Question

How much energy (in joules) is required to raise the temperature of 200g of liquid water from 20c to 50 c?

Heat Capacity of liquid water: 4.2 J/(g*K)

Latent Heat of fusion of water: 330 J/g

Latent heat of vaporization of water: 2200 J/g

Answer 1

`25200J`

Explanation:

`E = mcDeltatheta`

where `c` is specific heat capacity in `J//g//K`

(specific heat capacity: the amount of energy needed to raise the temperature of `1g` of a substance by `1K`)

and `Deltatheta` is the change in temperature.

here, `Deltatheta = 50^@C - 20^@C = 30^@C`.

`E = 200g * 4.2 J//g//K * 30K`

`= 25200J`

Answer 2

It's about 25 kJ - make sure you're consistent in your units.

Explanation:

The calculation is `E=M.c.theta`

Where `E` is the energy in J, `M` is the mass of substance in g, `c` is the specific heat (of water in this case) in `J/(g.K}`, and `theta` is the temperature change (which can be in celcius or kelvin - if you're only looking at the delta between the two temperatures it makes no odds which unit you choose).

So it works out like this

`E=M.c.theta`
`E=200 times 4.2 times30`

So E= 25,200 J (or 25.2 kJ).