If the gas tap to the Bunsen burner is turned on, the methane does not start burning until it is lit with a match. Why is heat from the match needed to start the methane burning?

The reaction has a high activation energy

Explanation:

The burning of methane is a spontaneous reaction. Once the burning begins, the flame is able to sustain itself without any additional input of energy. It is an exothermic reaction in which energy is given out in the form of heat.

The reason why heat from the match is needed to start the burning of methane is that the activation energy of the combustion of methane is high. Activation energy is the energy that must be supplied in order for the collision of reactants to result in chemical reaction.

As long as the activation energy is high, the reaction can not occur without an external input of energy (e.g striking a match). Hence the answer.

when [oh-] is 10-5  m, and [h3o+] is 10-9  m, the poh is 5 and ph is 9. again in both cases the sum of ph and poh is 14. however, the hydrogen ion concentration is not always going to be equal to exactly 1 x 10 raised to a negative number. for example, we skipped over the value of 2.0 x 10-7.