List of top Science Questions asked in CBSE Class X

Consider the following organic compounds:
\(\text{C}_2\text{H}_5\text{CHO}, \text{CH}_3\text{COOH}, \text{C}_2\text{H}_5\text{OH}, \text{CH}_3\text{COCH}_3\)
Give the chemical equation for the chemical reaction when \(\text{CH}_3\text{COOH}\) and \(\text{C}_2\text{H}_5\text{OH}\) react in the presence of conc. \(\text{H}_2\text{SO}_4\).

Name the (i) hormone released, and the (ii) gland which secretes it in human beings during scary situations. Explain how our body responds to enable it to deal with such situations.

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.

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

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

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.

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.

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.

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.

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.

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.

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

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

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

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

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

A student has three convex lenses A, B, and C of different focal lengths. He wants to observe the images formed by these lenses on a screen by placing a candle flame at different distances as given in the following table:

Case No.	Lens	Focal Length	Object Distance
1	\(A\)	50 cm	25 cm
2	B	20 cm	60 cm
3	C	15 cm	30 cm

Consider the unbalanced chemical equations of the chemical reactions listed below:

1. \(\text{CaO} + \text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2\)
2. \(\text{Pb(NO}_3\text{)}_2 \rightarrow \text{PbO} + \text{NO}_2 + \text{O}_2\)
3. \(\text{CuSO}_4 + \text{Fe} \rightarrow \text{FeSO}_4 + \text{Cu}\)
4. \(\text{Na}_2\text{SO}_4 + \text{BaCl}_2 \rightarrow \text{BaSO}_4 + \text{NaCl}\)

The maintenance functions of every living organism on the earth keeps going on even when they are not doing anything particular. The processes which together perform the job of maintenance of life are known as life processes. These processes are nutrition, respiration, transportation and excretion.

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.

List two constituents of Central Nervous System (CNS). How are these components protected from injuries?

“In human beings, the sex of a newborn child depends on the father and not the mother.” Justify this statement with the help of a flow diagram.

Explain by giving one example each:
(1) Unisexual flowers
(2) Bisexual flowers