Kinetic Particle Theory and Changes of State

Changes of state are reversible.
Substances change state because:
- When the matter is heated/cooled, the heat absorbed/given out causes the kinetic energy of the particles to change. Thus, the substance changes its state

Melting
Substance changes from solid to liquid.
Temperature which solid becomes a liquid is called melting point.
Graph is known as the heating curve
Heating curve shows how the temperature of a solid changes as it is heated to the melting point.


Freezing
Substance changes from liquid to solid
Temperature which liquid becomes a solid is called freezing point.
Graph is known as cooling curve.
Cooling curve shows how the temperature of a liquid changes as it is cooled to the freezing point.


Boiling
Substance changes from a liquid to gas
Temperature which liquid boils to become a gas is called boiling point.
- Bubbles of gas are seen when a liquid boils.

Evaporation
Liquid turns into a gas at temperatures lower than the boiling point
Particles have enough energy to escape as a gas from the surface of the liquid
Liquids that evaporate quickly at room temperature are called volatile liquids.
Example: Perfume and petrol

Similarity between Evaporation and Boiling:
Involves a liquid changing into a gas

Differences between Evaporation and Boiling:

Boiling	Evaporation
Occurs only at boiling point	Occurs at temperatures below boiling point
Occurs throughout the liquid	Occurs only at the surface of the liqiuid
Occurs rapidly	Occurs slowly

Condensation
Gas is cooled sufficiently and changes into a liquid
Water vapor touches a cold surface, condensation occurs and water droplets are obtained

Sublimation
Solid change directly into a gas.
Particles at the surface of the solid have enough energy to break away from the solid and escape as gas.
Examples: Iodine and Ammonium chloride
Substances that sublime might change directly from a gas into a solid without going through the liquid state.
- Keeps things cool

Kinetic Particle Theory and The Three States

All matter is made up of tiny particles and these particles are in constant, random motion.
Moving particles have kinetic energy, thus the name kinetic particle theory.

Kinetic Particle Theory
- Describes the states of matter
- Explains differences in properties of solids, liquids and gases
- Explains the changes of state

Solid state
Fixed shape:
- Closely packed in an orderly pattern
- Held together by very strong forces of attraction
- Cannot move about freely
Fixed volume:
- Cannot be compressed since the particles are very close to each other

Liquid state
- Particles have more kinetic energy than particles of the same substance in the solid state
No Fixed Shape:
- Forces of attraction between particles are weaker than in a solid
- Not held in fixed positions
- Arranged in a disorderly manner
- Can move freely
Fixed volume
- Particles are farther away from one another than in the solid
- Particles are still packed quite closely together
- Cannot be compressed

Gaseous state
No Fixed Shape:
- Particles are spread far apart
- Forces of attraction are very weak
No Fixed Volume:
- Particles have a lot of kinetic energy
- Particles are not held in a fixed position
- Particles have a lot more space between each other, thus they can be compressed

Lesson Notes

Crystallization

1.       Making a substance pure

2.      Solution should be saturated

3.       Change of state of substance from aqueous (aq) to solid.  (Solution was dissolved in water)

Chromatography

1.     To separate a mixture

2.    Find out number of components

3.     Depends on solubility of compounds or substances in a solvent

Green ink is less soluble thus it would choose to stay on the chalk and won’t move up as quickly

Red ink is more soluble thus it would move up with the water up the chalk

Filtration

1. Differentiate between differently-sized substances

How to separate Mixtures

For the HBL assignment, we basically learnt how to separate Mixtures. I'll post more info later:)
Fractional distillation!
Basically, our group did fractional distillation:)

Reflections on what I've learnt so far:)

Basically I think I really enjoy Chemistry:) Yay:) But I'm not sure if the feeling will change as we go deeper into the topic. But as of now, I like it:)

I guess learning about the elements and stuff was interesting, mainly because it's new... To be frank, I've never really heard of a periodic table until we started Chemistry and I think although the table looks scary, it's actually quite cool. I think it's cool how so many elements can be organized in such a neat table which everyone can understand.
I would say trying to understand the stuff about the three or two main groups of elements was slightly easier since we did something similar in primary school. It was probably the part that we just did today (trying to group the page of "letters" into three or four different groups. I had a few wrong, I think I understand but I'll try again to see whether I really understand before I make some clarifications. I thought the molecules, atoms, elements, compounds and mixtures thing was a little bit confusing but let's see how things go:)