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NCERT Solutions for Class 8 Science Chapter 17 Stars and the Solar System are part of NCERT Solutions for Class 8 Science. Here we have given NCERT Solutions for Class 8 Science Chapter 17 Stars and the Solar System.

NCERT Solutions for Class 8 Science Chapter 17 Stars and the Solar System

NCERT TEXTBOOK EXERCISES

Choose the correct answer in Questions 1-3:

Question 1.
Which of the following is NOT a member of the solar system?
(a) An asteroid
(b) A satellite
(c) A constellation
(d) A comet
Answer.
(c) A constellation.

Question 2.
Which of the following is NOT a planet of the Sun?
(a) Sirius
(b) Mercury
(c) Saturn
(d) Earth
Answer.
(a) Sirius.

Question 3.
Phases of the moon occur because:
(a ) we can see only that part of the moon which reflects light towards us.
(b) our distance from the moon keeps changing.
(c) the shadow of the Earth covers only a part of the moon’s surface.
(d) the thickness of the moon’s atmosphere is not constant.
Answer.
(a) we can see only that part of the moon which reflects light towards us.

Question 4.
Fill in the blanks:

1. The planet which is farthest from the Sun is………….
2. The planet which appears reddish in colour is…………
3. A group of stars that appear to form a pattern in the sky is known as a……………
4. A celestial body that revolves around a planet is known as…………
5. Shooting stars are actually not…………..
6. Asteroids are found between the orbits of and.…………

Answer.

1. Neptune
2. Mars
3. constellation
4. satellite
5. meteors
6. Mars, Jupiter.

Question 5.
Mark the following statements as True (T) or False (F):

1. Pole star is a member of the solar system.   (   )
2. Mercury is the smallest planet in the solar system. (   )
3. Uranus is the farthest planet in the solar system.   (   )
4. INSAT is an artificial satellite.   (   )
5. There are nine planets in the solar system.    (   )
6. Constellation Orion can be seen only with a telescope.   (   )

Answer.

1. False
2. True
3. False
4. True
5. False
6. False

Question 6.
Match items in column A with one or more items in column B.

Answer.

Question 7.
In which part of the sky can you find Venus if it is visible as an evening star?
Answer.
Venus appears in the western sky just after sunset.

Question 8.
Name the largest planet of the solar system.
Answer.
Jupiter (Brihaspati).

Question 9.
What is a constellation? Name any two constellations.
Answer.
A group of stars that has a recognizable shape is called a constellation. Ursa Major and Orion are two examples of constellations.

Question 10.
Draw sketches to show the relative positions of prominent stars in:
(a) Ursa Major and (b) Orion.
Answer.

Question 11.
Name two objects other than planets which are members of the solar system.
Answer.
Satellites and asteroids are the objects that too, are members of the Solar system.

Question 12.
Explain how you can locate the Pole Star with the help of Ursa Major.
Answer.
Pole stars can be located with the help of the two stars at the end of Ursa Major. Imagine a straight line passing through these stars as shown in Fig. 17.2. Extend this imaginary line towards the north direction. (About five times the distance between the two stars). This line will lead to a star which is not too bright. This is the Pole Star.

Question 13.
Do all the stars in the sky move? Explain.
Answer.
No, no star moves in the sky. They appear to move from east to west because the Earth rotates from west to east about its axis.

Question 14.
Why is the distance between stars expressed in light years? What do you understand by the statement that a star is eight light-years away from the Earth?
Answer.
The distance between stars is so large that it cannot be expressed in terms of a kilometer. That is why very large distances, are expressed in another unit known as light year. One light-year is the distance traveled by light in one year. If the distance of a star is eight light-years, it means that this distance is the distance traveled by light in eight years.

Question 15.
The radius of Jupiter is 11 times the radius of the Earth. Calculate the ratio of the volumes of Jupiter and the Earth. How many Earths can Jupiter accommodate?
Answer.

Question 16.
Boojho made the following sketch (See Fig. 17.29 of NCERT) of the solar system.
Is the sketch correct? If not, correct it.
Answer.
It is not correct. Figure 17.3 is a correct sketch of the solar system.

