Particle Model

PARTICLE MODEL

By: Metta

Particle in the Three States of Matter

Particles in Solid• Move a little• Do not change position• Vibrate to and fro in their position

Particles in Liquid• Weaker than in solid’s• Have some freedom• Can change position by sliding over each other

Particles in Gas• Can move away from each other• Travel in all direction• Move freely and in high speed

How Materials Change with Temperature

Changes in Solid•When a solid is heated it expands and when it cools it contracts.

•For example, the apparatus here. When the metal ball is heated, it will expand and when we try to put it in the gauze, it will not fit anymore. But when we try to put it in after about 5-10 minutes, it will fit again.


Metal pipes carrying hot water in large central heating systems are connected by expansion joints, which allow pipes to lengthen without pushing into each other.

Changes in SolidThe expansion of materials due to heating must be taken into account whenever materials are likely to encounter changes in temperature


Changes in SolidThe temperature changes due to the weather can also cause expansion and contraction.

The end of a bridge may be set on rollers so that as it lengthens it simply moves over its support and does not push into the adjoining roadway.


Changes in Solid Different solids expand by different amounts for a given temperature rise.

Brass expands more than iron. The picture above informs us that when the bimetallic strip is heated, it bends because the length of the brass strip becomes greater than the iron strip.

This fact also explains why bimetallic strip may be used in a fire alarm.


Changes in Liquid Liquid has a unique fact. It expands in between 0°C-4°C. The diagram here shows the expansion of liquid.

When water has a range of temperatures close to 0°C, the colder water rises above the warmer water and collects at the surface. This fact is used to explain why the fish beneath a pond in a very cold winter can stay warm and alive.


Changes in Gas


Hot Air Balloon1. When the air in a hot air balloon

is heated it expands and fills the balloon.

2. The surrounding air exerts a up-thrust force which is greater than the combined weight of the balloon, basket, pilot and passengers.

3. The density of the surrounding air decreases with an increase in height. The balloon will continue to rise until it reaches air that is sufficiently less dense for the weight and up-thrust to balance.


ExplosionAn explosion occurs when a gas is made to expand very strongly and very quickly. This creates large forces that push everything around. Explosives are used in quarries – the force of the expansion is strong enough to break up rocks.


Car Cylinder

A car engine has cylinders in which small explosions occur. A mixture of air and petrol vapor is ignited by a spark plug, and the hot gases, which expand quickly, push down a piston. The downward force of the piston is changed into a turning force by other parts of the engine, and this is used to turn the car’s wheels.

Melting and BoilingMelting

In a solid the particles are held firmly together but as they get hotter, they come to vibrate so strongly that they began to slide over each other.

When this occurs, the solid has melted and become a liquid. The temperature at which a solid melts is called the melting

point.

Melting and BoilingBoiling

As a liquid receives more and more heat, its particles become more and more active.

Eventually they become more active that they lose their grip of each other and become a gas.

This can occur at the surface if the liquid or inside the liquid where the gas particles form bubbles.

This process of forming bubbles is called boiling, and the temperature at which it occurs is called the boiling point of the liquid.

Thank You For Your Attention!

Particle Model

Education

colder expansion of

boiling boiling

liquid weaker

solid melts

boiling melting

solid different amounts

hot air balloon1

hot water