100g of water is heated from `30^@C to 50^@C`. Ignoring the slight expansion of the water, the change in its internal energy is (specific heat of water is `4184J//kg//K`):

Explanation

`dQ=dU+dW, dW=0(because dv "is neglected")`
`therefore dQ=dU=mSDeltatheta`
`=(100)(10^-3))(4180)(20)=8360J=8.4KJ`