Grade 8 SCIENCE Heat and Temperature

10/06/15

Concepts to remember

• Work is done on an object when the force is applied to it. It covers the distance of the applied force.
• When work is done by an object it loses energy.
• When work is done on an object it gains energy.

• The energy of an object enables it to do work. 36
• A moving object has energy called energy of motion or kinetic energy.
• An object above a specified level has energy due to its position called potential energy.
• An elastic object that is stretched or compressed or twisted has energy called potential energy.
• Power is the rate of doing work or the rate of using energy.

Heat transfer happens around us all the time. Although we do not see how this process actually takes place, its effects are evident. In fact, we rely on these effects everyday in many of the activities that we do. Understanding the concepts behind heat transfer therefore helps us do our activities more efficiently. You have learned in previous grades that heat transfer takes place between objects or places of different temperatures, and that heat transfers from an object of higher temperature to an object of lower temperature. You have also learned that heat can be transferred through conduction, convection, or radiation, and that heat transfers either through moving particles or electromagnetic waves. Lastly, you also learned about some factors that affect heat transfer, like the conductivity of the materials. 

Remember that heat is the transfer of energy between objects or places because of difference in temperature. Heat exists as ‘energy in transit’ and it is not contained in an object. The energy that is actually contained in an object due to the motion of its particles is called thermal energy. The thermal energy of an object is changed if heat is transferred to or from it. Since the amount of heat transferred relates to the amount of change in thermal energy, the term heat in this module is also used to refer to the measure of thermal energy transferred.

Activity 1

Explaining hotness or coldness

This first activity deals with one of the major effects of heat transfer, which is temperature change. You will describe the hotness or coldness of an object in terms of its temperature. You will also compare the changes in the temperature of water to determine the relationship between the amount of heat transferred and the resulting temperature change.

Materials Needed:

• 3 identical containers
• Thermometer
• hot water
• tap water (room temperature)
• cold water

Procedure

1. Arrange the containers respectively 1(hot) 2(normal) 3(cold)
2. Measure the temperature of each container using a thermometer.

The activity will help you figure out:

• Heat is a transfer of energy between objects to temperature difference.
• Heat transfers from high temperatures to low temperatures