Matter in Our Surroundings - Notes

Physical Nature of Matter

Matter is anything which has mass and occupies space. Everything we see around us is made up of matter.

• Matter is made of particles
• Matters are made of very small particles

Characteristic of particles of matter

• Particles of matter have space between them
• Particles of matter are continuously moving, they possess kinetic energy
• As the temperature rises, particles move faster, so does their kinetic energy
• Particles of matter attract each other

State of Matter

1. Solid

   Solids have a definite shape, distinct boundaries, and fixed volumes. Solids have negligible compressibility. Solids have a tendency to maintain their shapes when subjected to outside forces. They are rigid in nature.

2. Liquid

   Liquids have no fixed shape but have a fixed volume. They take up the shape of the container in which they are kept. Liquids flow and change shape, so they are not rigid but can be called fluid.

• Solids and liquids can diffuse into liquids. The gases from the atmosphere diffuse and dissolve in water. These gases, especially oxygen and carbon dioxide, are essential for the survival of aquatic animals and plants.

3. Gas

   • Gases are highly compressible compared to solids and liquids. The liquefied petroleum gas (LPG) cylinder that we get in our home for cooking or the oxygen supplied to hospitals in cylinders is compressed gas. Compressed natural gas (CNG) is used as fuel these days in vehicles.
   • In the gaseous state, the particles move about randomly at high speed. Due to this random movement, the particles hit each other and also the walls of the container. The pressure exerted by the gas is because of this force exerted by gas particles per unit area on the walls of the container.



4. Plasma

   • Plasma is an ionized gas and the fourth state of matter, consisting of free-moving ions and electrons along with neutral atoms or molecules.
   • Energy, such as intense heat or electrical fields, is applied to a gas, causing electrons to be stripped from atoms, creating electrically charged particles.
   • This electrically charged state makes plasma highly conductive and allows it to respond to electric and magnetic fields, giving it properties distinct from a neutral gas.

Melting Point

• The minimum temperature at which a solid melts to become a liquid at atmospheric pressure is called its melting point.
• The process of melting, that is, the change of solid state into liquid state, is also known as fusion.

Latent Heat of Fusion

The amount of heat energy required to change 1 kg of a solid into a liquid at atmospheric pressure at its melting point is known as the latent heat of fusion.

Boiling Point

• The temperature at which a liquid starts boiling at atmospheric pressure is known as its boiling point.
• Boiling is a bulk phenomenon.
• Particles from the bulk of the liquid gain enough energy to change into the vapor state.

Latent Heat of Vaporization

Water vapor at 373 K (100°C) has more energy than water at the same temperature. This is because particles in steam have absorbed extra energy in the form of latent heat of vaporization.

Sublimation

A change of state directly from solid to gas without changing into liquid state is called sublimation.

Deposition

Direct change of gas to solid without changing into liquid is called deposition.

Evaporation

The phenomenon of change of liquid into vapors at any temperature below its boiling point is called evaporation.

Factors Affecting Evaporation

1. Surface Area: Evaporation is a surface phenomenon; therefore, the larger the surface area, the greater the evaporation.
2. Temperature: With an increase in temperature, more particles gain enough kinetic energy to enter the vapour state.
3. Humidity: Evaporation decreases as humidity increases.
4. Wind Speed: Wind carries away evaporated particles, leaving space for more evaporation. Therefore, wind accelerates the evaporation process.

Evaporation Causes Cooling

Liquid keeps evaporating. The particles of liquid absorb energy from the surroundings to regain the energy lost during evaporation. This absorption of energy from the surroundings makes the surroundings cool.