NCERT Class – 9 Science solution: Chapter 2 Is Matter Around Us Pure-Part 6

Download PDF of This Page (Size: 276K)

Question 22:

What are the favourable qualities given to gold when it is alloyed with copper or silver for the purpose of making ornaments?

Answer:

  • Pure gold is very soft as compared to gold alloyed with silver or copper.

  • Thus for providing strength to gold, it is alloyed.

Image of properties of pure gold

Image of Properties of Pure Gold

Image of properties of pure gold

Question 23:

An element is sonorous and highly ductile. Under which category would you classify this element? What other characteristics do you expect the element to possess?

Answer:

This element is a metal. Other characteristics expected to be possessed by the element are – lustre, malleability, heat and electrical conductivity.

Question 24:

Give an example each for the mixture having the following characteristics.

Suggest a suitable method to separate the components of these mixtures

  1. A volatile and a non-volatile component.

  2. Two volatile components with appreciable difference in boiling points.

  3. Two immiscible liquids.

  4. One of the components changes directly from solid to gaseous state.

  5. Two or more coloured constituents soluble in some solvent.

Answer:

  1. Evaporation or distillation

  2. Distillation

  3. Separation by using separating funnel

  4. Sublimation

  5. Chromatography

Question 25:

Fill in the blanks

  1. A colloid is a __________ mixture and its components can be separated by the technique known as _____________.

  2. Ice, water and water vapour look different and display different __________ properties but they are ___________ the same.

  3. A mixture of chloroform and water taken in a separating funnel is mixed and left undisturbed for some time. The upper layer in the separating funnel will be of——— and the lower layer will be that of ———.

  4. A mixture of two or more miscible liquids, for which the difference in the boiling points is less than can be separated by the process called———.

  5. When light is passed through water containing a few drops of milk, it shows a bluish tinge. This is due to the ——— of light by milk and the phenomenon is called ———. This indicates that milk is a ——— solution.

Answer:

  1. A colloid is a heterogeneous mixture and its components can be separated by the technique known as centrifugation.

  2. Ice, water and water vapour look different and display different physical properties but they are chemically the same.

  3. A mixture of chloroform and water taken in a separating funnel is mixed and left undisturbed for some time. The upper layer in the separating funnel will be of water and the lower layer will be that of chloroform.

  4. A mixture of two or more miscible liquids, for which the difference in the boiling points is less than can be separated by the process called fractional distillation.

  5. When light is passed through water containing a few drops of milk, it shows a bluish tinge. This is due to the scattering of light by milk and the phenomenon is called tyndall effect. This indicates that milk is a colloidal solution.