The matter is everywhere. It is one of the building blocks of the visible. Everything that possesses volume (takes up space) and mass is matter. Matter occurs in different forms like gas, liquid, and solid. Every matter is made up of particles called atoms, ions, and molecules. These particles are continuously in motion, always vibrating and hitting each other. It is the movement of particles that generates a type of energy known as heat energy that exists in every matter.
Heat energy is the energy transmitted from one system to another system due to the variation in temperature. When two systems with different temperatures are placed close to each other, heat energy flows from the hotter system to the colder system. The consequence of the heat transfer is the increase in the colder system’s temperature and a decrease in the hotter system’s temperature. A material could absorb heat energy without a rise in temperature by varying from one physical phase or state to another. Melting, sublimation, boiling, and crystalline transition are familiar examples of this phenomenon.
The significant difference between temperature and heat is that temperature is the measure of the quantity of heat in a system, and heat is a type of energy. This clear distinction between heat and temperature was understood during the period of the 18th century.
Generally, the quantity of heat energy needed to raise a material’s unit mass through a particular temperature is known as the specific heat or heat capacity of the given material. The amount of heat required to increase a body’s temperature by one-degree changes depending upon the external constraints imposed on the body. When heat is transmitted to a gas with a constant volume, the heat required to raise its temperature by one-degree is less than the heat energy transmitted to the same gas free to expand, and so does work (as in a container fixed with an adjustable piston). In the first scenario, the entire energy goes into increasing the gas’s temperature. In the second scenario, the energy contributes to the increase in the gas’s temperature and provides heat energy essential for the work done by the given gas on the piston. So, the specific heat of the material relies on these conditions. The commonly measured specific heats are the specific heat at fixed volume and specific heat at a fixed pressure. In 1819, Alexis-Thérèse Petit and Pierre-Louis Dulong showed that the heat capacity of numerous solids was closely connected to their atomic weights. This is known as the Dulong Petit law. It is useful in calculating the atomic weight of some metallic elements. However, there are numerous exceptions to the law.
Heat is not energy stored in a system. Heat is just restricted to energy being transmitted. However, heat is not work even though work is also energy in motion.
Air is a combination of water vapour and gases. It is quite possible for water vapour in the air to change phase and become solid or liquid. To differentiate between the energy connected with the phase change or latent heat and the energy needed for a temperature change, the idea of sensible heat was put forward. In the mix of air and water vapour, the sensible heat is the heat required to generate a particular temperature variation except for any energy needed for a phase change.
The video is about the visualisation of heat
Important Heat Energy Questions with Answers
1) What is heat energy?
Heat energy is the energy transmitted from one system to another system due to the variation in temperature. When two systems with different temperatures are placed close to each other, heat energy flows from the hotter system to the colder system.
2) Explain the transformation of states by heat transfer.
Faster travelling particles energised nearby particles. When heated ideally, the motion of particles in a solid object rises and breaks the bonds that hold the individual particles together. The material changes its physical state from solid form to liquid form (melting). If the motion of the particles rises further in the liquid state, then the object is changed into the gaseous state (evaporation).
3) What is meant by heat transfer?
Heat energy is the energy transmitted from one system to another system due to the variation in temperature. When two systems with different temperatures are placed close to each other, heat energy flows from the hotter system to the colder system. The consequence of the heat transfer is the increase in the colder system’s temperature and a decrease in the hotter system’s temperature. A material could absorb heat energy without a rise in temperature by varying from one physical phase or state to another.
4) What are the three methods of transferring heat?
Heat energy is transferred in three distinct ways: convection, conduction, and radiation.
5) What is meant by convection?
Convection transmits heat energy through liquids and gases. When air is heated, the particles acquire heat energy enabling them to move further and faster, bearing the heat energy with the particles. Cold air is much denser than warm air, so hot air will rise. Relatively cooler air goes below to cover the region that has been abandoned by the warm air. Warm air particles heat up, rise and are again replaced by colder air particles, producing a cyclic flow known as a convection current.
