Published by: BhumiRaj Timalsina
Published date: 31 Jan 2022
All living beings including plants and animals need heat energy for their survival. You must have noticed that with the beginning of winter season, the leaves start to fall down from the trees. Most of the trees look bare and appear to be dry. Every year, we also get the news from different sources as radio, T.V, news papers, etc. that some persons died because of hypothermia. For our domestic cooking purposes, to run the factories, industries and transportation vehicles, a proper heat source is needed. Excess of heat energy than necessary is also harmful to us. We feel uneasy when the atmospheric temperature shoots up than a certain limit.
Thus excess of heat energy is not beneficial to the living beings. It cause more harm than benefit. Heat is a form of energy. It can be transformed to another form (type) of energy and vice-versa.
More or less, any hot body acts as a source of heat energy. Sun is the Taking heat of Sun Unit -4 prime source of heat energy in the earth. We feel chilly during the winter time, when we do not get sufficient amount of heat energy from the sun. It is the same reason that night time is cooler than the day time. In the absence of sun no life will survive on our planet, earth. The sun rays give warmth to the earth, air, water etc. In nature we get water cycle because of the sun. Water is constantly evaporated in nature and hence we get water cycle. At present the solar energy is also used to heat water and for other heating purposes. The solar cells collect solar heat energy and in return give current electricity which is used for lighting and other useful purposes.
The fuel energy which is obtained from living organisms such as bio-gas, dry cakes of cow and buffalo dung, straw, hay, wood, etc. is known as the biomass-fuel. In the villages these fuels are generally used for cooking and warming the rooms during winter season. The people even sit around the burning bio mass fire to avoid coldness. Some villagers generate the bio-gas by collecting dung in a specially made pit and get bio-gas from the decomposed biomass.
The fuels like, coal, kerosene, petrol, diesel, natural gas ,etc,. which are obtained from the earth's crust are called the fossil fuels. Domestic cooking is also done by burning coal and kerosene oil. The natural gas or the L.P.G. (liquefied petroleum gas) is mainly used for cooking, room heating etc. Fuels like petrol, diesel oil are generally used for running means of transport like motor cycles, cars, aeroplanes, etc. When these fuels are burnt, the necessary heat energy is produced for running the engine. So fossil fuel is one of the main source of heat energy.
Electricity is also one of the source for heat energy. In the city and in some villages, people use current electricity for room heating during winter and cooking as well. But as the electricity bill is expensive, people hesitate to use it. Since our nation has high potential to generate hydro-electricity, if we can exploit existing natural hydro resources, the electricity bill will come down to a level at which common people also can use it. In fact there are other sources as well for the heat energy. But in our nation only the above mentioned few sources are available.
Heat energy can give different effect on the body. It can change the volume and produce physical changes on the bodies.
1. Physical change
Matter can have three different forms, as a solid, a liquid and a gas. For example, the solid form is ice, liquid form is water and the gaseous form is vapour. How does ice change into water and then to steam? The solid ice when heated changes into water. Water when heated turns into steam or vapour. Thus heat is the prime agent which converts the matter into different forms.
2. Change in volume
Matter in all its three forms, changes its volume when heat is applied on it.
As discussed in the preceeding sections, we find that heat energy is essential for the survival of all living beings. Human beings use heat energy to achieve various aspects.
(a) It keeps our body warm.
In the winter season, the cool air takes away heat energy from our body and we feel chilly. To keep our body warm we do different activities. To get the necessary heat energy, we burn fire, or use electric heaters, gas heaters or stand on the sun. Thus heat energy help us to keep our body warm.
(b) Use for cooking our food.
Under cooked or uncooked food may be harmful for our health. Except the fruits, the food we take has to be cooked properly. A well cooked food is tasty and helpful for the health. (c) Use for drying wet cloths : We need to use neat and clean cloth to be healthy for which we have to wash them routinely to clean them. The wet cloths are better dried in the sun. The solar heat energy evaporates water from the wet cloth. In the cloudy day the drying process takes longer time.
(d) Use for industrial production.
Heat energy is very essential to achieve the different aspects in our life. Without the necessary amount of heat energy plants cannot give grains, vegetables, and fruits. We also like to have biscuits, chocolates, noodles, etc to eat. We need heat energy to make them. Similarly to bake bricks in the kiln, to produce iron rods, cement, plastic and plastic goods, electric cables, toys and domestic utensils, heat is extremely essential. The needful heat energy, we generally get from coal, wood, natural gas, electricity , etc.
(e) To sterilize water.
Water we get from different sources as river, pond, lake, etc is generally contaminated. Even though it looks clear, it might contain different types of invisible bacteria. When water is heated to its boiling point, the different bacteria in it dies and the water becomes drinkable.
(f) To preserve grain, meat, fish and other food stuff.
We need necessary heat energy to remove moisture from the food grains, meat, fish etc so that they can be stored for a longer period of time. The moisture content in these food spoils them when stored.