NCERT Class – 9 Science solution: Chapter 1 Matter in Our Surroundings-Part 2

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Question 8

The boiling points of diethyl ether, acetone and n-butyl alcohol are and respectively. Which one of the following correctly represents their boiling points in kelvin scale?

Answer: C

Question 9

Which condition out of the following will increase the evaporation of water?

  1. Increase in temperature of water

  2. Decrease in temperature of water

  3. Less exposed surface area of water

  4. Adding common salt to water

Answer: A

Question 10

In which of the following conditions, the distance between the molecules of hydrogen gas would increase?

(i) Increasing pressure on hydrogen contained in a closed container

(ii) Some hydrogen gas leaking out of the container

(iii) Increasing the volume of the container of hydrogen gas

(iv) Adding more hydrogen gas to the container without increasing the volume of the container

  1. (i) and (iii)

  2. (i) and (iv)

  3. (ii) and (iii)

  4. (ii) and (iv)

Answer: C

Short Answer Questions

Question 11

A sample of water under study was found to boil at at normal temperature and pressure. Is the water pure? Will this water freeze at Comment.

Answer:

Its freezing point will be below 0°C due to the presence of a non-volatile impurity in it.

Question 12

A student heats a beaker containing ice and water. He measures the temperature of the content of the beaker as a function of time. Which of the following (Figure) would correctly represent the result? Justify your choice.

Heating ice and water

Heating Ice and Water

Heating ice and water

Answer:

  • Since ice and water are in equilibrium, the temperature would be zero.

  • When we heat the mixture, energy supplied is utilized in melting the ice and the temperature does not change till all the ice melts because of latent heat of fusion.

  • On further heating, the temperature of the water would increase.

  • Therefore the correct option is (d).