Class 8 Science

Simple Magnetic Force Activity Using Paperclips For CBSE Class 8 Activity 1

Aim: To identify push or pull by observing the motion of objects.

Material Required: Pen and paper.

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Procedure:

1. Take a familiar situation of moving objects.
2. Draw a table as shown below.
3. Now, identify the action involved in each case and categorise it into push or pull.

Where To Find Class 8 Force And Pressure Lab Manual NCERT-Aligned Activity 2

Aim: To learn more about forces by exploring them.

Material Required: A heavy object like a table or box.

Procedure:

1. Push the box by yourself.
2. Now, ask your friend to help you in pushing it in the same direction. You will find that it is easier to move than before.
3. Now, ask your friend to push it from the opposite side. You will find that the box moves in the direction where the stronger push is applied.
4. Note the direction of motion in each case

Conclusion: When force is applied in the same direction, then the movement of the box increases, and when forces are applied from the opposite direction, the box moves slowly.

Common Viva Questions On Pressure Activities Class 8 Activity 3

Aim: To show that when a force is applied to an object at rest, it begins to move.

Material Required: A rubber ball and a table.

Procedure:

1. Place the rubber ball on the level surface of the table.
2. Push the ball very slowly along the level surface.
3. The ball will start moving, push the moving ball in the direction of its motion. You will observe that the speed of the moving ball increases.
4. Now, place your palm in front of the moving ball.
5. Remove your palm as soon as the ball touches it.
6. You will observe that the speed of the moving ball decreases.

Conclusion: Force can increase or decrease the speed of the object.

Common Viva Questions On Pressure Activities Class 8 Activity 4

Aim: To determine whether force can change the direction. Material Required: A ruler and a ball.

Procedure:

1. Place the ball on a level surface and push it.
2. Now, place a ruler in its path as shown in the figure

Note the motion of the ball when it strikes the ruler.

Repeat the activity by placing the ruler at different angles.

How To Calculate Force And Pressure In Class 8 Activities Activity 5

Aim: To study the effect of force on objects.

Material Required: Pen and paper.

Procedure:

1. List some phenomena as mentioned in the table.
2. Now, categorise them by observing the action of force.

Class 8 Science Chapter 8 Force And Pressure Activity 6

Aim: To study the type of force applied by the magnet.

Material Required: A pair of bar magnets and 3 round-shaped pencils.

Procedure:

1. Place the longer side of a magnet on the 3 rounded shape pencil as shown in the figure.
2. Now, bring one end of the other magnet near the end of the magnet placed on the pencil.
3. Do not touch the ends of a magnet, then observe the motion of the magnet.
4. Now, bring the other end ofthe magnet near the same end of the magnet placed on the pencil.
5. Again, observe the motion of the magnet.

Class 8 Science Chapter 8 Force And Pressure Activity 7

Aim: To identify the type of force (contact or non-contact) applied by electrically charged objects.

Material Required: A table, a long thread, a straw, and scissors.

Procedure:

1. Cut the plastic straw into nearly two equal pieces.
2. Suspend one of the pieces from the edge of the table with the help of a thread.
3. Now, take the other piece of straw and rub it with a sheet or paper.
4. Bring the rubbed end of the straw near the suspended straw.
5. Observe the movement in suspended straw. You will find that it will attract towards it.
6. Now, rub the free end of the suspended straw with the paper.
7. Again, bring the straw that was earlier rubbed with the paper.
8. Again, observe the motion of the suspended straw. You will find that it will repel each other.

Conclusion: Electrostatic force is a non-contact force.

Class 8 Science Chapter 8 Force And Pressure Activity 8

Aim: To demonstrate that liquid exerts pressure at the bottom of its container.

Material required: A transparent plastic pipe of length 25 cm and diameter about 5-7.5 cm, a balloon, and water.

Procedure:

1. Fix the rubber balloon at one end of the pipe.
2. Now, hold the pipe in a vertical position and ask your friend to pour some water into the pipe.
3. Note the height of the water column and the change in shape of the balloon.
4. Now, pour some more water and note the increase in the balloon.
5. Repeat the same process 2-3 times and try to find the relation between the bulge and the height of the water column.

Conclusion

1. A liquid exerts pressure at the bottom of its container.
2. The pressure exerted by a liquid depends on the height of the liquid column

Class 8 Science Chapter 8 Force And Pressure Activity 9

Aim: To demonstrate that the liquid exerts pressure on the walls of its container.

