# How long does it take to heat this water

1. Nov 2, 2007

### BuBbLeS01

1. The problem statement, all variables and given/known data
An immersion heater has a power rating of 1100 watts. It is used to heat water for coffee. How long (in minutes) should it take to bring 1.1 L of water from room temperature (20°C) to 82°C?

2. Relevant equations

3. The attempt at a solution
I am not sure what equation to use???

2. Nov 2, 2007

### BuBbLeS01

Is the 1100 W important or just there to confuse me? Because the chapter we are on doesn't have Power in it.

3. Nov 2, 2007

### S[e^x]=f(u)^n

whats the definition of power?

4. Nov 2, 2007

P = W/ch T

5. Nov 2, 2007

### hage567

So what is that telling you?

6. Nov 2, 2007

### BuBbLeS01

So the P = 1100 watts? And then what is W?

7. Nov 2, 2007

### hage567

W in this case means work. If you know the power then you how much energy is being put into the water.

8. Nov 3, 2007

### BuBbLeS01

How do I know the Work done?

9. Nov 4, 2007

### BuBbLeS01

Does anyone know how to do this?

10. Nov 4, 2007

### hage567

Do you know about heat capacity? Have you seen $$Q =mc\Delta t$$ before? Look it up in your book, it must be in there.

The power of the heater is telling you the rate that thermal energy ("Q") is being added to the water.

So, you need to figure out how much thermal energy is needed to raise the temperature of the water using the first equation I gave you. Once you have that, you can figure out how long it will take to add that much energy because you know rate that the heater is adding energy.