CBSE Class 7

Wastewater Story Class 7 Extra Questions and Answers Science Chapter 18 PDF are solved by experts and will guide students in the right direction. Students can get how to tackle different questions easily by solving the Extra Questions for Class 7 Science Question bank on a regular basis.

Class 7 Science Chapter 18 Extra Questions and Answers Wastewater Story

Extra Questions for Class 7 Science Chapter 18 Wastewater Story with Answers

Wastewater Story Class 7 Extra Questions Very Short Answer Type

Question 1.
Which day is celebrated as the ‘World Water Day’?
Answer:
22nd March.

Question 2.
What do you understand by ‘wastewater’?
Answer:
Rich in lather, mixed with oil, black-brown water that goes down the drains from sinks, showers, toilets, laundries is dirty. It is called wastewater.

Question 3.
Which period has been proclaimed as the International decade for action on “Water for life”?
Answer:
United Nations proclaimed the period 2005-2015 as the International Decade for action on “Water for life”.

Question 4.
What do you mean by cleaning of water?
Answer:
Cleaning of water is a process of removing pollutants before it enters a water body or is reused.

Question 5.
What is sewage treatment?
Answer:
The process of wastewater treatment is commonly known as “Sewage Treatment”.

Question 6.
Why is the speed of incoming wastewater decreased in the grit and sand removal tank?
Answer:
The speed of the incoming wastewater in the grit and sand removal tank is decreased to allow sand, grit and pebbles to settle down.

Question 7.
Why should we plant eucalyptus along sewage ponds?
Answer:
Eucalyptus absorb all surplus wastewater rapidly and release pure water vapour into the atmosphere.

Wastewater Story Class 7 Extra Questions Short Answer Type 1

Question 1.
How do sand, grit and pebbles settle down in the grit and sand removal tank?
Answer:
Jn grit amLsand removal tank, the speed of the incoming wastewater is decreased to allow sand, grit and pebbles to settle down.

Question 2.
Why is air pumped into clarified water?
Answer:
Air is pumped into the clarified water to help aerobic bacteria to grow. Bacteria consume human waste, food waste, soaps and other unwanted matter still remaining in- clarified water.

Question 3.
How is dry sludge used?
Answer:
Dried sludge is used as manure, returning organic matter and nutrients to the soil.

Question 4.
What is done to improve sanitation?
Answer:
To improve sanitation, low-cost onsite sewage disposal systems are being encouraged. Examples are septic tanks, chemical toilets, composting pits. Septic tanks are suitable for places where there is no sewerage system, for hospitals, isolated buildings or a cluster of 4 to 5 houses.

Wastewater Story Class 7 Extra Questions Short Answer Type 2

Question 1.
What is vermi-process toilet?
Answer:
Vermi-processing toilet is a design of a toilet in which humans excreta is treated by earthworms. It has been found to be a novel, low water-use toilet for safe processing of human waste. In the vermi processing toilet, the human excreta is completely converted to vermi cakes – a resource is much needed for soil.

Question 2.
What is done with the sludge produced in Wastewater Treatment Plant? Is it useful to us? If yes, how?
Answer:
The sludge produced IP Wastewater Treatment Plant is transferred to a separate tank when it is decomposed by the anaerobic bacteria. The biogas produced in the process can be used as fuel or can be used to produce electricity.

Question 3.
Why is air pumped into the clarified water? What is the role of aerobic bacteria in cleaning of water?
Answer:
Air is pumped into the clarified water to help aerobic bacteria to grow. These bacteria consume human waste, food waste, soaps and other unwanted matter still remaining in clarified water.

Wastewater Story Class 7 Extra Questions Long Answer Type

Question 1.
Suggest some better housekeeping practices.
Answer:
(i) Cooking oil and fats should not be thrown down the drain. They can harden and block the pipes. In an open drain the fats clog the soil pores reducing its effectiveness in filtering water. Oil and fats should be thrown in the dustbin.
(ii) Chemicals like paints, solvents, insecticides, motor oil, medicines may kill microbes that help purifying water. So, they should not be thrown in the drain.
(iii) Used tea leaves, solid food remains, soft toys, cotton, sanitary towels, etc. should also be thrown in the dustbin. These wastes choke the drains. They do not allow free flow of oxygen. This hampers the degradation process.

