1. Lesson three

2. 1. The sun. 2. friction.

3.  It is a method to generate heat as a principle of converting the kinetic energy (mechanical energy) into heat energy.  The production of heat:-  Mechanical energy change into heat energy by friction.  Kinetic energy change to heat energy be friction.

4.  It is a form of energy which is transferred from the object of higher temperature to that  of lower one.  The temperature:-  It is the heat condition which state the direction of heat energy whether from or to the object when it comes in cannot with another.

10.  It is the transfer of heat through solids from the part of higher temperature to the part of lower temperature.

11.  It is transfer of heat in gases and liquid,where hot molecules which have less density rise up words ,while colder molecules which have more density fall down.

13.  It is the transfer of heat from hot object to another without any need for material medium through which heat transfers.

17.  The electric heater is placed at the bottom of the room.  When air around the heater is heated, its density decreases so, it rise up to the room, while the colder air falls down to be heated again and so on.  The heat of the sun does not reach to ground by convection or conduction.  it is not transferred by convection,because there is vacuum between the sun and the air and it is not transferred by conduction because the air is bad conductor of heat.

18.  Some of these application work by:-  The solar energy(permanent resource of energy).  The petro (non-permanent resource of energy).  the electricity (a renewable resource of energy).

19. The effect on the environment. The kind of energy resource. The resource of energy depending on it. The device Non-pollutedrenewable electricity Electric heater: Water heater: Non-pollutedpermanent The sun Solar heater: Non-pollutedrenewable electricity Electric stove: pollutedNon- renewable Petroleum derivation Gas or petrol stove: pollutedNon- renewable Natural gas Gas oven: pollutedNon - renewable coal Coal fire