Material Required: A plastic bottle, a cylindrical glass tube of a few cm long, a balloon, and water.

Procedure:

1. Make a hole near the bottom of the bottle.
2. Fix the tube into the hole and attach a balloon (fixed tightly) on the other end of the tube. See the figure.
3. Now, fill the bottle upto half with water and note the bulge of the balloon.
4. Add some more water and again observe the change in the bulge.

Conclusion: From this activity, we can also conclude that

A liquid exerts pressure on the walls of its container.

The pressure exerted by the liquid on the walls of its container depends on the height liquid level from the bottom.

Class 8 Science Chapter 8 Force And Pressure Activity 10

Aim: To demonstrate that liquid exerts equal pressure at the same depth.

Material required: Empty plastic bottle and water.

Procedure:

1. Drill four holes all around near the bottom of the bottle.
2. Make sure the holes are at the same height from the bottom.
3. Pour the water into the bottle and measure the distance where the water jet falls from the bottle. You will find that the different streams of water coming out of the holes fall at the same distance from the bottle.

Conclusion Liquid: Exert equal pressure if they are at the same depth.

Class 8 Science Chapter 8 Force And Pressure Activity 11

Aim: To show the effect of pressure due to air.

Material Required: A rubber sucker.

Procedure:

1. Hold a good Quality of rubber sucker.
2. Try to press it on a flat, smooth surface, so most of the air between its cup and the surface escapes out.
3. We will notice that the sucker sticks to the surface.
4. Now, try to pull the sucker off the surface, you will find little hard to pull it off.
5. To pull the sucker off the surface, the applied force should be large enough to overcome the atmospheric pressure.

Conclusion: We have concluded that the sucher sticks to the surface because the pressure of the atmosphere acts on it.

Class 8 Science Chapter 4 Combustion And Flame Very Short Answer Questions

Question 1. Which type of substances produce flame? Does charcoal burn with flame?
Answer: The substances that vaporise during burning produce flame. No, charcoal does not burn with flame; it glows only.

Question 2. What are the products obtained when combustion takes place?
Answer: The products of combustion are carbon dioxide, water vapour, heat, and light.

Read And Learn More CBSE Class 8 Science Very Short Questions And Answers

Question 3. Name the substance that gives heat and light after combustion.
Answer: The substance that provides heat and light is called fuel

Question 4. If you burn a candle and a coal, what is the difference in their burning?
Answer: A Candle burns with a flame, whereas coal burns by producing light in the form of a glow.

Question 5. How is heat produced in our body?
Answer: In our body, food is broken down by reaction with oxygen. During such reactions, heat is produced. This heat keeps our body warm.

Question 6. Name two fuels that we use in our homes for cooking food.
Answer: Two fuels which we use in our homes for cooking food are LPG and kerosene oil.

Question 7. Like fuels, the Sun also provides heat and light. What is the source of heat and light in the Sun?
Answer: In the Sun, heat and light are produced by nuclear reactions.

Question 8. Out of kerosene oil or wood, which has a higher ignition temperature?
Answer: Wood has a higher ignition temperature than kerosene oil.

Question 9. In what form can CO2 be stored in cylinders?
Answer: CO2 can be stored in cylinders in liquid form.

Question 10. Do all the substances catch fire at the same temperature?
Answer: No, different substances need different temperatures to catch fire due to their different ignition temperature.

CBSE Class 8 Science Chapter 7 Reaching The Age Of Adolescence Multiple Choice Questions

Question 1. The most conspicuous visible change that occurs in boys during puberty is

1. Development in the voice box
2. Increase in height
3. Production of sperm
4. Increased sweating

Answer: Increase in height

Question 2. Pimples and acne are formed due to the increased activity of

1. Adrenal glands
2. Sebaceous glands
3. Thyroid gland
4. Sweat glands

Read And Learn More CBSE Class 8 Science Multiple Choice Questions

Choose the correct option

1. 1 and 2
2. 2 and 2
3. 1 and 3
4. 2 and 4

Answer: 2 and 4

CBSE Class 8 Science Chapter 7 Reaching The Age Of Adolescence MCQ with answers

Question 3. The dramatic changes in body features associated with puberty are mainly because of the secretions of

1. Thyroxine
2. Oestrogen
3. Adrenaline
4. Testosterone

Choose the correct Option 

1. (1) and (2)
2. (2) and (3)
3. (1) and (3)
4. (2) and (4)

Answer: 4. (2) and (4)

Question 4. The male hormone is

1. Oestrogen
2. Progesterone
3. Testosterone
4. All of these

Answer: 3. Testosterone

Question 5. How do the endocrine glands’ hormones secreted during puberty induce changes in the body?

