Science Class X (CBSE)
Sample Paper Set - IV (SOLVED)

Q1. Name any two gases whose presence in air causes green-house effect.
Ans1. Carbondioxide and methane

Q2. Name the main constituents of common brass.
Ans2. Copper and zinc

Q3. Which property of diamond gives it its special shine?
Ans3. Diamond is transparent, has a high refractive index, and posseses excellent cleavage along many planes which can be polished. These properties give the diamond an extraordinary shine.

Q4. Boiled milk does not spoil quickly. Why?
Ans4. Boiled milk does not spoil quickly because the spoilage causing bacteria and other micro- organisms get destroyed when the milk is boiled.


Q5) A farmer grows rice crop year after year in his field. He notices a gradual decrease in yield. What could be its cause?
Ans5. The yield decreases gradually over the years because the monoculture of rice crop depletes the soil of the necessary mineral nutrients, especially nitrogenous nutrients.



Q6. Mention any two differences between chemical and nuclear reaction.
Ans6.

Q7. Kerosene burns in a cooking stove to give a blue flame while it gives a yellow flame when burnt in a lantern. Give reasons for this difference.
Ans7. A flame is blue when the supply of oxygen is adequate for the fuel to burn completely.The flame becomes yellow when the supply of oxygen is inadequate and the fuel does not burn completely. In the cooking stoves the construction is such that the supply of sufficient air is ensured and the
fuel burns completely. Whereas, in the lanterns the wick does not provide for the complete burning of the fuel and the flame becomes yellow and sooty.

Q8. Give two differences between a star and a shooting star.
Ans8.

Q9. What is smog? Name any two diseases caused by smog.
Ans9. Smog is a combination of smoke and fog. Smoke is made up of tiny particles of carbon, ash, oil, etc. Fog is made up of water droplets suspened in the air. Smog does not rise up and stays close to the earth's surface.
Two of the diseases which are caused by smog are:
1. Irritation to the eyes, nose and throat;
2. Asthma and other respiratory disorders.

Q10. A trivalent metal X is manufactured by the process of electrolysis. It is the most abundant metal in the earth's crust. Identify the metal and state its two uses.
Ans10. The metal should be aluminium because Aluminium is the most abundant metal in the earth crust and the third most abundant element in nature. Aluminium is trivalent (Al³⁺) and is prepared by electrolytic refining. Aluminium is used for:
1. Preparing electricity conducting wires, and
2. Preparation of light weight alloys for aircrafts etc.


Q11. What is sickle cell anaemia? What is its direct effect?
Ans11. Sickle cell anaemia is found in persons whose red blood cells contain a deffective type of haemoglobin having the appearance of a sickle. The direct effect of this trait is that the oxygen carrying capacity of the blood gets decreased.

Q12. Mention the difference between the food habits of organism belong to the first and third trophic levels. Give one example of each of them.
Ans12. The first trophic level is the level of producers. Green plants are the producers and generate their food on their own.They have chlorophyll with which they trap solar radiations and convert it into the chemical bond energy.
The third trophic level is the level of carnivores. They prey on the herbivores.

Q13. Name the process involved in the liberation of energy in (i) the sun and (ii) a nuclear reactor.Mention any two differences between the two processes.
Ans13.(i) Process involved in liberation of energy in sun : Nuclear fusion
(ii) Process involved in liberation of energy in a nuclear reactor : Nuclear Fission

Q14. The mass of a star A is one tenth that of star B. If the mass of A is nearly equal to that of the sun, which one of the two stars will end up as supernova? What would happen to the other star at the end of red giant phase?
Ans14. Mass of A is nearly equal to that of sun. B has mass ten times that of A that is ten times that of the, Sun. Therefore, the star B is will end up as supernova.
The star A will end up as a White Dwarf Star.

The star A after entering the red giant stage will lose its expanding outershell.The core of red giant star left behind would gradually condense into an exremely dense ball of matter. Due to contraction of condensation, high temperature would be produced in the core. At this high temperature Helium present in the core would fuse to form higher elements like carbon and
liberate a lot of energy. The energy liberated by these fusion reactions cause the small core glow until helium lasts into it. This is how the white dwarf star would be formed from A.


Q15. Describe any three ways in which the water is important for the activities of living beings.
Ans15. Water is important for living beings:
As solvent: water is almost a universal solvent. Many things which the living animals have to ingest and need to take into their cell as metabolite have to be dissolved and water is the best solvent and carrier for such things.
As habitat of organisms: Aquatic organisms need water as a medium for living. Water was the medium where life originated first.
As temperature regulating agent: Water serves as a temperature regulating agent in a way that it spreads temperature uniformly among colder and warmer zones. It cools body by sweating and evaporation.

Q16. A cow is being fed on straw, oil cake, oilseeds, gram and bajra. To what classes of cattle feed do these items belong and what is their importance?
Ans16. Straw belongs to the class Roughage.
Oil-cake, oil-seeds, gram, and bajra belong to the class Concentrate.
Concntrates provide rich nutrition in one or the other nutrient. Roughage provide the fibres, and coarse low nutrients. Roughage also makes the bulk of the feed.

Q17. Moisture content of four food items P, Q, R and S is 10%, 15%, 25% and 50% respectively. Which of these require cold storage and which ones dry storage? Give reasons.
Ans17. A drier article with less moisture content can be "Stored Dry" whereas a watery article with more moisture content need be "Stored Cold".
Among P, Q, R, and S; P and Q have moderate moisture content (10% and 15% respectively) and therefore are suitable for Dry Storage, whereas R and S have high moisture content (25% and 50%) and therefore need Cold Storage.

Q19. Name the radiations absorbed by the ozone layer. Give any two causes of the depltetion of ozone layer. Name the disease likely to be caused due to its depletion.
Ans19. Ultraviolet radiation is absorbed by the ozone layer.
Causes of the depletion of ozone layer :
(1) the emmissions produced by the supersonic jets
(2) fluorocarbons and chloroflourocarbons, used in aerosol sprayers and refrigeration. The diseases likely to be caused due to depletion of ozone layer are skin cancer and severe sun-burns.

Q20. What is nitrogen fixation? Mention two points of difference between nitrification and denitrification processes. Name the organism involved in these processes.
Ans20. Nitrogen fixation is the process of converting molecular form of N₂ to a usable form, i.e. nitrates. Nitrogen fixation is achieved (1) Biologically: symbiotically as well as asybiotically; and
(2) Chemically: atmospherically as well as industrially.

Q21) (i) Name the elements that constitute proteins.
(ii) What are the end products of protien digestion and where are they absorbed.
(iii) Name any three types of protiens found in our body and mention thier functions.
Ans21(i) Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N) and Sulphur (S) constitute proteins
(ii) Proteins are broken into their constituent amino acids by the end of digestion. The digestion of proteins occurs in the small intestine, and the amino acids produced in the process are absorbed from the intestine.

(iii)