We hope the NCERT Solutions for Class 8 Science Chapter 17 Stars and the Solar System help you. If you have any query regarding NCERT Solutions for Class 8 Science Chapter 17 Stars and the Solar System, drop a comment below and we will get back to you at the earliest.

NCERT Solutions for Class 8 Science Chapter 16 Light are part of NCERT Solutions for Class 8 Science. Here we have given NCERT Solutions for Class 8 Science Chapter 16 Light.

NCERT Solutions for Class 8 Science Chapter 16 Light

NCERT TEXTBOOK EXERCISES

Question 1.
Suppose you are in a dark room. Can you see objects in the room? Can you see objects outside the room? Explain.
Answer.
We cannot see objects in the darkroom. But, we can see objects outside the room, in case there is light outside the room. It is so because to see an object, we need light which gets reflected from the object and enters our eyes.

Question 2.
Differentiate between regular and diffused reflection. Does diffused reflection mean the failure of the laws of reflection?
Answer.

No, diffused reflection does not mean, failure of the laws of reflection. It is due to irregularities in the reflecting surface, like that of cardboard.

Question 3.
Mention against each of the following whether regular or diffused reflection will take place when a beam of light strikes. Justify your answer in each case.

1. Polished wooden table
2. Chalk powder
3. Cardboard surface
4. Marble floor with water spread over it
5. Mirror
6. Piece of paper

Answer.

1. Polished Wooden Table: Regular reflection will take place. This is because a polished wooden table will have a plane surface.
2. Chalk Powder: Diffused reflection because the surface of the chalk powder is not smooth.
3. Cardboard Surface: Diffused reflection since cardboard has a rough surface,
4. Marble Floor with Water Spread Over it: Regular reflection as it will act as a plane surface.
5. Mirror: Regular reflection because the mirror has a shiny surface which is even.
6. Piece of Paper: Diffused reflection because the surface of the paper is rough.

Question 4.
State the laws of reflection.
Answer.
The laws of reflection are as follows:

1. The angle of reflection is equal to the angle of incidence.
2. The incident ray, the normal at the point of incidence, and the reflected ray all lie in the same plane.

Question 5.
Describe an activity to show that the incident ray, the reflected ray, and the normal at the point of incidence lie in the same plane.
Answer.

Question 6.
Fill in the blanks in the following:

1. A person 1 m in front of a plane mirror seems to be…….. m away from his image.
2. If you touch your………..ear with your right hand in front of a plane mirror it will be seen in the mirror that your right ear is touched with
3. The size of the pupil becomes………………..when you see in dim light.
4. Night birds have…………..cones than rods in their eyes.

Answer.

1. 2
2. left, left hand
3. large
4. lesser (fewer).

Choose the correct option in Questions 7 and 8.

Question 7.
The angle of incidence is equal to the angle of reflection:
(a) Always
(b) Sometimes
(c) Under special conditions
(d) Never
Answer.
(a) Always.

Question 8.
The image formed by a plane mirror is
(a) virtual, behind the mirror and enlarged,
(b) virtual, behind the mirror and of the same size as the object.
(c) real at the surface of the mirror and enlarged.
(d) real, behind the mirror and of the same size as the object.
Answer.
(b) Virtual, behind the mirror and of the same size as the object.

Question 9.
Describe the construction of a kaleidoscope.
Answer.
A kaleidoscope is an optical instrument used to see a number of beautiful patterns. It is made up of a circular cardboard tube or tube of thick chart paper in which rectangular mirror strips are joined together to form a prism. At one end of the tube, touching these mirrors, a circular plane glass plate is fixed and several, small pieces of colored glass (broken pieces of colored bangles) are placed upon it. This end is closed by a ground glass plate and beautiful patterns are seen through the other end of the kaleidoscope.

Question 10.
Draw a labelled sketch of the human eye.
Answer.

Question 11.
Gurmit wanted to perform, activity 16.8 (NCERT) using a laser torch. Her teacher advised her not to do so. Can you explain the basis of the teacher’s advice?
Answer.
Laser rays can cause a permanent defect in the eye. Thus, his friend will lose her eyesight if a laser torch is directed over her eyes.

