Matter in Our Surroundings Class 9 Notes

Matter in Our Surroundings Notes

Facts that Matter

Introduction

• Everything in this universe is made of materials which scientist has names ‘matter’.
• The matter is made up of very small tiny particles. It is not continuous but is particulate.
• The matter is anything that occupies space and has mass.
• Particles of matter have space between them and are continuously moving.
• Particles of matter attract each other.

States of Matter: It has 3 states.

Matter can change its state from solid to liquid and from liquid to gas and vice-versa.

Effect of temperature: On increasing the heat, the particles gain energy and start vibrating with greater energy. Due to increased kinetic energy the particles overcome the force of attraction and a new state is obtained.

Melting point: The temperature at which a solid melts to become a liquid at the atmospheric pressure is called its melting point.

Boiling point: The temperature at which a liquid starts boiling at the atmospheric pressure is known as its boiling point. Boiling is a bulk phenomenon.

Latent heat of fusion: The amount of heat energy required to change 1 kg of a solid into liquid at its melting point is called the latent heat of fusion of the solid.

Latent heat of vaporization: The amount of heat energy required to change 1 kg of a liquid to vapour at atmospheric pressure, at its boiling point is called the latent heat of vaporization of the liquid.

Effect of change of pressure on the matter: On applying pressure, the particles of matter can be brought close together and the state of matter can be changed. For example, CO₂ gas can be solidified by applying pressure and lowering temperature.

Evaporation: The phenomenon of changing of a liquid into its vapour state at any temperature below its boiling point is called evaporation. Evaporation is a surface phenomenon.

Factors affecting evaporation.

• An increase in surface area increases evaporation.
• An increase in temperature increases the rate of evaporation.
• A decrease in humidity increases the rate of evaporation.
• An increase in wind speed increases the rate of evaporation.
• Evaporation causes a cooling effect.

Some measurable quantities and their units