English Medium Class 10 - CBSE Important Questions for Science

What is meant by homologous series of carbon compounds?

State the reason why carbon can neither form C⁴⁺ cations nor C⁴⁻ anions but forms covalent compounds.

Why do soaps not form lather in hard water?

State significance of pollination.

Write one main difference between asexual and sexual mode of reproduction. Which species is likely to have comparatively better chances of survival – the one reproducing asexually or the one reproducing sexually? Give reason to justify your answer.

Define the power of a lens.

List two problems that arise due to the use of detergents instead of soaps.

Write the name and structural formula of the compound obtained when ethanol is heated at 443 K with excess of conc. H₂SO₄. Also write chemical equation for the reaction stating the role of conc. H₂SO₄ in it.

What are soaps?

Give one example of a unisexual flower.

Mention the changes a flower undergoes after fertilisation.

How do Mendel's experiment show that traits are inherited independently?

Mention the types of mirrors used as (i) rear view mirrors, (ii) shaving mirrors. List two reasons to justify your answers in each case.

Define the term dispersion of white light.

State the rule to determine the direction of a magnetic field produced around a straight conductor-carrying current.

What are alloys?

Write the name and general formula of a chain of hydrocarbons in which an addition reaction with hydrogen is possible. State the essential condition for an addition reaction. Stating this condition, write a chemical equation giving the name of the reactant and the product of the reaction.

For preparing soap in the laboratory we require an oil and a base. Which of the following combinations of an oil and a base would be best suited for the preparation of soap?

(a) Castor oil and calcium hydroxide

(b) Turpentine oil and sodium hydroxide

(c) Castor oil and sodium hydroxide

(d) Mustard oil and calcium hydroxide

Write the molecular formula of two consecutive members of homologous series of aldehydes. State which part of these compounds determines their

1. physical and 
2. chemical properties

State the reason to explain why covalent compounds "are bad conductors of electricity".