Warning - Science Content!!!

[henvanjamal]

8) 1 Calorie raises 1g of water 1 degree C

1 cal = 4.184 joules

therefore, 1Kg water needs 4184J per degree, and hence 4184 x (99+20) joules to heat to 99C from -20C = 497896J

100W = 100 J/s

Therefore, 497896 / 100 = 4978.96 secs (or 82.98 mins, or 1.38 hrs)

Waiting that long, you'd have died of thirst!!

[mcauleyab]

You're almost there. However, its not quite as simple a matter of multiplying heat capacity by difference in temperature. *HINT* There's a matter of changing the water from solid to liquid form, which requires energy. Once you work that out, you'll be there! So keep trying!

Originally Posted by henvanjamal

8) 1 Calorie raises 1g of water 1 degree C

1 cal = 4.184 joules

therefore, 1Kg water needs 4184J per degree, and hence 4184 x (99+20) joules to heat to 99C from -20C = 497896J

100W = 100 J/s

Therefore, 497896 / 100 = 4978.96 secs (or 82.98 mins, or 1.38 hrs)

Waiting that long, you'd have died of thirst!!

[henvanjamal]

Doh! The old 'latent heat' banana skin!! ;-)

80 cal required to melt 1 g ice

therefore 80 x 4.184J x 1000g = 334720J + 497896 (from earlier) = 832616J in total.

832616 / 100Js = 8326.16 secs
= 138.77 mins, or 2.31 hrs

Would you like a biscuit with that?

[mcauleyab]

Originally Posted by henvanjamal

Doh! The old 'latent heat' banana skin!! ;-)

80 cal required to melt 1 g ice

therefore 80 x 4.184J x 1000g = 334720J + 497896 (from earlier) = 832616J in total.

832616 / 100Js = 8326.16 secs
= 138.77 mins, or 2.31 hrs

Would you like a biscuit with that?

Yep, EVERYONE forgets about latent heat the first time around! Well done, that's 250 tokens on their way.