CBSE Class 10 Science Chapter 1 Chemical Reactions And Equations Very Short Question And Answers

Question 1. Out of rusting of iron or melting of iron, which one is a physical change?
Answer: Melting of iron

Question 2. In the electrolysis of water, why is the volume of gas collected over one electrode double that of gas collected over the other electrode?
Answer:

Because during electrolysis, water splits into two molecules of hydrogen and one molecule of oxygen.

2HO  → (Electrolysis )  → 2 H₂O

Question 3. Which one is a chemical change, electrolysis of water or Sodium chloride exposed to sunlight?
Answer: Electrolysis of water

Question 4. All decomposition reactions are endothermic reactions. Explain why?
Answer: Because energy in the form of heat, light or electricity is required for decomposition.

Question 5. What change in colour is observed when white silver chloride is left exposed to sunlight? State the type of chemical reaction in this change.
Answer:  Silver chloride becomes grey. It is a photochemical decomposition reaction.

Question 6. Balance the given chemical equation:

⇒ \(\mathrm{Fe}(\mathrm{s})+\mathrm{H}_2 \mathrm{O}(\mathrm{g}) \longrightarrow \mathrm{Fe}_3 \mathrm{O}_4(\mathrm{~s})+\mathrm{H}_2(\mathrm{~g})\)

Answer:

⇒ \(3 \mathrm{Fe}(\mathrm{s})+4 \mathrm{H}_2 \mathrm{O}(\mathrm{g}) \longrightarrow \mathrm{Fe}_3 \mathrm{O}_4(\mathrm{~s})+4 \mathrm{H}_2(\mathrm{~g})\)

Question 7. Balance the given chemical equation:
Answer: FeSO₄(s)   → (Heat) → Fe₂O₃(s) + SO₂(g) + SO₃(g)

Question 8. Balance the following chemical equation:

⇒ \(\mathrm{Fe}(s)+\mathrm{H}_2 \mathrm{O}(g) \longrightarrow \mathrm{Fe}_3 \mathrm{O}_4(s)+\mathrm{H}_2(g)\)

Answer:

⇒  \(3 \mathrm{Fe}(s)+4 \mathrm{H}_2 \mathrm{O}(\mathrm{g}) \longrightarrow \mathrm{Fe}_3 \mathrm{O}_4(\mathrm{~s})+4 \mathrm{H}_2(g)\)

Question 9. What type of coating is formed on silver articles when they get corroded?
Answer: The silver articles form a black coating of silver sulphide (Ag₂S).

Question 10. On what basis is a chemical equation balanced?
Answer: It is based on the law of conservation of mass.

Question 11. Balance the given chemical equation:

Al(s) + CuCl₂(aq)→  AlCl₃(aq) + Cu(s)

Answer: 2Al(s) + 3CuCl₂(aq)→ 2AlCl₃(aq) + 3Cu(s)

Question 12. What type of coating is formed on copper articles when they get corroded?
Answer: The copper articles form a green coating of basic copper carbonate

Question 13. State one basic difference between a physical change and a chemical change.
Answer:

In a physical change, no new substance is formed whereas in a chemical change, a new substance is formed.

Question 14. On adding dilute hydrochloric acid to copper oxide powder, the solution formed is blue-green. Predict the new compound formed which imparts a blue-green colour to the solution.
Answer:

The new compound formed is copper (II) chloride (CuCl2) which imparts a blue-green colour to the solution.

Question 15. Name the oxidising and reducing agent in the following reaction: Cu + H₂O→Cu + H₂O
Answer:

The oxidising agent is CuO.

The reducing agent is H₂.

Question 16. What is meant by the skeletal equation?
Answer: An unbalanced chemical equation is called a skeletal equation.

Question 17. If copper metal is heated over a flame, it develops a coating. What is the colour and composition of this coating?
Answer: The colour of the coating is black and it is composed of CuO or copper oxide.

Question 18. Which one is a chemical change – Electrolysis of water or sodium chloride exposed to sunlight?
Answer: Electrolysis of water

Question 19. A magnesium ribbon should be cleaned before burning it in the air. Why?
Answer: It should be cleaned to remove the dust particles and the oxide that may be present on its upper surface so that it comes directly in contact with air.

Question 20. Which of the following is a chemical change?

1. Burning of wax
2. Melting of wax

Answer: 1. Burning of wax

Question 21. Why do gold and platinum not corrode in moist air?
Answer: They are least reactive and do not react with substances present in moist air.

Question 22. Why do potato chip manufacturers fill the packet of chips with nitrogen gas?
Answer: To provide an inert atmosphere to prevent chips from getting oxidised. N₂ does not allow chips to get spoiled by oxidation.

Question 23. How will you define a reducing agent?
Answer: A reducing agent is a substance which can lose electrons or which can add hydrogen or remove oxygen.

Question 25. Name the process in which the gain ofelectrons takes place.
Answer: Reduction is a process which involves the gain ofelectrons

Question 24. A white salt on heating decomposes to give brown fumes and a residue is left behind. Name the salt.
Answer: Lead nitrate is white salt.

Question 25. Hydrogen is a highly inflammable gas and oxygen being a supporter of combustion, yet water which is a compound made up of hydrogen and oxygen is used to extinguish fire. Why?
Answer:

This is because the properties of the compound (H₂O) are different from the properties of its constituting elements i.e., H₂ and O₂.

