Download What`s meant by each of the following?

Port Said International Schools
Better education for future generations
Science Department
Grade: 7
Final revision sheet Answers
Unit (1&2)
(1) Complete the following:
1- Mass of object and distance from earth are the factors affecting the attraction
force between the Earth and the object.
2- The object’s weight increases as the height from Earth’s center Decreases.
3- Electromagnet is made by the idea of changing electric energy into magnetic energy.
4- Electromagnet is used in making cranes and electric bell.
5- Electric generator changes kinetic energy into electric energy.
6- Electric motor changes electric energy into kinetic energy.
7- Strong nuclear forces are used in producing military purposes and in
Generating electricity purpose.
8- Egypt seeks to use nuclear energy in producing electricity.
9- Friction force prevents feet from slipping on roads during motion
10- Transitional motion is not considered as periodic motion because it has
start and end points.
11- Sound waves and water waves are examples of mechanical waves.
12- Water waves is an example of mechanical waves, while light waves is
an example of electromagnetic waves.
13- Thunder sound transfers in a form of mechanical waves, where as
lightning flash transfers in a form of electromagnetic waves.
14- Light waves can spread out in all media and vacuum with velocity of 3 m/s.
15- When the displacement value of an object is fixed, it is said that the object at rest.
16- The irregular speed is represented graphically by a curved line.
(2) Choose the correct answer:
1- A force is an effect ……………..
a) always changes the phase of an object motion only
b) never changes the phase of an object motion
c) always changes both object’s phase and direction.
d) may change the phase of an object motion.
2- An object’s weight on the Earth’s surface is related to ……….. forces.
a) electromagnetic
b) attraction
c) weak nuclear
d) strong nuclear
3- The bar used in electromagnet is made of ……………..
a) isolated copper
b) steel iron
c) wrought iron
d) aluminium
4- Electromagnet is used in making the …………….. set.
a) calculator
b) electric bell
c) microscope
d) night vision 5The electric motor changes the ……………..
a) mechanical energy into electric energy.
b) electric energy into magnetic energy
c) electric energy into mechanical energy
d) magnetic energy into mechanical energy.
6- Some of electric power stations work by …………….. energy.
a) attraction
b) magnetic
c) nuclear
d) electromagnetic 7When the horse is tripped, the horse rider is suddenly rushed forward,
this is related the force of ……………..
a) inertia
b) centrifugal
c) attraction
d) horse pushing 8All the following forces are due to inertia except ……………..
a) once the car starts moving forward, the passengers are rushed back
b) passengers are rushed forward if the moving car stopping suddenly.
c) if a football player is tripped during running forward, he will be
rushed forward
d) the attraction of bodies to the Earth
9- Electric fan still works for few seconds after cutting the electric current due to
……………..
a) friction
b) gravity
c) inertia
d) electromagnet 10-
The car brake performance is an application of ……………..
a) attraction forces
b) friction forces
c) electromagnetic forces
d) forces of inertia
11- Car tires are covered with a very coarse substance to ……………..
a) reduce the friction with the road
b) reduce the air resistance
c) increase the attraction of wheels
d) increase the friction with the road.
12- …………….. is from the forces inside living systems.
a) the contraction and relaxation of muscles
b) forces of inertia
c) electrostatic forces
d) friction forces
13- All of the following are periodic motion except the ………….. motion
a) fan
b) pendulum
c) train
d) sunflower
14- Mechanical waves are characterized by ……………..
a) their speed is greater than electromagnetic waves
b) their speed is 300 million m/s
c) they need a medium to propagate through.
15- We see lightning before hearing thunder because ……………..
a) lightning occurs before thunder.
b) sound needs a medium to travel through.
c) the velocity of light is 340 m/s.
d) the velocity of light is much greater than that of sound.
