Heat Energy

Most of us associate the word “heat” with something that feels warm, but in science, heat is defined as the transfer of energy from a warm object to a cooler object. Actually, heat energy can be found everywhere – in volcanoes, icebergs, and even in your own body. Heat energy can be found in all matter.

Heat energy is the result of the movement of tiny particles known as atoms, molecules, or ions in solids, liquids, and gases, and it can be measured in degrees Celsius. The transfer of heat energy from one object to another is possible. Heat is defined as the transfer or flow of energy between two objects as a result of a temperature difference between the two objects.

The heat energy contained in an ice cube, for example, and the heat energy contained in a glass of lemonade. Putting ice in lemonade will cause the lemonade (which is warmer) to transfer some of its heat energy to the ice, resulting in a more refreshing drink. In other words, it will cause the ice to warm up. Eventually, the ice will melt, and the lemonade and the water from the ice will be the same temperature as each other again. Achieving a state of thermal equilibrium is the technical term for this.

Moving particles

Matter can be found all around you. Anything that has both mass and volume, as well as taking up space, is considered matter in the universe. Matter can be found in a variety of physical states, including solids, liquids, and gases.

Atoms, molecules, and ions are the smallest possible particles that make up all matter. These microscopic particles are constantly in motion, either bumping into one another or vibrating back and forth between them. The movement of particles results in the generation of a type of energy known as heat (or thermal) energy, which is found in all matter.

Solid particles are tightly packed and can only vibrate due to the tight packing. Similarly to solid particles, liquid particles vibrate and can move around by rolling over each other and sliding around on the surface of the liquid. In gases, the particles are free to move around in a rapid and random manner.

Transferring heat energy – particles colliding with one another

Particles have more energy when they are exposed to higher temperatures. The energy contained within these particles can be transferred to other particles that are at a lower temperature. For example, when a fast-moving particle collides with a slower-moving particle in the gas state, the fast-moving particle transfers some of its energy to the slower-moving particle, increasing the speed of the slower-moving particle.

Due to the collisions of billions of moving particles with one another, an area of high energy will gradually spread across the material until thermal equilibrium is reached (the temperature is the same across the material).

Heat transfer is responsible for changing states.

Particles that are moving faster than others ‘excite’ nearby particles. When a solid is sufficiently heated, the movement of particles within it accelerates and eventually overcomes the bonds that hold the particles together. The substance undergoes a transformation from a solid to a liquid state (melting). If the movement of the particles in the liquid continues to increase, a stage is reached at which the substance transforms into a gas.

There are three methods of transferring heat energy.

Convection is the process by which heat energy is transferred through gases and liquids. During the heating of air, the particles gain heat energy, which allows them to move faster and further apart while transporting the heat energy they have absorbed. Warm air is less dense than cold air, so it will rise in the atmosphere. Cooler air is drawn in from below to replace the hot air that has risen to the surface. It heats up, rises, and then is replaced by cooler air, resulting in a circular flow known as a convection current in the atmosphere. These currents circulate around the room, heating it.

In solids, conduction is the process by which heat energy is transferred. The moving particles of a warm solid material can increase the heat energy of the particles in a cooler solid material by transferring heat energy directly from one particle to the next as they move through the solid material. Solids conduct heat more efficiently than liquids or gases because their particles are closer together. 

Radiation is a method of heat transfer that does not require the transfer of heat energy by directly using the particles. Infrared waves, on the other hand, are used to transfer heat (part of the electromagnetic spectrum). Heat waves radiate out from hot objects in all directions, travelling at the speed of light, until they collide with another object and continue their journey. When this occurs, the heat energy carried by the waves can either be absorbed or reflected, depending on the situation.

The three different methods of heat transfer are illustrated by the flames. Convection, for example, will cause the firebox to heat up as it burns. Because of convection, the air above the fire will become warm. Radiant heat transfer allows you to warm your hands when they are close to the flames.

Expansion

When heated, gases, liquids, and solids all expand in volume, regardless of their composition. During the cooling process, they contract, or shrink in size. The reason for the expansion of gases and liquids is that when they are heated, the particles move around very quickly and are able to move further apart, resulting in the particles taking up more space. When a gas or liquid is heated in a closed container, the particles collide with the sides of the container, resulting in pressure being built up in the container. When there are a large number of collisions, the amount of pressure increases.

When a house is on fire, it is not uncommon for the windows to explode outwards. In part, this is due to increased heat generated in the house, which causes the excited molecules to travel at high speeds around the room. They are pushing up against the walls, the ceiling, the floor, and the windows of the building. Because the windows are the weakest part of the house’s structure, they break and burst open, allowing the increased pressure to be released from the structure.

Conclusion

Because of a temperature difference between two bodies, heat can be transferred from one to the other, transferring energy. Two bodies with different temperatures brought together result in the transfer of energy; in other words, heat is transferred from the hotter body to the colder body. It is usually, but not always, the case that the effect of this transfer of energy is an increase in the temperature of the colder body while a decrease in the temperature of the hotter body occurs.