Thermal energy, or heat energy, is one of the most accessible energies to experience. We understand the warmth of the sun, the joy of bathing in warm thermal springs, and the comfort of a warm beverage on a cold winter’s day. These examples seem similar yet are very different from each other — you can’t drink the sun or sunbathe under a cup of tea.
Heat, temperature, and thermal energy are all interlinked but slightly different; thermal energy is the more challenging one to define scientifically.
Let’s take an in-depth look at thermal energy and widen our appreciation of its extraordinary ubiquity.
What Is Thermal Energy?
First of all, it’s important to note that thermal energy and heat energy are names that describe the same thing. Thermal energy is the total amount of energy something has based on its temperature.
Solids, liquids, and gases are made of molecules and atoms moving around and colliding with each other. This movement is known as kinetic energy, and this movement, or vibration, gives off thermal energy.
Increasing the temperature of something makes these molecules and atoms move around more quickly, giving it more thermal energy. Hot water has more thermal energy than cold water.
Colder objects’ molecules and atoms move more slowly and have less thermal energy than warmer objects.
What Are the 3 Main Types of Heat Transfer?
When dealing with thermal energy, there are three main ways heat can be transferred to change the thermal energy of a system:
- Convection
- Conduction
- Radiation
As an example for all three, we’ll use an open campfire and a pan full of cold water to illustrate all three forms of heat transfer that change an object’s thermal energy.
Convection is the movement of heat between an object and a fluid. When we put our pan of cold water on the campfire, there is a transfer of thermal energy as convection currents occur in the water. The warmed water is less dense and rises, while the denser cooler water sinks to the bottom of the pot and then warms in convection currents.
Conduction is the internal transfer of heat through an object or between objects that are in contact. An object at a higher temperature sees its thermal energy flow to an object with a lower temperature. Let’s return to our pan. Conduction means the heat flows through the pan to its handle, warming it up. Many pots and pans are made of metal because metals conduct heat well.
Radiation is the transfer of energy by electromagnetic waves; the sun is the best example of this. The sun’s heat cannot reach Earth via convection or conduction — the surfaces do not touch, and there is no way for molecules to collide. It travels through space as a light wave, or electromagnetic radiation.
Our campfire is the same. Thermal energy can make light. You can see some of its light, and some of its light waves are not visible — however, they do carry thermal energy. When you stand closer to a campfire, you can see someone more clearly and feel warmer.
These flows of thermal energy can go from a warmer object to a cooler object or vice versa.
Thermal equilibrium occurs when no thermal energy is exchanged between objects because they are at the same temperature. This can happen naturally or when the entities exchange heat (one warming, one cooling) until they achieve parity.
How Do We Calculate Thermal Energy?
When we measure something’s thermal energy, it is gauged by its entire body. We take into account its:
- Temperature
- Mass
- Material
For example, a 24-ounce glass of water at 158 Fahrenheit (70 Celsius) has more thermal energy than a 12-ounce glass of water at the same temperature. They are at the same temperature – the water molecules of both have the same average kinetic energy — but the 24-ounce glass has twice as many molecules, giving it more thermal energy.
Does Heat Affect All Objects Differently?
Yes, different objects react differently to heat. Temperature and mass affect an object’s thermal energy, as does its material. An object’s ability to transfer heat depends on its composition.
For example, water requires a more significant amount of heat to warm up than fat. This is known as heat capacity. An object’s or substance’s heat capacity is measured by the amount of energy needed to heat one gram of it by one degree Celsius (1.8 degrees Fahrenheit).
What Is the Formula for Thermal Energy?
Materials have different specific heat capacities. This heat capacity changes based on the object’s material as well as its mass.
Specific heat capacity is measured in Joules, the quantity of heat required to raise the temperature of something, per kilogram (2.2 pounds) of that material, by one degree Celsius.
