Kinetic Particle theory

Kinetic Particle theory

Matter
- all matter is made up of tiny particles
- the particles of matter move or vibrate about randomly in all directions
- the three states of matter, solid, liquid and gas, result from the different arrangements and motion of these particles

Matter
-> No fixed volume (can be compressed)
Gases have...

• no fixed volume
• no fixed shape
• a low density

Arrangement of particles: The particles are very far apart and are are not held together.
Motion: The particles are free to move in any direction within a container and at very high speeds.

-> Fixed volume
No fixed shape- Liquids have...

• a fixed volume
• no fixed shape
• a medium density

Arrangement of particles: The particles are closely packed. They are held together but not rigidly.
Motion: The particles are able to slip and roll over one another.

Fixed shape- Solids have...

• a fixed volume
• a fixed shape
• a high density

Arrangement of particles: The particles are packed very closely together. They are held tightly in a rigid structure.
Motion: The particles can only vibrate about a fixed position.

Start->                                                            Process                                             -> End

Solid:

-Packed 

-Vibrate in fixed positions
-Forces of attraction-> very strong

Process:
- gain heat
- KE increases
- Forces of attraction weakens

Liquid:
-vibrates more vigorously

Relative density

Solid-> high

Liquid-> moderate

Gas-> Low

test- e.g. place in water

solid+ sublimation= gas

solid+ melting= liquid

Liquid+freezing= solid

liquid+boiling=gas

gas+deposition= solid

gas+ condensation= liquid

e.g. Melting of ice- physical change

photosynthesis in plant leaves- chemical change

dissolving sugar in water- physical change

burning a piece of wood- chemical change

Water in 3 states: 

Solid- e.g. iceberg

Liquid- e.g. sea

Gas- e.g. water vapor in surrounding air

Melting

- water spreads out and fills the container

- gases spread out even more, filling any space available

Arrangement of particles

Particles of a solid are in a fixed framework, held close together and vibrate.

Particles of a liquid are still in contact but free to move around

Particles in a gas are far apart. They move quickly and randomly in any direction.

- random movement of smoke particles caused by collisions with invisible air particles.

Diffusion in gases: e.g.

At first

In the process

In the end

It takes time because the air and bromine molecules are colliding with themselves and each other.

Rate of which different gases diffuse into the air

Lighter molecules-> diffuse more quickly

experiments:

 Diffusion in liquids:

Diffusion rate higher in higher temperatures.

                                          

Melting

solid-> liquid

increase in temp.

1. Heat energy is absorbed by particles in the solid. The heat energy is converted into kinetic energy. The particles start to vibrate faster about their fixed positions.
2. When the temp. is high enough, the vibrations of the particles become sufficient to overcome the attractive forces between them. The particles begin to break away from their fixed positions.
3. The particles are  no longer in their fixed positions. The particles slide over one another. The substance is now a liquid.

The temp. at which a solid becomes a liquid is called its melting point.

Freezing

liquid-> solid

decrease in temp.

1. Energy is given out by the particles of the liquid. The particles lose kinetic energy and begin to move more slowly.
2. When the temp. is low enough, the particles no longer have enough energy to move about freely. Some particles start to settle into fixed positions.
3. All the particles settle into fixed positions. Particles can only vibrate about their fixed positions. The substance is now a solid.

The temp. of which a liquid becomes a solid is called its freezing point. Heat energy is given out during the cooling process.

Boiling

liquid-> gas at the boiling temp. (boiling)

1. Energy is absorbed by particles in the liquid. The particles gain kinetic energy and start to move faster as the temp. rises.
2. Eventually the particles throughout the liquid have enough energy to overcome the forces holding them together. The particles can now spread far apart and move rapidly in all directions.
3. The substance is now gas.

The temp. at which a liquid boils to become a gas is called its boiling point. Different substances have different boiling points.

When a liquid boils, bubbles of gas are seen. These bubbles are formed when the liquid changes to vapor. The bubbles also consist of other gases dissolved in the liquid. The bubbles rise to the surface and escape into the air.

Evaporation

Sometimes a liquid can turn into a gas at temperatures lower than the boiling point. This process is called evaporation. Evaporation occurs because some particles have enough energy to escape as a gas from the surface of the liquid.

Liquids that evaporate quickly at room temp. are called volatile liquids. They usually have boiling points just above room temperature. e.g. petrol and perfume.

Both boiling and evaporation involve a liquid changing into a gas, but boiling is different from evaporation in these ways....

Condensation

gas is cooled sufficiently-> liquid

When water vapor touches a cold surface, condensation occurs and liquid water is obtained.

Heat energy is given out during condensation. As the temp. drops, the gas particles lose energy and move more slowly. Eventually, the movement of the particles becomes slow enough for the gas to change into a liquid.

Sublimation

e.g. when dry ice (solid carbon dioxide) is exposed to temperatures higher than -78 degree celsius, it turns directly into carbon dioxide gas without melting. like dry ice, some solids change into gas without going through the liquid state. This is called sublimation.

It occurs because particles at the surface of the solid have enough energy to break away from the solid and escape as a gas. e.g. Iodine and ammonium chloride. Substances that sublime may also change directly from a gas into a solid without going through the liquid state. This process is called condensation.

Dry ice :D

Diffusion in Gases

The process by which move freely to fill up any available space is called diffusion.

Gas particles of different masses diffuse at different rates. Besides being smaller,e.g. hydrogen particles are lighter than other air particles. Gases of different masses diffuse at different rates.

The mass of a gas particles is called its molecular mass. The smaller the molecular mass of the gas, the lighter it is. Hydrogen is the lightest of all gases and is about 20 times higher than air.

Experiment for rate of diffusion:

 
The fumes are formed when the two react. This end that the compound is formed nearer to means that the particles from  the other end moves faster than the particles from this end. Gases with lower molecular masses diffuse faster than those with higher molecular masses.

Diffusion in Liquids

Diffusion also takes place in liquids. 

e.g. a small crystal of potassium manganate(VII) is introduced into a beaker of distilled water. It dissolves to form a deep purple solution, which settles at the bottom of the beaker. Diffusion slowly takes place until the solution becomes uniformly purple.

Diffusion is the movement of particles from a region of higher concentration to a region of lower concentration. This applies to gases as well.

Effect of temperature on the rate of diffusion:

The rate of diffusion increases as the temperature of the solution increases. (The higher the temperature, the faster the rate of diffusion)

Particles gain more energy as the temperature increases. They can move faster and this increases the rate of diffusion.