List of top Science Questions asked in CBSE X

What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Will the impact of removing all the organisms in a trophic level be different for different trophic levels? Can the organisms of any trophic level be removed without causing any damage to the ecosystem?
What will happen if we kill all the organisms in one trophic level?
Which of the following are environment-friendly practices?
Which of the following constitute a food-chain?
Which of the following groups contain only biodegradable items?

Give two important uses of washing soda and baking soda.

What is a neutralization reaction? Give two examples.

Plaster of Paris should be stored in a moisture-proof container. Explain why?

What is the function of an earth wire? Why is it necessary to earth metallic appliances?

Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain your answer.

Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A, while acetic acid (CH3COOH) is added to test tube B. Amount and the concentration taken for both the acids are the same. In which test tube will the fizzing occur more vigorously and why?

Five solutions A,B,C,D and E when tested with universal indicator showed pH of 4, 1, 11, 7, and 9, respectively. Which solution is
(a) neutral?
(b) strongly alkaline?
(c) strongly acidic?
(d) weakly acidic?
(e) weakly alkaline?
Arrange the pH in increasing order of hydrogen-ion concentration.

Why do acids not show acidic behaviour in the absence of water?

When does an electric short circuit occur?
State the rule to determine the direction of a
  1. magnetic field produced around a straight conductor-carrying current,
  2. force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it,
  3. current induced in a coil due to its rotation in a magnetic field.

Why does distilled water not conduct electricity, whereas rain water does?

When is the force experienced by a current–carrying conductor placed in a magnetic field largest?
List two methods of producing magnetic fields.
State whether the following statements are true or false.
  1. The field at the centre of a long circular coil carrying current will be parallel straight lines.
  2. A wire with a green insulation is usually the live wire of an electric supply.

Write word equations and then balanced equations for the reaction taking place when:
(a) dilute sulphuric acid reacts with zinc granules.
(b) dilute hydrochloric acid reacts with magnesium ribbon.
(c) dilute sulphuric acid reacts with aluminium powder.
(d) dilute hydrochloric acid reacts with iron filings.

Which one of the following types of medicines is used for treating indigestion?

10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a given solution of HCl. If we take 20 mL of the same solution of NaOH, the amount HCl solution (the same solution as before) required to neutralise it will be

A solution reacts with crushed egg-shells to give a gas that turns lime-water milky. The solution contains

A solution turns red litmus blue, its pH is likely to be