Question 12.
Explain how you can take care of your eyes.
Answer.
The following measures should be taken to keep our eyes healthy and free from any defect:

1. We should not look at the sun or a powerful light source directly.
2. We should not try to see in too little or too much light. It is bad for the eyes. Insufficient light causes eye strain and headaches.
3. Too much light, like that of the sun, or powerful lamps, can injure the retina, which is very delicate.
4. If advised, suitable spectacles should be used.
5. We should wash our eyes frequently with clean water.
6. We should always read from a normal distance for distinct vision and not by bringing the book too close or keeping it too far.
7. We should never rub our eyes if any small particle of dust goes into the eyes. Instead, eyes should be washed with clean water and if the condition does not improve, a doctor should be consulted.
8. If food is deficient in some components, the eye may also suffer. Lack of vitamin A in our diet is responsible for many eye troubles. Most common amongst thorns is night blindness. Therefore, to get rid of this, we must include in our diet components that have vitamin A.

Question 13.
What is the angle of incidence of a ray if the reflected ray is at an angle of 90° to the incident ray?
Answer.

Question 14.
How many images of a candle will be formed if it is placed between two parallel plane mirrors separated by 40 cm?
Answer.
The infinite number of images of the candle will be formed if it is placed between two parallel plane mirrors.

Question 15.
Two mirrors meet at right angles. A ray of light is incident on one at an angle of 30° as shown in Fig. 16.5. Draw the reflected ray from the second mirror.

Answer.

Question 16.
Boojho stands at A just on the side of a plane mirror as shown in Fig. 16.6.
Can he see himself in the mirror? Also can he see the image of objects situated at P, Q and R?

Answer.
No, He can see images of objects at P but not of Q and R.

Question 17.
(a) Find out the position of the image of an object situated at A in the plane mirror (Fig. 16.7).
(b) Can Paheli at B see this image?
(c) Can Boojho at C see this image?
(d) When Paheli moves from B to C, where does the image of A move?

Answer.
(a) Fig. 16.7 (a)
(b) Yes
(c) Yes
(d) No change as the position of A is not changing

We hope the NCERT Solutions for Class 8 Science Chapter 16 Light helps you. If you have any query regarding NCERT Solutions for Class 8 Science Chapter 16 Light, drop a comment below and we will get back to you at the earliest.

NCERT Solutions for Class 7 Science Chapter 1 Nutrition in Plants are part of NCERT Solutions for Class 7 Science. Here we have given NCERT Solutions for Class 7 Science Chapter 1 Nutrition in Plants.

NCERT Solutions for Class 7 Science Chapter 1 Nutrition in Plants

Question 1.
Why do organisms need to take food?
Answer:
Organisms need to take food to

1. get the energy to do work.
2.  build up the body.
3. repair damages in the body.
4.  maintain the functions of the body.

Question 2.
Distinguish between a parasite and a saprotroph.
Answer:

 Question 3.
How would you test the presence of starch in leaves?
Answer:

1. Take two healthy green potted plants of the same kind in order to remove all the starch from the leaves.
2.  Keep one in the darkroom (or in a black box) for 72 hours and the other in the sunlight.
3.  Now, take one leaf from each of the plants.
4. Put few drops of iodine solution on each of the leaves.
5.  The leaf kept in the sunlight will turn blue-black due to the presence of starch.
6. The leaf kept in the dark will not turn blue-black because of the absence of starch.

Question 4.
Give a brief description of the process of synthesis of food in green plants.
Answer:
The leaves of a plant have a green pigment called chlorophyll. In the presence of sunlight, they use carbon dioxide and water to synthesize carbohydrates.
Carbon dioxide + Water \(\xrightarrow [ Sunlight ]{ Chlorophyll } \) Carbohydrade + Water + Oxygen
During the process, oxygen is released. The carbohydrates ultimately get converted into starch.
Carbon dioxide from the air is taken through stomata. Water and minerals are absorbed by the roots and transported to the leaves.

Question 5.
Show with the help of a sketch that plants are the ultimate source of food.
Answer:

Fig. Plants capture solar energy by a unique process called photosynthesis

Question 6.
Fill in the blanks:

1. Green plants are called …….. since they synthesize their own food.
2. The food synthesized by the plants is stored as ………
3. In photosynthesis solar energy is captured by the pigment called ……….
4. During photosynthesis plants take in ……… and release ……….

