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Class - 10 Science

NCERT Class 10 Science Chapter 7 Control and Coordination

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INTEXT QUESTIONS AND ANSWERS of NCERT Class 10 Science Chapter 7 Control and Coordination

 

PAGE – 119

 

  1. What is the difference between a reflex action and walking?

Ans : Reflex action is a spontaneous involuntary or automatic nerve mediated response to a stimulus produced at the unconscious level. But walking is a voluntary action , which requires our thinking and is within our control .

 

2. What happens at the synapse between two neurons ?

Ans : A synapse is a gap between the two neurons . At the synapse , the electrical signals are converted into chemicals that can easily cross over the gap and pass on to the next neurons where it is again converted into an electrical signal.

NCERT Class 10 Science Chapter 7 Control and Coordination

3. Which part of the brain maintains posture and equilibrium of body ?

Ans : Cerebellum .

This is the back of the brain . It co ordinates voluntary muscle movements and helps to maintain posture , balance and equilibrium .

 

4. How do we detect the smell of an agarbatti ( incense sticks ) ?

Ans : Smell of an incense stick is detected by the olfactory receptors present in the nose . The information is transmitted to olfactory lobe located in the fore brain which interprets the information .

 

5. What is the role of brain in reflex action ?

Ans : in a reflex action , the brain plays no part . The spinal cord , which reacts without thinking about how to respond to stimuli , is in charge of these automatic actions . They receive information from all parts of the body and integrate it.

NCERT Class 10 Science Chapter 7 Control and Coordination

 

PAGE – 122

 

  1. What are plant hormones ?

Ans : Plant hormones are chemical compounds present in very low concentration in plants . Plant hormones help to co – ordinate growth , development and responses to the environment .

 

2. How is the movement of leaves of sensitive plant is different from movement of a short towards light ?

Ans: The type of movement of leaves of the sensitive plant is known as a nastic movement . But the movement of shoot is diectional towards light.

This type of movement does not depend on the direction of stimuli. The movement of the shoot towards light is due to growth controlled by growth hormone .

 

3. Give an example of plant hormone that promotes growth .

Ans : Auxin.

Auxin is a plant hormone that promotes growth .

NCERT Class 10 Science Chapter 7 Control and Coordination

4. How do auxin promote growth of a tendril around a support ?

Ans : Some plants like the pea plant climb up other plants or support by means of tendrils. These tendrils are sensitive to touch . When a tendril comes in contact with a support, auxin stimulates faster growth of the cells on the opposite side that’s why the tendril forms a coil around the support . This causes the tendril to circle around the object and thus cling to it . It is due to accumulation of auxin .

NCERT Class 10 Science Chapter 7 Control and Coordination

5. Design an experiment to demonstrate hydrotropism .

Ans : Growth movements in response to the stimulus of moisture are termed as hydrotropic movements.

place some ready to germinate seeds of pea in moist sawdust in a shallow box whose bottom has been replace by a wire gauze .

Keep the apparatus undisturbed for 2-3 days. Keep the sawdust moist. After some time radicles will pass through the sieves . Then the  radicles curve upwards again to enter into the moist sawdust ,the roots are positively hydrotropic and the curvature is more than that due to entropic effect .

NCERT Class 10 Science Chapter 7 Control and Coordination
NCERT Class 10 Science Chapter 7 Control and Coordination

NCERT Class 10 Science Chapter 7 Control and Coordination

PAGE – 125

 

1. How does chemical co ordination take place in animals ?

Ans : Chemical co ordination takes place in animals with the help of chemical messengers called as hormones . They are secreted by endocrine glands. The hormones are carried by the blood to the site of action . The hormones are consumed during their action . Hormones regulate the growth , development and homeostasis of the animals .

 

2. Why is the use of iodized salt advisable ?

Ans : Iodine is essential for the thyroid  gland to produce thyroxin hormone. Thyroxin regulates carbohydrate , protein and fat metabolism in the body so as to provide the best balance for growth . Iodine is essential for the synthesis of thyroxin . In case iodine is deficient in our diet,there is a possibility that we might suffer from goitre. This deficiency disease is known as goitre . Therefore iodized salt is advised.

 

3. How does our body respond when adrenaline is secreted into the blood ?

Ans : When secreted in large amounts it speeds up the heartbeat and hence supplies more oxygen to the muscles. The breathing rate also increases due to contractions of diaphragm and rib muscles . It also increases the blood pressure. All these responses enable the body to deal with any stress or emergency .

 

4. What are some patient of diabetes treated by giving injections of insulin ?

Ans : Insulin is a hormone which is produced by the pancreas and helps in regulating blood sugar levels . If  it is not secreted in proper amounts the sugar level in the blood rises causing many harmful effects .

NCERT Class 10 Science Chapter 7 Control and Coordination

 

EXERCISES

 

  1. Which of the following is a plant hormone ?
  1. Insulin
  2. Thyroxin
  3. Oestrogen
  4. Cytokinin

 

Ans : d. Cytokinin

 

2. The gap between two neurons is called a 

  1. Dendrite
  2. Synapse
  3. Axon
  4. Impuls

Ans : b. Synapse

 

3. The brain is responsible for

  1. Thinking
  2. Regulating the heart beat
  3. balancing the body
  4. All of the above

Ans: d. All of the above

NCERT Class 10 Science Chapter 7 Control and Coordination

4.What is the function of receptors in our body ? Think of a situation where receptors do not work properly . What problems are likely to arise ?

Ans: Receptors are present in all parts of the body for example in the ski , eyes , nose, tongue, etc.

The function of receptors is to detect information from the environment.

If receptors do not detect the information there will not be any co – ordination. It may lead to accidents. Body response will not be there .

 

5. Draw a structure of a neuron and explain its function .

Ans : Structure of neuron :

 

 

 

 

 

 

 

 

NCERT Class 10 Science Chapter 7 Control and Coordination

 

Function : 

  1. Dendrites of a neuron collect information from the receptor.
  2. Axon conducts information as electrical impulse.
  3. Terminal arborization pass the information as chemical stimulus at synapse for onward transmission.

 

NCERT Class 10 Science Chapter 7 Control and Coordination

6. How does phototropism occur in plants ?

Ans : Phototropism is the directional response of a plant that allows the plant to grow towards or some cases away from the light. These directional or tropic movements can be either towards the stimulus or away from it , so, in two different kind of phototropic movement, shoots respond by bending towards light while roots respond by bending away from it.

 

7. Which signals will get disrupted in case of a spinal cord injury ?

Ans: Reflex action will be disturbed because reflex arcs are located in the spinal cord . so, the quick responses needed to safe guard the body will not take place . The delayed responses may cause harm to the body.

As both of these signals meet in a bundle in the spinal cord , so, if there is any spinal cord injury then botyh of these signals will  be disrupted.

