Fot
6
4
Eramrner's
Use i
A freezer containing 2 kg of ice at a temperature of -2oC is def rosied within 30 minutes using
hot water at a temperature oi 80'C. The final temperature of the defiosted ice is 10'C. The
speciiic latent heat of fusion of ice is 340000J/kg and lhe specific heat capaoity of ice is
2000 J/(kg"C). The specific heat capaciiy of water is 4200J(kg"C)'
Calculate:
(a)
the amount of heat energy needed to melt all the ice;
t
energy
3 .,"'..'-""',""""":"""" "'
{b}
th'e amount of energy needed to warm the water from OoC to 10"C;
{c}
the mass of the hoi water;
rfloss
(d)
=
the rate at which heat was supplied by the hot water.
"""
"'12]
.'...."....'. t2l
4
3 (a) State two differences
For
Examiner's
between boiling and evaporation.
Use
1.
2.
121
(b) An athlete does
some intensive training and starts to sweat.
Explain why the athlete feels cold after the training.
tzt
(c)
When it is cold, people wear jackets to keep warm.
Explain how a jacket keeps the body warm.
121
F.r l
4
_t
bxamners
Use
Fig. 3.1 shows an immersion heater and a thermometer placed in a vacuum flask containing
a liquid.
thermometer
I
l
-to
immersion heater
liquid
silvered glass
vacu
Fig. 3.1
The heater is switched on and the temperature of the liquid is recorded every minute.
Table 3.1 shows the results obtained.
fl
Table 3.1
time/minutes
0
1
2
3
4
5
6
temperature/"C
24
46
68
90
105
105
105
(a) State the boiling point of the liquid.
boiling point =
t1l
(b) The information in Table 3.1 can be used to find the specific heat capacity of the liquid.
State two other quantities needed to find the specific heat capacity of the liquid.
1................
(c)
............ t2l
State two features of the vacuum flask that help to minimise heat loss from the liquid
and explain how each stated feature works.
feature
I
power supply
plastic lid
2................
I
1
explanation
feature 2
explanation
l4l
i
5
Liquid vvax at B0 'C is ccoled to 20'C, Ai 35 "C the v,,ax stalls to soiidify.
iai
Cn the axis
rryax
beioia;. sketch a cooling curve for the iryax between
B0"C and 20"C if the
iakes 20 ntinuies to stad soiidifying.
temperature/"C
4A
t
time/min
l3l
I( .,,
-\,
J
\
(b) Describe the motion of particles in wax at the following
1.
For
jExenr;ner.c
temperatures.
above 35 "C
below 35 "C
121
4
For
Examiner's
Two rods are left in a freezer overnight. The freezer is kept at a temperature of -10'C. The
rods are identical in size, but one is made of plastic and the other is made of aluminium.
(a)
Use
Explain why the temperature of the rods decreases when they are left in the freezer.
11I
(b)
State and explain which rod feels colder when they are both touched.
rod
explanation
.......;..........
:
t1I
..
t2I
:
,...
(c) (i)
....
..
....
Name the process by which heat is transferred through the rods.
t1l
(ii)
Describe the method by which heat is transferred through the rods.
121
(.j
I
7
For
xaminer's
Use
(a) Fig 7.1 shows a computer chip fitted with a 'heatsink'. The 'heatsink' cools the
computer chip.
heatsink
black metalfins
metal base
computer chip
Fig. 7.1
Complete Table 7.1 to show how each feature is suitable for its purpose.
Table 7.1
design feature
how it is suitable for its Purpose
black metalfins
many fins
metal base
l3l
(b)
Fig 7.2 shows a small plastic beaker floating upside down in a large beaker
containing cold water. Water in the beaker is heated but it does not boil.
small plastic
large beaker
Fig.7.2
State and explain what is observed as the temperature of the water increases.
observation
reason
""""""'[1]
For
Exailnels
Use
B
Fig. 8.1 shows an electric heater.
coiled thin tungsten wire
Fig.8.1
(a) Name the type of radiation produced by the tungsten wire when the current is flowing.
....[1]
(b) Give a reason why the tungsten wire is
(i)
coiled,
(ii)
made thin.
...................... t2l
(c)
Explain why the surface of the heater is
(i)
shiny,
(ii)
curved.
12)
Examiner's
Use
Fig.6.1 shows the side view of a solar panel.
winding
copper PiPe
glass
COVCT
water
V
OUt
black painted
surf ace
Fig.6.1
Explain whY the:
(a)
bottom surface is painted black;
lrl
(b)
(c)
(d)
is covered with
r0t'
Ii:antiner s
L/ss
A
Fig. + 1 shovrrs a ligltt buli:,
.--,.
I'utlgste tt
f
iI
anie nt
ineri gas
)
\
coniacts
'
FiE.4.1
Wtren the bulb is switched on, the filament glows ai a temperature of 2500 "C'
(ai (i)
Explain how thermai energy from
tlre hot filament is transferred to
the
surroundings.
(ii)
by
Two contpottents of the eleciromagnetic spectrum are produced
the 'iilatttent'
v'raveletrgth.
Name the twc componenis and indicate the one wiih the longer
Component wiih ionger
(iii)
rnravelen gth
state two physicalproperties that the filament should lrave,
tol
....'.LUl
rat
ii:mrneri
B
I
1r:
(b)(i)CalculatetheCui-rentinthebulbwhaniiisop:i,aiinga|240V'60W
curreni =
(ii)
Calculaie the resistance of ihe filament'
resistance
(iii)
=,....'.......'."
caicuiate tlre ierrgth of ihe
one metre of ihe filament has a resistance of i280Q'
filament in the bulb.
i
|
.i'
lengih =
(iv)Expiainhowthislengihoftlrewireisablet'ofitirrtothebulb,
(c)
Another ligiri bulb is rated
12 v,
that in (b)'
60w' lts filament is'the same iength as
a smaller
the same power as tlrat in (b) from
Explain how this bulb is abie to produce
potential diiference.
t,,:
11l
''
i