Answer:

1. autotrophs
2. starch
3. chlorophyll
4. carbon dioxide, oxygen

Question 7.
Name the following:

1. A parasitic plant with a yellow, slender, and branched stem.
2. A plant that is partially autotrophic.
3. The pores through which leave exchange gases.

Answer:

1. Cuscuta
2. Insectivorous plants
3. Stomata

Question 8.
Tick the correct answer:
(a) Amarbel is an example of:
(i) Autotroph
(ii) Parasite
(iii) Saprotroph
(iv) Host
(b) The plant which traps and feeds on insects is:
(i) Cuscuta
(ii) China rose
(iii) Pitcher plant
(iv) Rose
Answer:
(ii) Parasite
(iii) Pitcher plant

Question 9.
Match the items given in Column I with those in Column II.

Answer:

 Question 10.
Mark T if the statement is true and ‘F’ if it is false:
(i) Carbon dioxide is released during photosynthesis. (T/F)
(ii) Plants which synthesize their food are called saprotrophs. (T/F)
(iii) The product of photosynthesis is not a protein. (T/F)
(iv) Solar energy is converted into chemical energy during photosynthesis. (T/F)
Answer:
(i) F
(ii) F
(iii) T
(iv) T

Question 11.
Choose the correct option from the following:
Which part of the plant takes in carbon dioxide from the air for photosynthesis?
(i) Root hair
(ii) Stomata
(iii) Leaf veins
(iv) Petals
Answer:
(ii) Stomata

Question 12.
Choose the correct option from the following:
Plants take carbon dioxide from the atmosphere mainly through their:
(i) roots
(ii) stem
(iii) flowers
(iv) leaves
Answer:
(iv) leaves

Question 13.
Why do farmers grow many fruits and vegetable crops inside large greenhouses? What are the advantages to the farmers?
Answer:
Most of the crops require a lot of nitrogen to make protein. After the harvest, the soil becomes deficient in nitrogen. Though nitrogen gas is available in the air, plants cannot use it directly. They need nitrogen in a soluble form. The bacterium called Rhizobium can take atmospheric nitrogen and convert it into soluble nitrogenous components. Rhizobium is present in the roots of some fruits and vegetables and legumes plants which provides nitrogen to them. By crop rotation, farmers increase the nitrogenous compounds in soil. So there is no need to add nitrogenous fertilizers to the soil in which leguminous plants are grown. By this practice, farmers provide good quality crops and save money.

We hope the NCERT Solutions for Class 7 Science Chapter 1 Nutrition in Plants help you. If you have any query regarding NCERT Solutions for Class 7 Science Chapter 1 Nutrition in Plants, drop a comment below and we will get back to you at the earliest.

NCERT Solutions for Class 8 Science Chapter 15 Some Natural Phenomena are part of NCERT Solutions for Class 8 Science. Here we have given NCERT Solutions for Class 8 Science Chapter 15 Some Natural Phenomena.

NCERT Solutions for Class 8 Science Chapter 15 Some Natural Phenomena

NCERT TEXTBOOK EXERCISES

Select the correct option in Questions 1 and 2.

Question 1.
Which of the following cannot be changed easily by friction?
(a) A plastic scale
(b) copper rod
(c) An inflated balloon
(d) A woolen cloth.
Answer.
(b) A copper rod.

Question 2.
When a glass rod is rubbed with a piece of silk cloth the rod
(а) and the cloth both acquire a positive charge.
(b) becomes positively charged while the cloth has a negative charge.
(c) and the cloth both acquire a negative charge.
(d) becomes negatively charged while the cloth has a positive charge,
Answer.
(d) becomes negatively charged while the cloth has a positive charge.

Question 3.
Write T against true and ‘F’ against false in the following statements:
(a) Like charges attract each other. (T/F)
(b) A charged glass rod attracts a charged plastic straw. (T/F)
(c) Lightning conductor cannot protect a building from lightning. (T/F)
(d) Earthquakes can be predicted in advance. (T/F)
Answer.
(a) False
(b) True
(c) False
(d) False

Question 4.
Sometimes, a crackling sound is heard while taking off a sweater during winters. Explain.
Answer.
The crackling sound is heard because when the sweater is rubbed while taking it off, it acquires a small charge.

