Explain in detail. The particles of water vapour move away with the wind, decreasing the amount of water vapour in the surrounding. What happen to the rate of diffusion if the temperature is increased? Why are we able to sip hot tea or milk faster from a saucer rather than a cup? The intermingling of molecules of one substance with that of the other is called diffusion. Which among the following can exist in vapour state? Pressure and temperature determine the state of a substance. Give reasons for the following observation: Cold drink is a liquid state of matter. When this water comes on the surface of leaf the water evaporates thereby causing cooling effect. (b) because water has intermolecular space What is dry ice? (b) Why should one be more careful with CNG cylinders during summer? Answer: (a) Naphthalene balls disappear with time without leaving any solid, because naphthalene balls sublime and directly changes into vapour state without leaving any solid. These molecules constantly vibrate, move and hit the walls of the container thereby exerting pressure on it. Which of the following are matter? other, there is no intermolecular space, it cannot be compressed, it cannot flow, all these characteristics are of solid. Question 2. Download the NCERT Solutions app for quick access to NCERT Solutions Class 9 Science Chapter 1 Matter In Our Surroundings. Why is ice at 273 K more effective in cooling than water at the same temperature? Question 18. A balloon when kept in sun, bursts after some time. Question 3. The balloon when kept in sun gets heated and the air inside it also gets heated. The pressure of air is measured in atmosphere and pascal. 293 – 273 = 20°C Answer: Ice is solid at 0°C i.e., 273° K. The molecules of ice are tightly packed. Question 2. air < exhaust from chimneys < cotton < water < honey < chalk < iron. Chair and almond are forms of matter in the solid state. (1) Solids have fixed shape and are rigid. (i) Particles of matter have spaces between them. Sita lived in a village and could, not afford refrigerator in her house. Answer: The molecules of water present on the surface of the exposed area which are in very small fraction, gains the energy from the surrounding. (1) Particles have intermolecular space. After you have studied lesson, you must be looking for answers of its questions. (a) 98°C (b) 100°C (a) because water is a good solvent Here you can get complete NCERT Solutions for Class 9 Maths Chapter 1 Matter In Our Surroundings in one place. (a) boiling point Define matter. Why do we see water droplets collected on the outer surface of a glass container, containing ice? Question 1. Question 8. Ans : Anything that occupies space and has mass is called matter. 4. The gas can fill the container. (3) On applying pressure and reducing temperature we can liquefy gases or change them into solid. Question 7. Answe: We should wear light coloured cotton clothes in summer. (a) 293 K (b) 470 K. (3) Particles of matter are moving continuously. Class 9 Science NCERT Textbook – Page 9 The melting point of ice is 273.16 K. What does this mean? The characteristics of the particles of matter are: Matter can exist in three physical states—solid, liquid, and gaseous. This is due to an increase in the kinetic energy of solid particles. The given substances in the increasing order of their densities can be represented as: Air < Exhaust from chimney < Cotton < Water < Honey < Chalk < Iron, NCERT Solutions for Class 9 Social Science, NCERT Solutions for Class 9 – Latest Maths, Science, English, Hindi, Social Science, NCERT Solutions for Class 9 English – Beehive & Moments Supplementary Reader, NCERT Solutions for Class 9 Maths Chapter 15 Probability, Click here to buy NCERT Book for Class 9 Science. Define latent heat of vaporization. Akshay’s friend visited his house in Mumbai and he was surprised to see air conditioners installed in all of his rooms.