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The Importance of the high specific heat capacity of water

Hi, everybody. Thank you for watching my video on Physics.

In this video, we shall discuss about the importance of the high specific heat capacity

of water.

Recall that specific heat capacity or simply specific heat is a measure of the ability

a substance to store heat. Alternatively, it indicates the degree of difficulty in raising

the temperature of a substance. The higher is the specific heat capacity, the more it

is difficult to raise its temperature. Water has the highest specific heat compared with

all other materials. It means that it requires the largest amount of energy to raise the

temperature of 1 kg of water by one degree Celsius compared with all other materials

also of mass 1 kg and also by a change in temperature of 1 oC.

This special property of water is used by people in many daily applications. It also

explains many phenomena.

In one daily application, water is used as a coolant to remove excessive heat from engines.

All vehicles that consume fossile fuel, such as petroleum or diesel, burns the fuel inside

the engine. This process is called combustion and the process turns liquid fuel into hot

gases. The dramatical increase in volume provides the propelling force of vehicles. The hot

gas produced is at a temperature higher than 1000oC, heating up the engine.However, the

temperature of the engine should not increase uncontrollably. Otherwise, the bearings and

other parts will melt and the engine will fail to work. Therefore, the excessive heat

must be removed to keep the engine working at its operating temperature.

The cooling system of an engine consists of a set of water pipes filled with a coolant,

which is mainly water, and a pump which drives the water through the engine. When water passes

through the outer surface of the engine cylinders, it absorbs the excessive heat through conduction.

On leaving the engine, the temperature of water can be as high as 100oC. It needs to

be cooled so that the whole process can be repeated. This is done by the radiator. The

radiator consists of many narrow pipes to increase the surface area so that heat from

the hot water can be transferred to air. A fan is used to blow cool air through the pipes

to enhance the heat removal through convection. Fins are installed on the surface of the pipes

to further increase the surface area.

No matter what price of the car is, water is used as the coolant. The advantage of using

water is that it is cheap and readily available. However, water may cause rusting and it may

freeze when temperature falls below 0oC. As long as the engine is working, rusting will

not occur. On the other hand, there are many places in this world at sub-freezing temperature.

Freezing of water inside the engine will cause great problem because when water freezes,

it will expand. This will cause damages to the water pipes. The solution is to use anti-freeze

coolant. It is a mixture of Ethylene glycol and water. With the antifreeze, the melting

point can be lowered from 0oC down to -37oC. It means that the coolant will remain in liquid

form in many cases.

Water is used in cooling the steam turbines of all power stations. It is also used in

bringing away the heat from nuclear reactors. This explains why white mists are often seen

emerging from the chimney of nuclear power plants. The catastrophic explosion of the

nuclear power plant in Fukushima, Japan after the earthquake in 2011, was caused by the

malfunctioning of the cooling system. Since the pump that drives the water through the

hot nuclear core failed to work, the high temperature causes chemical reaction that

produces hydrogen gas to take place. As the hydrogen gas accumulated beneath the roof,

an explosion subsequently occured, blowing off the roofs of three nuclear power reactors.

Water is used in some central air-conditioning systems, installed in the place where commercial

buildings, shopping mall, airport, or hotel, comprising of several floors. Here, water

is cooled first by the refrigerant to a very low temperature of about 6 to 8 degree Celsius.

This cold water is pumped to different rooms through water pipes. Air is blown through

the pipes. This air passing over the pipes gets cooled and is then passed to the air

conditioned space.

In biology, some animals have to maintain their body within a small temperature range,

because temperature affects the rate of chemical reactions and this, in turn, affects the functions

of the organs inside the animals. In humans, the normal body temperature is 37.0 °C (98.6

°F). For example, we may feel uncomfortable if our body temperature is too high, when

we are in fever. Thanks to water which makes up 70% of our body, our temperature will remain

more or less steady even though the external temperature changes rapidly. This effect is

called temperature damping.

Temperature damping is important to the survivals of animals in case of dangers. For example,

if there is a forest fire, the external temperature may rise quickly. Thanks to water which exists

in all animals, the body temperature of the animals will not increase suddenly. Temperature

damping allows the animals to have enough time to escape from the dangers, once they

feel the heat from the fire.

The high specific heat capacity of water moderates our climate and allows for life on Earth.

Currently, the average Earth’s surface temperature is about 14oC. Since the industrial Revolution

200 years ago, people have been burning a huge amount of fossil fuel everyday. How much?

According to IEA (International Energy Agency) reports, more than 80 million barrels of oil

and liquid fuel are consumed everyday! This gives out a huge amount of internal energy.

On the other hand, the carbon dioxide produced by burning fossil fuel will trap the heat

from the Sun. This further increases the amount of internal energy stored in the atmosphere.

However, regardless of this huge amount of extra heat supplied, the average temperature

of the Earth’s surface does not change too much. Since the Industrial Revolution 200

years ago, it has increased by 1oC only. This shows that our Earth has a very very large

large heat capacity and the ocean plays an important role. Scientists predict that at

4 to 5oC global warming, all ice sheets will disappear and rain forests will have burnt

up. At 6oC global warming, there will be no living things on Earth anymore. Therefore,

it is an urgent task for us to control global warming.

On the other hand, the high specific heat capacity of water explains the difference

in the daily temperature ranges between coastal region and inland region. Since it takes a

great deal of heat to warm up water, water stays cool longer, and acts as an effective

coolant. On the other hand, once the water is warmed up, it takes a great deal of heat

release to cool the water. This explains why the difference in daily maximium and minimum

temperatures in coastal regions like Hong Kong is only several degree Celsius.

In summary, you have learned the effects of the high specific heat capacity of water.

We have learnt that water is used as coolant for engines, central air-conditioning systems,

and power stations. Water accounts for the temperature damping of animals. It also explains

the climate of our Earth and the small daily temperature range in coast regions.

Question. 1. Suggest other examples of using water as coolant. 2. Explain why fishes in

ocean disappear when water temperature increases. 3. What will you do to help controlling global

warming?

Be the first to write your answers in the comments below. You are welcome to comment

on the answers of other people.

I hope this video can help you understand more about the importance of high specific

heat capacity of water. Thank you for watching.