1. It decreases the muscle mass
2. It reduces the metabolism, increasing the food intake
3. It stimulates changes in different parts of the body
4. It doubles the capability of body parts to function

Answer: 3. It stimulates changes in different parts of the body

Question 6. The beginning of menstruation at puberty is called

1. Ovulation
2. Menstruation
3. Menarche
4. Menopause

Answer: 3. Menarche

Question 7. Given below are events that lead to pregnancy and the development of the embryo.

1. Fertilisation of the egg
2. Maturation of the egg
3. Release of egg
4. Embedding of the embryo in the uterus

Which of the following options gives the correct order of sequence in which they occur?

1. (1). (2). (3), (4)
2. (2), (1), (3), (4)
3. (1), (4), (2), (3)
4. (2), (1) (3) (4)

Answer: (4). (2), (1). (4)

Question 8. Structures present in a cell which Is responsible for determining the sex of a baby are

1. Cytoplasm
2. Cell membrane
3. Nucleus
4. Chromosome

Answer: 4. Chromosome

Question 9. The number of chromosomes present in a human cell

1. 22 pairs
2. 23 pairs
3. 24 pairs
4. 26 pairs

Answer: 2. 23 pairs

Question 10. The belief that the mother is completely responsible for the sex of the child is wrong because the child

1. Gets sex chromosome only from the mother
2. Develops in the body of the mother
3. Gets one sex chromosome from the mother and the other from the father
4. Gets sex chromosome only from the father

Answer: 3. Gets one sex chromosome from the mother and the other from the father

Real-Life Examples To Explain Adolescence Changes: Class 8 Long Answer Type Questions

Question 1. During adolescence, the body of boys and girls undergoes critical changes. Given below of those changes

1. Broad shoulders
2. Wider chosts
3. Wider region below the waist
4. Development of muscles
5. Development of mammary glands
6. Growth of facial hair
7. Acne and pimples on the face
8. Development of sex organs
9. High-pitched voice
10. Growth of pubic hair

Categorise these changes into those that occur in boys and those that occur in girls, and fill in the table given below.

Body changes during adolescence

Answer: Body changes during adolescence are given below

Question 2. In the figure, mark the position of the endocrine glands that release the hormones that control the release of sex hormones.
Answer: Pituitary gland. It releases hormones that control the release of sex hormones, i.e., testosterone in males and oestrogen in females.

Answer:

Testis. It releases testosterone, which is responsible for the secondary sexual characteristics in boys prevents diabetes.

The Pancreas releases insulin, which prevents diabetes

Maintain the correct salt balance in the blood.

The adrenal gland releases aldosterone, which maintains the correct salt balance in the blood.

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Question 3. Choose the correct option.

1. Adolescents should be careful about what they eat, because

1. A proper diet develops their brains
2. A proper diet is needed for the rapid growth taking place in their body
3. Adolescents feel hungry all the time
4. Taste buds are well developed in teenagers

2. Reproductive age in women starts when their

1. Menstruation starts
2. Breasts start developing
3. Body weight Increases
4. Height increases

The right meal for adolescents consists of

1. Chips, noodles, cake
2. Chapati, dal, vegetables
3. Rice, noodles, and a burger
4. Vegetable cutlets, chips and lemon drink

Answer: Adolescents should be careful about what they eat because a proper diet is needed for the rapid growth taking place in their bodies.

1. Reproductive age in women starts when their menstruation starts.
2. The right meal for adolescents consists of chapati, dal and vegetables
3. Question 8 Write notes on
4. Adam’s apple.
5. Secondary sexual characteristics.
6. Sex determination of the unborn baby.

Answer:

Adam’s apple: In males, the protruding part of the growing voice box is called Adam’s apple. In boys, the voice box (larynx) develops larger than in girls, and this protruding part is seen as a bulge in the neck area.

Secondary sexual characteristics: The physical features that help to distinguish males from females are called secondary sexual characteristics. These characters develop at the time of puberty. The secondary sexual characteristics in humans are given below. In males,

1. Growth of pubic hair, beard, and moustaches.
2. Hair on chest and underarms.

In females,

1. Enlargement of breasts.
2. Appearance of pubic hair, hair underarms.

Sex determination of the unborn baby. The Sex of the unborn baby is determined by the sex chromosomes, i.e., X and Y.

