is thesame. The temperature of the hot water is noted.  And the final temperature of the mixture also noted

Calculations

   (reaction vessel)

  Where    is the specific heat capacity of the iron bob to be obtained.

Precautions

1. The calorimeter must be lagged to eliminate heat loss.
2. Stirring of the mixture must be started immediately the hot bob is transferred and must be done thoroughly.
3. The heated iron bob must be transferred as fast as possible to reduce heat lost during transfer.
4. Make sure the hot metal is covered with water in the calorimeter.

This experiment can be used to obtain the specific heat capacity C of any insoluble solid. For soluble solids , another liquid with known specific heat capacity can be used  to replace the cold water.

The same experiment can also be used to obtain the specific heat capacity of a liquid  with known specific heat capacity of the solid. In this case the liquid will replace the cold water and the result will be;

THEREFORE

Determination of specific heat capacity of a solid by Electrical method

The calorimeter  is as shown above.

1. Lagged calorimeter
2. Thermometer
3. Electric Heater
4. Iron bob

The same method is used in the first experiment

The source of heat is from the Electrical Heater

Heat loss from the Electrical Heater = Heat gain by the iron bob + Heat gain by the water + Heat gain by the calorimeter.

Energy from the Electrical souce = IVt

The current , voltage and time can be measured with Ammeter, voltmeter and stop watch respectively.

The same  method  can be used  to determine the specific heat capacity of  a liquid .

Heat lost by Electrical Heater = Heat gain by the liquid + Heat gain by the calorimeter

The same precaution apply to all these experiments to determine specific heat capacity  as stated in experiment 1

Error  due to parallax should be eliminated during reading  of the ammeter and voltmeter.

Read more about PHYSICS for High Schools