10th CBSE Science Question Paper Pre Board II 2018-19

10th CBSE Science Question Paper Pre Board II 2018-19

School Name: Himalaya Public School, Sector 13, Rohini, Delhi 110085 India
Time: 3 hours
Maximum Marks: 80
Class: 10th
Date: ?? / ?? / 2018/19
Subject: Science

General Instructions:

• All questions are compulsory. However there is an internal choice in one question of two marks, three question of three marks each, three question of five marks each and three questions of practical based question.
• Question No. 1 and 2 are one marks question.
• Question No. 3 to 5 are two marks question.
• Question No. 6 to 15 are three marks question.
• Question No. 16 to 21 are five marks question.
• Question No. 22 to 27 are two marks question.

10th CBSE Science Question Paper: Section A

Question: 1. Name a salt which contains 5 molecules of water of crystallization.

Question: 2. Name any two forest product, each of which is basis for some industry.

Section B

Question: 3. With the help of a ray diagram explain why a convex mirror is preferred for rear view mirrors in cars.

OR

Locate the image of an object placed between ‘F’ and ‘2F’ of a convex lens.

Question: 4. Why do harmful chemicals concentrate as we go up in a food chain?

Question: 5. Name the following:

1. A metal which is preserved in Kerosene.
2. A lustrous non-metal.
3. A metal which can melt while kept on palm.
4. A metal which is a poor conductor of heat.

Section: C

Question: 6. Name a carbonate or of zinc. How is it converted into oxide? Write chemical equation. How i zinc obtained from Oxide? Give chemical equation.

Question: 7. Write the chemical equation of the reaction in which the following changes have taken place with an example of each:

1. Change in colour
2. Change in Temperature
3. Formation of Precipitate

OR

1. Why potato chips manufacturers fill the packet of chips with nitrogen gas?
2. A student has been collecting silver coins and copper coins. One day she observed a black coating on silver coins and a green coating on copper coins. Which chemical phenomenon is responsible for these coatings? Write the chemical name of black and green coatings.

Question: 8. What happens to the force acting on current carrying conductor placed in magnetic field when:

1. Direction of magnetic field is reversed without changing the direction of current.
2. Direction of the current is reversed without changing the direction of magnetic field.
3. Direction of both the current and the magnetic field is reversed.

OR

What is meant by the term  ‘Power of Accommodation’ of human eye? How does it help a person to see nearby as well as distant objects clearly?

Question: 9. A convex leans has a focal length of 10 cm. At what distance from the lens should the object be placed so that it forms a real and inverted image 20 cm away from the lens? What would be the size of the image formed if the object is 2 com high?

Question: 10.

1. Define variation.
2. All the variations in a species do not have equal chances of survival. Why?
3. Name two human traits which show variation.

OR

Distinguish between homologous organs and analogous  organs. In which category would you place wings of a bird and wings of a bat? Justify your answer.

Question: 11.

1. How opening and closing of stomata takes place?
2. “The breathing cycle is rhythmic whereas exchange of gases is a continuous process”. Justify this statement.

Question: 12. Draw a well labelled diagram of male reproductive system.

Question: 13.

1. How does chemical coordination take place in animal.
2. Why is the use of iodized salt advisable?

Question: 14.

1. Define tidal energy.
2. Explain how is tidal energy harnessed and write one limitation of the use of tidal energy.

Question: 15. In a circuit three identical bulbs B₁, B₂ and B₃ are connected in Parallel with a battery of 4.5V.

1. What will happen to the glow of other two bulbs if the bulb B₃ gets fused?
2. Find the total resistance of the circuit.
3. If the wattage of each bulb is 1.5W, how much reading will the ammeter A show when all the three bulbs glow simultaneously?

10th CBSE Science Question Paper: Section D

Question: 16.

1. Define isomerism. Draw all the isomers of C₅H₁₂ and write their IUPAC names.
2. Tendency to lose electron decreases when we move from left to right in a period. Justify this statement.

Question: 17.

1. What is Pollination? Explain its significance.
2. Explain the process of fertilization in flowers.
3. Name the parts of the flower that develop after fertilization into:
   (i) Seed   (ii) Fruit

Question: 18. Explain the process of digestion of food in mouth, stomach and small intestine in human body.

OR

What is speciation? List four factors that could lead to speciation? Which of these cannot be a major factor in the speciation of a self-pollinating plant species? Explain.

Question: 19.

1. Mineral acids are used in laboratory and vinegar is used as preservative in pickles.
   (i) Explain why vinegar is weak acid HCI is strong acid?
   (ii) Compare vinegar with glacial acetic acid?
2. Why are detergents harmful for environment whereas soaps are not?
3. Balance and complete the following reaction:  CaCO₃ + HNO₃ →

OR

1. (a) Identify and name the elements whose electronics configuration given below:
   (i) 2,8,1
   (ii) 2,8,8,2
   (iii) 2,1
   (iv) 2,8,6
2. Identify the groups to which they belong to?
3. Which of them is most reactive and why?

Question: 20. Explain the following:

1. Why is the tungsten used almost exclusively for filament of electric lamp?
2. Why is the series arrangement not used for domestic circuits?
3. How does the resistance of a wire vary with its area of cross section?
4. Why are copper and aluminium wires usually employed for electricity transmission?

Question: 21. Draw an appropriate schematic diagram showing common domestic circuits and discuss the importance of fuse. Why is it that a burnt out fuse should be replaced by another fuse of identical rating?

OR

Explain the following:

1. The existence of decomposers is essential in biosphere.
2. Flow of energy in a food chain is unidirectional.
3. What will happen if we kill all the organisms in one tropic level?
4. Will the levels of magnification be different at different levels of the eco-system?

10th CBSE Science Question Paper: Section E

Question: 22. In acidic and basic solutions pH detects the concentration of which ion? Do bases also have H⁺ ions?. If they have H⁺, then why are they basic?

OR

A student added ‘Al’ metal to ferrous sulphate solution. What will be change in colour of solution and colour of metal deposited? Justify your answer.

Question: 23.

Which two positions correspond closely to the colour of:

1. A Brinjal
2. ‘Danger’ or stop signal lights

OR

How will you distinguish between a concave and convex mirror?

Question: 24. When soap is added to hard water, it reacts with the salts to form a scum. Why does this scum form?

Question: 25. Name the type of asexual reproduction in which two individuals are formed from a single parent and the parental identity is lost. Draw the initial and final stages of this type of reproduction.

Question: 26. What is the function of seed coat?

OR

How are monocots different from dicots?

Question: 27. The diagram below shows the refracted ray QR through a convex lens.

 

Complete the diagram by drawing the corresponding incident ray.