4.25 predict the effects of changing the pressure and temperature on the equilibrium position in reversible reactions

NOTE: It is important to remember in reversible reactions one reaction is endothermic and the other is exothermic.

The temperature and pressure of the reactants have a very strong effect on the position of the equilibrium. For example...

Temperature
If you increase the temperature - the endothermic reaction will increase to use up the heat
If you decrease the temperature - the exothermic reaction will increase to raise the heat

Pressure
If you increase the pressure - the reaction will produce the side of the equation that has the least moles (to work this out, just look at the ratio of moles on either side of the equation)
If you decrease the pressure - the reaction will produce the side of the equation that has the most amount of moles

4.24 understand the concept of dynamic equilibrium

Okay so this may need a few reads as it is a little complicated but this was the easiest way i could explain it... good luck :)

If a reversible reactions occurs (in a closed system), a dynamic equilibrium will be reached. All this means is that the relative % of reactants and products will reach a balance and stay there (NOTE: it is not always 50-50), the reactions will then continue to occur (basically the reaction takes place both ways, at the same time BUT there is no overall effect (one being made more than the other) as the relative % of reactants to products is balanced (remember :D) so the reactions kind of cancel each other out (as both reactions occur at the same rate)

NOTE: A closed system just means that none of the products/reactants can escape (this enables dynamic equilibrium to occur)

4.23 describe reversible reactants such as the dehydration of hydrated copper(II) sulfate and the effect of heat on ammonium chloride

Dehydration of hydrated copper(II) sulfate
Copper(II) sulfate is a white solid. When you added water to copper(II) sulfate it forms blue crystals, forming hydrated copper(II) sulfate. If heat this hydrated copper(II) sulfate it turns white as the water evaporates, forming (dehydrated) copper(II) sulfate. If you add water, it will turn blue again, if you heat it again it will turn white... etc

Ammonium chloride
Ammonium chloride is a white solid, when it is heated it breaks down into ammonia gas and hydrogen chloride gas. However, if you let these products (ammonia gas and hydrogen chloride) cool down, they will react with each other, forming ammonium chloride.

4.22 understand that some reactions are reversible and are indicated by the symbol ⇌ in equations

22. 22. ⇌ is the symbol for reversible reaction
23. 
    
24. NOTE: a reversible reaction is just a reaction where the products of the reaction can themselves react to produce the original reactants