Question 26.

• AgNO₃(aq) + NaCl(aq)→ AgCl(s) ↓ + NaNO₃(aq)
• FeS + H₂SO₄ →FeSO₄ + H₂S ↑

Consider the above-mentioned two chemical equations with two different kinds of arrows(↑ and ↓) along with products. What do these two different arrows indicate?
Answer:

↑ shows the gas evolved whereas shows insoluble substance (precipitate) formed.

Question 27. What is the colour of FeS04.7H20 crystals? How does the colour change upon heating? Give a balanced chemical equation for the change. 
Answer:

FeSO₄. 7H₂O is green in colour and loses water of crystallisation when it is heated. It is then decomposed to Fe₂O₃ (brown-coloured), SO₂ and SO₃

img reaction

Question 28. Oil and fat-containing food items are flushed with nitrogen. Why?
Answer: To keep food items fresh and to save from the oxidising effect of oxygen, food items are flushed with nitrogen gas.

Question 29. Why do we store silver chloride in dark-coloured bottles?
Answer: Because silver chloride on exposure to sunlight undergoes dissociation.

Question 30. A boy has been collecting silver coins and copper coins. One day he observed a black coating on silver coins and a green coating on copper coins. Which chemical phenomenon is responsible for these coatings?
Answer: The phenomenon responsible for these coatings is corrosion.

Question 31. FeSO₄. 7H₂O, green colour crystals on heating changes colour. Why?
Answer:  The green colour of ferrous sulphate crystals is due to the presence of 7 water molecules (water of crystallisation).

CBSE Class 10 Science Light-Reflection And Refraction Very Short Questions and Answers

Question 1. Define the term reflection.
Answer: The bouncing back of light when it strikes a polished surface is called the reflection of light.

Question 2. State the laws of reflection.
Answer:

1. The angle of incidence is equal to the angle of reflection i.e. Li = r.
2. The incident ray, the normal and the reflected ray, all lie in the same plane.

Question 3. What is the radius of curvature of a plane mirror?
Answer: Infinity

Question 4. How will you identify a convex lens by touching it?
Answer: A convex lens is thinner at the center and thicker at the edges.

Question 5. What is the velocity of light in a glass slab with a refractive index of 1.5?
Answer:

v\(=\frac{c}{\mu}=\frac{3 \times 10^8}{1.5}=\)2 × 10⁸ m/s.

Question 6. The refractive index of a diamond is 2.42. What is the meaning of this statement about the speed of light?
Answer: It means that light travels 2.42 times faster in a vacuum than in a diamond.

Question 7. For the same angle of incidence, the angle of refraction in three media A, B, and C are 15°, 25°, and 35° respectively. In which medium is the velocity of light minimum?
Answer: In medium C.

Question 8. What will be the focal length of a lens whose power is given as +2.0 D?
Answer:

Given

f = ?, P = + 2.0 D

P = \(\frac{1}{f}\)

⇒ \(\frac{1}{\mathrm{P}}=\frac{1}{2}=0.5 \mathrm{~m}\)

Question 9. Define the term power of a lens.
Answer: It is defined as the ability of a lens to converge or diverge a beam of light falling on it.

Question10. What does positive magnification imply?
Answer: It means that the image formed is erect and virtual.

Question 11. An incident ray falls normally on a glass slab, what is the angle of refraction?
Answer: Zero

Question 12. What type of lens behavior will an air bubble inside water show?
Answer: It will act as a concave lens.

Question 13. What is the expression for the magnification of a lens?
Answer:

⇒ \(m=\frac{-v}{u}\)

Question 14. A thin lens has a focal length of -12 cm. Is it a convex lens or a concave lens?
Answer: Concave lens

Question 15. When the light of 2 colors, A and B is passed through a plane boundary, A is bent more than B. Whcolorlour travels more slowly in the second medium.
Answer: Colour A travels slowly.

Question 16. Between which 2 points related to a concave mirror should an object be placed to obtain on a screen an image twice the size of the object?
Answer: Real image – Between F and C.

Question 17. The speed of light in a transparent medium is 0.6 times that of its speed in a vacuum. What is the refractive index of the medium?
Answer:

⇒ \(n=\frac{c}{v}\)

⇒ \(n=\frac{c}{0.6 c}=\frac{1}{0.6}=1.66\)

Question 18. A person wants a full-length image of a tall building in a small mirror. What type of mirror is used by him?
Answer: Convex mirror

Question 19. Does the value of the speed of light change with the medium?
Answer: Yes, in a denser medium, it becomes less than that in free space.

Question 20. When the angle of incidence is 90°, what is the angle of refraction?
Answer:

n = \(\frac{\sin i}{\sin r}\)

For i = 90°

r = \(\sin ^{-1}\left(\frac{1}{n}\right)\)

Question 21. How does the frequency of a beam of ultraviolet light change when it goes from air into glass?
Answer: Frequency remains the ins same on change of medium.

Question 22. What is the unit of power of a lens?
Answer: Dioptre

Question 23. Give two uses of a convex lens.
Answer:

1. Used in camera.
2. Used in projectors.

Question 24. Mention two properties the the of image formed by a convex mirror.
AnswThe image

1. mage produced is virtuTheimagee mage produced is erect.

