how many calories of heat are needed to raise the temperature of 200 PHY 220 . 1
ID: 1521196 • Letter: H
Question
how many calories of heat are needed to raise the temperature of 200 PHY 220 . 1) How many calories of heat are needed to raise the temperature of 200 grams of iron from 20°C to l00°C. (c = .1 07cal/(gm-°C) 2) A 0.004kg sample of a metal is at 20°C.If 200J of heat is added to the metal ,the final temperature is 90°C, what is the specific heat? Give correct units also. 3) A bathtub contains 70kg of water at 260C. If 20kg of water at 90°C are poured in, what is the final temperature of the mixture? Neglect the heat absorbed by the bathtub. Gwater 4190J/(kg.°C) How much heat in calories is needed to change a 20gram ice cube at -20°C to water at 10°C?Explanation / Answer
1) m =200 gm , T1 =20 oC, T2 =100 oC c =0.107 cal/gm.oC
Q = mC(T2 -T1) = 200*0.107*(100-20) =1712 cal
2) Q = mCdT
200 = 0.004*C(90-20)
C = 714.3 J/kg.oC
3) heat gain by water =heat lost by hot water
70*4190*(T-26) =- 20*4196*(T-90)
T =40.24 oC
4) m =20 gram, specific heat of water C = 1cal/gm. oC
latent heat of ice = 80 cal/gm
specific heat of ice = 0.48 cal/gm.oC
Q = (20*0.48*(0+20)) +(20*80)+(20*1*(10 -0))
Q =1992 cal
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