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# GCSE Grade 9 Question - help pls? watch

1. I've tried answering it myself and I think I have the right answer, could some1 pls give it a go?

Calculate the amount of heat required to completely convert 50g of ice at 0 degrees Celsius to steam at 100 degress Celsius. The specific heat capacity of water is 4.18kJ/kg/C, the specific hlatent heat of fusion of ice is 334kJ/kg and the specific heat of vaporisation of water is 2260kJ/kg.

Thx!
2. What you'd do is convert to correct units: 50g is 0.05kg and all kJ to J by multiplying by 1000, then since it's ice you'd work out the energy to convert to water: 0.05 × 334000J gives 16700J to get to water.
Then you'd work out the energy required to heat to 100 degrees Celsius: 0.05 x 4180J = 209J
You'd finally calculate the energy for vaporization as it completely converts to steam as 0.05 x 2260000J = 113000J
Finally total these to get 129909J required or 129.909kJ depending on the questions unit preferences

EDIT:
Forgot to factor in the change in temperature:
0.05 x 4180 × 100 = 20900J
New total would be 150600J or 150.6kJ
3. (Original post by AmmarTa)
What you'd do is convert to correct units: 50g is 0.05kg and all kJ to J by multiplying by 1000, then since it's ice you'd work out the energy to convert to water: 0.05 × 334000J gives 16700J to get to water.
Then you'd work out the energy required to heat to 100 degrees Celsius: 0.05 x 4180J = 209J
You'd finally calculate the energy for vaporization as it completely converts to steam as 0.05 x 2260000J = 113000J
Finally total these to get 129909J required or 129.909kJ depending on the questions unit preferences
YESSS! Now I can tick it - thx my teacher's a little too fast paced!
4. (Original post by streetdude28)
YESSS! Now I can tick it - thx my teacher's a little too fast paced!
You're welcome
5. (Original post by AmmarTa)
Thanks, you wouldn't mind +rep right?
np
6. (Original post by AmmarTa)
Thanks, you wouldn't mind +rep right?
youre not meant to ask shhh
7. (Original post by amaraub)
youre not meant to ask shhh
Didn't know, woops:O
8. (Original post by AmmarTa)
What you'd do is convert to correct units: 50g is 0.05kg and all kJ to J by multiplying by 1000, then since it's ice you'd work out the energy to convert to water: 0.05 × 334000J gives 16700J to get to water.
Then you'd work out the energy required to heat to 100 degrees Celsius: 0.05 x 4180J = 209J
You'd finally calculate the energy for vaporization as it completely converts to steam as 0.05 x 2260000J = 113000J
Finally total these to get 129909J required or 129.909kJ depending on the questions unit preferences
Isn't this incorrect? E= mc delta T for heating water, you haven't multiplied by 100 for the temperature change.
9. (Original post by haarithiop)
Isn't this incorrect? E= mc delta T for heating water, you haven't multiplied by 100 for the temperature change.
Oh crap you're right, my bad! energy is shc×massxchange in temp
10. (Original post by AmmarTa)
Oh crap you're right, my bad! energy is shc×massxchange in temp
150.6kJ

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