In females, the gamete (i.e., egg) has only one X chromosome, but in males, the gamete (i.e. sperm) may have an X chromosome or Y chromosome.

If the egg fertilises with sperm containing an X chromosome, the zygote will develop into a female (XX), and if the egg fertilises with sperm containing a Y chromosome, the zygote will develop into a male (XY)

Question 4. The table given below shows the trend in likely heights of boys and gills os they grow in age. Draw graphs showing height and Ago for both boys and girls on the same graph paper. What conclusions can be drawn from this graph?

Answer: We conclude that initially. Girls grow faster than boys, hitting about 18 years of age. Both reach their maximum height. The rate of growth in brightness varies in Different individuals.

Question 4. The heights of students of four different sections of grade 8 are measured. The table shows the percentage of maximum height up to which the students in each section have grown

In which class have both the boys and the girls reached the end of puberty?

1. Section A
2. Section B
3. Section C
4. Section D

Answer: Section B.

What can be concluded from the table?

1. Girls are taller than boys in all four classes
2. Girls attain their maximum height earlier than boys
3. Girls grow faster than boys throughout their childhood
4. Girls and boys attain their maximum height at the same age

Answer: Girls attain their maximum height earlier than boys.

Question 5. An ovum contains one X chromosome. A sperm contains an X or a Y chromosome. A sperm can fertilise an ovum to produce two different zygotes.

1. Which chromosome does the female zygote receive from the mother and the father?

Answer: 1. Mother X-chromosome, father X-chromosome

Which of those stntomonts is supported by the picture?

Circle ‘Yes’ or ‘No’ for the correct response

Answer: A. Yes B. Yes C. No

Question 6. Diabetes is a condition in which the blood sugar level of a person rises above the normal level. The table below shows the average range of blood sugar levels at fasting

Doctors prescribe insulin injections for patients with high blood sugar levels. However, glucagon is injected in an emergency if the blood sugar level of a person drops too low.

Which of these is true about the gland that secretes insulin in the human body?

1. It has no ducts
2. It is located on the skin
3. It controls the function of all other glands
4. It releases hormones that help in growth

Answer: It has no ducts

Under what conditions of blood sugar level is glucagon likely to be injected?

1. Below 60 mg/dL
2. 80-100 mg/dL
3. 100-120 mg/dL
4. Above 120 mg/dL

Answer: Below 60 mg/dL

CBSE Class 8 Science Chapter 7 Reaching The Age Of Adolescence Short Answer Questions

Question 1. Define adolescence as stated by the WHO. Why is adolescence also called teenage?
Answer: The World Health Organisation (WHO) defines adolescence as the period of life between 11 and 19 years of age. Since adolescence covers the teen period, i.e., 13-19 years of age, adolescence is also called ‘teenage’.       

Question 2. Salma had very soft and smooth skin during her childhood. As she entered adolescence, she developed pimples on her face. The skin specialist advised her to wash her face at regular intervals. Can you explain the reasons for the appearance of pimples on her face and suggest ways to prevent them? Competency-Based Question
Answer: During adolescence, the secretion of sweat glands and sebaceous glands increases, leading to acne and pimples. Regular face wash keeps the face clean and dry and helps to reduce pimples.

Read And Learn More CBSE Class 8 Science Short Answer Questions

Question 3. Mention any two features that are seen in boys and girls, each to distinguish them from each other at puberty.
Answer: Two features seen in boys at puberty are

• Growth of facial hair.
• Voice becomes hoarse.
• Two features seen in girls at puberty are
• Development of breasts.
• The region below the waist becomes wider

Question 4. In human females, each time during maturation and release of an egg, the Inner wall of the uterus thickens. Is this thickening permanent? Give reasons.
Answer: No, this thickening of the uterine wall is not permanent. If the egg gets fertilised, it starts developing and gets embedded in the uterine wall, resulting in pregnancy. During pregnancy, no more eggs are released, and the thickened lining is discharged only when the baby Is born. However, if fertilisation does not occur, the released egg and the thickened lining are shed off, resulting in menstruation.

Question 5. Fill the blank circles in the figure and identify the sex of child A and B

Answer:

Question 6. Name the hormone that would be released during the following situations.

• A frightened person
• Growth of a child into an adult
• Development of the caterpillar into the moth
• Development of tadpole to frog

Answer: Adrenaline is secreted from the adrenal gland during stress conditions like fright or fear, anger, worry or embarrassment.