Question 25. A lens X has a focal length of 20 cm and a lens Y has a focal length of 40 cm. Which lens would you select to obtain a more convergent beam of light?
Answer: The lens has an ing focal length of 20 cm as it will have more power.

Question 26. the the Can refractive index of a medium be less than unity? What is the value of the refractive index of a vacuum?
Answer: No, because the use speed of light a  in vacuum is maximThe refractivetive index for a vacuum is 1.

Question 27. An object is placed at a distance ‘u’ from the lens of focal length ‘The image is formed at a distance ‘v’ from the lens. Write the relation between u, and v, f.
Answer:

⇒ \(\frac{1}{f}=\frac{1}{v}=\frac{1}{u}\)

Question 28. What is the value of the speed of light in free space?
Answer: L = 3 × 10⁸ m/s

Question 29. Does the refractive index vary with the color of light?
Answer: Yes, (n_v>n_r).

Question 30. What is the importance of the optical center of a lens?
Answer: It signifies the point through which if a light goes, there will not be any direction.

CBSE Class 10 Science Chapter 6 Life Processes Very Short Answer Questions

Question 1. In the experiment “Light is essential for photosynthesis”, why does the uncovered part of the leaf turn blue-black after putting iodine solution?
Answer: Starch is produced in the uncovered part of the leaf which turns blue-black in the presence of iodine solution.

Question 2. State the basic difference between the process of respiration and photosynthesis.
Answer: Respiration uses O₂ and releases CO₂ but in photosynthesis, CO₂ is used and O₂ is released.

Question 3. Which pancreatic enzyme is effective in digesting proteins?
Answer: Trypsin is the pancreatic enzyme that is effective in digesting proteins.

Question 4. Why does lack of oxygen in muscles often lead to cramps among cricketers?
Answer: This is due to the conversion of pyruvate to lactic acid in the absence of oxygen.

Question 5. What is peristaltic movement?
Answer: The contraction and expansion movement of the walls of food-pipe is called peristaltic movement. This pushes the food in a forward direction in the alimentary canal.

Question 6. Why is anaerobic respiration less efficient?
Answer: Anaerobic respiration is the incomplete breakdown of glucose and produces less energy, so it is less efficient.

Question 7. Why do mammals require a more extensive respiratory surface?
Answer: Mammals need more oxygen to meet the requirements of their high metabolic rate. Therefore they need extensive respiratory surface.

Question 8. How many chambers are present in the heart of fishes? How many times does blood flow through the heart during each cycle?
Answer: Two chambers are present in the heart of fishes. Blood flows one time through the heart during each cycle.

Question 9. What is the main function of Adam’s Apple?
Answer: The main function of Adam’s Apple is to produce voice in the presence of air.

Question 10. When we breathe out, why does the air passage not collapse?
Answer: The air passage does not collapse because it is supported by cartilaginous rings which prevent its collapsing.

Question 11. Mention the raw materials required for photosynthesis.
Answer: The raw materials required for photosynthesis are carbon dioxide and water in the presence of sunlight and chlorophyll.

Question 12. Mention the purpose of making urine.
Answer: The purpose of making urine is to filter out waste products (urea or uric acid) from the blood.

Question 13. In which part of the digestive system is water absorbed?
Answer: In the large intestine.

Question 14. Which type of nutrition is present in tapeworms?
Answer: Heterotrophic nutrition.

Question 15. Where does the digestion of fat take place in our body?
Answer: In the small intestine by the use of bile and lipase.

Question 16. What is the function of platelet cells in blood?
Answer: The platelet cells in blood circulate the body and help to clot the blood at the point of injury.

Question 17. The volume of glomerular filtrate produced is 18 L but the volume of urine excreted is just 1-2 L. Give a suitable reason for this statement.
Answer: It is because the remaining filtrate is reabsorbed in the kidney tubules.

Question 18. Name any two substances which are selectively reabsorbed from the tubules of a nephron.
Answer: Water, glucose, amino acid.

Question 19. How does the transportation of water occur at night in the absence of transpiration?
Answer: At night, the transportation of water occurs due to the root pressure.

Question 20. Why is the rate of breathing in aquatic organisms much faster than that in terrestrial organisms?
Answer: Because the amount of dissolved oxygen is fairly low compared to the amount of oxygen in the air.

Question 21. What role does bile play in digestion?
Answer: Emulsification of fats.

Question 22. Why do ventricles have thicker walls than auricles?
Answer: Some ventricles have to pump blood into various organs, therefore they have thicker muscular walls than the auricles.

Question 23. Name the component of food that is not digested in the stomach.
Answer: Roughage.

Question 24. During the breathing cycle, what is the advantage of residual volume of air in the lungs? Explain.
Answer: The advantage of residual volume of air in the lungs is that there is sufficient time for oxygen to be absorbed and for CO₂ to be released.

Question 25. Why do the walls of the trachea not collapse when there is less air in it?
Answer: The presence of rings of cartilage in the throat ensures that the air passage does not collapse.

Question 26. Name the component of blood that helps in the formation of blood clots in the event of a cut.
Answer: Platelet.

Question 27. What is ‘translocation’ in plants?
Answer: The transport of soluble products of photosynthesis is known as translocation.

Question 28. Name the intermediate and the end products of glucose breakdown in aerobic respiration.
Answer:

Question 29. Mention how organisms like bread molds and mushrooms obtain their food.
Answer: Organisms like bread molds and mushrooms break down the food materials outside the body and then absorb it.

