MATTER IN OUR SURROUNDING

MATTER IN OUR SURROUNDING

MATTER: Anything that has mass and takes up space (has volume) is referred to as matter.

Examples: Hydrogen and oxygen, sugar and sand, air and water, etc.

Physical Nature of Matter

→ Matter is made up of particles. All matter constitutes of very small particles. These small particles are called atoms.

→ These particles of matter are too small so they cannot be seen by naked eyes or simple microscope.
→ Particles of matter are continuously moving as they possess kinetic energy, with the increase of temperature kinetic energy of particles also increases so particle moves faster.

Characteristics of Particles of Matter

1. Particles of matter have spaces between them: This characteristic is one of the concepts behind the solubility of a substance in other substances. For example, on dissolving sugar in water, there is no rise in the water level because the particles of sugar get into the interparticle spaces between the water particles.

2. Particles of matter are always in motion

• Particles of matter show continuous random movements due to the kinetic energy they possess.
• A rise in temperature increases the kinetic energy of the particles, making them move more vigorously.

3. Particles of matter attract each other: In every substance, there is an interparticle force of attraction acting between the particles. To break a substance, we need to overcome this force. The strength of the force differs from one substance to another.

 STATES OF MATTER

Property	Solid	Liquid	Gas
Shape and volume	Fixed shape and volume	No fixed shape but has volume	Neither definite shape nor volume
Energy	Lowest	Medium	Highest
Compressibility	Difficult	Nearly difficult	Easy
Arrangement of molecules	Regular and closely arranged	Random and little sparsely arranged	Random and more sparsely arranged
Fluidity	Cannot flow	Flows from higher to lower level	Flows in all directions
Movement	Negligible	Depends on interparticle attraction	Free, constant and random
Interparticle space	Very less	More	Large
Interparticle attraction	Maximum	Medium	Minimum
Density	Maximum	Medium	Minimum
Rate of diffusion	Negligible	It depends on interparticle attraction.	Maximum

 Diffusion: When the particles of matter intermix on their own with each other, the phenomenon is called diffusion. For example, spreading of ink in water.

• During diffusion, the particles occupy the interparticle spaces.
• The rate of diffusion increases with an increase in temperature due to increase in the kinetic energy of the particles.

 Atomic View of the Three States of Matter

 CHANGE OF STATE OF MATTER

A.    MELTING: Change of matter from solid to liquid due to increase in temperature is called melting.

Melting Point: The melting point of a solid is defined as the temperature at which solid melts to become liquid at the atmospheric pressure.

• At the melting point, these two phases, i.e., solid and liquid, are in equilibrium, i.e., at this point, both solid state and liquid state exist simultaneously.

·        The melting point at which ice, a solid, turns to water, a liquid, is 32°F (0°C).

·        Latent Heat of Fusion: It is the amount of heat energy that is required to change 1 kg of a solid into liquid at atmospheric pressure at its melting point.

 B.    EVAPORATION: The phenomenon by which liquid state changes to the gaseous phase at any temperature below its boiling point is called evaporation. For example, the gradual drying of damp clothes is caused by the evaporation of water-to-water vapour.

Factors Affecting Evaporation

• Temperature: The rate of evaporation increases with an increase in temperature.
• Surface area: The rate of evaporation increases with an increase in surface area.
• Humidity: The rate of evaporation decreases with an increase in humidity.
• Wind speed: The rate of evaporation increases with an increase in wind speed.

Cooling Due to Evaporation

During evaporation, the particles of a liquid absorb energy from the surroundings to overcome the inter-particle forces of attraction and undergo phase change. The absorption of heat from the surrounding makes the surroundings cool.

For example, sweating cools down our body.

Applications of Evaporative Cooling

• To keep water cool, it is kept in earthenware containers. Similar to the pores in cotton fabric, the pores in the earthen pot’s surface area allow for more evaporation.
• To keep our bodies, cool, we sweat a lot. Evaporation is what transpiration ultimately is. Our body’s water evaporates, using energy in the process and lowering our body temperature as a result.
• We dress in cotton during the summer. Since cotton is a powerful water absorbent, it allows more perspiration to come into touch with the air, promoting more evaporation. We have a cooling effect when wearing cotton clothing because of this.

Latent Heat of Vaporisation: It is the amount of heat energy that is required to change 1 kg of a liquid into gas at atmospheric pressure at its boiling point.

Boiling Point: The boiling point of a liquid is defined as the temperature at which the vapour pressure of the liquid is equal to the atmospheric pressure.

The boiling point for any material is the temperature point at which the material transforms into the gas phase in the liquid phase. This happens at 100 degrees centigrade for water. The Celsius scale was in fact created on the basis of the ice/water melting point and the liquid water/vapor boiling point.

C.    DEPOSITION: When gaseous particles get deposited on a surface to produce a solid film/coating/layer, we call the process deposition.

D.    SUBLIMATION: The transition of a substance directly from its solid phase to gaseous phase without changing into the liquid phase (or vice versa) is called sublimation.

The solid substance that undergoes sublimation is called sublime.

The solid obtained after cooling the vapours is called sublimate.

Effect of Change in Pressure on the State of Matter

By applying pressure, the interparticle spaces between particles of matter decrease. Thus, by applying pressure and reducing temperature, we can convert a solid to liquid and a liquid to gas.

Effect of Change of Temperature on the State of Matter: On increasing the temperature, the kinetic energy of the particles of the matter increases, and they begin to vibrate with higher energy. Therefore, the interparticle force of attraction between the particles reduces, and particles get detached from their position and begin to move freely.

• As a result, the state of matter begins to change.
• Solids undergo a phase change to form liquids.
• Similarly, liquids also undergo a phase change to form gases.

Some Important Measurements

→ The SI unit of mass is kilogram (kg).

→ The SI unit of volume is cubic metre (m³). The common unit of measuring volume is litre (L) such that 1L = 1 dm³, 1L = 1000 mL, 1 mL = 1 cm³.

→ Kelvin is the SI unit of temperature, 0° C = 273.16 K. For convenience, we take 0° C = 273 K
after rounding off the decimal. To change a temperature on the Kelvin scale to the Celsius scale
you have to subtract 273 from the given temperature, and to convert a temperature on the
Celsius scale to the Kelvin scale you have to add 273 to the given temperature.

→ Atmosphere (atm) is a unit of measuring pressure exerted by a gas. The unit of pressure is Pascal (Pa): 1 atmosphere = 101325 Pa. The pressure of air in atmosphere is called atmospheric pressure. The atmospheric pressure at sea level is 1 atmosphere, and is taken as the normal atmospheric pressure.