3.5 I can recall the reaction of methane and bromine

       Alkanes react with bromine in the presence of UV light

·         Explain why this condition is necessary

UV light is needed to supply the energy to break the covalent bonds between hydrogen and carbon

3.       What is this type of reaction called

substitution reaction

4.       State and explain the observations

It would turn from brown to colourless. This is because the concentration of the brown bromine molecule decreases while the concentrations of the product increase (colourless).

5.       Draw the displayed formula of the reaction between methane and bromine (upload a photo)

6.       Write out a balanced (with state symbols) the reaction between ethane and chlorine
C₂H_6 (l)+ Cl_2(g) -> C₂H₅Cl(l) + Hcl (aq)

7.       State and explain the observations in this chemical reaction

It turns from green to colourless. The reactants (chlorine) are green and the products (ethanechloride and hydrochloric acid) are colourless. This is a substitution reaction where the concentration of  the green chlorine molecule decreases and the colourless products increase.