NCERT Class 10 Science Chapter 7 Control and Coordination

8. How does chemical co ordination occur in plants ?

Ans : Chemical co ordination occurs in plants with the help of phytohormones or plant hormones secreted by plants. Auxin, cytokinin, gibberellin , abscisic acid are plant hormones. These hormones regulate the growth and development of the plants. They also regulates various metabolic activities in the plants. All growth processes are regulated by one or more phytohormones acting synergistically or antagonistically.

NCERT Class 10 Science Chapter 7 Control and Coordination

9. What is the need for a system of control and co ordination in an organism ?

Ans : An organism needs control and co ordination system for the following functions :

  1. To save the body of the organisms from the harmful changes in the environment.
  2. To control the speed of voluntary and involuntary actions .
  3. To have the capability to think and learn for responding to any stimuli.

 

10. How are involuntary actions and reflex actions different from each other ?

Ans : Reflex actions are the spontaneous responses by voluntary organs but involuntary actions are by the involuntary organs.

The difference between involuntary actions and reflex actions are :

Involuntary actions Reflex actions
i. Involuntary actions are the actions which are not controlled by our will. i. Reflex actions are the sudden action in response to something.
ii. They do not need any kind of stimulus to work. ii. They required stimulus for its action
iii. These actions are regulated by the brain.  iii. These actions are regulated by the spinal cord.
iv. They do not involve skeletal muscle. iv. They do involve skeletal muscle.
v. these actions are performed throughout one’s life. v. These actions are produced in response to an event of an emergency.
vi. This action may be quick or slow. vi. Reflex actions are always quick.
vii. For example : The beating of the heart is an involuntary action . salivating when food is put in the mouth.  vii. For example : Immediate withdrawl of hands upon touching a hot cup of tea. closing the eyes , when bright light is focused.

NCERT Class 10 Science Chapter 7 Control and Coordination

NCERT Class 10 Science Chapter 7 Control and Coordination

11. Compare and contrast the nervous and hormonal mechanism for control and co ordination in animals .

Ans: 

 

Nervous System Hormonal System
i. It consists of the central nervous system (CNS) and peripheral nervous system(PNS) i. It consists of endocrine glands.
ii. Nervous system has a network of nerves spread through out the body. ii. Hormonal system does not has such a network.
iii. Neural responses are quick and short lived.  iii. Hormonal effects are slow but are long term.

 

 

12. What is the difference between the manner in which movement takes place in a sensitive plant and the first movement in our legs ?

Ans : The movement in the sensitive plant is involuntary action , but the change in our legs is a voluntary action. 

Plants have some specialized protein for the movement in sensitive plants. But animals have some concentrated protein . This protein helps the muscles to move.

There are two types of tissues helps to transfer the information in the animal cell, but there is no cell is available in a plant cell.

Our legs are provided with nerves which have connection with muscles. To lift the leg, the brain passes information to nerves.

 

NCERT Class 10 Science Chapter 7 Control and Coordination

NCERT Class 10 Science Chapter 7 Control and Coordination

  NCERT Class 10 Science Chapter 7 Control and Coordination

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NCERT Class 10 Science Chapter 7 Control and Coordination

Class – 10 HSLC HUMAN EYE AND COLOURFUL WORLD INTEXT QUESTIONS AND ANSWERS

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Class – 10 HSLC HUMAN EYE AND COLOURFUL WORLD INTEXT QUESTIONS AND ANSWERS

INTEXT QUESTIONS AND ANSWER of Page No – 190

  1. What is meant by power of accommodation of the eye ?

Ans : The  power of accommodation of the eye is the maximum variation of its power for focusing on near and far (distant) objects . For a normal eye the power of accommodation is about 4 dioptres.

2. A person with myopic eye can not see objects beyond  1.2 m distinctly . What should be the type of the corrective lens used to restore proper vision ?

Ans: A person with a myopic eye can use concave or diverging lens to restore proper vision.

Class – 10 HSLC HUMAN EYE AND COLOURFUL WORLD INTEXT QUESTIONS AND ANSWERS

3. What is the far point and near point of the human eye with normal vision?

Ans: For a normal eye with normal vision the far point is at infinity and the near point is at 25 cm from the eye.

4. A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from ? How can it be corrected ?

Ans : The child is suffering from myopic . He should use concave lenses of suitable focal length.

Class – 10 HSLC HUMAN EYE AND COLOURFUL WORLD INTEXT QUESTIONS AND ANSWERS

 

Class - 10 HSLC HUMAN EYE AND COLOURFUL WORLD INTEXT QUESTIONS AND ANSWERS
Class – 10 HSLC HUMAN EYE AND COLOURFUL WORLD INTEXT QUESTIONS AND ANSWERS

Class 10 Science Chapter 11 The Human Eye and the Colourful World answer 

TEXTBOOK EXERCISE

  1. The human eye can focus objects at different distances by adjusting the focal length of the eye lens . This is due to
  1. Presbyopia
  2. accommodation
  3. near- sightedness
  4. far- sightedness

Ans : b. accommodation

2. The human eye forms the image of an object at its

  1. Cornea
  2. Iris
  3. Pupil
  4. Retina

Ans: d. Retina

3. The least distance of distinct vision for a young adult with normal vision is about

  1. 25 m
  2. 2.5 m
  3. 25 cm
  4. 2.5 cm

Ans : a. 25 m

4. The change in focal length of an eye lens is caused by the action of the

  1. pupil
  2. retina
  3. ciliary muscles
  4. iris

Ans : c. ciliary muscles

Class – 10 HSLC HUMAN EYE AND COLOURFUL WORLD INTEXT QUESTIONS AND ANSWERS

5. A person needs a lens of power – 5.5 dioptres for corecting his distant vision . For correcting his near vision he needs a lens of power + 1.5 dioptre . What is the focal length of the lens required for correcting (i) distanct vision and (ii) near vision ?

Ans : (i) Power of distant viewing part of the lens, P1 = – 5.5 D

Focal length of this part , f1 = 1 / P1

= 1/ -5.5 m

= – 18.73 cm

(ii) As power of the near vision part is measured relative to the main part of the lens of power – 5.5 D , so we use

=P1  + P2 = P

=> -5.5 + P2 = +1.5

=> P2 = + 1.5 + 5.5

=> P2 = + 6.5 D

Focal length of near vision part, f2 = 1 / P2

=1/ + 6.5  m

= + 15.4 cm

Class – 10 HSLC HUMAN EYE AND COLOURFUL WORLD INTEXT QUESTIONS AND ANSWERS

6. The far point of a myopic person is 80 cm in front of the eye . What is the nature and power of the lens required to correct the problem ?

