When an alkane is combusted in the presence of excess Oxygen, it produces Carbon Dioxide and water. The flame burns blue.$^1$
$$ CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O $$
When an alkane is combusted in the presence of limited Oxygen, it produces Carbon Monoxide and water. The flame burns red or yellow.$^1$
$$ 2CH_4 + 3O_2 \rightarrow 2CO + 4H_2O $$
When an alkane is combusted in the presence of extremely limited Oxygen, it produces soot(Carbon) and water.$^1$
$$ CH_4 + O_2 \rightarrow C + 2H_2O $$
Also called photochemical substitution reaction, this takes place when an alkane is allowed to react with a halogen in presence of sunlight.$^1$
In general: $^1$
$$ \text{alkane }+ X_2 \underset{sunlight}{\overset{E=h\nu}{\longrightarrow}} \text{halogenoalkane + hydrogen halide} $$
An example is $^1$
$$ CH_4 + Cl_2 \overset{h\nu}{\rightarrow} CH_3Cl + HCl $$
When an alkene undergoes an addition reaction with hydrogen, it produces an alkane.$^1$
$$ CH_2CH_2 + H_2 \rightarrow CH_3CH_3 $$
When an alkene undergoes an addition reaction with water, it produces an alcohol.$^1$