why does a kettle boil

PHYS1110 Lab report: “Why does your kettle boil”.

To do this investigation, I agree that I will follow all the risk control methods and conduct the experiment in a very safe condition.

The aim of this investigation is to find out more about boil water by using a kettle. For example, time taken to boil different volumes of water, specific heat of water and power of kettle.

Equipment:

This picture shows all the equipment that I used to do the experiment including a stop watch, a measuring jug and an electric kettle with power between 1850w-2200w.

Table 1: Time taken to boil five different volumes of water

Volume (L)

Time 1 (s)

Time 2 (s)

Time 3 (s)

Average

uncertainty

time (s)

in

the

average time (s)
0.25

57

57.5

58

57.5

0.5

0.5

95

94

96

95

1

0.75

132

135

134

133.7

1

1

169

171

168

169.3

1.5

1.25

209

211

212

210.7

1.5

To keep the data more accurate, I empty and cooling the kettle thoroughly before doing the next boiling.

Diagram 1

Average Time taken to boil water
250
y = 152.28x + 19.03

Time (s)

200
150
100
50
0
0

0.2

0.4

0.6

0.8

1

1.2

1.4

Volume (L)

As shown on the graph, there is a positive relation between time taken to boil water and the volume of water. The equation for this line is y = 152.28x + 19.03. Therefore, the

gradient of this line is 152.28.

As initial and final temperature are set at 25.0o C and 100o C and the power of the kettle is 2025w (middle of the power range 1850w-2200w). Therefore, the heat of water can be calculated by using the equation: gradient =

??∆?
?

Where gradient is 152.28, cw = the heat of water, ΔT= change in temperature, P= power of the kettle. Therefore, cw =

????????×?
ΔT

=

152.28×2025?
100o C−25.0o C

=

308367
75

= 4111.56J/kg °
C,

which means it costs 4111.56J of energy to rise 1kg of water by 1°
C