6) What is meant by conduction?
Conduction transmits heat in solids. The moving solid particles of a warm solid substance can raise the particles’ heat energy in a colder solid substance by transmitting it directly from one individual particle to the next. As solid particles are very close to each other, solid materials conduct heat energy better than gases or liquids.
7) What is meant by radiation?
Radiation is a way of heat transfer where it does not need particles to bear the heat energy. In this case, heat is transmitted in infrared waves (an electromagnetic form). Heat waves come out from hot materials from every direction, propagating at light speed until they strike another material. When this occurs, the heat energy possessed by the moving waves can be either reflected or absorbed.
8) Explain the concept of sensible heat.
Air is a combination of water vapour and gases. It is quite possible for water vapour in the air to change phase and become solid or liquid. To differentiate between the energy connected with the phase change or latent heat and the energy needed for a temperature change, the idea of sensible heat was put forward. In the mix of air and water vapour, the sensible heat is the heat required to generate a particular temperature variation except for any energy needed for a phase change.
9) Explain the different heat transferring methods shown by fire.
Fire displays distinct ways of heat transfer. The firebox acquires heat due to convection. We can warm our hands near the fire due to the heat radiating from the firebox.
10) Explain the concept of expansion produced by heat.
Expansion is an effect caused by heat. When solids, liquids, and gases are heated, they expand spontaneously according to their binding forces. The expansion of liquids and gases happens as particles move very fast when they are being heated and are able to travel further away from each other so that they can take up more space. If the liquid or gas is heated in an enclosed vessel, each particle collides with the sides of the vessel, and this generates pressure. The higher the count of collisions, the higher the pressure.
When a building is on fire, the windows might explode outwards. This is mainly due to the expansion of air in the building as the fire heats up the entire region. The energised molecules travel at high speed in the region. As windows are the most fragile part of the building structure, they explode and release the inflicted pressure.
11) Can sound waves produce heat?
Yes, sound can produce heat. Sound waves always produce a small amount of heat as they propagate and could end up as heat when the waves are absorbed. Both heat and sound are explicit descriptions of the motion of molecules and atoms. Sound is the motion of atoms and molecules in ordered wave patterns. Heat is a type of disordered motion of molecules and atoms. Therefore, to convert sound waves into heat is by transforming the ordered motion of the molecules and atoms into disordered motion.
12) What is the difference between temperature and heat?
The significant difference between temperature and heat is that temperature is the measure of the quantity of heat in a system, and heat is a type of energy. This clear distinction between heat and temperature was understood during the period of the 18th century.
13) What is the relationship between temperature and kinetic energy?
At greater temperatures, particles typically have more kinetic energy. This extra energy can be transferred to other particles or systems which are at a lesser temperature. In the case of the gas state, when vigorously moving particles collide with slower-moving particles, these faster-moving particles transmit their energy to the slower-moving particles, raising the speed of those particles. As billions of particles collide with each other, areas of high energy slowly transfer across the system until thermal equilibrium is attained (identical temperature all across the system).
14) What is specific heat or heat capacity?
Generally, the quantity of heat energy needed to raise a material’s unit mass through a particular temperature is known as the specific heat or heat capacity of the given material. The amount of heat required to increase a body’s temperature by one-degree changes depending upon the external constraints imposed on the body.
15) What is meant by latent heat?
Latent heat (heat of vaporisation) is the amount of energy required to convert a liquid to a vapour form at constant pressure and temperature. The heat of fusion is the energy needed to change a solid to a liquid. The energy required to transform a solid body directly to its vapour state is called heat of sublimation. These transformations also occur under constant pressure and temperature.
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Practice Questions
1) What is the cause of heat?
2) How do you measure heat?
3) What are the laws governing the flow of heat?
4) What is the relationship between temperature and heat?
5) What is the connection between the kinetic energy of particles and temperature?
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