Friday, 5 January 2018

What produces more severe burns, boiling water or steam?

Answer : Steam produces more severe burns as compare to boiling water as it has extra high heat energy.

This is an answered question from Chapter 1. MATTER IN OUR SURROUNDINGS of CBSE Class 9th Science

Check for Complete Exercise Solution for Chapter 1. MATTER IN OUR SURROUNDINGS | CBSE Class 9th Science

Why is ice at 273 K more effective in cooling than water at the same temperature?

Answer : The heat energy  absorbed by ice to change to liquid state, without showing any rise in temperature is known as the latent heat. We already know, the  heat can change the physical state of a matter by overcoming the forces of attraction between the particles. For water freezing point and melting point is 0°C. So water has extra amount of hidden energy as compare to ice.

This is an answered question from Chapter 1. MATTER IN OUR SURROUNDINGS of CBSE Class 9th Science

Check for Complete Exercise Solution for Chapter 1. MATTER IN OUR SURROUNDINGS | CBSE Class 9th Science

Give two reasons to justify Question 6 from Chapter 1. MATTER IN OUR SURROUNDINGS

(a) water at room temperature is a liquid.
(b) an iron almirah is a solid at room temperature.

Answer :  (a) water at room temperature is a liquid because its melting temperature is with in range of room temperature. As we know force of molecular attraction of a substance becomes high at low temperature and weak  at high temperature. Due to this  water at 0°C becomes solid due to increased molecular particles attraction.At room temperature arround 20 °C, due to increase in tempreture,  kinetic energy of the water particles increases. Due to the increase in kinetic energy, the particles start vibrating with greater speed. The energy supplied by heat overcomes the forces of attraction between the water particles. The
particles leave their fixed positions and start moving more freely. A stage is reached when the solid ice melts and is converted to water a liquid.

(b) an iron almirah is a solid at room temperature.This is because the melting point of iron is  1536 °C or 2797 °F or 1809 K where as room temperature is around 20°C. At this temperature, kinetic energy of the iron molecules is not enough to  overcomes the forces of attraction between the water particles. There for iron almirah is solid at room temperature.

This is an answered question from Chapter 1. MATTER IN OUR SURROUNDINGS of CBSE Class 9th Science

Check for Complete Exercise Solution for Chapter 1. MATTER IN OUR SURROUNDINGS | CBSE Class 9th Science