• Growth hormone is secreted from the pituitary gland to regulate the normal growth ofa person, i.e., growth of a child to adult.
• Insect hormones control the development of the caterpillar and the lo moth.
• Thyroxine is produced by the thyroid gland to control the development of a tadpole into a frog.

Question 7. A tadpole is kept in a lagoon with deficient water. How will it affect its growth? Explain
Answer: Tadpoles growing in Iodine deficient water have retarded growth. This is because the growth and development is regulated by thyroxine hormone which is produced by thyroid gland As loodine required for thyroxine production, retarded growth Is seen In tadpoles When kept In Water.

Question 8. Liia always eats only dal and rice in everyday meals; she often falls and has become prone to diseases. Can you suggest changes in her diet Which can make her healthy and free from diseases?
Answer: Lila’s diet is not balanced because her meals do not contain (lie adequate nutrition. She likes only proteins mid airliohydriilcn In every mail. She requires vitamins mid minerals in her meal to protect her from various diseases, Thus, I would suggest her lo include fruits and vegetables in her meal as a source of vitamins and minerals.

CBSE Class 8 Chapter 7 Reaching The Age Of Adolescence Very Short Answer Type Questions

Question 1. Adolescence is the period from 13-19 years of age. Is there any other term for this period?
Answer: Yes, the other term for adolescence is teenage.

Question 2. Do all the parts of the body grow at the same rate? State yes or no.
Answer: No, all parts of the body do not grow at the same rate.

Question 3. What is the common name of the bulge (or projection) at the front of the throat in grown-up boys?
Answer: Adam’s apple.

Question 4. Some characters distinguish a boy from a girl. What are they called?
Answer: Secondary sexual characteristics distinguish a boy from a girl

Question 5. Name the hormone that is released by the testes at the onset of puberty.
Answer: Testosterone is the male hormone that is released from the testes at the onset of puberty.

Question 6. Name the female hormone produced by the ovaries that helps in the development of mammary glands.
Answer: Oestrogen is the female hormone produced by the ovaries that helps in the development of breasts/mammary glands.

Question 7. State the function of the male sex hormone testosterone.
Answer: Testosterone is involved in the development of the reproductive organs and controls secondary sexual characteristics.

Question 8. Give a suitable word for each of the following statements.

1. The site that responds to a hormone.
2. Name of a gland which transports secretions through ducts.
3. Chemicals that control changes at the adolescent stage.
4. It marks the beginning of the reproductive period.

Answer:

1. Target site
2. Sweat glands
3. Hormones
4. Puberty

Question 9. Out of the two sexes of humans, which one has a longer reproductive phase of life?
Answer: Men have a longer reproductive phase oflife than women.

Question 10. What is the name of the process in which the thickened uterus lining along with its blood vessels is removed from the body of a woman through vaginal bleeding.
Answer: Menstruation cycle.

Question 11. Which comes earlier in the life of a woman, menarche or menopause?
Answer: The reproductive life of a woman starts at menarche and ends at menopause. Thus, menarche comes earlier.

Question 12. What is menstruation? Explain.
Answer: Menstruation is the monthly reproductive cycle that occurs in women once in about 28-30 days.

It is the release of unfertilised eggs along with blood. If the egg released from the ovary does not get fertilised, the released egg and the thickened lining of the uterus, along with its blood, are released from the body.

CBSE Class 8 Science Chapter 7 Reaching The Age Of Adolescence Activitys

Activity 1

Aim: To determine the maximum height that would be reached at the end of the growth period.

Materials Required: Graph paper, pencil, table, etc

Read And Learn More CBSE Class 8 Science Activities

Procedure:

1. Use the data given in the table in the previous activity to draw a graph.
2. Take age as an X X-axis and per cent growth in height on the Y-axis.
3. Mark the point representing your age on the graph (Let the age of a girl be 11 years, height be 120 cm).
4. Find out the percentage of height already reached and calculate the height she might eventually reach

Observation

At the age of 11 years (girl), the point of age touches the 88% mark on the height axis. So, the maximum height that will eventually be reached

Present height / % of full height at this age x = 100 = 136.36 cm

Conclusion: From this activity, we conclude that we can determine the maximum height that would be reached at the end growth period using the formula.

CBSE Class 8 Science Chapter 4 Combustion And Flame Activity Ideas Activity 1

Aim: To show that the quality of the burning flame depends on the amount ofair available around it.

Materials Required: A candle, a glass chimney, a few wooden blocks and a glass plate.

