Which one of the following processes involves chemical reactions?

$A$ solution of potassium chloride when mixed with silver nitrate solution, an insoluble white substance is formed. $(i)$ State two types of this reaction.

Observe the following diagram and answer the questions that follow:
$(i)$ Identify the gases evolved at anode and cathode.
$(ii)$ Why are the amounts of gases collected in the two test tubes not of the same volume?
$(iii)$ What type of reaction is this?
$(iv)$ Why should we use salt water?

The following reaction is an example of a:
$4 NH_{3}(g) + 5 O_{2}(g) \rightarrow 4 NO(g) + 6 H_{2}O(g)$
$(i)$ Displacement reaction
$(ii)$ Combination reaction
$(iii)$ Redox reaction
$(iv)$ Neutralisation reaction

State one basic difference between a physical change and a chemical change.

Write a balanced chemical equation for the process of photosynthesis and the conditions of the reaction,including the physical states of all the substances.