1. Fill in the blanks:

1.

Device	Energy it uses	Energy it produces
Simple cell
Electric motor
Solar batteries cell in your calculator
Car engine
	Electric	Light
	Electric	Sound

2.

Device	Energy used	Energy produced
T elevision
C ellular phone (mobile)
S ewing machine
A larm clock

2. C a hoose the correct answer:

1. The mechanical energy of the ball at position A =…………………………

(kinetic energy only – potential energy only – kinetic energy x potential energy)

2. The work done to raise a book to a high shelf is stored in the book as……………energy.

(heat – potential – chemical)

3. The dynamo produces ………………energy.

(chemical – kinetic – electric)

3. Write the scientific term:

   Energy is neither created nor destroyed.
   The sum of potential energy & kinetic energy is constant.

4. Explain some of the harms of using nuclear weapons in wars.

… ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

5. Use the opposite figure to fill in the blanks.

1. The kinetic energy = the potential energy at position(s)……………………………….

2. The kinetic energy is maximum at position(s)………………………………………….

3. The potential energy is maximum at……………………………………………………

1. Ice cubes are placed in a glass of juice to make the juice cooler. Heat is transferred from the high temperature juice to the lower temperature ice. The ice melts & the juice is cooler.

2. Rub your hands together & notice that they become hot. As the speed of rubbing increases so does the heat energy.

3. W hen the cyclist presses the brakes to stop the bicycle, the tyres rub against the ground & become heated friction produced heat energy.

How is heat transferred through different mediums ?

1. Through solids:

• L eave a metal spoon in a cup of hot tea. Touch the end of the spoon outside the cup. It feels hot because heat was transferred in the spoon by conduction.

2. Put some tea dust in a beaker that contains water. Heat the beaker with Bunzen burner. Observe: how tea dust moves up then falls down in circles.

• Conclusion: when heated, the molecules of liquids move up & are replaced by cooler water, falling down. This way of heat transfer is called convection. Heat is transferred in liquids & gases by convection.

3. Heat is transferred from the Sun through space to the Earth by radiation.

A ir conditioners are placed in a high place in the room because cold air is denser than warmer air, therefore cold air moves downwards. Convection distributes cold air in the room.

Heaters are usually placed on the floor because the density of hot air is low, therefore hot air rises up. The heat is distributed in the room by convection.

Some domestic devices which produce heat are listed in the following table.

Device	Energy used	Energy produced	Effect on the environment
Gas heater & gas cooker	Chemical	Heat	Pollute the environment
Electric heater & cooker	Electric	Heat
Solar heater	Solar	Heat	Don’t Pollute the environment

Energy resources

1. The origin of energy resources & forms on Earth is solar energy.

2. Some energy resources are forever (permanent) like the sun, others are renewed like the wind. Fuel is not renewed when used, therefore it’s called non- renewable resource of energy.

Energy resources	Type (permanent, renewable or non – renewable)	Effect of its use on the environment.
Solar energy	Permanent	Not Polluting
Wind & water falls	Renewable	Not Polluting
Fuel & nuclear energy	Non – renewable	Polluting