Ans : For the myopic eye

u = – a

v = – 80 cm

f = 1

1/ v – 1/ u  = 1/f

=> (1 / – 80)   – ( 1 /  – a)   = 1 / f

=> f = – 80 cm

therefore, f = – 0. 80 m

Power of the lens is P = 1 / f

=> P = 1 / – 0.80

=> P = – 1. 25 D

A concave lens , P = – 1.25 D

Class – 10 HSLC HUMAN EYE AND COLOURFUL WORLD INTEXT QUESTIONS AND ANSWERS

7. Make a diagram to show how hypermetropia is corrected . The near point of a hypermetropic eye is 1 m . What is the power of the lens required to correct this defect ?

Assume that the near point of the normal eye is 25 m.

Ans:  The object placed at 25 cm from the correcting lens must produce a virtual image at 1 m or 100 cm.

v = – 25 cm

u = – 100 cm

by lens formula ,

1 / f  =  1 / v   –   1 / u

=> 1 / f   =  1 / -100  –  1 / – 25

=> 1 / f   =  1/ – 100  + 1 / 25

=> 1 / f  =  3 / 100

=> f     =    100 / 3  cm

f  =  1  / 3  m

therefore, Power , P =  1 / f

=  1 /  (1/3)

= + 3 D

Class – 10 HSLC HUMAN EYE AND COLOURFUL WORLD INTEXT QUESTIONS AND ANSWERS

8. Why a normal eye not able to see clearly the objects placed closer than 0.5 cm ?

Ans : A normal eye is unable to clearly see the objects place closer than 25 cm because the ciliary muscles of the eye unable to contract beyond a certain limit .

If the object is placed at the distance less than 25 cm from the eye than the object appears blured and produces strain in the eyes .

9. What happens to the image distance in the eye when we increase the distance of an object from the eye ?

Ans : The image distance remain same equal to the distance of the retina from the eye lens . They change in object distance is compensated by the change in the focal length of the eye lens due to the action of ciliary muscles so that a clear image is formed on the same retina .

Class – 10 HSLC HUMAN EYE AND COLOURFUL WORLD INTEXT QUESTIONS AND ANSWERS

10 . Why do stars twinkle ?

Ans : Twinkling of stars : The apparent position of star is slightly different from the actual position due to refraction of star light by the atmosphere . Further , this apparent position is not stationery but keeps on changing due to the change in atmospheric conditions like density , temperature etc. The path of the rays of light coming from the star goes on varying slightly . The amount of light entering our eyes from a particular star increases or decreases randomly with time . Sometimes , the star appears bright and other times , it appears fainter . This gives rise to the twinkling effect of the star.

Class – 10 HSLC HUMAN EYE AND COLOURFUL WORLD INTEXT QUESTIONS AND ANSWERS

11. Explain Why the planet do not twinkle ?

Ans: Planets do not twinkle because they appear larger in size than the stars as they are relatively closer to earth . Planets can be considered as a collection of a larger number of  point – size sources of light . The different parts of these planets produce either brighter or dimmer effect is zero . Hence , the twinkling effect of the planets are nullified and they do not twinkle .

12. Why does the sun appear reddish early in the morning ?

Ans : During sunrise , the light rays coming from the sun have to travel a greater distance in the earth’s atmosphere before reaching our eyes . In this journey, the shorter wave length of lights are scattered out and only longer wave length are able to reach our eyes. Since blue colour has a shorter wave length and red colour has a longer wave length. The red colour is able to reach our eyes after the atmospheric scattering of light. Therefore , the sun appears reddish early in the morning .

Class – 10 HSLC HUMAN EYE AND COLOURFUL WORLD INTEXT QUESTIONS AND ANSWERS

13. Why does the sky appear dark instead of blue to an astronaut ?

Ans : The sky appears dark instead of blue to an astronaut because there is no atomsphere in the outerspace that can scatter the sunlight . As the sunlight is not scattered light reach the eyes of the astronaut and the sky appears black to them .

Class – 10 HSLC HUMAN EYE AND COLOURFUL WORLD INTEXT QUESTIONS AND ANSWERS

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Class – 10 HSLC HUMAN EYE AND COLOURFUL WORLD INTEXT QUESTIONS AND ANSWERS

Class – 10 HUMAN EYE AND COLOURFUL WORLD Additional Questions and Answers mcq

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Class – 10 Human Eye and Colourful World Additional Questions and Answers mcq

Class 10 Science has a fascinating syllabus that introduces new concepts of human physiology to the students. Chapter 11 of this syllabus explains the basic and advanced concepts of the human eye. It is about how the human eye performs to provide a colourful world to the beholder. To understand these concepts, study this chapter well and solve the Class 10 Human Eye MCQ framed by the experts.

HSLC SEBA Class 10 Science MCQs Chapter 11 The Human Eye and the Colourful World with Additional Question Answers

CBSE Class 10 Science MCQs Chapter 11 The Human Eye and the Colourful World help students learn important concepts efficiently. Students preparing for Class 10 Science Board exams must not forget to practise the multiple-choice questions. Here, we have provided the MCQs of Chapter 11, The Human Eye and the Colourful World, so that students can memorise the fundamental concepts with ease. The Human Eye and the Colourful World MCQs will help students to fetch marks from this chapter easily. These multiple choice questions on Human Eye and the Colourful World are based on the latest Class 10 Science Syllabus and are designed by our subject experts.

MCQ Questions on Human Eye and Colourful World PDF

Class – 10 HUMAN EYE AND COLOURFUL WORLD Additional Questions and Answers mcq

Class – 10 HUMAN EYE AND COLOURFUL WORLD Additional Questions and Answers mcq

 

  1. What is pupil ? What is the function of pupil human eye ?

Ans : Pupil is a narrow hole through which light enters in the eye and falls on eye lens.

The pupil regulates and controls the amount of light entering the eye .

 

2. Name the light sensitive cell present in the retina of an eye .

Ans: Rods and cones.

 

3. What do you mean by the term accommodation ?

Ans : The power of accommodation of the eye is the maximum variation of its power for focusing on near and for objects .

 

4. What is blind spot ?

Ans : At the junction of the optic nerve and the retina there are no sensory cells. so , no vision is possible at the spot. This is called the blind spot.

 

5. What is night blindness ?

Ans: Night blindness is a disease caused due to deficiency of vitamin A when patient can not see clearly in dimlight .

Class – 10 HUMAN EYE AND COLOURFUL WORLD Additional Questions and Answers mcq

6. what is color blindness ?

Ans : If some cone cells are absent from retina the person is not able to distinguish the colour of object . It is called colour blindness.

 

7. Define the part of the eye that has real , inverted image of the object formed on it .

Ans : Retina.

 

8. What is the function of ciliary muscle ?

Ans : Ciliary muscles can increase or decrease the focal length of eye lens to focus the images at retina .