Question 5.
Explain why a charged body loses its charge if we touch it with our hand.
Answer.
When we touch a charged body the total charge is transferred into the earth through our body and it loses its charge.

Question 6.
Name the scale on which the destructive energy of an earthquake is measured. An earthquake measures 3 on this scale. Would it be recorded by a seismograph? Is it likely to cause much damage?
Answer.
The destructive energy of an earthquake is measured on a scale called the Richter scale. An earthquake that measures 3 on the Richter scale Will be recorded by a seismograph. However, it is not likely to cause much damage.

Question 7.
Suggest three measures to protect ourselves from lightning.
Answer.

1. We should not use TV or cable phone during lightning.
2. After hearing the last thunder, wait for at least 30 minutes before coming out of the safe place.
3. A house or a building is a safe place. If you are travelling by car or by bus, you are safe inside with the windows and doors of the vehicle shut.

Question 8.
Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon?
Answer.
A charged balloon is repelled by another charged balloon because both have the same charge. And we know similar charges repel each other. But a charged balloon attracts an uncharged balloon and loses its own charge to the other balloon.

Question 9.
Describe with the help of a diagram an instrument which can be used to detect a charged body.
Answer.
Electroscope: An electroscope is a device used to detect the presence of charge of an object.
Principle: It works on the principle that like charges repel while unlike charges attract each other.

Structure and Working: An electroscope has a metal rod with a thin metal strip or leaf attached to it at the bottom. At the top, the rod enters into a cup. The bottom part of the rod and leaf is enclosed in a glass box for protection. When the knob of the electroscope is touched with a charged ebonite or glass rod, the leaves open out or diverge. The extent of divergence depends upon the amount of charge on the electroscope.

Question 10.
List three states in India where earthquakes are more likely to strike.
Answer.
The states that fall in seismic zones are more earthquake-prone. Jammu and Kashmir, Himachal Pradesh, and Gujarat are a few such states.

Question 11.
Suppose you are outside your home and an earthquake strikes. What precautions would you take to protect yourself?
Answer.

1. Find a safe place, that will be away from buildings, trees and overhead power lines. Do not be on the ground but squat low on it to make yourself the smallest target to be struck.
2. If we are in a car or a bus, we should not come out, as the driver needs to drive slowly to a clear spot. Do not come out till the earthquake stops.

Question 12.
The weather department has predicted that a thunderstorm is likely to occur on a certain day. Suppose you have to go out on that day. Would you carry an umbrella? Explain.
Answer.
No, I would not carry an umbrella. Because the pointed rod of the umbrella can become a target of lightning.

We hope the NCERT Solutions for Class 8 Science Chapter 15 Some Natural Phenomena help you. If you have any query regarding NCERT Solutions for Class 8 Science Chapter 15 Some Natural Phenomena, drop a comment below and we will get back to you at the earliest.

NCERT Solutions for Class 8 Science Chapter 14 Chemical Effects of Electric Current are part of NCERT Solutions for Class 8 Science. Here we have given NCERT Solutions for Class 8 Science Chapter 14 Chemical Effects of Electric Current.

NCERT Solutions for Class 8 Science Chapter 14 Chemical Effects of Electric Current

NCERT TEXTBOOK EXERCISES

Question 1.
Fill in the blanks:

1. Most liquids that conduct electricity are solutions of……..,……………and …………..
2. The passage of an electric current through a solution causes…………..effects.
3. If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the………..terminal of the battery.
4. The process of depositing a layer of any desired metal on another material by means of electricity is called.………

Answer.

1. acids, bases, salts
2. chemical
3. negative
4. electroplating.

Question 2.
When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?
Answer.
Yes, it is because the solution conducts electricity.

Question 3.
Name three liquids, which when tested in the manner shown in Fig. 14.1, may cause the magnetic needle to deflect.

Answer.
Tap water/sodium chloride solution, hydrochloric acid.