CBSE Class 10 Science Chapter 7 Control and Coordination Very Short Answer Questions

Question 1. At the time of puberty, both boys and girls show lots of changes in appearance. Name the hormones responsible for these changes.
Answer: Testosterone in males and estrogen in females.

Question 2. Give one example of chemotropism.
Answer: The growth of a pollen tube towards a chemical produced by an ovule during fertilization of a flower is an example of chemotropism.

Question 3. Where are Nissl’s granules found and what is their nature?
Answer: Nissl’s granules are found in cyton and dendrites. These are formed of ribonucleic acid (RNA).

Question 4. A young green plant receives sunlight from one direction only. What will happen to its shoots and roots?
Answer: Shoot will bend towards the light and root away from the light.

Question 5. Name the part of the brain which is concerned with muscular coordination in the body.
Answer: Cerebellum.

Question 6. A potted plant is made to lie horizontally on the ground. Which part of the plant will show?

1. Positive geotropism.
2. Negative geotropism.

Answer:

1. Root
2. Shoot

Question 7. All information about our environment is detected by the specialized tips of some nerve cells. Write the name given to such tips and also mention where they are located.
Answer: Receptors. They are located in the sense organizer:

Question 8. Why do endocrine glands release their secretions into the blood?
Answer: It is because endocrine glands are ductless.

Question 9. Name the main hormone secreted by the thyroid gland and state its one function.
Answer:

The main hormone secreted by the thyroid gland is thyroxine. It regulates the metabolism of carbohydrates, fats, and proteins in the body to provide the best growth balance.

Question 10. Name the part of the hindbrain which takes part in the regulation of respiration.
Answer: The Pons part of the hindbrain takes part in regulating respiration.

Question 11. Name the place of the human body where the largest number of neurons are found.
Answer: Human brain.

Question 12. What is the stimulus in:

1. Phototropism
2. Geotropism
3. Chemotropism

Answer:

1. Phototropism – Light
2. Geotropism – Gravity
3. Chemotropism – Chemicals

Question 13. State the function of:

1. Gustatory receptors
2. Olfactory receptors

Answer:

1. Gustatory receptors receive a taste.
2. Olfactory receptors receive smell.

Question 14. Define ‘reflex action’.
Answer: Reflex action is a sudden, involuntary spontaneous response to the stimulus that is usually helpful to protect ourselves from any kind of harm.

Question 15. What type of movement is responsible for the growth of pollen tubes towards ovules?
Answer: Nastic movement.

Question 16. What is a synapse?
Answer: Synapse is the functional junction between two neurons.

Question 17. Name one organ where growth hormone is synthesized in the case of plants and man.
Answer:

1. Shoot tip in plants.
2. The pituitary gland in man.

Question 18. What is the function of the ‘Hypothalamus’?
Answer: It regulates the secretion of hormones from the pituitary gland.

Question 19. Name two tissues that provide control and coordination in multicellular animals.
Answer:

1. Nervous tissue.
2. Endocrine tissue.

Question 20. Define ‘chemotropism’.
Answer: It is a nastic response towards the chemicals like the germination of pollen tubes when the pollen grains land on the stigma.

Question 21. Which system facilitates the communication between the central nervous system and other parts of the body?
Answer: Endocrine system.

Question 22. Why is it advised to use iodized salt in our diet?
Answer: Iodised salt contains iodine which is necessary for the thyroid gland to synthesise thyroxine hormone. Thyroxine regulates carbohydrate, protein, and fat metabolism in the body to provide growth balance.

Question 23. Why is the pituitary called the master gland?
Answer: The pituitary gland controls the activity of other endocrine glands, so it is called the master gland.

Question 24. Name the sensory receptors found in the nose and on the tongue.
Answer: Olfactory receptors, gustatory receptors.

Question 25. Where is glucagon secreted? What is its function?
Answer: Glucagon is secreted in the L-cells of islets of Langerhans Function of glucagon is to increase the blood glucose level.

Question 26. Why are endocrine glands called ductless glands?
Answer: Because they do not have any external duct to discharge their secretion into the bloodstream.

Question 27. Why hormones are called ‘Chemical messengers’?
Answer: Hormones are carried in the bloodstream to all parts of the body, so they are called ‘Chemical messengers’.

Question 28. Name the plant hormone responsible for the promotion of cell division.
Answer: Cytokinin.

Question 29. Name the hormone that helps regulate the level of sugar in our blood. Name the gland that secretes it.
Answer: Insulin helps in regulating blood sugar levels. This hormone is secreted by the pancreas gland.

Question 30. Mention the function of the hindbrain in humans
Answer: The hindbrain coordinates the body’s movement and posture. It also controls respiration.

CBSE Class 10 Science Chapter 9 Heredity And Evolution Very Short Answer Questions

Question 1. Name one reptile in each case where a higher incubation temperature leads to the development of

1. Male progeny
2. Female progeny.

Answer:

1. Lizard
2. Turtle

Question 2. What are the carriers of factors or genes?
Answer: Chromosomes.

Question 3. Which type of sex chromosomes are carried by male gametes in human males? What is their percentage?
Answer: X and Y chromosomes. 50% of sperms carry X chromosomes and 50% carry Y chromosomes.

