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"What is the change in temperature of 2kg of water heated by a kettle using a voltage of 230V at 0.5A of current for 10 seconds? Assume no heat losses."

By assuming no heat losses, we are essentially saying that all of the electrical energy supplied to the kettle is equal to the heat energy that has been transmitted from the kettle to the water.
Electrical energy input = Heat energy output

With that in mind, we can easily calculate the amount of heat energy supplied using the formula for electrical power:
P = VI
Where P=electrical power, V=voltage supply, I=current

So: P = 230  0.5 = 115 W
We also know that:
P = Q/t,
Where Q=heat energy, t=time
Therefore: 
Q = Pt
So, the amount of heat energy supplied:
Q = 115 . 10 = 1150 J
Now, we use the formula of specific heat capacity:
Since:
Q = mcΔT,
Therefore:
ΔT = Q/mc
Where T=change in temperature, m=mass of water, c=specific heat capacity

So now we simply plug in the values!
ΔT = 1150/2 . 4200=0.137 deg C

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