Question 4.
The bulb does not glow in the setup shown in Fig. 14.2. List the possible reasons. Explain your answer.
Answer.
List of possible reasons:

1. The liquid solution might be conducting electricity, but the current produced is too small so that the filament of the bulb does not get heated and the bulb does not glow.
2. Or, it is possible that the connections are loose.
3. Or, the bulb is fused.
4. Or, the cells are used up.
   

Question 5.
A tester is used to check the conduction of electricity through two liquids, labelled A and B. It is found that the bulb of the tester glows brightly for liquid A while it glows very dimly for liquid B. You would conclude that
(i) liquid A is a better conductor than liquid B.
(ii) liquid B is a better conductor than liquid A.
(iii) both liquids are equally conducting.
(iv) conducting properties of liquid cannot be compared in this manner.
Answer.
If the bulb glows brightly with liquid A, it means that liquid A is a better conductor of electricity than B. So the answer will be (i).

Question 6.
Does pure water conduct electricity? If not, what can we do to make it conducting?
Answer.
Pure water does not conduct electricity. It can be made conducting if acid, base, or salt is dissolved in it.

Question 7.
In case of a fire, before the firemen use the water hoses, they shut off the main electrical supply of the area. Explain why they do this.
Answer.
The water used in water hoses is not pure water and it conducts electricity. Firemen shut off the main electrical supply of the area because if the supply of electricity continues there may be a high risk of electrocution in the whole area due to water.

Question 8.
A child staying in a coastal region test the drinking water and also the seawater with his tester. He finds that the compass needle deflects more in the case of seawater. Can you explain the reason?
Answer.
The impure water is the conductor of electricity. Seawater contains more impurity (salt) than drinking water. Therefore, seawater conducts more electricity than drinking water. That is why the compass needle deflects more in the case of seawater.

Question 9.
Is it safe for the electrician to carry out electrical repairs outdoors during heavy downpours? Explain.
Answer.
It is not safe for the wireman to carry out electrical repairs outside during heavy downpours. Because during heavy downpour there is a high risk of electrocution.

Question 10.
Paheli had heard that rainwater is as good as distilled water. So she collected some rainwater in a clean glass tumbler and tested it using a tester. To her surprise, she found that the compass needle showed deflection. What could be the reasons?
Answer.
Rainwater is, of course, as good as distilled water but, when it passes through the atmosphere, it dissolves a lot of dust, dirt, and impurities and becomes conductive. So, when Paheli used a tester, its compass showed deflection.

Question 11.
Prepare a list of objects around you that are electroplated.
Answer.
Ornaments, wheel rims of vehicles, the handlebar of cycle and motorcycle, pots of one metal coated with other, bath taps, kitchen gas burner, the bottom of cooking utensils, handles of doors, tin cans, etc.

Question 12.
The process that you saw in Activity 14.7 (NCERT) is used for the purification of copper. A thin plate of pure copper and a thick rod of impure copper are used as electrodes. Copper from impure rod is sought to be transferred to the thin copper plate. Which electrode should be attached to the positive terminal of the battery and why?
Answer.
To perform such activity we have to arrange copper sulphate crystals and two copper plates each having a size around 10 cm long and 4 cm wide. Now take 250 mL distilled water in a clean and dry beaker. Dissolve two teaspoonfuls of copper sulphate crystals in it to obtain copper sulphate solution. (You may add few drops of dilute sulphuric acid to copper sulphate solution to make it more conducting). Clean each copper plate with sandpaper. Now rinse it with water. With the help of wires, connect one copper plate to each terminal of two cell batteries (Take care that the two plates do not touch each other).

Immerse two plates in copper sulphate solution as shown in Fig. 14.3. Allow the current to pass through for 5 to 7 minutes.

When an electric current is passed through the copper sulphate solution, copper sulphate dissociates into copper and sulphate. The free copper gets drawn to the plate connected to the negative terminal of the battery and thus gets deposited on that plate. Gradually, a layer of copper builds upon the plate.

We hope the NCERT Solutions for Class 8 Science Chapter 14 Chemical Effects of Electric Current help you. If you have any query regarding NCERT Solutions for Class 8 Science Chapter 14 Chemical Effects of Electric Current, drop a comment below and we will get back to you at the earliest.