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Procedure:

• Fix a lit candle on a table.
• Put a glass chimney on the candle.
• Rest this arrangement of the chimney on the wooden blocks.
• Make sure that air can enter the chimney
• Remove the wooden blocks and let the chimney rest on the table.
• Finally, put a glass plate over the chimney
• Note the observations.

Observation: When the chimney is on wooden blocks, the candle burns freely as the air enters the chimney. When the wooden blocks are removed, the air does not enter the chimney.

Due to this, the candle starts to produce smoke. You will also observe the flame of a candle flickering. Now, when we put the glass plate over the chimney, the flame finally goes.

Conclusion: We can conclude that air is necessary for burning. Partial availability ofair causes the smoke to be produced. Complete lack ofair causes the flame to go off.

Class 8 Science Chapter 4 Combustion And Flame Hands-On Experiments Activity 2

Aim: To show the supply of oil needed for combustion.

Materials Required: A Piece of wood or charcoal, an Iron plate or tawa, a glass jar or a transparent plastic jar.

Procedure:

1. Place a piece of burning wood or charcoal on the Iron plate or tawa.
2. Cover it with the glass jar or the transparent plastic jar.
3. Note the observation.

Observation: Wood or charcoal burns under the jar and continues burning for some time. But, after some time burning stops.

Conclusion: Wood and charcoal stop burning after they are covered with a glass or transparent plastic jar, which shows that air is necessary for combustion.

CBSE Class 8 Science Chapter 4 Combustion And Flame Simple Experiments Activity 3

Aim: To show that ignition temperature is essential for substances like paper to burn.

Materials Required: A Sheet of paper, water and candles.

Procedure:

1. Make two paper cups by folding a sheet of paper.
2. Pour about 50 ml of water into one of the cups.
3. Heat the cups separately with the help of a candle.
4. Note your observations.

Observation: We see that the empty paper cup catches fire easily and starts burning. On the other hand, the paper cup containing water does not catch fire. The water in the cup becomes hot gradually. If continued heating, water will start even boil in the paper cup.

Conclusion:

• When we heat an empty paper cup, its ignition temperature is reached quickly. It catches fire and starts burning.
• When we heat the paper cup having water, the heat is transferred to the water by conduction. The Ignition temperature of paper is not reached, and hence, it does not burn.
• This shows that ignition temperature is essential for a substance to burn.

Class 8 Science Chapter 4 Combustion and Flame Activity With Step-By-Step Guide Activity 4

Aim: To show that the innermost zone of a candle flame consists of unburnt wax vapour.

Materials Required: A candle, a glass tube, a pair of tongs and a matchstick.

Procedure:

1. Light the candle carefully.
2. Hold the glass tube with a pair of tongs.
3. Introduce one end of the glass tube in the dark zone of a non-flickering candle flame.
4. Bring the lit matchstick near the other end of the glass tube as shown in the figure given above.

Note your observations.

Observation: When a lit matchstick is brought near the other end ofthe glass tube, we observe a flame at this end. It is because the innermost zone (dark zone) of the candle flame consists of unburnt wax vapours. Some vapours from it enter the glass tube. When the lit matchstick is brought near it, the wax vapours start burning and produce a flame.

Conclusion: A flame burns at the other end of the glass tube when a matchstick is lit near it. Hence, we can conclude that the innermost zone (dark zone) candle flame has unburnt wax vapours.

Activity 5

Aim: To show that the middle zone of a candle flame consists of unburnt carbon particles.

Materials Required: A candle, a glass plate, and a pair of tongs.

Procedure:

1. Light the candle.
2. Hold the glass plate with a pair of tongs as shown in the figure.
3. Introduce the glass plate in the middle zone.
4. Hold it for 10 seconds and then remove.

Note the observation.

Observation: When the glass plate is kept over the middle zone of the flame, a blackish circular ring is formed. The blackish ring is produced due to the deposition of unburnt carbon particles present in the luminous zone of the flame.

Conclusion: The observation concludes that the partial combustion of wax vapours in the luminous zone produced unburnt carbon particles.

CBSE Class 8 Science Chapter 4 Combustion And Flame Activity With Observation Notes Activity 6

Aim: To show that the outermost zone of a flame is the hottest

Materials Required: A copper wire, a pair of tongs and a candle.

Procedure:

1. Take a copper wire.
2. Hold it’s one end with a pair of tongs.
3. Introduce its other end just inside the flame (outermost zone) for about 30 seconds.

Note the observation.

Observation: We observe that the portion of the copper wire just inside the flame gets red hot.

