List of top Science Questions

One mole of a hydrocarbon, on combustion in air, produces two moles of \( \text{CO}_2 \), two moles of \( \text{H}_2\text{O} \), and a large amount of heat. This hydrocarbon is:

Write one chemical equation each for the chemical reaction in which the following have taken place:
(i) Change in colour
(ii) Change in temperature
(iii) Formation of precipitate
Mention colour change/temperature change (rise/fall)/compound precipitated along with equation.

In case of four wires of same material, the resistance will be minimum if the diameter and length of the wire respectively are

Two resistors of 1 Ω and 3 Ω are connected in parallel in a circuit. If a current of 1 ampere is flowing through the circuit, the current flowing through the 3 Ω resistor is:

Identify the organ in the human female reproductive system where the sperm encounters the egg cell. What will happen if it is blocked? Name the technique by which it can be blocked.

Mention the pathway of urine starting from the organ of its formation. Name any two substances which are reabsorbed from the initial filtrate in the tubular part of the nephron.

How does the embryo get nourishment inside the mother’s body? Explain briefly.

List two functions each of the following parts of the human female reproductive system: (1) oviduct (2) uterus (3) ovary

Select two plants from the following which are obtained by this technique: Banana, Papaya, Jasmine, Mustard

List three advantages of practising the process/technique by the farmers.

What is vegetative propagation? Is this process sexual or asexual? Justify your answer.

Name and explain the process used to obtain sodium hydroxide from the aqueous solution of sodium chloride (Brine). Name the two gases which are given at the anode and the cathode respectively. List two uses of each of these gases.

An electrical heater of resistance 10 Ω draws a steady current of 5 A from the service mains for 2 hours. Find the power of this heater and the amount of energy consumed by the heater in kilowatt-hour.

Obtain an expression for the amount of heat produced in a conductor of resistance R when a steady current I flows through it for a time t.

The resistance of a metallic wire of 100 m is 20 \(\Omega\). If the radius of the wire is 5 mm, find the resistivity of the metal of the wire.

Write the relation between resistivity (\(\rho\)) and resistance (\(R\)) for a uniform metallic conductor of length (\(l\)) and area of cross-section (\(A\)). Use this relation to obtain the SI unit of resistivity.

What does a food chain represent? “The number of trophic levels in a food chain is limited.” Give an example stating reason to justify this statement.

What are decomposers? Explain how the decomposers (i) keep the environment clean, and also (ii) replenish the soil nutrients.

Is it possible that a trait gets inherited, but not expressed? Give an example to justify your answer.

Name the plant growth hormone which is synthesized at the shoot tip. Explain why the shoot of a potted plant bends towards light coming from a window.