(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Ok, so my book has the following problem: A kettle can heat 20°C water to 100°C in 5 minutes. How long will it take to completely boil it away assuming the same rate of heat addition.

2. Relevant equations

I think Q=mcΔT is relevant but beyond that I am struggling.

3. The attempt at a solution

Hi, I've just enrolled in my first ever physics class at the age of 34. I've been doing well but this has stumped me, any guidance as to how to even start the question would be very useful. I feel that once I get a start I can finish it myself.

So, I've worked through the equation using Q= 2260kJ as this is the heat vaporisation of water, c i've assumed to be 4186J (the specific heat of water) and Δ T is 80°C. This gives me a mass of 6.75kg.

The rate of heat addition is 80°C / 5 minutes = 16°C per minute.

However, I'm not sure I've used the correct values, and I'm not certain on how to proceed from here. I'm not even sure I need to know the mass. The problem is the book (Energy, its use and the Environment) doesn't have any examples like this, and I am completely new to physics.

I've been doing well so far but this has completely thrown me.

Perhaps I should use the formulae W(work)=Qh-Qc where Qh equals end temperature and Qc equals initial temperature...and work out from that the amount of work done on the water and then somehow get to how much work needs to be done to boil away the water....

But without being given the mass how do I proceed? Ugh....I am doing well in this course but this has stumped me.

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# Homework Help: Thermodynamics, calculating the time it will take water to boil away

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