1.4 Describe and explain experiments to investigate the small size of particles and their movement including: i dilution of coloured solutions ii diffusion experiments

Dilution: when a substance (eg food coloring) is placed in a solvent (eg water) to reduce its concentration 

Diffusion: The random movement of particles in a liquid or gas from an area of high concentration to an area of low concentration.

Diffusion in gases experiment (Fig. 1)

1. Place a cotton ball dipped in hydrochloric acid (HCl) on one end of a tube. Seal it with a cork thingie.
2. Place a cotton ball dipped in ammonia (NH3) solution on the other end of the tube. Again, seal with a cork thingie.
3. As the gases produced diffuse down the tube, you will see a white ring forming nearer to the end with the HCl. This is ammonium chloride (gas).

Figure 1

From this, you can observe that the ammonia particles are lighter, as they have travelled further than the HCl in the same amount of time.

LIGHT PARTICLES TRAVEL FASTER THAN HEAVIER ONES

Diffusion in liquids (also dilution) experiment (Fig. 2)

1. Place a spatula of potassium permanganate (or any other strongly colored substance) in a gas jar full of water, right at the bottom. (note that for best results, use a straw to do this)
2. You will see the purple color is most concentrated at the bottom and very light at the top. 
3. Diffusion will happen, as the color eventually evens out. In liquids this is very slow, so leave it to diffuse over a couple of days
4. When the color has evened out, it has reached equilibrium. 

Figure 2: Potassium permanganate in water over time.

Diffusion is slow in liquids because (colored) particles do not have a lot of space to move between the particles of the solute, unlike in gases, where the particles are very far apart. This will happen faster if heat is added to the liquid, as then particles gain more energy and move faster :)

1.3 Explain the changes in arrangement, movement and energy of particles during these interconversions.

Figure 1: A perfect explanation of the particles and properties of each state.

Solid → liquid

• Particles move faster as heat is added
• Forces of attraction weaken
• No longer in fixed arrangement, particles begin to slide over each other
• Begin to vibrate more
• Can move around relatively freely
• Particles gain more energy

(for liquid → solid, process is the same but in reverse. i.e. instead of vibrating more, particles begin to vibrate less)

Liquid → gas

• Particles begin to vibrate even faster
• Forces of attraction become extremely weak
• Particles are now able to move around completely freely
• No arrangement whatsoever
• Particles gain more energy

(for gas → liquid, process is the same but in reverse. i.e. instead of vibrating more, particles begin to vibrate less)

1.2 understand how the interconversions of solids, liquids and gases are achieved and recall the names used for these interconversions

Figure 1

As can be seen in Figure 1, the conversions are as follows:

• Solid → Liquid = melting
• Liquid → Solid = freezing
• Liquid → Gas = boiling
• Gas → Liquid = condensing
• Solid → Gas = subliming 

THE REASON LIQUID to GAS IS BOILING AND NOT EVAPORATING:

Because when its evaporating only the particles at the top are gaining energy and so becoming a gas. When its boiling all the particles are gaining energy

How it works:

• When heat is added, the particles begin to move faster until they move so much that the forces of attraction are no longer strong enough to hold them. This is when the change of state takes place.
• When heat is "removed", the process happens in reverse.  The particles begin to lose energy, and move slower. The forces of attraction become strong enough to pull the particles closer to each other and hold them there.

1.1 Understand the arrangement, movement and energy of the particles in each of the three states of matter: solid, liquid and gas

Solid:
- Particles closely packed, arranged in rows
- All touching
- Hardly move, only vibrate
- Little energy
- Very strong forces of attraction

Liquid:
- Particles mostly touching, pretty close
- Move past each other
- Some energy
- Relatively strong forces of attraction

Gas:
- Particles very far apart
- Move very fast
- Lots of energy
- Weak forces of attraction