16- …………….. are used in night vision apparatus.
a) Infrared rays
b) Ultraviolet rays
c) Gamma rays
d) X-rays
17- Visible light is used in all the following applications except ………….
a) night vision apparatus
b) television cameras
c) photographic cameras
d) data shows
(3) Write the scientific term:
1- The ability of the Earth to attract an object to its center.(object’s weight)
………………………………………………………………………………………….
2- An instrument used to change electric energy into magnetic
energy.(electromagnet)
…………………………………………………………………………………..........
3- The force that accompanies the massive amount of energy and it is
stored in the nucleus.(nuclear energy)
………………………………………………………………………………………….
4- Property of an object has to resist the change of its phase unless an external
force acted on it.(inertia)
……………………………………………………………………………………….......
5- Resistant forces originate between the object in motion and the medium.(friction)
………………………………………………………………………………………..…
6- Forces that help living organisms to do its biological operations.(contraction and
relaxation)
…………………………………………………………………………………………….
7- It is the motion of an object in which its position changed relative to a fixed
point from initial to final position.(transitional motion)
……………………………………………………………………………………………
8- The motion which is regularly repeated in equal periods of time.(periodic motion)
………………………………………………………………………………………….
9- Waves which are accompanied by electromagnetic forces.(electromagnetic
waves)
…………………………………………………………………………………............
10- A speed by which the body moves equal distances every second at
certain direction.(regular speed)
……………………………………………………………………………………..……
(4)
(×) of the following:
1- As the height from the Earth’s surface increases, the value of Earth’s gravity
acceleration decreases.
(true )
2- The electric current has a magnetic effect.
( true
)
3- Dynamo changes electric energy into mechanical energy.
(false
)
4- Strong nuclear forces are used in medicine.
( false
)
5- Friction is a property of an object has to resist the change of its phase. ( false)
6- Friction prevents feet from slipping on roads during walking.
(true )
7- Heart muscle contraction and relaxation is one of the forces inside
living organisms.
(true )
(5) Give reasons:
1- Object’s weight changes from one place to another on the Earth’s surface.
Due to the change of gravity acceleration so the attraction force changes
2- Gravity acceleration changes of Earth’s surface from one place to another.
Due to the non-spherical shape of the earth
3- The importance of dynamo in the case of cutting off the electric current.
Change mechanical energy into electric energy
4- The car passengers are rushed forward when the moving car stops suddenly.
Due to inertia force
5- In a car at rest, passengers are rushed backward when the car moves suddenly.
Due to inertia force
6- Policemen advise drivers using safety belts in cars.
To protect them from being injured to decrease the effect inertia
7- Cars tires are covered with a very coarse substance.
To increase the friction between tiers and the road
8- Lubricants and oiling mechanical machines.
To reduce friction force and the damages that cause from it
9- Circular motion is a periodic motion.
Because it repeated regularly in equal periods of time
10- We receive the sunlight, while we can’t hear the sound of solar explosions.
Because sunlight is electromagnetic wave that do not need medium to pass through and
have great speed. while explosions are sound mechanical waves the need medium to pass
through and relatively low
11- Astronauts can’t hear each other voices directly in space.
Because voice is sound mechanical waves the need medium to pass through and
relatively low
12- The importance of chemical reactions in our life.
Because they commonly used in many industries such as medicine, fertilizers,
fuel, plastics
13- The chemical equation should be balanced.
The total mass of reactants should be equal to the total mass of products
14- White fumes rise when you place a glass rod wetted with Hydrochloric acid
close to Ammonia solution. (Write the chemical equation).
NH3 + HCl ____conc____> NH4Cl (white fumes)
Due to the formation of ammonium chloride
15- Fuel burning is considered an environmental pollutant.
Because it causes air pollution and emit harmful gases that may cause diseases
16- Carbon Monoxide has a dangerous impact on the human beings.
Causes fainting – headache – stomach aches – may lead to death
17- Sulphur Oxides have a dangerous impact on the human beings.
Respiratory system malfunction – building erosion
18- Nitrogen Oxides have a dangerous impact on the human beings.
