List of top Science Questions asked in CBSE X

atmospheric air is being passed

In the experimental set-up shown above in diagram (I) atmospheric air is being passed into lime water with a syringe while in diagram (II) air is being exhaled into lime water. The time taken for the lime water to turn milky in both the test tubes is different. Give reason.
Draw the diagram of an open stomatal pore and label (I) Guard cells, and (II) Chloroplast on it. Mention two functions performed by stomata.
What is dispersion of white light ? State its cause. Draw a diagram to show dispersion of a beam of white light by a glass prism.
Design an experiment to demonstrate that carbon dioxide is essential for photosynthesis. Write the observation and conclusion of the experiment.
Name the ore of mercury and state the form in which it is found in nature. Write the chemical equations along with the condition required for the reactions involved in the extraction of mercury from its ore.
What is the mass ratio of the gases collected at the anode and cathode?
Differentiate between food chain and food web. In a food chain consisting of deer, grass and tiger, if the population of deer decreases, what will happen to the population of organisms belonging to the first and third trophic levels?
Name a plant growth hormone synthesized at the shoot tip. Explain its effect on the growth of a plant in response to light.
“The linear magnification produced by a spherical mirror is +3.”Based on this statement answer the following questions:
(a) What is the type of mirror?
(b) Where is the object located?
(c) List two properties of the image formed (other than the size/magnification).
The filament of an electric lamp draws a current of 0.5 A, which lights for 2 hours. Calculate the charge that flows through the circuit.
Why is the electrolysis of water called a decomposition reaction?
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.
Write the formula and the molecular mass of the third homologue of alcohols. State how the boiling point of an alcohol changes as one moves from lower to higher homologues.
Copper powder is taken in a china dish and heated over a burner.Name the product formed and state its colour. Write the chemical equation for the reaction involved.
Is the reaction exothermic or endothermic?
Write chemical equation for the chemical reaction which occurs when the aqueous solutions of barium chloride and sodium sulphate react together. Write the symbols of the ions present in the compound precipitated in the reaction.
Name the gases collected at the anode and cathode.
Assertion (A): Electrons move from lower potential to higher potential in a conductor. Reason (R): A dry cell maintains electric potential difference across the ends of a conductor.
Sometimes while running, athletes suffer from muscle cramps. Why? How is the respiration in this case different from aerobic respiration?
Assertion (A): Sex of the children will be determined by what they inherit from their mother. Reason (R): Women have XX sex chromosomes.
Assertion (A): Green plants trap only 1% of the energy of sunlight that falls on their leaves. Reason (R): All green plants are the producers in a food chain.
Write the other name given to lymph. State its two functions.
Assertion (A): Some vegetable oils are healthy. Reason (R): Vegetable oils generally have long unsaturated carbon chains.
The phenomena of light involved in the formation of a rainbow are:
Which one of the following is not a natural ecosystem?