What Happens to Water Temperature and State After Heating for 25 Minutes?

  • Thread starter Lennonlim123
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In summary: So, in summary, the heater adds 500 Joules of energy each second to the tank of water. This results in a temperature increase of 25 degrees Celsius over the 25 minutes.
  • #1
Lennonlim123
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A heater so P=500Js^-1,heats up a tank of water of 200ml from 25°C for 25 minutes. What is the final form(solid ,liquid or gas)and the final temperature of the water?
The answer:
Final form : Liquid+vapour
Final temperature: 100°C

I have no idea how to do this!
Plz help!
 
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  • #2
Welcome to PhysicsForums, Lennonlim123.

Start by understanding the physical situation. Even without looking at the answer, do you see that you are heating water, maybe until some or all of it evaporates?

Do you know how to figure out how much water heats from adding a given amount of energy?
 
  • #3
I only know Q=mctheta
But how to apply it here?
Wait, I forgot.
The latent heat of vapourise is 2x10^6
The heat capacity of water is 4200
Heat capacity of vapour is 2100
 
  • #4
Hi Lennonlim123. Welcome to PF!

Generally, you have to follow the rules and tell us what you have tried first. I will assume you don't know where to start. To get a start, answer these questions:

How much energy does the heater add to the water in 25 min.? (hint: you are given the amount of energy is added to the water each second).
How much energy does it take to raise a kg of water one degree C.? How much energy does it take to raise .2kg one degree C?
How much energy does it take to raise .2 kg of water to the boiling point?
How much energy does it take to vaporize one kg of water at that boiling point? How much for .2 kg of water?

(Note: assume the tank is at atmospheric pressure).

AM
 
  • #5
Lennonlim123 said:
I only know Q=mctheta
I usually see that written as Q=mc∆T
It says that the the amount of heat (Q) added to a body equals the product of the mass (m), the heat capacity (c) and the change of temperature (∆T)

That let's you see where Andrew Mason's first leading question comes in:
How much energy does the heater add to the water in 25 min.? (hint: you are given the amount of energy is added to the water each second).

The answer to that will give you the value to substitute for Q (assuming all the heat goes into the water and stays there until the water boils).
 

1. What is thermal energy and how does it differ from temperature?

Thermal energy is the total kinetic energy of all the particles in a substance. Temperature, on the other hand, is a measure of the average kinetic energy of those particles. In simpler terms, thermal energy is the total amount of heat energy present in a substance, while temperature is a measure of how hot or cold something is.

2. How is thermal energy transferred between objects or substances?

Thermal energy can be transferred through three main mechanisms: conduction, convection, and radiation. Conduction is the transfer of heat through direct contact between two objects or substances. Convection is the transfer of heat through the movement of fluids (liquids or gases). Radiation is the transfer of heat through electromagnetic waves.

3. How does insulation affect thermal energy?

Insulation is a material that reduces the transfer of thermal energy. It works by creating small pockets of air that help to slow down the movement of particles and thus, reduce the transfer of heat. This is why insulation is commonly used in homes to keep them warm in the winter and cool in the summer.

4. What is specific heat capacity and why is it important in thermal energy?

Specific heat capacity is the amount of heat energy required to raise the temperature of a substance by 1 degree Celsius. It is an important factor in thermal energy because substances with a higher specific heat capacity require more energy to increase their temperature, while substances with a lower specific heat capacity require less energy.

5. How can thermal energy be converted into other forms of energy?

Thermal energy can be converted into other forms of energy through different processes. For example, in a power plant, thermal energy from burning fossil fuels is used to produce steam, which then turns a turbine to generate electricity. In a car engine, thermal energy is converted into mechanical energy to power the vehicle. Other examples include converting thermal energy into electrical energy through solar panels or into chemical energy through batteries.

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