Question

Q8

a) Define (i) Specific Heat Capacity, (ii) Specific Latent
Heat.

b) 500g of water at temperature of 15°C is placed in a
freezer. The freezer has a power rating of 100W and is 80%
efficient.

(i) Calculate the energy required to convert the water into
ice at a temperature of -20°C.

(ii) How much energy is removed every second from the air in
the freezer?

(iii) How long will it take the water to reach a temperature
of -20°C?

(iiii) Explain the process that cools the air in the
freezer.

(v) The freezer causes the room temperature to rise. Explain
why.

Specific heat capacity of ice =2100J kg-1K-1; Specific heat
capacity of water

=4180J kg-1K-1; Specific latent heat of fusion of water =
3.3x105Jkg-1

Answer #1

500g of water at temperature of 15°C is placed in a
freezer. The freezer has a power rating of 100W and is 80%
efficient.
1- Calculate the energy required to convert the water
into ice at a temperature of -20°C.
2- How much energy is removed every second from the air
in the freezer?
3- How long will it take the water to reach a
temperature of -20°C?
4- Explain the process that cools the air in the
freezer.
5-...

1. A gallon of water is receiving 100 J of latent heat. In that
process its temperature
a. increases
b. decreases
c. remains constant
2. A 100 kg rock is at rest. It is then dropped and falls
through a height of 20 m. How fast is it approximately
moving after dropping that distance?
a. 10 m/s
b. 15 m/s
c. 20 m.s
d. 25 m/s
e. None of the above
3. Of the following processes, which one involves the...

A 60 kg block of ice begins at -60 degrees the specific heat of
ice is 2090 j/(kg)C. The latent heat of fusion of water is 3.3 x
10^5 and the latent heat of vaporization is 2.3 x 10^6 J/kg. How
much energy is required to heat the ice to 0 degrees Celcius
(melting point)?
How much energy is required to heat the ice from -50C to the
melting point and melt the ice?
How much energy is required to...

How much heat is needed to convert 10 kg of water at 30◦C
to:
(a) water at 100◦C?
(b) steam?
(c) ice?
Take:
Specific heat capacity of water = 4.186 kJ/kg◦C
Latent heat of vaporization of water = 2264 kJ/kg
Latent heat of fusion of water = 333 kJ/kg.

The specific heat of water in its solid phase (ice) is 2090
J/(kg K), while in the liquid phase (water) its specific heat is
4190 J/(kg K). Water's latent heat of fusion is 333,000 J/kg.
If you have a 2kg block of ice at -90 degrees C and you add
1,000,000 J of heat, what is its new temperature?

8.33 kg of steam at temperature of 150 ∘C has 2.23×107 J of heat
removed from it. Determine the final temperature and phase of the
result once the heat has been removed if the heat is removed at
constant pressure during the gas phase.
For this problem, use the specific heat (at constant pressure)
for water as 1850 J/kg∘C , the latent heat of vaporization as
2.256×106 J/kg , the specific heat of liquid water as 4186 J/kg∘C ,
the...

The latent heat of vaporization (Lv) is similar to
the latent heat of fusion (Lf), except that it relates
to boiling rather than melting. For water, Lv = 2.26 x
106 J/kg. .970 kg of steam at 100°C (the boiling point
of water) is put in contact with a 13.5 kg piece of metal. The
initial temperature of the piece of metal is 70.0°C. When the piece
of metal reaches 100°C, .0420 kg of steam has condensed.
a. How
much heat...

The latent heat of vaporization (Lv) is similar to
the latent heat of fusion (Lf), except that it relates
to boiling rather than melting. For water, Lv = 2.26 x
106 J/kg. .970 kg of steam at 100°C (the boiling point
of water) is put in contact with a 13.5 kg piece of metal. The
initial temperature of the piece of metal is 70.0°C. When the piece
of metal reaches 100°C, .0420 kg of steam has condensed.
a. How
much heat...

1. You need design a freezer that will keep the temperature
inside a -5.0 C and will operate with a temperature inside at 5.0 C
and will operate in a room with a temperature of 22.0 C. The
freezer is to make 20.0 kg of ice at 0.0 C starting with water at
20.0 C. For water, the specific heat is 4190 J/kg-K, the heat of
fusion is 333 kj/kg.
a. How much energy must be removed from the water...

8.33 kg of steam at temperature of 150 ∘C has 2.23×107 J of heat
removed from it. Determine the final temperature and phase of the
result once the heat has been removed if the heat is removed at
constant pressure during the gas phase. For this problem, use the
specific heat (at constant pressure) for water as 1850 J/kg∘C , the
latent heat of vaporization as 2.256×106 J/kg , the specific heat
of liquid water as 4186 J/kg∘C , the...

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