how many joules would it take to raise the temp of 1kg water from room temp to boiling?

Question

How many joules are required to raise 1.0-kg of water from room temperature of 22 degrees Celsius to its boiling point? (B)If this workk were used to lift a 50-kg boy instead, how high could he be lifted?

a. (A)33 x 10^5 J (B)67.0 m
b. (A)3.3 x 10^5 J (B)670 mm
c. (A)3.3 x 10^5 J (B)670 m
d. (A)3.0 x 10^5 J (B)600 m

Answer 1

Q=ms(t2-t1)
Q=Heat energy (to be found)
m=mass (1kg)
s=Sp heat capacity (4200J/Kg.K)
t1=22C=22+273=295K
t2=100C=100+273=373K
sub:
Q=1*4.2*(373-295)*1000=3.276 x 10^5 = 3.3 x 10^5(approx)

(B PART)

the energy is used to lift the boy.ie its used to do work against gravity.which means its used to increase the Potential Energy of the boy.
therefore,

3.3 x 10^5 = mgh
=> h = 3.3 x 10^5/mg
taking g=9.8 we get
h=670 m (approx) [673.54 exact]

HENCE ans is option (c)

i back "ag_iitkgp"

Answer 2

Water has a heat capacity of 4.184 J/g-C. If the water is at 22 C you need to warm it by 78 C to reach boiling point, 100 C.

So..... 4.184 J/g-C X 1000 g X 78 C = 3.3X10^5 J

3.3X10^5 = mgh (m=50 kg, g=9.81 m/s^2)

h = (3.3X10^5)/(50*9.81) = .665 m = ~670 mm

Answer is B

Answer 3

H = 1*4200*(100-22) = 4200 * 78 J = 3.3x10^5J

So, ht = 3.3x10^5/(50x9.8) = 670 m

Thus c

Answer 4

I forget it