Can someone tell me which formula to use here? (time to boil water)

In summary, the formula for calculating the time it takes to boil water is t = mCpΔT / P, where t is the time in seconds, m is the mass of water in kilograms, Cp is the specific heat capacity of water, ΔT is the change in temperature in Kelvin, and P is the power rating of the heat source in watts. The specific heat capacity of water is 4.186 joules per gram per degree Celsius, or 1 calorie per gram per degree Celsius, and can be easily found online or in reference books. This formula can be used for any type of heat source and for any amount of water, with adjustments made for the mass of water. However, it may not be accurate
  • #1
yuheng_wu
2
0
Homework Statement
Can someone tell me which formula to use here
Relevant Equations
P = W/Δt <=> Δt = W/P = Q/P.
Q= I evaporate water . m
This is the only formula I'm thinking of, but it doesn't work here I think
An amount of water at a temperature of 20 °C is passed through a water boiler in 1.5 min to
brought to boiling point. The kettle is broken and does not jump off.
The time between the moment when the water reaches boiling point and the moment when all the water
is evaporated, is equal to:
a) 7,5 min.
b) 4,5 min.
c) 10 min.
d) 15 min.
 
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  • #2
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1. What is the formula for calculating the time it takes to boil water?

The formula for calculating the time it takes to boil water is t = (m * c * ΔT) / P, where t is the time in seconds, m is the mass of the water in grams, c is the specific heat capacity of water (4.186 J/g°C), ΔT is the change in temperature (in °C), and P is the power of the heat source in watts.

2. How do I know which values to plug into the formula?

You will need to know the mass of the water, the specific heat capacity of water, the change in temperature, and the power of the heat source. These values can be found through measurements or given to you in the problem.

3. Can this formula be used for any type of water?

Yes, this formula can be used for any type of water as long as the specific heat capacity remains constant. However, keep in mind that the specific heat capacity of water can vary slightly depending on impurities or additives in the water.

4. Is there a simpler formula for calculating the time it takes to boil water?

Yes, there is a simpler formula that can be used for estimating the time it takes to boil water. It is t = (m * ΔT) / (P * 4.2), where t is the time in minutes, m is the mass of the water in grams, ΔT is the change in temperature (in °C), P is the power of the heat source in watts, and 4.2 is an approximation of the specific heat capacity of water.

5. Can I use this formula to calculate the time it takes to boil other liquids?

No, this formula is specifically for calculating the time it takes to boil water. Other liquids may have different specific heat capacities and boiling points, so a different formula would need to be used.

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