Question 2.
What is the composition of sewage?
Answer:
Sewage is a complex mixture containing suspended solids, organic and inorganic impurities, nutrients, saprotrophic and disease-causing bacteria and other microbes.

Organic impurities – Human faeces, animal waste, oil, urea (urine), pesticides, herbicides, fruit and vegetable waste, etc.

Inorganic impurities – Nitrates, Phosphates, metals.
Nutrients – Phosphorus and Nitrogen.
Bacteria – Such as which causes cholera and typhoid.
Other microbes – Such as amoeba which cause dysentery.

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Light Class 7 Extra Questions and Answers Science Chapter 15 PDF are solved by experts and will guide students in the right direction. Students can get how to tackle different questions easily by solving the Extra Questions for Class 7 Science Question bank on a regular basis.

Class 7 Science Chapter 15 Extra Questions and Answers Light

Extra Questions for Class 7 Science Chapter 15 Light with Answers

Light Class 7 Extra Questions Very Short Answer Type

Question 1.
What is the path travelled by light?
Answer:
Path travelled by a light is a straight line.

Question 2.
What is reflection?
Answer:
The phenomenon of change of direction of light when it falls on a polished surface is called reflection.

Question 3.
What makes objects visible to us?
Answer:
Objects are visible to us only when light reflected from them reaches o.ur eyes.

Question 4.
How is the word ‘AMBULANCE’ written on an ambulance?
Answer:
The word ‘AMBULANCE’ is written laterally inverted on an ambulance. It appears as ‘ONAJUBMA’.

Question 5.
A hollow rubber ball is cut. Which are its convex and concave surfaces?
Answer:
The inner surface of the cut ball is called concave and the outer surface is called convex.

Light Class 7 Extra Questions Short Answer Type 1

Question 1.
Draw concave and convex mirrors.
Answer:

Question 2.
Draw convex and concave lens.
Answer:

Question 3.
Draw real image formed by a convex lens.
Answer:

Light Class 7 Extra Questions Short Answer Type 2

Question 1.
Draw real image formation by a concave mirror.
Answer:

Question 2.
Draw image formation by a convex mirror.
Answer:

Question 3.
Draw real image formed by a convex lens.
Answer:

Question 4.
Draw virtual image formed by a convex lens.
Answer:

Light Class 7 Extra Questions Long Answer Type

Question 1.
How will you show that mixing of seven colours, gives white colour.
Answer:
A circular cardboard disc of about 10 cm diameter is taken. This disc is divided into seven segments. The seven rainbow colours are painted on these segments as shown in Fig. (a). A small hole is made at the centre of the disc. The disc is fitted loosely on the tip of a refill of a ball pen so that the disc rotates freely [(Fig. (6)]. The disc is rotated in the daylight. When the disc is rotated fast, the colours get mixed together and the disc appeals to be whitish.

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Forests: Our Lifeline Class 7 Extra Questions and Answers Science Chapter 17 PDF are solved by experts and will guide students in the right direction. Students can get how to tackle different questions easily by solving the Extra Questions for Class 7 Science Question bank on a regular basis.

Class 7 Science Chapter 17 Extra Questions and Answers Water: A Precious Resource

Extra Questions for Class 7 Science Chapter 17 Forests: Our Lifeline with Answers

Forests: Our Lifeline Class 7 Extra Questions Very Short Answer Type

Question 1.
Write one food chain in forest.
Answer:
Grass → insects → frog → snake → eagle.

Question 2.
Which type of environment remains in a forest ?
Answer:
Forest environment is peaceful and a cool breeze keeps blowing because of transpiration by plants.

Question 3.
Name two trees found in forests.
Answer:
Neem, Sheesham.

Forests: Our Lifeline Class 7 Extra Questions Short Answer Type 1

Question 1.
Name some animals that live deep inside forest.
Answer:
Animals like boar, bison, jackals, porcupine, elephants live in the deeper areas of the forest.

Question 2.
What do the forests provide to the human beings?
Answer:
Many people live in the forest. Some of them may belong to different tribes. These people depend mostly on the forests. The forest provides them with food, shelter, water and medicines. In additional, human extracts timber, pulp, resin, gum etc. from forest for his use.

Question 3.
How is forest beneficial for the environment for man living nearby forest?
Answer:
Due to the surrounding forests, they receive good rainfall. The air also remain cool. Noise pollution, too is less because the forest absorbs the noise of the nearby highway.