 

9. Mention the common defects of vision of the human eye .

Ans: Defects of vision : A normal eye can see objects clearly at any distance between 25 cm and infinity from the eye. Sometimes , a human eye gradually loses its power of accommodation . Then we can not see the object clearly our vision becomes defective. There are mainly four common defects of vision which can be corrected by the suitable use of eye glasses.These defects are :

 

  1. Myopia or near sightedness
  2. Hypermetropia or for sightedness
  3. Presbyopia
  4. Astigmatism .

Class – 10 HUMAN EYE AND COLOURFUL WORLD Additional Questions and Answers mcq

Human Eye and Colourful World Additional Questions and Answers mcq
Class – 10 HUMAN EYE AND COLOURFUL WORLD Additional Questions and Answers mcq

10. What is myopia ? Suggest how this defect can be corrected ?

Ans : Myopia is also known as near sightedness . A person with myopia can use nearby objects but can not see distant objects distinctly .

Myopia can be corrected by using a concave lens of suitable power .

Class – 10 HUMAN EYE AND COLOURFUL WORLD Additional Questions and Answers mcq

11. What is hypermetropia ? Suggest how this defect can be corrected .

Ans : Hypermetropia is also known as far sightedness . A person with hypermetropia can see distant objects clearly but can not see near by objects distinctly.

Hypermetropia can be corrected by using a convex lens of suitable power.

 

12. Write two reasons of myopia .

Ans : Causes of myopia :

i. Excessive curvature of the eye lens .

ii. Elongation of the eye ball.

 

13. What are the causes of hypermetropia ?

Ans: Causes of hypermetropia :

i. The focal length of the eye lens is too long .

ii. The eye ball has become to small .

Class – 10 HUMAN EYE AND COLOURFUL WORLD Additional Questions and Answers mcq

14. What is presbyopia ? How is presbyopia rectified ?

Ans : The power of accommodation of the eye usually decreases with aging . For most of the people , the near point gradually reduces away . They find it difficult to see nearby objects comfortably and distinctly without corrective eye glasses .

The defect is presbyopia can be rectified by using bi focal lenses of suitable power .

 

15. What is astigmatism ? How it is corrected ?

Ans : Astigmatism : It is a defect of vision in which a person can not simultaneously see both the horizontal and vertical views of an object with the some clearily .

Causes of astigmatism : This defect occurs when the cornea of the eye is not perfectly spherical . This results in objects in one direction using well focused while those in perpendicular direction are not well focused .

Correction of astigmatism : Astigmatism can be corrected by using cylindrical lenses . They have different curvatures in horizontal and vertical directions and so they can be oriented suitably  to compensate for irregularities in the cornea .

Class – 10 HUMAN EYE AND COLOURFUL WORLD Additional Questions and Answers mcq

16. What is cataract ?

Ans : Due to development of membrane over the eye lens the eye become ineffective or the image becomes hazy . This problem is called cataract .

 

17. What do you mean by dispersion of light ? What is its cause ?

Ans : When a white light pass through a glass prism it splits into its seven constituent colour . This phenomenon is called dispersion of light .

Causes of dispersion of white  light  : Light rays of different colour travel  with some speed in vaccum . But in refracting medium like glass , water etc. Light or different different colours travel with different speeds . The speed of violet colour is least , while the speed of red colour is the largest in glass . As a result , the refractive index of glass is larger for violet colour and least for red colour . The violet colour is deviated most while the red colour is deviated least on passing through the prism . Other colours are deviated by immediate angles . so , different component colours of white light get dispersion on passing through a glass prism .

Class – 10 HUMAN EYE AND COLOURFUL WORLD Additional Questions and Answers mcq

18. Explain the formation of rainbow in the sky ?

Ans : A rainbow appears in the sky after as hover in the direction opposite to the sun . It is a natural spectrum of the sunlight . The water droplets in the atmosphere act as small prism . The sun light suffers a refraction and dispersion in them . They are then the internally reflected in the drop and finally refracted out . When such rays reach a observer he sees a rainbow .

 

Explain the formation of rainbow in the sky ?
Explain the formation of rainbow in the sky ?

 

 

Class – 10 HUMAN EYE AND COLOURFUL WORLD Additional Questions and Answers mcq

19. What do you mean by atmospheric refraction ?

Ans : Light coming from the celestial objects like the sun or the stars suffer refraction in the air . This is called atmospheric refraction . Several interesting phenomenon such as the twinkling of stars and early sunrise and delayed sunsets are results of atmospheric refraction .

 

20. What is tyndall effect ?

Ans : The Earth’s atmosphere contains smoke , tiny water droplets and dust grains . It resembles a colloidal solution on which small particles remain suspended when a beam of light gets scattered from such particles. The path of the beam becomes visible . The effect is called tyndall effect . This effect is usually caused by suspended particles of relatively clag size .

We can observe the tyndall effect when light enters a dusty or smoke filled enclosure through a small hole .

Class – 10 HUMAN EYE AND COLOURFUL WORLD Additional Questions and Answers mcq

21. Why is the colour  of the clear sky blue ?

Ans : When  the sunlight passes through the atmosphere it suffers on the molecules of air and suspended fine particles . The molecules of the air such as N2 and O2    and other fine particles of the atmosphere which are smaller than the wave length of light of any colour scatter the shorter wavelength more effectively. Thus the blue colour of light is scattered the most while the red is scattered the least in the atmosphere. The blue colour of the sky is due to the scattering of sunlight by molecule of the atmosphere . When we look at the sky the scattered light enters our eyes and thus light contains blue light in a large proportion . That is why the sky appears blue .

Class – 10 HUMAN EYE AND COLOURFUL WORLD Additional Questions and Answers mcq

22. Why does sun appear reddish at sunrise and sunset ?

Ans : During the sunrise and sunset the sun remain near the horizon . The light rays have to pass through a larger thickness of the atmosphere when the sum is overhead at non consequently , the lower wavelengths in the blue region are almost completely scattered away by air molecules . The higher wavelengths of the red region are least scattered and reach our eyes. Hence the sun appears almost reddish at sunrise and sunset .

 

23. The sun is visible to us about 2 minutes before the actual sunrise and about 2 minutes after actual sunset. Give reason . 

Ans : The sun is visible to us about 2 minutes before the actual sunrise and about 2 minutes about actual sunset because of atmospheric refraction . By actual sunrise by the sun . The time difference between the actual sunset and the appearance sunset is about 2 minutes .

 

24. Why are the traffic light signals ear danger signals of red colour ?

Ans : In the visible spectrum the colour has the largest wave length the red colour is least scattered by fog or dust particles . So, we can also observed red colour easily even in foggy and dusty condition .

Class – 10 HUMAN EYE AND COLOURFUL WORLD Additional Questions and Answers mcq

25. Which is the cause of blue colour of the ocean ?

Ans : The water molecules of the ocean scatter blue light more strong that light of other colours . So, ocean appears bluish .

