For burning or increase in temperature to take place, heat will have to be supplied to the two different water volumes. Heat will provide kinetic energy to water molecules, enabling their motion. For the same amount of heat supplied, molecules in 100 ml will receive more energy as compared to 200 ml water (since the number of molecules are double and the energy will be divided over all of them). Both the specific heat capacity and Latent heat of vaporization are intensive properties and hence are dependent on mass of the substance. Since 100 ml water has half the mass of 200 ml water, for the same heat applied, its temperature will rise earlier and it will change the phase earlier (from liquid to gaseous phase).
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