List of top Science Questions

Give reason for the following:
A. A solution of sports electrolyte drink conducts electricity, but coconut oil does not.
B. Milkiness disappears when excess of carbon dioxide is passed through lime water.
C. An iron bridge near the sea rusts much faster than an iron bridge located in a dry hilly region.

Ramya performs an experiment in the following two steps:
Step 1: Heats ethanol with conc. \(\mathrm{H_2SO_4}\) at 170\(^\circ\)C to get product A.
Step 2: Passes hydrogen gas over product A, using Ni as a catalyst and gets product B.
(i) Name the products A and B.
(ii) Write the reactions involved in both the steps.

I. Observe both the diagrams A and B. Which diagram indicates inhalation? Describe how it occurs.

II. If diffusion were to move oxygen in our body, it is estimated that it would take 3 years for a molecule of oxygen to get to our toes from our lungs. Then, how is oxygen delivered to all parts of our body?

Observe the structure of hearts A, B and C shown above and answer the following questions
I. Which of the hearts depicted above is present in both birds and Mammals and how are they able to maintain their body temperature? Give reason for your answer.
II. Which of the hearts depicted above is present in fishes, how does circulation of blood take place in them?

Study the food chain given below:

A. In the given food chain, the amount of energy available at the fourth trophic level is 10 kJ, what will be the energy available at the producer level?
B. Is it possible to have three more trophic levels in the above food chain? Justify.
C. Which of these trophic levels will have the maximum amount of pesticide, if it had washed down in the water body from agricultural fields. Why?

Which parts of the brain perform certain actions for which we do not have any thinking control? What are such actions called, give two examples.

How is the information of touch in the 'sensitive plant' controlled and coordinated?

How do muscles move at the cellular level and respond when processed messages are received from the brain?

What changes are observed in the uterus subsequent to implantation of the young embryo in a human female?

A. Due to narrowing of the bile duct, the bile secretion from the liver to the small intestine was obstructed. How will the process of digestion be affected?
B. How does the length of the intestine depend on the nature of food habit in different animals?

A spherical mirror and a thin spherical lens have each a focal length of −15 cm. The mirror and the lens are likely to be

An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be –

What happens when dilute hydrochloric acid is added to iron fillings? Tick the correct answer.

Which of the following methods is suitable for preventing an iron frying pan from rusting?

At the time of short circuit, the current in the circuit

The brain is responsible for

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.

Which of the following is a plant hormone?

A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of them were short. This suggests that the genetic make-up of the tall parent can be depicted as

A piece of wire of resistance R is cut into five equal parts. These parts are then connected in parallel. If the equivalent resistance of this combination is R′, then the ratio \(\frac {R}{R^′}\) is –

Which of the following groups contain only biodegradable items?

The human eye forms the image of an object at its

The change in focal length of an eye lens is caused by the action of the