ICSE ICSE Class 8 - CISCE Question Bank Solutions for Chemistry

State the following pertaining to the physical properties of hydrogen: Effect on moist blue litmus paper.

With reference to the uses of hydrogen, give reason for the following:

Hydrogen is not used in air balloons

With reference to the uses of hydrogen, give reason for the following:

A mixture of hydrogen & oxygen on burning, find application in welding & cutting metals.

With reference to the uses of hydrogen, give reason for the following:

Reaction of hydrogen with nitrogen under specific conditions finds industrial utility.

Explain how the modern atomic theory contradicted Dalton’s atomic theory.

With reference to the discovery of the structure of an atom, explain in brief – William Crookes experiment for the discovery of cathode rays, followed by – J.J. Thomsons experiment pertaining to the constituents of the cathode rays. State which sub-atomic particle was discovered from his experiment.

Explain in brief – Goldstein’s experiment which led to the discovery of the proton.

Draw a neat labelled diagram representing an atom. Name the three sub-atomic particles in the atom and represent them symbolically showing the mass and charge of each. State where the sub-atomic particles are present in the atom.

If an atom ‘A’ has an atomic number of eleven, state the number of protons and electrons it contains.

State how electrons are distributed in an atom. Explain in brief the rules which govern their distribution.

Select the correct answer from the choice in the bracket to complete the sentence:

An element ‘X’ has six electrons in its outer or valence shell. Its valency is __________.

Select the correct answer from the choice in the bracket to complete the sentence:

A ________ is a sub-atomic particle with no charge and unit mass.

Select the correct answer from the choice in the bracket to complete the sentence:

Magnesium atom with electronic configuration 2, 8, 2 achieves stable electronic configuration by losing two electrons, thereby achieving stable electronic configuration of the nearest noble gas _______.

Change is the law of nature which occurs in everyday life.
State when a substance [i.e. matter] undergoes a kind of change. 

Give a reason why

Freezing of water is a reversible change while burning of a candle – an irreversible change.

Give a reason why

Change of seasons is a periodic change while the change of weather is a non-periodic change.

State which of the following pertain to – chemical changes.

1. Substance retains its identity.
2. The change is permanent.
3. No new substance is formed.
4. Is easily reversible.
5. Produces one or more new substances by a change in its composition.
6. The change is temporary.
7. The composition and properties of the original substance are not altered.

Give four reasons why the burning of a magnesium ribbon in the air is considered a chemical change.

Compare the energy changes involved during a physical and a chemical change.

Is a change of state of matter – a physical or a chemical change. Give reasons.