Class – 10 HUMAN EYE AND COLOURFUL WORLD Additional Questions and Answers mcq

Human eye and Colourful World Class 10 Important Questions 
IMPORTANT WEB-LINKS
✅ Official WebsiteClick Here
✅ WhatsApp Group For All HSLC SolutionsClick Here
✅ For Jobs Update Government job opportunitiesClick Here
✅ Telegram Groupclick here

Class – 10 HUMAN EYE AND COLOURFUL WORLD Additional Questions and Answers mcq

Class – 10 Science Solution for SEBA HSLC 2025

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Science is the accumulation of knowledge. To acquire this scientific idealism, we should be inquisitive and interested. Interest and importance for the work is very essential to make it successful. | To gain knowledge of science, we are to stress on three principle factors namely what, why and how. To sight an example ‘REFLECTION’ is a science related topic. To gather knowledge on this topic, first we | are to have the general idea on Reflection; secondly why this phenomenon happens and thirdly how this | phenomenon concludes. Class – 10 Science Solution for SEBA HSLC 2025

বিজ্ঞান হৈছে জ্ঞান সঞ্চয়।  এই বৈজ্ঞানিক আদৰ্শবাদ অৰ্জন কৰিবলৈ আমি অনুসন্ধিৎসু আৰু আগ্ৰহী হোৱা উচিত।  কামটো সফল কৰিবলৈ হ’লে কামটোৰ প্ৰতি আগ্ৰহ আৰু গুৰুত্ব অতি প্ৰয়োজনীয়।  |  বিজ্ঞানৰ জ্ঞান আহৰণৰ বাবে আমি তিনিটা নীতিগত কাৰকৰ ওপৰত গুৰুত্ব দিব লাগে যেনে কি, কিয় আৰু কেনেকৈ।  এটা উদাহৰণ চাবলৈ ‘REFLECTION’ এটা বিজ্ঞান সম্পৰ্কীয় বিষয়।  এই বিষয়ত জ্ঞান সংগ্ৰহ কৰিবলৈ প্ৰথমে আমি |  প্ৰতিফলনৰ ওপৰত সাধাৰণ ধাৰণাটো থাকিব লাগে;  দ্বিতীয়তে এই পৰিঘটনা কিয় ঘটে আৰু তৃতীয়তে এই |  পৰিঘটনাটো শেষ হয়।

If a science teacher or anyone dealing with scientific guidance discusses the chapter or topic in! this light, students will be more benefitted and initially cultivate in their the scientific temperment and attitude, modify his behaviourial pattern and as such purposefully would his personality.

Class – 10 Science Solution for SEBA HSLC 2025

Class – 10 English Solution for English – click here


যদি কোনো বিজ্ঞান শিক্ষক বা বৈজ্ঞানিক নিৰ্দেশনাৰ সৈতে জড়িত কোনোবাই অধ্যায় বা বিষয়টোৰ বিষয়ে আলোচনা কৰে!  এই পোহৰত ছাত্ৰ-ছাত্ৰীসকলে অধিক উপকৃত হ’ব আৰু প্ৰথম অৱস্থাত তেওঁলোকৰ বৈজ্ঞানিক স্বভাৱ আৰু মনোভাৱ গঢ়ি তুলিব, তেওঁৰ আচৰণৰ ধৰণ সলনি কৰিব আৰু সেইবাবেই উদ্দেশ্যপ্ৰণোদিতভাৱে তেওঁৰ ব্যক্তিত্বক পৰিৱৰ্তন কৰিব। Class – 10 Science Solution for SEBA HSLC 2025

He high school leaving certificate examination determines the qualitative standard that is mental | ability and intelligence of an individual student. Based on the certified marks they walk in the path of choosing a career in their future life. So the H.S.L.C. examination approves to be the most important examination. To cross out successfully and with flying colours it becomes necessary that the students | should lay an aim in front of there and then prepare themselves accordingly. To achieve their aim, the students should plan stratagies and be very emphasasive, meditative and indulgent. The planing can be in two ways. Firstly the examinee is to think out how he will prepare or where from to begin. In this regard, this book published by us can be very useful and students friendly.



To acquire knowledge on any subject, the students should have a clear cut conception about the | particular ‘topic’ idea about the questions that arises or any more probable questions, idea about how to | give a meaningful and quality answer systematically arranged the materials of the answer excellant writting practice and skill are very essential if the student has no through conception on a particular subject matter, it is simply waste of time and energy by making castles in the air. That so why first to conceive the conception in its correct form is the foundation stone of learning and then should be followed by preparing and solving the questions. Class – 10 Science Solution for SEBA HSLC 2025

SEBA HSLC Class – 10 Voice Change of Last 23 year’s Solved – click here

Generally in the Assam H.S.L.C examinations three sets of questions are asked objectives or very short type, short type and long type. This book will give a detailed knowledge on question pattern. The I student should understand what the question wants for an answer and release accordingly. Answers should always be to the point, clear and legible. To prevent the answer script in their mind, students should tie! I it up as their binding rule to write the answers repeatedly for memorising. Class – 10 Science Solution for SEBA HSLC 2025

Class – 10 Science Solution for SEBA HSLC 2025

Class - 10 Science Solution for SEBA HSLC 2025

যদি কোনো বিজ্ঞান শিক্ষক বা বৈজ্ঞানিক নিৰ্দেশনাৰ সৈতে জড়িত কোনোবাই অধ্যায় বা বিষয়টোৰ বিষয়ে আলোচনা কৰে!  এই পোহৰত ছাত্ৰ-ছাত্ৰীসকলে অধিক উপকৃত হ’ব আৰু প্ৰথম অৱস্থাত তেওঁলোকৰ বৈজ্ঞানিক স্বভাৱ আৰু মনোভাৱ গঢ়ি তুলিব, তেওঁৰ আচৰণৰ ধৰণ সলনি কৰিব আৰু সেইবাবেই উদ্দেশ্যপ্ৰণোদিতভাৱে তেওঁৰ ব্যক্তিত্বক পৰিৱৰ্তন কৰিব। Class – 10 Science Solution for SEBA HSLC 2025

