List of top Science Questions asked in CBSE X

A milkman adds a very small amount of baking soda to fresh milk.
(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline?
(b) Why does this milk take a long time to set as curd?

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

How are fats digested in our bodies? Where does this process take place?

State two ways to prevent the rusting of iron.

What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.

Why does the sky appear dark instead of blue to an astronaut?
Light enters from air to glass having refractive index 1.50. What is the speed of light in the glass? The speed of light in vacuum is 3 × 108 m s−1.
Which of the statements about the reaction below are incorrect?
\(\text{ 2PbO(s) + C(s) → 2Pb(s) + C}O_2\text{(g)}\)
(a) Lead is getting reduced. 
(b) Carbon dioxide is getting oxidized. 
(c) Carbon is getting oxidized. 
(d) Lead oxide is getting reduced.
How does phototropism occur in plants?

Compounds such as alcohols and glucose also contain hydrogen but are not categorized as acids. Describe an Activity to prove it.

One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.
You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.
Why is a normal eye not able to see clearly the objects placed closer than 25 cm?

What are the necessary conditions for autotrophic nutrition and what are its byproducts?

What are the differences between the transport of materials in xylem and phloem?
Find the focal length of a convex mirror whose radius of curvature is 32 cm.
An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be –
Differentiate between metal and non-metal on the basis of their chemical properties.
Which of the following lenses would you prefer to use while reading small letters found in a dictionary?

Butanone is a four-carbon compound with the functional group

At the time of short circuit, the current in the circuit
Which of the following correctly describes the magnetic field near a long straight wire?
Draw a labelled diagram of the longitudinal section of a flower.

Describe double circulation of blood in human beings.Why is it necessary?

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