Calculate time to raise temperature of water

In summary, the conversation discusses the concept of heat capacity and its relationship to specific heat capacity. The question at hand is how long it will take to raise the temperature of water in a kettle to boiling point. The formula for specific heat capacity is mentioned, but there is confusion about where heat capacity fits into the calculation. It is then clarified that heat capacity is used when considering an object as a whole, rather than just a specific mass. The final formula is arrived at by combining the energy required to heat the water and the kettle, and dividing it by the power input. Eventually, the concept is fully understood and the conversation ends on a positive note.
  • #1
polyperson
38
0
The problem I have is in understanding what is meant by heat capacity (as opposed to specific heat capacity).

I have been given the heat capacity (J kg-1) of a kettle plus the power input (IV), the mass of water and given that the water must be raised from room temp to boiling point.

The question asked is how long will this take.

I know that Specific Heat Capacity = I V t / m (change in temp) but where does the heat capacity come in all of this?

Any help appreciated!
 
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  • #2
Well, a specific heat capacity is in J/kg*C while your heat capacity is simply in J/C. It's called a heat capacity basically when you're just using an object as opposed to different masses. For example, I'd use a crucible as a calorimeter that has a heat capacity of 180J/C because the mass doesn't change, its simply an object whose mass remains constant.
 
  • #3
Thanks peng. I can understand that part - I just can't see how it fits into the calculation. The way I see it:

The energy required to heat the water = mass x specific heat capacity of water x change in temp

And:

Time to change temp = Energy required / Power input

I know this is not correct but I don't know why
 
  • #4
Well remember... the water isn't the only thing being heated up...
 
  • #5
Yes, I see where you are coming from now. I need to think about it some more.
 
  • #6
Time = (Energy to heat water + Energy to heat kettle) / Power input

Energy to heat kettle = Heat capacity x change in temp ?
 
  • #7
exactly!

good job.
 
  • #8
Thanks peng. I got there in the end!
 

What factors affect the time it takes to raise the temperature of water?

The time it takes to raise the temperature of water can be affected by several factors, including the initial temperature of the water, the heat source used, the amount of water, and the surrounding temperature.

How can I calculate the time it will take to raise the temperature of water?

To calculate the time it takes to raise the temperature of water, you can use the formula: time = (mass of water x specific heat capacity x change in temperature) / heat input. This will give you the time in seconds. You can also use online calculators or tables that provide the specific heat capacity of water at different temperatures.

Does the type of container affect the time it takes to raise the temperature of water?

Yes, the type of container can affect the time it takes to raise the temperature of water. Materials with high thermal conductivity, such as metal, will transfer heat more efficiently and therefore heat up the water faster than materials with low thermal conductivity, such as plastic.

Why is it important to consider the specific heat capacity of water when calculating the time to raise its temperature?

The specific heat capacity of water is the amount of heat needed to raise the temperature of 1 gram of water by 1 degree Celsius. Since water has a high specific heat capacity, it requires more heat to raise its temperature compared to other substances. Therefore, considering the specific heat capacity is important to accurately calculate the time it takes to raise the temperature of water.

Are there any shortcuts or tricks to quickly calculate the time to raise the temperature of water?

There are no shortcuts or tricks to quickly calculate the time to raise the temperature of water. However, using the formula mentioned in the second question and using online calculators or tables can help make the calculation process easier and faster.

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