List of top Science Questions asked in CBSE Compartment Exam Class X

Assertion (A): Kilowatt-hour (kWh) is the commercial unit of electrical energy.
Reason (R): \( 1\, \text{kWh} = 10^6\, \text{Joules} \)
"Sex of a newborn baby in humans depends on the father, not the mother." Confirm this statement with the help of a flow chart.
A real image of a body is formed by a concave mirror of 50 cm focal length at a distance of –1 focal length. What is the distance between the image and the object?
Identify one organ in (i) male and (ii) female reproductive system of humans which produces gametes and also acts as an endocrine gland. Also name the hormone secreted by each.
Choose the correct statement regarding the given reaction: \[ \text{CuO} + \text{H}_2 \rightarrow \text{Cu} + \text{H}_2\text{O} \]
What is photosynthesis? Name the organs and organelles (cell structures) where photosynthesis occurs.
Where is oxygen released during this process? What happens to the carbohydrates that are not immediately used by plants?
When two compounds — sodium chloride and calcium chloride — are burned in a flame one by one, the flame turns into different colours.
(i) Write the name of the flame colours produced by:
Sodium chloride
Calcium chloride
(ii) Are these compounds soluble in non-polar solvents like kerosene or petrol? Justify your answer.
In which of the following reactions is a combination reaction taking place?
I. CuO + H$_2$ $\xrightarrow{\Delta}$ Cu + H$_2$O
II. ZnO + C → Zn + CO
III. 4Na + O$_2$ → 2Na$_2$O
IV. CH$_4$ + 2O$_2$ → CO$_2$ + 2H$_2$O
Write a four-step aquatic food chain. Among them, which group of organisms is most important and why?
Draw a ray diagram to show image formation by a concave mirror when the object is placed between focus and center of curvature.
In the following reaction, what is the name of compound ‘A’? \[ \text{NaCl} + \text{NH}_3 + \text{H}_2\text{O} + \text{CO}_2 \rightarrow \text{A} + \text{NH}_4\text{Cl} \]
In the bread mould (Rhizopus), the structures labeled A and B are respectively:
The movement of the sunflower plant is a response to which type of stimulus?
Mention any two ways by which plants absorb carbon dioxide. Also explain the reason for opening and closing of stomata.
Write the chemical formula of bleaching powder. Write the balanced chemical equation for its preparation. List three uses.

As shown in the diagram, an electron enters perpendicularly into a magnetic field. Using Fleming’s Left-Hand Rule, determine the direction of the force experienced by the electron. 

A person must hold reading material at a distance greater than 25 cm for clear vision.
(i) What is the name of this visual defect?
(ii) Draw a ray diagram to show its correction.
With the help of a labeled diagram, show the pattern of magnetic field lines around a current-carrying straight conductor. Explain how we can use the right-hand thumb rule to find the direction of magnetic field due to current.
Assertion (A): Both plants and animals exhibit chemical coordination.
Reason (R): Plant hormones regulate directional growth while in animals, hormones do not control directional growth.
Assertion (A): Soap does not form lather with hard water.
Reason (R): Hard water contains salts of calcium and magnesium which react with soap to form insoluble substances (scum).
What is meant by biomagnification?

Consider the following statements: 
Every step in a food chain is called a trophic level. 
Decomposers convert complex organic matter into simple substances that mix with the soil. 
In a food chain, energy increases from lower to higher trophic level.
Interlinking of multiple food chains forms a food web. 
Which of the above statements are correct?

In plants, waste products like resin and gum are stored in:
Select the hydrocarbon from the following which contains one C$\equiv$C triple bond and one C–C single bond:
The acid present in nettle leaves is: