Temperatures rising..

Question

A cup of water is heated with a heating coil that delivers 130 W of heat.

In one minute, the temperature of the water rises by 20 degrees celsius. What is the mass of the water?

Answer 1

130 W = 130J/s.

1 min. = 60sec.

Specific Heat of water = 4.184J/g/°C. Temp. change = 20°C.

Mass (g) x 4.184J/s/°C x 20°C = 130J/s x 60s

Mass. = (130 x 60) / (4.184 x 20)

= 7,800J / 83.68 = 93.2 grams of water..

(Check: 93.2g x 4.184J/g/°C x 20°C = 7,799J).

Answer 2

ΔQ = mc ΔT

the specific heat c of water is 4180 J / kg - C

Assuming that all of the energy from the coil was used to heat the water...

( 130 W ) ( 60 sec ) = m ( 4180 J / kg - C ) ( 20 C )

m = .093 kg = 93 g of water.

Answer 3

specific heat of water is 4.186 kJ/kgC

in one minute, 130 watts delivers 130*60 =7800 Joules of energy.

7.8 = 4.186 kJ/kgC x 20 x M

M = 0.0932 kg