A student measures 250g of water and pours it into a beaker. They heat the water over a Bunsen burner for five minutes, then measure the mass of the water again; this time it is 200g. The specific latent heat of vaporisation of water is 2260kJ/kg.How much energy has been transferred in evaporating the water?
Question
A student measures 250g of water and pours it into a beaker. They heat the water over a Bunsen burner for five minutes, then measure the mass of the water again; this time it is 200g. The specific latent heat of vaporisation of water is 2260kJ/kg.How much energy has been transferred in evaporating the water?
Solution
To calculate the energy transferred in evaporating the water, we need to use the formula for heat energy, which is:
Q = m * L
where:
- Q is the heat energy,
- m is the mass of the substance, and
- L is the specific latent heat of the substance.
First, we need to find the mass of the water that has evaporated. This is the initial mass minus the final mass, which is 250g - 200g = 50g. But we need this mass in kilograms, so we convert it by dividing by 1000, which gives us 0.05kg.
Next, we plug the values into the formula. The specific latent heat of vaporisation of water is given as 2260kJ/kg, so:
Q = 0.05kg * 2260kJ/kg = 113kJ
So, the energy transferred in evaporating the water is 113 kilojoules.
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