Question 4. An organism which is a worm, has very simple ‘eyes’, which are eye spots that detect light. Name that organism.
Answer: Planaria.

Question 5. Why is the progeny always tall when a tall pea plant is crossed with a short pea plant?
Answer: The trait that represents the tallness in a pea plant is dominant over the other trait shortness.

Question 6. What is heredity?
Answer: Transmission of characters from parents to their offspring.

Question 7. Mendel observed the contrasting traits of the position of flowers. Mention those traits.
Answer:

1. Terminal → Recessive and
2. Axial → Dominant

Question 8. How can the chromosomes be identified?
Answer: In human beings, the individual chromosomes are identified by their length, position of centromere, and banding pattern on staining.

Question 9. Where does the process of gene flow take place?
Answer: Gene flow or gene migration takes place between populations that are partly but not completely separated.

Question 10. How many pairs of chromosomes are present in human beings?
Answer: 23 pairs.

Question 11. What is the phenotype ratio of a dihybrid cross in F₂ generation?
Answer: 9:3:3:1

Question 12. Give the respective scientific terms used for studying:

1. The mechanism by which variations are created and inherited.
2. The development of new types of organisms from the existing ones.

Answer:

1. Heredity
2. Species.

Question 13. What type of reproduction gives rise to more number of successful variations?
Answer: Sexual reproduction.

Question 14. What will be the sex of a child who inherits X chromosomes from his/her father?
Answer: Female.

Question 15. No two individuals are alike in a population. Why?
Answer: All individuals have different kinds of DNA. So all individuals are not alike to each other.

Question 16. Define speciation
Answer: Speciation means the origin of a new species from the existing one.

Question 17. Define evolution.
Answer: A gradual genetic change in a group of living beings to produce new forms.

Question 18. Give an example where sex determination is regulated by environmental factors.
Answer: In snails, sex is determined by environmental factors (temperature).

Question 19. Name the term used for the traits that are exhibited externally.
Answer: Phenotype.

Question 20. Write the sex of the baby that inherits Y chromosomes from the father.
Answer: Male.

Question 21. Are the wings of a butterfly and the wings of a bat analogous organs or homologous organs? Justify your answer.
Answer: Analogous. They are analogous as they have the same function but different basic structures.

Question 22. What are fossils?
Answer: Preserved traces of living organisms.

Question 23. What is genetic drift?
Answer: The change in the frequency of certain genes in a population over generations.

Question 24. Name any three different traits the pea plant possesses.
Answer: Round and wrinkled seeds Tall and short plant white and violet flowers i.e., seed shape, plant height, flower color.

Question 25. What are the basic events in evolution?
Answer: The changes in DNA during reproduction are the basic events in evolution.

Question 26. What are analogous organs?
Answer: The organs that have similar functions but different structures are called analogous organs

Question 27. Name the plant on which Mendel performed his experiments.
Answer: Garden pea.

Question 28. Give an example of a homologous organ from the plant kingdom.
Answer: Thorns and tendrils.

Question 29. Name the genetic material that is responsible for the inheritance of traits.
Answer: Gene.

Question 30. What is a gene?
Answer: It is the unit of inheritance. Gene is the part of a chromosome that controls the appearance of a set of hereditary characteristics.

Question 31. Species A shares ten characteristics with species B, and species C shares fifteen characteristics with D, which of the two pairs shares a closer relation?
Answer: C and D

CBSE Class 10 Science Chapter 13 Magnetic Effects Of Electric Current Very Short Answer Questions

Question 1. Draw a diagram to represent a uniform magnetic field in a given region.
Answer:

Question 2. Why is earthing important for electrical appliances?
Answer: It saves the person operating the device from electric shock and also saves the device from excessive current due to some fault.

Question 3. What is the capacity of a fuse commonly used in domestic electrical fitting?
Answer: Fuses of capacity 5 A or 15 A are commonly used in domestic electrical fittings.

Question 4. What will you do if you see a person coming in contact with a live wire?
Answer: Such a person should be provided with an insulated support like wood, plastic, or rubber to disconnect the person from the wire.

Question 5. What does the closeness of field lines in a magnetic field signify?
Answer: It indicates the strength of the magnetic field in the region.

Question 6. Name the alloy which is mainly used for making permanent magnets.
Answer: Alnico (an alloy of aluminum, nickel, cobalt, and iron).

Question 7. An alternating electric current has a frequency of 50Hz. How many times does it change its direction in one second?
Answer: Since AC changes its direction twice in a cycle, it will change its direction 100 times (50 x 2) in one second as its frequency is 50 Hz.

Question 8. Mention the voltage and frequency of current that we receive at our house.
Answer:

1. Voltage-220 V
2. Frequency-50 Hz

Question 9. State the direction ofthe magnetic field inside the bar magnet.
Answer: From south to north pole.

Question 10. Name the factors on which force acting on a current-carrying conductor depends.
Answer:

1. Strength of the magnetic field.
2. The current through the conductor
3. The length of the conductor.

Question 11. What is meant by electromagnetic induction?
Answer: It is the phenomenon of producing an electric current in a conductor by changing the magnetic field through the conductor.

Question 12. Name the rule used to find the direction of force on a current-carrying conductor.
Answer: Fleming’s left-hand rule

Question 13. What is the shape of magnetic field lines around a straight current-carrying conductor?
Answer: Concentric circles.

