Important 3 Marks Questions for CBSE 10th Science Exam

Q1:

Write the structural formula of ethanol. What happens when it is heated with excess of conc. H2SO4 at 443 K ? Write the chemical equation for the reaction stating the role of conc. H2SO4 in this reaction.

Q2:

Distinguish between esterification and saponification reactions with the help of the chemical equations for each. State one use of each (i) esters, and (ii) saponification process.

Q3:

Write the number of periods and groups in the Modern Periodic Table. How does the metallic character of elements vary on moving (i) from left to right in a period, and (ii) down a group ? Give reason to justify your answer.

Q4:

Na, Mg and Al are the elements of the 3rd period of the Modern Periodic Table having group number 1, 2 and 13 respectively. Which one of these elements has the (a) highest valency, (b) largest atomic radius, and (c) maximum chemical reactivity ? Justify your answer stating the reason for each.

Q5:

Reproduction is one of the most important characteristics of living beings. Give three reasons in support of the statement.

Q6:

What is vegetative propagation ? State two advantages and two disadvantages of this method

Q7:

List three techniques that have been developed to prevent pregnancy. Which one of these techniques is not meant for males ? How does the use of these techniques have a direct impact on the health and prosperity of a family ?

Q8:

How did Mendel explain that it is possible that a trait is inherited but not expressed in an organism ?

Q9:

‘‘Evolution and classification of organisms are interlinked.’’ Give reasons to justify this statement.

Q 10:

If the image formed by a lens for all positions of an object placed in front of it is always erect and diminished, what is the nature of this lens ? Draw a ray diagram to justify your answer. If the numerical value of the power of this lens is 10 D, what is its focal length in the Cartesian system ?

Q 11:

State the cause of dispersion of white light by a glass prism. How did Newton, using two identical glass prisms, show that white light is made of seven colours ? Draw a ray diagram to show the path of a narrow beam of white light, through a combination of two identical prisms arranged together in inverted position with respect to each other, when it is allowed to fall obliquely on one of the faces of the first prism of the combination.

Q 12:

(a) Water is an elixir of life, a very important natural resource. Your Science teacher wants you to prepare a plan for a formative assessment activity, ‘‘How to save water, the vital natural resource’’. Write any two ways that you will suggest to bring awareness in your neighbourhood, on ‘how to save water’.

(b) Name and explain any one way by which the underground water table does not go down further.

Q 13:

(a) Water is an elixir of life, a very important natural resource. Your Science teacher wants you to prepare a plan for a formative assessment activity, ‘‘How to save water, the vital natural resource’’. Write any two ways that you will suggest to bring awareness in your neighbourhood, on ‘how to save water’.

(b) Name and explain any one way by which the underground water table does not go down further.

Q 14:

What is ‘dispersion of white light’ ? State its cause. Draw a ray diagram to show the dispersion of white light by a glass prism.

Q 15:

Draw ray diagrams to show the formation of three times magnified (a) real, and (b) virtual image of an object by a converging lens. Mark the positions of O, F and 2F in each diagram.

Q 16:

Describe reproduction by spores in Rhizopus.

Q 17:

With the help of two suitable examples, explain why certain experiences and traits earned by people during their lifetime are not passed on to their next generations. When can such traits be passed on?

Q 18:

Explain esterification reaction with the help of a chemical equation. Describe an activity to show esterification

Q 19:

What happens when

(write chemical equation in each case)

(a) ethanol is burnt in air ?

(b) ethanol is heated with excess conc. H2SO4 at 443 K ?

(c) a piece of sodium is dropped into ethanol ?

Q 20:

(a) Water is an elixir of life, a very important natural resource. Your Science teacher wants you to prepare a plan for a formative assessment activity, ‘‘How to save water, the vital natural resource’’. Write any two ways that you will suggest to bring awareness in your neighbourhood, on ‘how to save water’.

(b) Name and explain any one way by which the underground water table does not go down further.

Q 21:

What is ‘‘dispersion of white light’’ ? Draw a labelled diagram to illustrate the recombination of the spectrum of white light. Why is it essential that the two prisms used for the purpose should be identical and placed in an inverted position with respect to each other ?

Q 22:

‘‘A lens can form a magnified erect image as well as magnified inverted image of an object placed in front of it.’’ State the nature of this lens and draw ray diagrams to justify the above statement. Mark the positions of O, F and 2F in the diagram.

Q 22:

What is vegetative propagation ? State two advantages and two disadvantages of this method.

Q 23:

List the two types of reproduction. Which one of the two is responsible for bringing in more variations in its progeny and how ?

Q 24:

What is an organic evolution ? It cannot be equated with progress. Explain with the help of a suitable example.

Q 25:

Write the electronic configuration of two elements X and Y whose atomic numbers are 20 and 17 respectively. Write the molecular formula of the compound formed when element X reacts with element Y. Draw electron-dot structure of the product and also state the nature of the bond formed between both the elements.

Q 26:

What is periodicity in properties of elements with reference to the Modern Periodic Table ? Why do all the elements of the same group have similar properties ? How does the tendency of elements to gain electrons change as we move from left to right in a period ? State the reason of this change.


Practise This Question

Under what conditions do the farmers treat the soil with quick lime, slaked lime or calcium carbonate?