Question 4.
What puts pressure on forest?
Answer:
Construction of roads, buildings, industrial development and increasing demand of wood create pressure on the forests.

Question 5.
Sum up the importance of forests.
Answer:
Forests provide us with oxygen. They protect soil and provide habitat to a large number of animals. Forests help in bringing good rainfall in neighbouring areas. They are a source of medicinal plants, timber and many other useful products.

Forests: Our Lifeline Class 7 Extra Questions Short Answer Type 2

Question 1.
Why are forests called green lungs?
Answer:
Plants release oxygen through the process of photosynthesis. The plants help to provide oxygen for animal respiration. They also maintain the balance of oxygen and carbon dioxide in the atmosphere. That is why forests are called green lungs.

Question 2.
Draw a figure to show the dependence of plant, soil, and decomposers in a forest.
Answer:

Forests: Our Lifeline Class 7 Extra Questions Long Answer Type

Question 1.
Why is forest called ‘dynamic living entity’?
Answer:
By harbouring greater variety of plants, the forest provides greater Opportunities for food and habitat for the herbivores. Larger number of herbivores means increased availability of food for a variety of carnivores. The wide variety of animals helps the forest to regenerate and grow. Decomposers help in maintaining the supply of nutrients to the growing plants in the forest. Therefore, the forest is a ‘dynamic living entity’ – full of life and vitality.

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Water: A Precious Resource Class 7 Extra Questions and Answers Science Chapter 16 PDF are solved by experts and will guide students in the right direction. Students can get how to tackle different questions easily by solving the Extra Questions for Class 7 Science Question bank on a regular basis.

Class 7 Science Chapter 16 Extra Questions and Answers Water: A Precious Resource

Extra Questions for Class 7 Science Chapter 16 Water: A Precious Resource with Answers

Water: A Precious Resource Class 7 Extra Questions Very Short Answer Type

Question 1.
When is the World Water Day celebration?
Answer:
22 March.

Question 2.
What is minimum limit of water prescribed by United Nations?
Answer:
The amount of water recommended by the United Nations for drinking, washing, cooking and maintaining proper hygiene is a minimum of 50 litres per person per day.

Question 3.
How much of earth’s surface is covered by water?
Answer:
About 71%.

Question 4.
How much water (by percentage) is available for us to use?
Answer:
Roughly 0.006%.

Question 5.
Where is solid form of water present in the earth?
Answer:
The solid form, snow and ice, is present as ice caps at the poles of the earth, snow- covered mountains and glaciers.

Question 6.
How is water present in the atmosphere?
Answer:
As water vapour.

Question 7.
What is Bawril
Answer:
Bawri is the traditional way of collecting water.

Water: A Precious Resource Class 7 Extra Questions Short Answer Type 1

Question 1.
Which year was observed as International Year of Freshwater and why?
Answer:
Year 2003 was observed as the International Year of Freshwater to make people aware of this dwindling natural resource.

Question 2.
Where is most of the water in earth contained?
Answer:
Almost all the water on the earth is contained in the seas and oceans, rivers, lakes, ice caps, as groundwater and in the atmosphere.

Question 3.
Give two tips to save water.
Answer:

1. Turn off taps while brushing.
2. Mop the floor instead of washing.

Water: A Precious Resource Class 7 Extra Questions Short Answer Type 2

Question 1.
What could be the effect of scarcity of water?
Answer:
Without water, no animals and plants can survive. The green character of the planet shall be lost. For a world without plants shall mean no food, no oxygen, not enough rain, and innumerable other problems. This may mean the end of all life.

Question 2.
How is water distributed on the earth in its three forms?
Answer:

1. The solid form, snow and ice, is present as ice caps at the poles of the earth, snow-covered mountains and glaciers.
2. Liquid water is present in oceans, lakes, rivers, and even underground.
3. The gaseous form is the water vapour present in the air around us.

Water: A Precious Resource Class 7 Extra Questions Long Answer Type

Question 1.
Write some methods to save water.
Answer:
Scarcity of water can be tackled only through its judicious use. We cannot create water but can save water. Here are some tips for saving water:

1. While brushing teeth or shaving turn off the water tap until it is time to rinse.
2. Use a bucket of water while washing dishes instead of washing them under the tap.
3. Never put water down the drain when there may be another use for it such as watering a plant in the garden or cleaning.
4. Verify that your home is leak-free. Repair any leakage.
5. Use minimum water for bath. If there is shower in the bathroom, use the ultra-low-flow version and take short showers.
6. Avoid the installation of ornamental water features (such as fountains) unless the water is recycled.
7. Report all significant water losses (broken pipes, open hydrants, etc.) to the property owner or authorities.
8. Do not pollute water.