হাইস্কুল শিক্ষান্ত পৰীক্ষাত গুণগত মান নিৰ্ধাৰণ কৰা হয় যিটো মানসিক |  ব্যক্তিগত ছাত্ৰৰ ক্ষমতা আৰু বুদ্ধিমত্তা।  প্ৰমাণিত নম্বৰৰ ভিত্তিত তেওঁলোকে ভৱিষ্যত জীৱনত কেৰিয়াৰ বাছি লোৱাৰ পথত খোজ কাঢ়ে।  গতিকে এইচ.এছ.এল.চি.  পৰীক্ষাটোৱেই আটাইতকৈ গুৰুত্বপূৰ্ণ পৰীক্ষা বুলি অনুমোদন জনায়।  সফলতাৰে আৰু উৰন্ত ৰঙৰ সৈতে ক্ৰছ আউট কৰিবলৈ প্ৰয়োজনীয় হৈ পৰে যে ছাত্ৰ-ছাত্ৰীসকলে |  তাৰ সন্মুখত এটা লক্ষ্য ৰাখিব লাগে আৰু তাৰ পিছত সেই অনুসৰি নিজকে প্ৰস্তুত কৰিব লাগে।  নিজৰ লক্ষ্যত উপনীত হ’বলৈ ছাত্ৰ-ছাত্ৰীসকলে কৌশল পৰিকল্পনা কৰিব লাগে আৰু অতি জোৰদাৰ, ধ্যানশীল আৰু ভোগবাদী হ’ব লাগে।  প্লেনিং হ’ব পাৰে দুটা ধৰণেৰে।  প্ৰথমতে পৰীক্ষাৰ্থীয়ে কেনেকৈ প্ৰস্তুতি চলাব বা ক’ৰ পৰা আৰম্ভ কৰিব সেইটো চিন্তা কৰিব লাগে।  এই ক্ষেত্ৰত আমাৰ দ্বাৰা প্ৰকাশিত এই গ্ৰন্থখন অতি উপযোগী আৰু ছাত্ৰ-ছাত্ৰীৰ অনুকূল হ’ব পাৰে।  Class – 10 Science Solution for SEBA HSLC 2025

Class – 10 Science Solution for SEBA HSLC 2025


যিকোনো বিষয়ৰ ওপৰত জ্ঞান আহৰণ কৰিবলৈ ছাত্ৰ-ছাত্ৰীসকলৰ |  উত্থাপিত প্ৰশ্ন বা অধিক সম্ভাৱ্য প্ৰশ্নৰ বিষয়ে বিশেষ ‘বিষয়’ ধাৰণা, কেনেকৈ |  ছাত্ৰজনে যদি কোনো বিশেষ বিষয়ৰ ওপৰত কোনো থ্ৰু কনচেপচন নাথাকে, তেন্তে ই কেৱল বতাহত দুৰ্গ নিৰ্মাণ কৰি সময় আৰু শক্তিৰ অপচয়।  সেইবাবেই কিয় প্ৰথমে ধাৰণাটোক ইয়াৰ সঠিক ৰূপত কল্পনা কৰাটোৱেই হৈছে শিক্ষণৰ আধাৰশিলা আৰু তাৰ পিছত প্ৰশ্নবোৰ প্ৰস্তুত আৰু সমাধান কৰা উচিত। Class – 10 Science Solution for SEBA HSLC 2025

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সাধাৰণতে অসম H.S.L.C পৰীক্ষাত তিনিটা গোটৰ প্ৰশ্ন উদ্দেশ্য বা অতি চুটি ধৰণৰ, চুটি ধৰণৰ আৰু দীঘলীয়া ধৰণৰ প্ৰশ্ন কৰা হয়।  এই গ্ৰন্থখনত প্ৰশ্নৰ আৰ্হিৰ ওপৰত বিশদ জ্ঞান দিয়া হ’ব।  I ছাত্ৰজনে প্ৰশ্নটোৱে উত্তৰৰ বাবে কি বিচাৰে সেইটো বুজিব লাগে আৰু সেই অনুসৰি মুকলি কৰি দিব লাগে।  উত্তৰবোৰ সদায় মূল কথা, স্পষ্ট আৰু পাঠ্য হ’ব লাগে।  উত্তৰ লিপিখন মনৰ ভিতৰত ৰোধ কৰিবলৈ ছাত্ৰ-ছাত্ৰীয়ে বান্ধিব লাগে! 

Class – 10 Science Solution for SEBA HSLC 2025

SCIENCE CONTENT

LessonsLinks
1. Chemical reaction and Equationsclick here
2. Acids , Bases and Saltsclick here
3. Metals and Non- Metalclick here
4. Carbon and its Compounds click here
5. Periodic Classification of Element click here
6. Life Processclick here
Life Process Extra Questions click here
7. Control and Coordinationclick here
8. How do Organism Reproduce ?click here
9. Heredity and Evolution click here
10. Light – Reflection and Refractionclick here
11. Human Eye and Colourful Worldclick here
Human Eye and Colourful World Additional Questionsclick here
12. Electricityclick here
13. Magnetic Effects of Electric Currentclick here
14. Source of Energyclick here
15. Our Environment click here
16. Management of Natural Resourcesclick here

Class – 10 Science Solution for SEBA HSLC 2025

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Class 10 Science : Chapter 1: Chemical Reaction and Equations All Question Answers

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INTEXT QUESTION || Class 10 Science : Chapter 1: Chemical Reaction and Equations All Question Answers

INTEXT Question Answers

Page No – 6

  1. Why should a magnesium ribbon be cleaned before burning in air?

Ans:- Magnesium is very  reactive metal like ( Na,Ca etc.). when we kept in air for a long time it reacts with oxygen to form a layer magnesium oxide ( MgO) on its surface. Mg(magnesium) + O2(oxygen) –>2MgO(magnesium oxide)

This layer of magnesium oxide is quite stable and prevents further reaction of magnesium with oxygen . This magnesium ribbon is cleaned by sand paper to remove this layer so that the underlaying metal can be used for the reaction.

Class 10 Science : Chapter 1: Chemical Reaction and Equations All Question Answers

2. Write the balanced equation for the following chemical reactions;

i. Hydrogen + Chlorine ——> Hydrogen Chloride

ii. Barium Chloride + Alluminium Sulphate —–> Barium Sulphate + Alluminium Chloride

iii. Sodium + Water —–> Sodium Hydroxide + Hydrogen 

Ans:- H2 + Cl2 —-> HCL

Balanced equation : H2 + Cl2 —-> 2HCL

BaCl2+ Al2(SO4)3 —–> BaSO4 + AlCl3

Balanced equation :  3BaCl2+ Al2(SO4)3 —–>3BaSO4 + 2AlCl3

Na + H2O—–> NaOH + H2

Balanced equation : 2Na +2 H2O—–>2 NaOH + H2

3. Write a balanced chemical equation with state symbols for the following reactions.

  1. Solutions of Barium Chloride and sodium sulphate in water reacts to give insoluble barium sulphate and the solution of sodium chloride.
  2. Sodium Hydroxide solution (in water ) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution in water
  1. BaCl2 (aq) + Na2SO4 (aq) —–> BaSO4(ppt) + 2NaCl(aq)
  2. NaOH(aq) + HCL(aq)——>NaCl (aq) + H2O(l)

Class 10 Science : Chapter 1: Chemical Reaction and Equations All Question Answers

PAGE NO: 10

  1. A solution of a substance X is used for white washing .

 

  1. Name the substance X and write its formula.
  2. Write the reaction of the substance X named in (i) above the water.

Ans :

 

  1. X is a quick lime,CaO
  2. CaO (s)  (quick lime) + H2O(l) ——> Ca(OH)2(aq)  (Slaked lime or calcium hydroxide)

 

2. Why  is the amount of gas collected in one of the test tubes in activity 1.7 double of the amount  collected in the other ? Name the gas.