Question 14. Name the type of current:

1. Used in household supply
2. Given by cell

Answer: Alternating Current (AC) and Direct Current (DC)

Question 15. What type of core is used to make an electromagnet? 
Answer: Soft, iron

Question 16. Mention the special feature regarding the shape of magnetic field lines.
Answer: They are closed curves.

Question 17. How is a fuse connected in an electric circuit?
Answer: It is connected in series in the circuit.

Question 18. What is short-circuiting1?
Answer: The coming together of the live and neutral wire is called short-circuiting.

Question 19. Why is the metallic body of electrical devices connected to the earth wire?
Answer: This is because it provides a low-resistance conducting path for the current to flow to The earth. Thereby protecting the user from a severe electric shock.

Question 20. Write any one method to induce a current in a coil.
Answer: By moving a magnet towards a coil.

Question 21. Suggest one way of discriminating between a wire carrying current and a wire carrying no current.
Answer: Bring a magnetic needle near the wire. A current-carrying wire will produce a deflection in the needle whereas a wire without current will not.

Question 22. How can you magnetize a piece of magnetic material?
Answer: We can do so by placing it inside a current-carrying solenoid.

Question 23. How is the circuit overloaded?
Answer: By connecting too many devices to it.

Question 24. Mention the angle between a current-carrying conductor and a magnetic field for which the force experienced by this current-carrying conductor placed in a magnetic field is the largest.
Answer: The angle is 90°.

Question 25. How does a current-carrying solenoid behave?
Answer: It behaves like a bar magnet.

Question 26. On which effect of electricity does the fuse work?
Answer: Heating effect of current.

Question 27. Why is a fuse usually made of tin-copper alloy?
Answer: A fuse is usually made of tin or tin-copper alloy because it has a low melting point.

Question 28. What is a solenoid?
Answer: A Solenoid is a coil of many turns of wire wrapped in the shape of a cylinder.

Question 29. What does the direction of thumb indicate in the right-hand thumb rule?
Answer: The thumb indicates the direction of current in the straight conductor held by curled Angers.

Question 30. How is the magnetic field produced in a solenoid used?
Answer: It is used to magnetize a soft iron piece to form an electromagnet.

Question 31. Why does a compass needle get deflected when brought near a bar magnet?
Answer: The magnetic field of the magnet exerts force on both the poles of the compass needle. The forces experienced by the two poles are equal and opposite. These two forces form a couple which deflects the compass needle.

Question 32. Draw magnetic field lines around a bar magnet. (PBQ)
Answer: A complete pattern of the magnetic field lines around a bar magnet is shown in the
figure

Question 33. List two methods of producing magnetic fields.
Answer: Permanent magnets and electromagnets.

CBSE Class 10 Science Chapter 14 Sources Of Energy Very Short Answer Questions

Question 1. Name the chemical compound that is added to LPG to detect its leakage.
Answer: Ethyl mercaptan (C2H5- SH)

Question 2. Name some devices for harnessing solar energy.
Answer: Solar cookers, solar heaters, and solar cell panels, are the devices that harness solar energy directly into heat or electricity.

Question 3. Name the greenhouse gases.
Answer: CO2, CH4

Question 4. State two merits of hydroelectricity.
Answer: Hydroelectricity is a clean and renewable energy source. This natural renewable energy can be stored in high-level reservoirs and can be used whenever required which is not the case with wind energy and solar energy.

Question 5. Which out of biogas and LPG has a lower calorific value?
Answer: Biogas has a lower calorific value.

Question 6. What kind of energy transformation takes place at a thermal power station?
Answer: Chemical energy into electrical energy.

Question 7. Name the major constituent of natural gas.
Answer: Methane

Question 8. How is slurry left over after the generation of biogas in the Gobar gas plant used?
Answer: As a manure.

Question 9. Why are gaseous fuels preferred to solid fuels in chemical industries?
Answer: Gaseous fuels are preferred because

1. They can be transported easily through pipelines.
2. They leave no ash on burning.
3. They burn completely and cause less pollution than solid fuels.

Question 10. Where is natural gas usually found?
Answer: Natural gas is usually found over petroleum deposits deep under the surface of the earth.

Question 11. Write the characteristic features ofthe micro-organisms which help in the production of biogas in a biogas plant.
Answer: The micro-organisms are anaerobic bacteria that break down organic matter anaerobically and produce biogas.

Question 12. Name two combustible components of biogas.
Answer: Methane (CH4) and hydrogen (H2)

Question 13. Mention the minimum wind velocity required for obtaining electric power with a windmill generator.
Answer: The wind speed should be higher than 15 mph.

Question 14. What are the causes of acid rain?
Answer: Acidic oxides of carbon, nitrogen, and sulfur get dissolved in water during rain and cause acid rain.

Question 15. Blowing wind carries kinetic energy. Mention the two factors that cause the wind to blow.
Answer: Unequal heating of the landmass and water bodies by solar radiation generates air movement and causes wind to blow.

Question 16. Name the reaction responsible for large energy production in the sun.
Answer: Nuclear fusion.

Question 17. What is geothermal energy?
Answer: The heat from inside the earth heats the water below the surface. This energy with hot water below the earth is called geothermal energy.

