How long does it take for the water to start boiling?

Answer 1

That varies depending on the conditions. For example, if water is already at 99 degrees and the boiling point is 100 degrees, and the amount of water is small, it can boil almost instantly. If you have a fairly large amount of cold water, it will of course take longer. More specifically, the answer to your question will depend on all of the following factors:

• The amount (mass) of the water
• (The water's heat capacity can be assumed to be constant, but you need that in your calculations)
• The mass of the pot, cauldron, or whatever you use to boil the water in
• The heat capacity of this container (which will depend on the material from which it is made)
• The initial temperature of the water + container
• The atmospheric pressure, which affects the boiling point
• How fast the energy is provided to the water, i.e., the power - for example, in the case of a gas stove, how big the fire is
• How much of this heat energy gets wasted

Answer 2

There are multiple variables involved - i.e., initial temperature of water, amount of heat used, amount of water, ambient pressure.

With domestic appliances, such as an electric kettle, it would take about two minutes to boil a litre of water from a domestic supply.