Harm the nervous system and eye
(5) What’s meant by each of the following?
1- Object’s weight.
The force at which the body attracted to the earth, is the result of the object’s
mass × Earth’s gravity acceleration
2- Inertia.
The property of an object to resist the change of its phase from rest to
motion unless an external force acted upon it.
3- Friction force.
The resistance forces originated between the surface of the object in motion& the
medium touching it
4- The motion.
The change in an object position or direction as the time passes
5- Translational motion.
is the motion which the object position is changed in proportion to a fixed frame of
reference from time to time from an initial position to a final one, such as the train motion
– the bike motion – the car motion
6- Periodic motion.
The motion which is regularly repeated in equal periods of time such as:
a. Vibrating motion: such as the pendulum.
B.Circular motion: such as the fan arms
7- Speed.
Distance that covers in one second
Chemical reaction:The breaking of the existing bond in reactants molecules and form a new chemical
bond in the products molecules.
Chemical equation:A set of symbols and chemical formulas representing the reactants molecules,
products molecules and the conditions of reactions as well.
10- The force.
is an effect which attempts to change the object phase from being static to
motion or vice versa, or attempt to change the motion direction.
(6) Problems:
1) If the earth’s gravity acceleration in a place is 9.8 m/s2, find the weight of the
following:
a) 0.3 kg mass ball
b) 50 kg mass boy
2) l- A 0.3 Kg mass ball.
3) Weight = mass× gravity acceleration
4) W=0.3×9.8= N
5) 2- A 50 kg mass boy.
6) W= 50×9.8= N
(7)Give an example indicating each of the following:
1- Translational motion train
2- Vibrating motion pendulum
3- Circular motion fan
4- Wave motion throwing g cork in water
5- Mechanical waves…sound wave
(8)Compare between mechanical waves and electromagnetic waves.
1234-
Mechanical waves
Vibration of the medium
particles.
It needs a medium to transfer
through.
Its speed is relatively slow.
Such as: sound waves –
water waves.
1234-
Electromagnetic waves
Accompanied with the
electromagnetic forces.
Spread in all media and space.
The speed is extremely great
300milion m/s.
Such as light waves – wireless
waves – radio and television
waves – ultra violet and infrared
rays which accompanied by the
sun rays.
(9) Write the chemical equation representing the following reactions, then
indicate the type of each reaction:
1- Burning of magnesium in the presence of oxygen.
2 Mg + O2 ________> 2 MgO
(white powder)
2- Burning of carbon in the presence of oxygen.
3- Reaction of ammonia gas and hydrochloric acid.
4- Reaction of carbon monoxide with oxygen.
knowing that the mass of carbon C= 12 and Oxygen O= 16 Find the total masses of
reactants and products through the following reaction
C + O2
∆
CO2
12 + (2×16)
12+ (2×16)
44 g =
44 g
The total amounts of reactants masses is equal to the
total amount of products masses
Unit (3)
(1) Complete the following:
1. The types of telescopes are reflecting and refracting.
2. The planets revolve around the sun in elliptical orbits.
3. The nearest planet to the sun is Mercury and the farthest one from the sun is
Neptune
4. Mercury, Venus, Earth and mars are the inner planets.
5. Uranus planet has 27 moons revolving around it, while Neptune planet has
12 moons revolving around it.
6. The comet consists of two parts, which are head and tail.
7. The planet Earth occupies the third position according to the distance from the sun
8. Green plants use carbon dioxide gas in photosynthesis process.
9. Granite rock consists of quartz, feldspar, mica minerals, while basalt rock
consists of olivine, pyroxene, and feldspar minerals.
10. Sandstone consists of sand particles and mainly quartz.
11. Marble is resulted from transformation of limestone.
12. Seismograph is used for recording the intensity of earthquakes and the time
of its occurrence.
13. The volcano is It is an opening in earth’s crust which permits the passage
of molten materials (Lava) and trapped gases.
