Efficiently Heat Soup: Calculate Time Needed with 350W Immersion Heater

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Homework Help Overview

The discussion revolves around calculating the time required to heat a cup of soup using a 350W immersion heater. The specific context involves heating 250 mL of water from 15 degrees Celsius to 75 degrees Celsius, touching on concepts of heat capacity and energy transfer.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the definition of power and its relation to work and time. There is an exploration of heat capacity and how it relates to the energy required to change the temperature of water. Some participants express uncertainty about how to approach the problem, particularly regarding the calculation of energy needed.

Discussion Status

Some guidance has been offered regarding the use of specific heat capacity and the need to convert units. Participants are actively engaging with the problem, raising questions about the necessary calculations and the definitions involved, but there is no explicit consensus on the next steps.

Contextual Notes

Participants note the importance of converting units to standard measurements and the need to understand the concept of specific heat capacity in the context of the problem.

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I know this is a simple problem, but I don't know where to begin.
Please help!

A small immersion heater is rated at 350W. Estimate how long it will take to heat a cup of soup (assume this is 250 mL of water) from 15 degrees celsius to seventy-five degrees celsius
 
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What do you know about heat capacity? What is the definition of power?
 
i know that power is the change of work divided by the change in time. the problem is asking for the time so i need to solve for the change of work. the change in work isn't as simple as the difference in temperature, right?
 
can some one help me with this problem. i am stuck. i don't know where to go from here...
 
It takes a certain amount of energy to heat a volume of water up 1 degree celsius. That energy is "specific heat capacity". Work from there.

In this case, you're using volumetric heat capacity which Wiki defines as 4.181 joules per cubic centimetre per kelvin for water at 25*C.

You have to:

1.) Convert all the given units into standard units (mL = cm^3)

2.) Work out the energy needed to heat that volume of water to that temperature

3.) Calculate how long it will take for the 350W (joules per second) heater to give out energy equal to the amount needed for the water.
 
Last edited:

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