Ans: It is because water is formed when hydrogen and oxygen combine in the ratio of 2:1 by volume, the gas with double volume is hydrogen . Two atoms of hydrogen combine with one atom of oxygen to form water.Hence ,volume of hydrogen is double.

Class 10 Science : Chapter 1: Chemical Reaction and Equations All Question Answers

 

HSLC All Previous Year Questions – click here

Class 10 Science : Chapter 1: Chemical Reaction and Equations All Question Answers

PAGE NO. 13

  1. Why does the colour of copper sulphate solution change when an iron nail dipped in it ?

Ans: When an iron nail is dipped in copper sulphate solution , it becomes brownish in colour and the colour of the copper sulphate fades due to the following reactions :

Fe(s) + CuSO4 (aq) ——-> FeSO4(aq) + Cu(s)

In this reaction , iron has replaced copper from its solution .

Thus amount of copper sulphate decrease and its colour fades.

2. Give an example of a double displacement reaction other than the one given in activity 1.10

Ans: When a solution of hydrochloric acid is added to a solution of lead nitrate , a white

precipitate of lead chloride is found .

Pb(NO3)2 (aq) + 2HCL (aq) ——> PbCl(s) ( lead chloride) + 2HNO3(aq)(nitric acid)

Pb2+ ions form lead nitrate combine with 2Cl– ions from hydrochloric acid and a precipitate of lead chloride is formed . Thus, there is a exchange of ions between the two reactants i.e lead nitrate and hydrochloric acid and thus this reaction is a double displacement reaction.

3. Identify the substances that are oxidised and the substances that are reduced in the following reactions.

 

  1. 4Na(s) + O2(g) ——-> 2Na2O(s)
  2. CuO(s) + H2(g) ——–> Cu(s) + H2O

Ans

  1.  Sodium metal is oxidized and oxygen is reduced to Na2O.
  2. Copper oxide is reduced to copper and hydrogen is oxidized to H2O

SEBA HSLC Previous Year Question Paper – click here

 

Class 10 Science : Chapter 1: Chemical Reaction and Equations All Question Answers
Class 10 Science : Chapter 1: Chemical Reaction and Equations All Question Answers

 

EXERCISE || Class 10 Science : Chapter 1: Chemical Reaction and Equations All Question Answers

 

 

  1. Which of the statements about the reaction below are incorrect?

2PbO (s) + C (s) ——-> 2Pb(s) + CO2 (g)

  1. Lead is getting reduced.
  2. Carbon dioxide is getting oxidized.
  3. Carbon is getting oxidized.
  4. Lead oxide is getting reduced.
  1. (a) and (b)
  2. (a) and (c)
  3. (a) ,(b) and (c)
  4. all

Ans: (i) (a) and (b)

 

2.  Fe2O3 + 2Al —–> Al2O3+ 2Fe

The above reaction is an example of a 

 

  1. combination reaction
  2. double displacement reaction
  3. decomposition reaction
  4. displacement reaction

Ans: (d) Displacement reaction

 

3. What happens when dilute hydrochloric acid is added to iron fillings?

 

  1. Hydrogen gas and iron chloride are produced
  2. chlorine gas and iron hydroxide are produced
  3. no reaction takes place
  4. iron salt and water are produced.

 

Ans: (a) Hydrogen gas and iron chloride are produced

 

4.  What is a balanced chemical equation? Why should Chemical equation be balanced?

Ans: In a balanced equation , the number of atoms of each elements on both sides of the equation are equal. The balanced equation satisfied mass balance as well as charge balance.

The chemical equation must be balanced with respect to mass because matter can neither be created nor be destroyed.

The equation must be balanced with respect to charge because the electrons lost by atoms to form cations are equal to the electrons gained by other atoms to form anions.

Class 10 Science : Chapter 1: Chemical Reaction and Equations All Question Answers

5. Translate the following statements into chemical equations and then balance them.

  1. Hydrogen gas combines with nitrogen to form ammonia.
  2. Hydrogen sulphide gas burns in air to give water and sulphur dioxide.
  3. Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.
  4. Potassium metal reacts with water to give potassium hydroxide and hydrogen gas is released.

Ans:

  1.  3 H2 (g) + Na2(g) ——> 2NH3(g)
  2. 3H2S (g) + 3O2(g) ——-> 2H2O (l)+  2SO2(g)
  3. 3BaCl2(aq) + Al(SO4)3(aq)——-> 2AlCl3(aq) + 3BaSO4(s)
  4. 2K(s) + 2 H2O(l) ——-> 2KOH + H2(g) (released)

 

6. Balance the following chemical  equations.

  1. HNO3 + Ca(OH)2 ——> Ca(NO3)2 + H2O
  2. NaOH + H2SO4——–> Na2SO4 + H2O
  3. NaCl + AgNO3 ——-> AgCl + NaNO3
  4. BaCl2 + H2SO4 ——> BaSO4 + HCl

Class 10 Science : Chapter 1: Chemical Reaction and Equations All Question Answers

Ans:

  1. 2HNO3 (aq)+ Ca(OH)2(aq)——> Ca(NO3)2 (aq)+ 2H2O(l)
  2. 2NaOH (aq)+ H2SO4(aq)——–> Na2SO4(aq) + H2O(l)
  3. NaCl (aq)+ AgNO3(aq) ——-> AgCl(s) + NaNO3(aq)
  4. BaCl2(aq) + H2SO4(aq) ——> BaSO4(s) + 2HCl(aq)

7. Write the balanced chemical equations fo the  following reactions .

  1. Calcium hydroxide + carbon dioxide ———> calcium carbonate + Water 
  2. zinc + silver nitrate ———> Zinc nitrate + Silver 
  3. Aluminium + Copper Chloride ——–> Aluminium Chloride + copper
  4. Barium Chloride + Potassium sulphate ——–> Barium sulphate + potassium chloride

 

Ans :

  1. Ca(OH)2 + CO2 (g) ——–> CaCO3(s) + H2O
  2. Zn(s) + 2AgNO3 (aq)——–> ZnNO3 (aq) + 2Ag(s)
  3. 2Al (s) + 3CuCl2(aq) ———> 2 AlCl3 (aq) + 3 Cu(s)
  4. BaCl2(s) + K2SO4 ( aq) ——> BaSO4(s) + 2 KCl(aq)

