Important Questions (1 mark): Matter in our Surroundings - Class 9 MCQ

Fusion refers to the process where a solid changes into a liquid state upon reaching its melting point. During fusion, the solid absorbs latent heat to overcome the forces of attraction between its particles, allowing them to move more freely and change state.

At 373 K, particles in steam are in the gaseous state. When water reaches this temperature, it transitions from liquid to gas, marking the boiling point. This change in state is essential for various natural processes and technological applications.

Mercury is the only metal that is a liquid at normal temperatures and pressure. Because of the behavior of the valence electrons, mercury has a low melting point, is a poor electrical and thermal conductor and doesn't form diatomic mercury molecules in the gas phase.

Blood is not a pure substance. Blood is made up of many different components like cells, salts, proteins, water, etc.

• In the gaseous state, particles exhibit high kinetic energy due to their rapid random motion.
• This movement results in frequent collisions, contributing to the pressure exerted by gases.
• Therefore, both the Assertion and Reason are true, and the Reason provides a correct explanation for the Assertion.
• Hence, Option A is the correct answer.

The smell of hot cooked food reaches us quickly due to the fast diffusion property of gases. Gases have the ability to mix and spread rapidly in the air, allowing the aroma to travel over distances efficiently.

• Statement (i) is correct because matter is made up of particles. This can be deduced from experiments showing that substances like salt and sugar dissolve due to their particulate nature.
• Statement (ii) is correct as particles of matter are continuously moving, which is evident from activities showing diffusion of substances like ink or perfume in different media.
• Statement (iii) is incorrect because particles of matter do have space between them. This is demonstrated by activities where substances like salt dissolve in water, filling the spaces between water particles.
• Statement (iv) is correct since particles of matter attract each other. This is shown through various activities where the strength of attraction between particles varies in different states of matter.