14. The earthquake is Rapid and successive shakes of ground which take place
one after other.
(2) Choose the correct answer:
1- The distance between stars are measured in ……………… unit. light year
2- The distance covered by light in two years equals ……………… km.
9.467 × 10 12
3- The telescope is used to study the ………………
Celestial bodies
4- The big-sized, less dense planet, which consists of gaseous elements is the
Jupiter
5- Which of the following planets has the largest gravity on its surface? …
Earth
6- The mass of the biggest meteorite found up till now reaches ……… tons.
80
7- …………… comet is the most famous one.
Halley’s
8- Regarding the volume, the Earth occupies the …………… order in the solar
system.
Fifth
9- Ozone layer protects life on the Earth by absorbing …………… rays.
Ultraviolet
10- …………… rock is characterized by that it is heavy, rough, solid,
cohesive and it isn’t easily broken.
Granite
11- Seismograph is used for identifying the ……………
Earthquakes
(3) Write the scientific term:
1- The farthest four planets from the sun.
2- A layer of molten metals with a thickness 2100 km.
Neptune
outer core
3- A molten material that exists at depths beneath the crust.
lava
4- A fracture in the crust that rocks slide on its sides.
Faults
5- The type of rocks which is formed from the molten matter underneath the
earth's crust.
Plutonic igneous rocks
(4) Give reasons for:
1- Astronomers do not measure the distance between stars in kilometers.
Because they are very distant from each other’s they use the light years.
2- Mercury, Venus, Earth and mars are called the inner planets.
Because they are the nearest four planets to the sun, have high density, formed of
rocky masses and smaller in size.
3- The density of outer planets is low.
Because they are consisting of gaseous elements.
4- The presence of white color surrounds the planet Earth.
Because the earth is surrounded by the atmosphere that consists of group of gases.
5- Steadfastness of the hydrosphere on the Earth’s surface.
Due to the force of gravity of the earth.
6- The importance of atmosphere in our life.
Science book page 86
7- Volcanic rocks contain small circular holes.
Due to the extruding of gases from the volcanic flows during their cooling down
and the formation of the rock.
8- The components of basalt rock cannot by seen by the naked eye.
Because it is a volcanic rock that has very small crystals due to cooling down
quickly on the earth surface.
(5) Compare between:
1- Outer planets and inner planets
Points
Size
Distance from the sun
Density
Composition
Names
Inner planets
small
close
High ranging between 3.3. to
5.5 g/cm3
solidified masses except
mercury
Mercury
Venus
Earth
Mars
Outer planets
large
far
low ranging between 0.7 to
1.3 g/cm3
gaseous element
( hydrogen and helium)
Jupiter
Saturn
Uranus
Neptune
2- Sandstone and limestone
Points
Color
Texture
Structure
Sandstone
yellow
Coarse
Sand grains and quartz
Limestone
White
Smooth
calcite
(6) What’s meant by each of the following?
1. asteroids
They are rocky celestial bodies that rotate around the sun in the region of the belt of
wonderer asteroids between mars and Jupiter.
2. meteorites
The remaining parts of rocky masses without burning, that
fall on the surface of the earth
3. comets
They are masses of rocks, ice and solidified gases that revolve around the sun in
more elongated elliptical orbits intersecting with the orbits of the planets.
Have (head and tail)
4- Meteors.
They are luminous arrows that can be seen in the sky due to complete burning of
small rocky masses in the earth's atmosphere
5- Volcanoes.
It is an opening in earth’s crust which permits the passage of molten materials
(Lava) and trapped gases.
6- Earthquakes.
Rapid and successive shakes of ground which take place one after other.
7- Fault.
It is a fracture in earth’s crust that leads to sliding of rocks in a vertical direction or
horizontal direction on both sides of fracture.
8- Rocks.
Natural soild materials exists in earth crust and is formed of one mineral or group
of minerals.