Question 2.
How is increasing population responsible for depletion of groundwater?
Answer:

1. Increasing population creates demand for construction of houses, shops, offices, roads and pavements. This decreases the open areas like parks, and playgrounds. This, in turn, decreases the seepage of rainwater into the ground.
2. Moreover a huge amount of water is required for construction work. Often groundwater is used for this purpose.
3. So, we are not only consuming more groundwater, but we also are allowing lesser water to seep into the ground. This results in depletion of water table.

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Electric Current and Its Effects Class 7 Extra Questions and Answers Science Chapter 14 PDF are solved by experts and will guide students in the right direction. Students can get how to tackle different questions easily by solving the Extra Questions for Class 7 Science Question bank on a regular basis.

Class 7 Science Chapter 14 Extra Questions and Answers Electric Current and Its Effects

Extra Questions for Class 7 Science Chapter 14 Electric Current and Its Effects with Answers

Electric Current and Its Effects Class 7 Extra Questions Very Short Answer Type

Question 1.
Which terminal of a cell is represented by longer line?
Answer:
Positive.

Question 2.
Where should be the key placed in a circuit?
Answer:
The key or switch can be placed anywhere in the circuit.

Question 3.
What is a filament?
Answer:
In the bulb there is a thin wire, called the filament, which glows when an electric current passes through it.

Question 4.
What is the full form of CFL?
Answer:
Compact Fluorescent Lamp.

Question 5.
What is the full form of MCB?
Answer:
Miniature Circuit Breaker.

Question 6.
Who discovered magnetic effect of electric current?
Answer:
Hans Christian Oersted.

Electric Current and Its Effects Class 7 Extra Questions Short Answer Type 1

Question 1.
What are complete and incomplete circuits?
Answer:
When the switch is in the ‘ON’ position, the circuit from the positive terminal of the battery to the negative terminal is complete. The circuit is then said to be closed and the current flows throughout the circuit instantly.

When the switeh is in the ‘OFF’ position, the circuit is incomplete. It is said to be open. No current flows through any part of the circuit.

Question 2.
Why should we not touch a lighted electric bulb connected to the mains?
Answer:
We should not touch a lighted electric bulb connected to the mains because it may be very hot and our hand may get burnt badly.

Question 3.
How does a fuse work?
Answer:
Every fuse is designed to carry current up to a certain maximum limit. If the current crosses that limit, the fuse wire melts due to heating effect of current and breaks the circuit. Thus, the circuit is saved.

Question 4.
What are the uses of electromagnets?
Answer:

1. The electromagnets are also used to separate magnetic material from the junk.
2. Doctors use tiny electromagnets to take out small pieces of magnetic material that have accidentally fallen in the eye.
3. Many toys also have electromagnets inside them.
4. Electromagnets are used in electric bells.

Electric Current and Its Effects Class 7 Extra Questions Short Answer Type 2

Question 1.
Discuss the reason for excessive currents in electrical circuits.
Answer:
(i) One reason for excessive currents in electrical circuits is the direct touching of wires. This may happen if the insulation on the wires has come off due to wear and tear. This may cause a short circuit.
(ii) Another reason for excessive current can be the connection of many devices to a single socket. This may cause overload in the circuit.

Electric Current and Its Effects Class 7 Extra Questions Long Answer Type

Question 1.
Write construction and working of an electric bell.
Answer:
Construction: It consists of a coil of wire wound on an iron piece. The coil acts as an electromagnet. An iron strip with a hammer at one end is kept close to the electromagnet. There is a contact screw near the iron strip.

Working: When the iron strip is in contact with the screw, the current flows through the coil which becomes an electromagnet. It, then, pulls the iron strip. In the process, the hammer at the end of the strip strikes the gong of the bell to produce a sound. However, when the electromagnet pulls the iron strip, it breaks the circuit. The current through the coil stops flowing.

The coil is now no longer an electromagnet. It no longer attracts the iron strip. The iron strip comes back to its original position and touches the contact screw again. This completes the circuit. The current flows in the coil and the hammer strikes the gong again. This process is repeated in quick succession. The hammer strikes the gong every time the circuit is completed. This is how the bell rings.