Question 18. Give two limitations in the use of solar cells.
Answer: Limitation of solar cells

1. The efficiency of solar cells is low.
2. It produces direct current.

Question 19. Mention any one reason due to which most of the thermal powerplants are set up near coal or oil fields.
Answer: Transportation of electricity is more efficient than transporting coal or petroleum over some distance.

Question 20. List two forms of energy in which solar energy manifests itself in one answer:
Answer: Ocean thermal energy Wave energy

Question 21. Give one example of each renewable and non-renewable source of energy.
Answer: Renewable- Solar energy, wind energy. Non-Renewable- Coal, petroleum.

Question 22. Why are solar cookers painted black?
Answer: They are painted black to ensure maximum heat absorption, as black surfaces are good absorbers of solar radiation.

Question 23. In which form can cow dung be used to maximum advantage?
Answer: Cow dung is put to maximum advantage by using it to produce biogas.

Question 24. What is calorific value?
Answer: The heat generated by burning the unit mass of a fuel is called its calorific value.

Question 25. A student constructed a box-type solar cooker and covered it with a glass plate. Write the purpose of a glass plate in a cooker.
Answer: It is used to trap solar heat inside the solar cooker.

Question 26. The use of dry wood as domestic fuel is not considered as good. State two reasons for it
Answer: Lots of smoke on burning. Lots of residue after burning.

Question 27. The construction of dams submerges large areas of forests, how does this contribute to the greenhouse effect?
Answer: Submerged forests decompose anaerobically, this produces methane which is a greenhouse gas.

Question 28. What is the main purpose behind the use of a mirror in solar cookers?
Answer: A mirror in a solar cooker acts as a reflector of sunlight into the box and thus gives a higher concentration ofheat rays at a point.

Question 29. Name the chief component of solar cells. What energy conversion takes place in a solar cell?
Answer: Silicon. It converts solar energy into electrical energy.

Question 30. What steps would you suggest to minimize environmental pollution caused by the burning of fossil fuels?
Answer: Use of smokeless appliances.

CBSE Class 10 Science Chapter 8  How do Organisms Reproduce Very Short Questions and Answers

Question 1. Where is DNA found in a cell?
Answer: Genes/Chromosomes

Question 2. Why cannot all multicellular organisms divide cell-by-cell like spirogyra?
Answer:

The higher multicellular organisms have differentiation of structure and function, unlike spirogyra in which all the cells are similar and independent units.

Question 3. Name the two plants which are grown using the plant tissue culture method.
Answer:

1. Orchids
2. Asparagus

Question 4. Name some plants which are usually propagated by cutting method.
Answer: Rose, cactus, sugarcane, pineapple

Question 5. What is the function of pollen grains in flowers?
Answer: Pollen grains fertilise the egg cells present in the embryo sac of an ovule.

Question 6. State an advantage of vegetative propagation.
Answer:

This method can be practised for growing such plants which usually do not produce seeds or produce non-viable seeds.

Question 7. Name the type of cells which undergo regeneration.
Answer:

Specialised cells are called regenerative cells which can proliferate and make a large number of cells.

Question 8. Name two organisms having the ability to regenerate.
Answer: Hydra and Planaria

Question 9. Name two plants that reproduce through spores.
Answer: Mushrooms and ferns

Question 10. State how the copper-T serves as an effective contraceptive device.
Answer:

Copper-T is placed inside the uterus by a doctor, which prevents implantation in the uterus.

Question 11. How can the chromosomes be identified?
Answer: Chromosomes can be seen as thread-like structures when a cell divides.

Question 12. List two functions performed by ovaries in a human female.
Answer:

1. Production of ovum (gamete).
2. Secretion of female hormones (estrogen and progesterone).

Question 13. Why is DNA copying an essential part of the process of reproduction?
Answer:

DNA is an essential part because errors in DNA copying lead to variation which not only gives survival advantage to an organism but also leads to evolution.

Question 14. Why is the temperature of the scrotal sac 2°C less than the body temperature?
Answer:

It is less because testes require a temperature of 2°C less than the body temperature for the production of sperins.

Question 15. Which group of plants shows double fertilisation?
Answer: Angiosperms

Question 16. What happens during pollination?
Answer: Pollen grains from stamen get transferred to carpels.

Question 17. Mention one physiological advantage of grafting quality roses on the wild rose stock.
Answer:

The rose stock is derived from a plant resistant to diseases and pests and is efficient in the absorption of water and minerals.

Question 18. Why is sexual reproduction considered to be superior to asexual reproduction in terms of evolution?
Answer: Sexual reproduction is a source of variation which ensures the survival of the species.

Question 19. Why is regeneration considered a method of reproduction?
Answer:

Regeneration is considered a method of reproduction because an entirely new organism can be made from its fragmented body.

Question 20. Write one example of a plant showing vegetative propagation by leaves.
Answer: Bryophyllum

Question 21. What is the significance of the sexual mode of reproduction?
Answer: It promotes variation in organisms.

Question 22. Regeneration is not possible in all types of animals. Why?
Answer:

Regeneration is carried out by specialised cells. The organisms which have those cells only can show regeneration.

Question 23. What happens if the egg is not fertilized?
Answer: Menstruation occurs, i.e., blood and mucus come out through the vagina.

Question 24. Which part becomes a new plant in vegetative propagation?
Answer: Root, stem and leaves

Question 25. What is the advantage of reproducing through spores?
Answer:

In the form of a cyst, it can survive in adverse conditions. Easy dispersal through wind is possible as they are more in number and light in weight.