Conclusion: The observation concludes that the outermost, non-luminous zone of the flame has a high temperature. Hence, it is the hottest part of the flame.

CBSE Class 8 Science Chapter 4 Combustion and Flame worksheet With Answers Fill In The Blanks

Question 1. A __________ process in which a substance reacts with _____ to give off heat is called combustion.
Answer: chemical, oxygen

Question 2. When the clothes of a person catch __________, the person is covered with a __________ to extinguish the fire.
Answer: Fire, blanket

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Question 3. The substances that give very __________ ignition temperatures and can easily catch fire with a flame are called __________ substances.
Answer: Low, inflammable

Question 4. The substances which vaporise during _____________ given flame.
Answer: Burning

Question 5. Wood, paper, and CNG are substances.
Answer: Combustible

Question 6. Burning of wood and coal causes _______ of air.
Answer: Pollution

Question 7. A liquid fuel used in homes is ________.
Answer: Kerosene

question 8. Fuel must be heated to its _______ before it starts burning.
Answer: Ignition temperature

Question 9. Fire produced by oil cannot be controlled by ________.
Answer: Water

Question 10. ___________ fuel is cheap, readily available, and causes less
Answer: Ideal

Question 11. ___________ gas is a promoter of combustion
Answer: Oxygen

Class 8 Science Chapter 4 Extra Questions And Answers For Exam Preparation: True or False

Question 1. Air is necessary for combustion.
Answer: True

Question 2. Magnesium is a non-combustible metal.
Answer: False, magnesium is a combustible metal.

Question 3. Carbon dioxide is an excellent fire extinguisher.
Answer: True

Question 4. Water is the best extinguisher for fires involving electrical equipment.
Answer: False, carbon dioxide is the best extinguisher for fires involving electrical equipment.

Question 5. The middle zone is the hottest zone of a flame.
Answer: False, the outer zone is the hottest zone of a flame.

Question 6. LPG fire is an inflammable substance.
Answer: True

Question 7. Spontaneous combustion takes place in the absence of external heat.
Answer: True

Class 8 Science Chapter 4 Combustion And Flame Match The Columns

Question 1. Match Column 1 with Column 2.

Answer: A—4, B—6, C—5, D—3, E—1, F—2

Question 2. Match the following for the flame of a candle

Answer: A-3—x, B-2—z, C-l—y

Question 8. Match Column 1 with Column 2.

Answer: A-3, B-1. C-4, D-2

Class 8 Science Chapter 4 Combustion and Flame

The following questions consist of two statements: Assertion (A) and Reason (R). Answer these questions by selecting the appropriate option given below.

1. Both A and R are true, and R is the correct explanation of A
2. Both A and R are true, but R is not the correct explanation of A
3. A is true, but R is false
4. A is false, but R is true

Question 9.

1. Assertion (A): Electrical components can catch fire.
2. Reason (R) Electrical fire can be extinguished using water.

Answer: 3. A is true, but R is false

Question 10.

1. Assertion (A) A Candle can burn a block of wood.
2. Reason (R) The Ignition temperature of wood is high.

Answer: 4. A is true, but R is false

The following questions consist of two statements. Assertion (A) and Reason (R). Answer the following questions by selecting the appropriate options given below.

1. Both A and R are true, and R is the correct explanation of A.
2. Both A and R are true, but R is not the correct explanation of A.
3. A is true, but R is false.
4. A is false, but R is true.

Question 1.

Assertion (A) Fireworks produce different colours.
Reason (R) Different chemicals are used in the fireworks to produce different colours.

Answer: 1. Both A and R are true, and R is the correct explanation of A.

Question 2.

Assertion (A) Spontaneous combustion can occur in materials like dry leaves.
Reason(R) Spontaneous combustion happens due to the presence of excess oxygen in materials.

Answer: 3. A is true, but R is false. R can be corrected as Spontaneous combustion occurs in materials that have a low ignition temperature. Through internal chemical reaction with oxygen, they release heat and burn on their own.

Question 3.

Assertion (A) LPG gas can catch fire easily.
Reason (R) LPG has a high ignition temperature.

Answer: 3. A is true, but R is false. R can be corrected as LPG has a low ignition temperature, so it catches fire easily.

Question 4.

Assertion (A) When a burning candle is covered with a glass jar, the flame goes out.
Reason (R) The glass jar prevents the flow of oxygen to the candle flame.

Answer: 1. Both A and R are true, and R is the correct explanation of A.

CBSE Class 8 Chapter 5 Conservation of Plants And Animals MCQs With Answers PDF Review Exercise Multiple Choice Questions

Question 1. There is a list of some events.