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Motion and Time Class 7 Extra Questions and Answers Science Chapter 13 PDF are solved by experts and will guide students in the right direction. Students can get how to tackle different questions easily by solving the Extra Questions for Class 7 Science Question bank on a regular basis.

Class 7 Science Chapter 13 Extra Questions and Answers Motion and Time

Extra Questions for Class 7 Science Chapter 13 Motion and Time with Answers

Motion and Time Class 7 Extra Questions Very Short Answer Type

Question 1.
Write formula for speed.
Answer:
Speed = \(\frac{\text {Total distance travelled}}{\text {total time taken}}\)

Question 2.
Define a day.
Answer:
The time between one sunrise and the next is called a day.

Question 3.
What is a year?
Answer:
A year is fixed as the time taken by the earth to complete one revolution around the sun.

Question 4.
What is a month?
Answer:
A month is measured from one new moon to the next.

Question 5.
What is bob?
Answer:
The metallic ball hanging with the thread is called the bob of the pendulum.

Question 6.
What is oscillatory motion?
Answer:
The to and fro motion of an object is called periodic or an oscillatory motion of that object.

Question 7.
What is speedometer?
Answer:
It is a device that is used to measure speed directly in km/h.

Question 8.
What is odometer?
Answer:
Meter that measures the distance moved by the vehicle is known as an odometer.

Motion and Time Class 7 Extra Questions Short Answer Type 1

Question 1.
“Speed of a car is 50 km/h.” What does it mean?
Answer:
When we say that a car is moving with a speed of 50 kilometres per hour, it implies that it will cover a distance of 50 kilometers in one hour.

Question 2.
What are microseconds and nano-second?
Answer:
One microsecond is one-millionth of a second. A nanosecond is one-billionth of a second.

Question 3.
Name different types of graphs.
Answer:
Bar graph, line graph, pie graph.

Motion and Time Class 7 Extra Questions Short Answer Type 2

Question 1.
How is speed of car in non-uniform motion measured?
Answer:
The speed is calculated as the total distance covered divided by the total time taken. Thus,
speed = \(\frac{\text {Total distance covered}}{\text {Total time taken}}\)
This is called average speed.

Motion and Time Class 7 Extra Questions Long Answer Type

Question 1.
Suggest some points to be kept in mind while choosing the most suitable scale for drawing a graph.
Answer:
Some of the points to be kept in mind while choosing the most suitable scale for drawing a graph are:

1. the difference between the highest and the lowest values of each quantity.
2. the intermediate values of each quantity, so that with the scale chosen it is convenient to mark the values on the graph, and
3. to utilize the maximum part of the paper on which the graph is to be drawn.

Question 2.
A ball moves 30 m in 6s. Find its speed.
Answer:
Here, d = 30 m
t = 6 s
s = ?
We know,
s = \(\frac {d}{t}\)
= \(\frac {30m}{6s}\) = 5 ms^-1

Question 3.
A body is moving with a speed 10 m/s. After 1 minute, what is the distance traveled?
Answer:
Here, s = 10 m/s
t = 1min = 60 s
d = ?
we know,
s = \(\frac {d}{t}\)
⇒ d = s.t
= 10 m/s × 60 s
= 600 m

Question 4.
Find the distance covered by a car moving at 50 km/h in 2 hours.
Answer:
Given, s = 50 km/h
t = 2 h
d = ?
We know that,
s = \(\frac {d}{t}\)
or, d = st
= 50 km/h × 2 h
= 100 km

Question 5.
The bowling speed of Shoaib Akhtar is 144 km/h. Find in what time the ball reaches the batsman. Consider that the batsman is standing at a distance 20 m from the bowling crease.
Answer:
Given,

Question 6.
Write briefly about the development of pendulum clock.
Answer:
It is said that once Galileo (AD 1564 – 1642) was sitting in a church. He noticed that a lamp suspended from the ceiling with a chain was moving slowly from one side to the other. He was surprised to find that his pulse beat the same number of times during the interval in which the lamp completed one oscillation.

Galileo experimented with various pendulums to verify his observation. He found that a pendulum of a given length takes always the same time to complete one oscillation. This observation led to the development of pendulum clocks. Winding clocks and wristwatches were refinements of the pendulum clocks.

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