8. Write the balanced chemical equation for the followimg and identify the type of reaction in each case.

  1.  Potassium Bromide (aq)+  Barium iodide(aq) ——–> potassium iodide (aq) + Barium bromide
  2. Zinc  carbonate(s) ——–> zinc oxide (s) + Carbon dioxide(g)
  3. Hydrogen(g) + Chlorine (g) ——–> Hydrogen chloride(g)
  4. Magnesium (s) + hydrochloric acid (aq) —-> Magnesium chloride (aq) + Hydrogen(g)

 

Ans:

 

  1. 2KBr(aq) + BaI2(aq) ——> 2KI (aq) + BaBr2(s)
  2. ZnCO3(s) —–> ZnO (s) + CO2(g)
  3. H2(g) +Cl2(g) —–> 2HCl(g)
  4. Mg(s) + 2HCl(aq) —–> MgCl2(aq) + H2(g)

Class 10 Science : Chapter 1: Chemical Reaction and Equations All Question Answers

9. What does one mean by exothermic and endothermic reactions ? Give examples.

Ans: (i)Exothermic reaction :

Chemical reaction in which energy is envolved (or given out) are known as Exothermic reaction. For example :

C(s) + O2 (g) ——-> CO2(g) + Δ H

Formation of ammonia from nitrogen and Hydrogen is an exothermic reaction.

N2 (g) 3H2(g) ——-> 2 NH3 (g) + 92 kJ

 

(ii) Endothermic reaction : Reaction in which energy is absorbed are called endothermic reaction . For example :

When carbon reacts with sulphur 92 KJ of heat is absorbed during the process.

C(s) + 2S(s) ——> CS2(l) – 92 KJ

 

10.  Why is respiration considered an exothermic reaction ? Explain .

Ans: During digestion, food is broken down into simpler substances . Food like rice , potato and  bread are made up of carbohydrates are further  broken down to  glucose . glucose during respiration ( inhalation of oxygen ) is oxidized with the liberation of energy as shown below :

C6H12O6(aq) [glucose] + O2(aq) ——> CO2(aq)  + 6H2O (l) + energy

Thus , respiration is an exothermic reaction.

Class 10 Science : Chapter 1: Chemical Reaction and Equations All Question Answers

11. Why are decomposition reactions called the opposite of combination reaction ? write equations for these reactions.

Ans: The decomposition reaction is the opposite of combination reaction .

In a decomposition reaction , a single compound breaks down to produce two or more simpler substances. E.g. Mercuric oxide on heating decomposes to mercury and oxygen .

2HgO —(heat)—–>2Hg + O2

In a combination reaction , two or more substances simply combine to form a new substance .

E.g. -> Magnesium combine with oxygen to give magnesium oxide .

2 Mg + O2-—-> 2MgO

Class 10 Science : Chapter 1: Chemical Reaction and Equations All Question Answers

12. Write one equation each for decomposition reactions where energy is supplied in the form of heat , light or electricity.

Ans : Heat —–>  CaCO3 (s) —(heat)—> CaO (s) + CO2(g)

Light ——> 2AgBr(s) —-(sunlight)—> 2Ag + Br2(g)

Electricity —–> 2 H2O (l) —-(electric current)—–> 2H2(g) + O2(g)

13. What is the difference between displacement and double displacement reactions?

Ans: In displacement reaction, a more reactive metal displaces a less reactive  metal from its solution while in double displacement reactions, two or more compounds exchange  their ions and form new compounds .

(i) Fe(s) + CuSO4(aq) —–> Cu(s) +FeSO4(aq)

This is a displacement reaction where iron displace copper from its solution .

(ii) AgNO3 (aq) + NaCl (aq) —–> AgCl (s) + NaNO3

This is a double displacement reaction where silver  nitrate and sodium chloride exchange Cl and NO3 ions between them.

Class 10 Science : Chapter 1: Chemical Reaction and Equations All Question Answers

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14. In the refining of silver , the recovery of silver from silver nitrate solution involved displacement by copper metal . Write down the reaction involved.

Ans : 2AgNO3 (aq) + Cu(s) ——-> Cu(NO3)2 (aq)+ 2Ag(s)

 

15. What do you mean by a precipitation reaction ? Explain by giving examples.

Ans: When two reactants in solution react and one or more of the products is insoluble or forms a precipitate the reaction is called a precipitation reaction . For example , when a solution of iron chloride and ammonium hydroxide are mixed , a brown precipitate of iron hydroxide is formed

FeCl2(aq) + 3 NH4OH(aq) ——–> Fe(OH)3 (s) + 3 NH4Cl(aq)

16. Explain the following in terms of gain or loss of  oxygen with two examples each.

(a) Oxidation (b) Reduction

 

Ans:(a) Oxidation : A chemical reaction in which a substance gains oxygen and losses hydrogen  is called oxidation.

Example : 2Mg (s) + O2(g) [burning ]——> 2 MgO (s)

Mg is oxidized to MgO

(b) Reduction : A chemical reaction in which  a substance losses oxygen and gains hydrogen is called Reduction.

Example : CuO (s) + H2(g) [heat]——> Cu(s) + H2O (g)

CuO is reduced to form Cu.

 

17. A shiny brown coloured element ‘X’ on heating in air becomes black in color . Name the element ‘X’ and the black coloured compound formed. 

Ans: Element ‘X’ = copper (Cu)

Compound = copper Oxide (CuO)

2 Cu (s) [brown]+ O2 (g)—-(heat)–> 2CuO (s) [black]

Class 10 Science : Chapter 1: Chemical Reaction and Equations All Question Answers

18. Why do we apply paint on iron articles? 

Ans: Paint acts as anti oxidant saves iron articles from damage due to corrosion . It acts as buffer between iron articles and moisture.

 

19. Oil and fat containing food items are flushed with nitrogen . Why? 

Ans : To keep food items fresh and save these from oxidizing effect of oxygen , food items are flushed with nitrogen.

 

20. Explain the following terms with one example each.

(a) Corrosion (b) Rancidity

 

Ans: (a) Corrosion :  Due to the effect of moisture and oxygen metals get corroded . i.e metals particularly iron forms a porous layer on the surface and thus gets damaged . The effect is called corrosion .

Corrosion causes damages to metal articles like car bodies , bridges , iron railings , ships, and other substances of daily use.

 

(b) Rancidity : Fats and oils in food kept for long time get oxidized and become rancid and taste of food changes and causes infection on eating . This is called rancidity.

To prevent rancidity antioxidants are added to foods containing fats and oils. Rancidity can also be prevented by flushing to oxygen with an inert gas like nitrogen . For example, packets of food items like chips are flushed with nitrogen so that these can be used even afṭer long duration.

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Class 10 Science : Chapter 1: Chemical Reaction and Equations All Question Answers