1. Tilting of soil for sowing seeds on a deserted land.
2. Cutting down trees to make tables and chairs.
3. Establishing a forest on land that had trees before.
4. Clearing forests for building houses.

Deforestation will be caused by which of the following events?

1. 1 and 2
2. 3 and 1
3. 2 and 4
4. 2 and 3

Answer: 3. 2 and 4

Read And Learn More CBSE Class 8 Science Multiple Choice Questions

Question 2. How is a decline in trees connected to a water shortage?

1. Deforestation increases Earth’s temperature, resulting in less rainfall
2. Deforestation decreases Earth’s temperature, which reduces the moisture content of the air
3. Deforestation disturbs the soil composition, leading to high water retention by the soil
4. Deforestation prevents the absorption of water by the plants, reducing the groundwater level

Answer: 1. Deforestation increases Earth’s temperature, resulting in less rainfall

Question 3. Deforestation increases the level of one of the following in the atmosphere.

1. Ozone
2. Carbon dioxide
3. Oxygen
4. Water vapour

Answer: 2. Carbon dioxide

Question 4. In our country, large patches of forests are being cleared for the cultivation of crops. The environmental impact of such a practice will lead to

1. Soil erosion
2. Soil pollution
3. Soil conservation
4. Soil fertility

Answer: 1. Soil erosion

Question 5. The amount of soil erosion is lower in areas with more trees. How do trees stop the Earth from eroding?

1. The roots of the trees hold die top layer of the soil firmly
2. The trees absorb more sunlight, which increases soil density
3. The trees store extra food in the soil, which increases the soil content
4. The trees add dead leaves to the soil, which increases the soil.

Answer: 1. The roots of the trees hold die top layer of the soil firmly

Question 6. Which one of the following changes may occur due to desertification?

1. A decrease in atmospheric temperature
2. Increase in water holding capacity of soil
3. Increased chances of floods
4. Conversion of fertile land into a desert

Answer: 4. Conversion of fertile land into a desert.

Question 7. Cutting down trees and clearing forests are common construction methods for industries. What is its potential impact on nature?

1. A decrease in the number of wildlife
2. Sudden boost in the plant growth
3. Availability of more food for wildlife
4. Increase in the percentage of land occupied by trees

Answer: 1. Decrease in the number of wildlife

Question 8. Which one of the following statements is true about a biosphere reserve?

1. It is a protected area where only endemic species live
2. It is meant only for the conservation of plants and animals
3. It is meant to conserve both the biodiversity and the culture of that area
4. There are no other protected areas within its limits

Answer: 3. It is meant to conserve both the biodiversity and the culture of that area

Question 9. Radha went for a trip to a Pachmarhi Biosphere Reserve in Madhya Pradesh and Jim Corbett National Park in Uttarakhand. Which common activity is likely to be observed in both the protective areas?

1. Both provide a protective environment for fauna only
2. Both provide shelter to humans as well as wildlife
3. Both allow human activities for interaction with wild animals
4. Neither interferes with the natural environment of the wildlife

Answer: 4. Both do not interfere with the natural environment of the wildlife

Question 10. The place of living of an organism in the environment is called

1. Home
2. Habitat
3. Resort
4. Reservoir

Answer: 3. Resort

Most Important MCQs From The Conservation Chapter, Class 8 Science

Question 11. What do the black buck, elephant, python, and golden cat together represent in a forest?

1. Fauna
2. Flora
3. Ecosystem
4. Species

Answer: 1. Fauna

Question 12. Them Is n list of some organisms.

1. Star fish
2. Cheetah
3. Fern
4. Shrub
5. Cactus
6. Wolf

Which choice properly categorises the flora and fauna?

Answer: 2.

Question 13. Which one of the following statements is true about endemic species?

1. They are found exclusively in a specific habitat
2. Endemic species can never become endangered
3. They are found only in zoos and botanical gardens
4. They are not affected by the destruction of their habitat

Answer: 1. They are found exclusively in a specific habitat

Question 14. Satpura National Park and Bori sanctuary are present in the Pachmarhi Biosphere Reserve. How do these regions contribute to the protection of wildlife and plants?

1. These large areas provide artifical habitat to wildlife
2. These large areas conserve organisms and their habitats
3. These large areas control the number of wildlife by preventing natural breeding
4. These large areas prevent the interaction of organisms with wildlife to keep them safe

Answer: 2. These large areas conserve organisms and their habitats