Question 26. What is reproduction?
Answer:

Reproduction is a process of producing new individuals of the same species by existing organisms, i.e., parents.

Question 27. Which is the most basic event in reproduction?
Answer: Creation of a DNA copy.

Question 28. Differentiate between pollen grain and ovule.
Answer: Pollen grain contains male gametes in plants and ovule contains female gametes.

Question 29. Why is vegetative propagation practised for growing some plants?
Answer: Vegetative propagation is used for growing some plants which do not produce viable seeds.

Question 30. Differentiate between germination and fertilization.
Answer:

1. Germination-Development of the embryo into a seedling.
2. Fertilisation-Fusion of male and female gametes.

Our Environment Very Short Answer Questions

Question 1. What is the physical environment of an ecosystem called? Give one example.
Answer:

The physical environment of an ecosystem is called the abiotic or non-living component of an ecosystem. This includes physical factors like temperature, rainfall, wind, etc.

Question 3. What is meant by consumers in an ecosystem1?
Answer:

Those organisms cannot manufacture their food by the process of photosynthesis and depend either on plants or on other organisms.

Question 4. The first trophic level in a food chain is always a green plant. Why?
Answer:

Because only plants can utilize the radiant energy ofthe sun and transform it into chemical form during photosynthesis.

Question 6. Write the full forms of UNEP and PEC.
Answer:

UNEP = United Nations Environment Programme

PFC = Perfluorocarbon

Question 7. In an ecosystem, rats feed on grain. Name the tropic level to which the rat belongs.
Answer:

Second tropic level.

Question 8. Write the mode of nutrition in fungi.
Answer: Saprophytic.

Question 9. In a certain study conducted d on the occurrence of DDT along food chains in an ecosystem, the concentration of DDT in the grass was found to be 0.5 ppm, in sheep it was and in Inman it was 10 ppm. Why was the concentration of DDT maximum in the case of man?
Answer:

DDT is non-biodegradable and accumulates at each tropic level. Since man is at the highest tropic level, there is a maximum accumulation of DDT in him (biological magnification).

Question 10. Write any consequences if decomposers are removed from the ecosystem.
Answer:

• Dead organisms will pile up.
• There will be no replenishment of soil.

Question 11. Which chemical is used in fire extinguishers? How is it harmful?
Answer: Chlorofluorocarbons-CFCs.It causes depletion of the ozone layer.

Question 12. What is meant by biological magnification?
Answer:

Accumulation of non-biodegradable chemicals progressively at each trophic level in a food chain is called biological magnification.

Question 13. Mention the role of microorganisms like bacteria and fungi in the ecosystem.
Answer:

They break down the dead remains and waste products of organisms.

Question 14. Write the names of aquatic organisms to form a food chain of at least three steps.
Answer:

Algae →  insect → mall fish→  big fish

Question 15. Give one property of ultraviolet radiation.
Answer: Ultraviolet radiation causes skin cancer in humans.

Question 16. The “Save the Tiger” campaign is being overemphasized these days by our government. What may be the possible reason?
Answer: To maintain ecological balance in nature and to preserve the gene pool.

Management Of Natural Resources Very Short Questions And Answers

Question 1. State one reason for the conservation of forests and wildlife.
Answer: Restoring of ecological balance.

Question 2. List two items that can easily be recycled, but we generally throw them in the dustbins.
Answer:

Polythene bags/paper bags/soft drink bottles/glass jars.

Question 3. Name two gases other than CO₂ produced by the burning of coal and petroleum.
Answer: Sulfur dioxide and nitrogen oxide.

Question 5. Why should biodegradable and noil-biodegradable wastes be discarded in two separate dustbins?
Answer:

Because biodegradable wastes can be dumped to convert them into manure whereas non-biodegradable waste is to be dumped separately as it persists in the environment for a long time and harms the environment.

Question 6. Name the group of bacteria the presence of which confirms the contamination of the water of a river.
Answer:  Coliform bacteria.

Question 7. What is meant by ‘biodiversity hotspots’?
Answer:  It is a biogeographic region that is a significant reservoir of biodiversity.

Question 8. What is the mode of nutrition in human beings?
Answer: Heterotrophic.

Question 9. Write two methods of waste disposal.
Answer:

1. Ideal method:

1. Recycling the wastes
2. Reuse after repairing if required

2. Traditional methods:

1. Throwing them in the dustbin and dumping them in the sanitary landfills.
2. Burning or flowing water or rivers.

Question 10. State one reason for the conservation of forests and wildlife.
Answer: Restoring of ecological balance.

Question 11. Why do we need alternative sources ofenergy?
Answer:

Our resources are not unlimited and with the increase in population, the demand for all resources is increasing at an exponential rate, so we need alternative sources ofenergy.

Question 12. Give one protective function of the forest.
Answer:

Forest is the habitat of many wildlife species of animals and plants, that are not found elsewhere, and plays an important role in maintaining a balance in biodiversity.

Question 13. Define sustainable development.
Answer:

It encourages forms of growth that meet current basic human needs while preserving the resources for the needs of future generations.

Question 14. Name any two household wastes that can be easily recycled but are generally thrown in the dustbins by us.
Answer: Paper, plastic and (broken) glass, etc