NCERT Class – 9 Science solution: Chapter 2 Is Matter Around Us Pure-Part 7

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Question 26:

Sucrose (sugar) crystals obtained from sugarcane and beetroot are mixed together. Will it be a pure substance or a mixture? Give reasons for the same.

Answer:

It is a pure substance because chemical composition of sugar crystals is same irrespective of its source. According to law of constant composition or definite proportions; irrespective of the source a chemical compound it is always found to be made of the same elements combined together in the same fixed proportion by mass. Thus, in the light of the above law, it will be a pure substance. It is because sugar obtained by different sources like sugarcane and beetroot will have the same composition.

Question 27:

Give some examples of Tyndall effect observed in your surroundings?

Answer:

Tyndall effect can be seen when light passes through a heterogeneous mixture. Example, when sunlight passes through the canopy of a dense forest.

Image of Tyndall Effect

Image of Tyndall Effect

Image of Tyndall Effect

Question 28:

Can we separate alcohol dissolved in water by using a separating funnel?

If yes, then describe the procedure.

If not, explain.

Answer:

No, alcohol cannot be separated from water by using a separating funnel because alcohol is completely miscible in water.

Question 29:

On heating calcium carbonate gets converted into calcium oxide and carbon dioxide.

  1. Is this a physical or a chemical change?

  2. Can you prepare one acidic and one basic solution by using the products formed in the above process? If so, write the chemical equation involved.

Answer:

  1. Chemical change.

  2. Acidic and basic solutions can be prepared by dissolving the products of the above process in water.

Question 30:

Nonmetals are usually poor conductors of heat and electricity. They are non-lustrous, non-sonorous, and non-malleable and are coloured.

  1. Name a lustrous non-metal.

  2. Name a non-metal which exists as a liquid at room temperature.

  3. The allotropic form of a non-metal is a good conductor of electricity. Name the allotrope.

  4. Name a non-metal which is known to form the largest number of compounds.

  5. Name a non-metal other than carbon which shows allotropy.

  6. Name a non-metal which is required for combustion.

Answer:

  1. Iodine

  2. Bromine

  3. Graphite

  4. Carbon

  5. Sulphur, phosphorus

  6. Oxygen