Download First term Science Al – Karma Language School Prep 1 Revision on

First term
Al – Karma Language School
Science
Prep 1
Revision on unit 2 (Model answer)
Question One:
A)-Complete the following statements:
1. Heat is a form of energy which transfers from the object of high
temperature to another of low temperature.
2. Heat transfers by three methods which are conduction , convection and
radiation.
3. Heat is transferred through air by convection and radiation.
4. The potential energy increases by increasing the weight of the body and
its height from the ground.
5. The measuring unit of work is Joule, while that of force is Newton.
6. The measuring unit of energy is Joule.
7. Sun is a permanent resource of energy, while wind or water movement is a
renewable source of energy.
8. Mechanical energy = Potential energy + Kinetic energy.
9. Potential energy = weight x height.
10. Kinetic energy = ½ x mass x Velocity2.
11. In the simple cell, the chemical energy changes into electric energy.
12. The simple cell consists of acidic solution dipped in it two different
metals( zinc and copper).
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First term
Al – Karma Language School
Science
Prep 1
13. Friction turns mechanical energy into heat energy.
14. By increasing the particles movement, the temperature increases.
15. Heat transfers through solids from one end to another by conduction.
B)- Choose the correct answer:
1. An object of 5 Kg moves with velocity of 5 m/s, its kinetic energy is ----------joules.
(62.5 – 125 – 12.5 – 25)
2. When the height of an object is doubled, its --------------.
(kinetic energy will be doubled – mechanical energy will be four times its
value – potential energy will be doubled – potential energy will be three times
its value)
3. On rubbing your hands, the ----------------.
(heat energy is converted into sound energy – kinetic energy is converted into
heat energy – heat energy is converted into kinetic energy – sound energy is
converted into heat energy)
4. The heat is transferred through solids by ---------------.
(conduction & convection – conduction & radiation – radiation only – conduction
only)
5. The sun is -------------------.
(a resource of permanent energy – a resource of non permanent energy –not
an energy resource – producing no energy)
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First term
Al – Karma Language School
Science
Prep 1
6. In the electric bulb, electric energy changes into -------------.
(heat energy only – light energy only – chemical energy – heat energy and
light energy)
7. In home when gas stove is working there is a change from ---------.
(heat energy into a chemical one – chemical energy into a heat one – chemical
energy into a sound one – light energy into heat one)
8. Mechanical energy is converted into heat energy by -------------.
(chemical reaction – friction – electric lamp)
9. Food and fuel are sources of energy -----------.
(Chemical – mechanical – electric –sound)
10. --------- is from the clean sources of energy.
(Petrol –Coal –Wood – Wind)
11. In the simple pendulum, the ------------.
(mechanical energy changes into sound energy – mechanical energy changes
into light energy – Kinetic energy changes into heat energy – Potential energy
changes into kinetic energy and vice versa)
12. In the solar cells, the solar energy changes into --------- energy.
(kinetic – potential – sound – electric)
Question (2)
A)- Give reason for:
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First term
Al – Karma Language School
Science
Prep 1
1. The fuel inside the car is similar to the food inside the body of living bodies.
Because fuel gives the car energy needed for its motion and food gives us energy
needed to do our activities.
2. The freezer is found at the top of the fridge.
Because when the air is cooled, its density increases so it falls down to cool the
fridge and the hot air rises up to be cooled because it has less density.
3. The production of electricity from solar energy is preferred than burning
of fuel.
Because the solar energy from the clean energy sources and is not polluted to the
environment.
4. Heater is put at the bottom of the room.
Because the heater heats the air and when the air heats, it density decreases and
rises up to warm the room while the cold air falls down because it has more
density.
5. Energy is neither created nor destroyed.
Because it can be changed from one form to another form without loss such as
the electric lamb and electric fan.
B)- From the opposite figure:
Picture page 25
What happens to the compass?
The compass will deflect due to the electric current flows through the circuit.(
changing from chemical energy into electric energy)
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First term
Al – Karma Language School
Science
Prep 1
C)- In the opposite figure, what does the arrows indicate?
(1). Zinc rod.
(2).Copper rod.
(3). Acidic solution.
Picture page 24
(4).Glass beaker.
(5).Electric bulb.
Question (3)
Problems:
1. Find the weight of an object of potential energy 88 joules when
found at a height 11 m.
Solution:
Given:
Law:
Height = 11 m , potential energy = 88 joules , weight = ?
Potential energy = weight x height =
Weight = potential energy = 88 = 8 Newtons
Height
11
2. An object has a kinetic energy 46 joule and is moving at a
speed 4 m/s find the object mass.
Solution:
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First term
Al – Karma Language School
Given: Kinetic energy= 46 joules
Law:
Science
Prep 1
, speed = 4 m/s , mass =?
Kinetic energy = ½ x mass x speed2
So mass = 2 x kinetic energy = 2 x 46 = 2.75 Kg
Speed2
42
Question (4):
A)-Write the scientific term:
1. A form of energy stored in the food.
(Chemical energy)
2. The ability to do work or to make a change.
(Energy)
3. The energy stored in the object due to work done on it. (Potential energy)
4. The way by which the heat is transferred through gases and liquids.
(Convection)
B)- Study the opposite figure then answer the following questions:
1. Heat will transfer from Body (A) to body (B).
60 °C
(A)
2. The transfer of heat will stop when the two bodies have the same
temperature.
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40 °C
(B)
First term
Al – Karma Language School
Science
Prep 1
C)- What is meant by:
1. Potential energy of an object = 50 joules.
The energy stored in the object due to work done on it equals 50 joules
2.
Kinetic energy of an object = 10 joules.
It means the energy of the moving body equals 10 joules.
3. Mechanical energy of a moving body = 100 joules.
It means the summation of the potential energy and the kinetic energy of a
moving body equal 100 joules.
D)- Mention the changes of energy in each of the following:
1. Sewing machine: From electric energy into kinetic (mechanical) energy.
2. Alarm clock: From chemical energy into kinetic and sound energies.
3. Television: from electric energy into light and sound energies.
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