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# Thermal physics help needed watch

1. can someone help me do both parts.
i used the specific heat capacity formula for part one but that didn't give me the right answer.

for part 2 i dont know how to start it
2. (Original post by assassinbunny123)
can someone help me do both parts.
i used the specific heat capacity formula for part one but that didn't give me the right answer.

for part 2 i dont know how to start it
this is the question
Attached Images

3. bump
4. For part i you need to calculate the energy thermal required to increase the temperature of the ice from -15 degrees using Q=mc detla theta. But also it changes state so you have to add the energy required for ice to change into water which is Q=ml where l is the specific latent heat of fusion of ice
5. yes thank you i got it at the end, how about part 2?
For part i you need to calculate the energy thermal required to increase the temperature of the ice from -15 degrees using Q=mc detla theta. But also it changes state so you have to add the energy required for ice to change into water which is Q=ml where l is the specific latent heat of fusion of ice
6. Is the answer 16.7 degrees
7. mark scheme says 16 degrees how did you do it?

8. where did you get the 200 from?
mark scheme says this :
dont understand the second part where they made the 2 equations equal.

(Original post by haphazardsoph)
I think for part 2 you would use:

mcΔθ of the water = the energy value you just calculated

where Δθ would be (200 - θ)
Attached Images

9. (Original post by assassinbunny123)
where did you get the 200 from?
mark scheme says this :
dont understand the second part where they made the 2 equations equal.

It is using conservation of energy.

Energy lost by the warm water is used to heat up the ice to the equilibrium temperature T.

Energy lost by the warm water = Energy gained by ice to increase the temperature from −15°C to 0°C + Energy gained by the ice to change to water + Energy gained by the water (change from ice) at 0°C to increase the temperature to the equilibrium temperature T

I think
Energy gained by ice to increase the temperature from −15°C to 0°C + Energy gained by the ice to change to water = 8676
10. For some reason I can't upload a picture

But basically you get 2 simulataneous equations. One for energy lost by the water and one for the energy gained by the ice. The energy lost is a negative though.

Water: -Q=mc(T-28) where m is mass of the water and c is the heat capacity of water
Ice: Q=ml + mc(T+15) where m is the mass of the ice and c is the heat capacity of water
Then just find T

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