- Water: 4,200 Joules
- Iron: 450 Joules
- Lead: 130 Joules
- Wood: 1,700 Joules
Formula: Specific heat capacity = thermal energy input / (mass) x (temperature change)
Some of these materials can be in solid, liquid, or gas form.
An object’s specific latent heat is the amount of energy required to change the state of one kilogram (2.2 pounds) of that material — for example, turning an ice cube into water.
We also measure thermal energy held by fuels and energy sources in British Thermal Units (Btu).
What Is a British Thermal Unit?
A British Thermal Unit (Btu) quantifies the heat content contained by energy sources. However, the Btu uses Fahrenheit and pounds instead of Celsius and kilograms and is specific to water.
Water is most dense at 39 degrees Fahrenheit (3.88 Celsius). One British Thermal Unit is the quantity of heat needed to heat one pound of water by one degree Fahrenheit, from 39 degrees to 40 degrees Fahrenheit.
One Btu is a relatively small energy measurement; burning a match releases around one British Thermal Unit.
The Btu is valuable because it allows us to compare energy sources on an equal basis.
Why Is Thermal Energy Important in Daily Life?
We’ve looked at what thermal energy is and how we quantify it. Now, let’s see how it impacts our daily lives.
Thermal energy plays an intrinsic part in almost every aspect of the globe. As we’ve seen, when we talk about it being hot at a certain time of day, that’s not thermal energy. Here’s how thermal energy interacts with our environment.
What’s the Difference Between Heat and Temperature?
People often interchange the words heat and temperature, and we understand their meaning. Heat and temperature are very similar, but they are different.
Heat, measured in Joules in the International System of Units (SI), is a form of energy that can transfer from one object to another. You can make cocoa powder warmer by adding hot milk to it. Heat can do useful work; heating cocoa as the flow of thermal energy moves from the milk into the cocoa powder. Heat is the transfer of thermal energy.
Temperature is just that, a snapshot of the temperature of an object. In the scientific world, it is measured in Kelvin as an SI unit. Temperature measures a variable in the way we record speed or weight.
What Is a Practical Example of a Thermal Energy Increase?
Temperature is not the same as thermal energy. Temperature is a snapshot of the average kinetic energy in a body (solid, liquid, or gas).
Let’s assume we are inside a house or building and our body is at room temperature. We move outside on a warm, sunny day to sunbathe and immediately notice a temperature difference. After a short while, we feel warmer. Our body’s molecules and particles move around more quickly. This increase in our temperature, or temperature change, occurs because there has been an increase in thermal energy.
Other examples include the heat our hands make when we rub them together, burning rubber when car tires skid, and a saw blade heating up as we saw wood.
How Do We Use Thermal Energy, Day to Day?
Thermal energy is all around us, from opening the curtains to greet the morning to keeping warm on cold winter evenings.
The sun’s thermal energy warms the Earth, helping plants grow and powering wind energy and solar panels. Many countries have embraced geothermal energy, harnessing energy from below the Earth’s crust to heat homes and create electrical energy.
Burning fossil fuels like oil and coal create heat and thermal energy, which we use to drive turbines to produce electricity.
On a micro-scale, we cook food, dry clothes, and light fires to keep us warm, all making the most of thermal energy. If we use electrical items, it’s a double dose of thermal energy use — the first to make electricity, the second to use that electricity to heat your food or home.
Does Thermal Energy Harm the Environment?
Thermal energy affects the environment in many ways. The sun shines, and it may start wildfires or burn crops, but this is part of the world’s natural cycle.
However, the ways humans use thermal energy can harm the environment.
Fossil fuel extraction is a polluting business. Burning these fuels to create electricity or power vehicles adds carbon emissions to the atmosphere. These contribute to climate change and global temperature rises.
Similarly, nuclear reactors use thermal energy to create electricity. The process has byproducts of steam and hot water that pollute and damage if released into the local environment. Geothermal plants may discharge steam or hot water into surrounding waterways, harming wildlife.
Some thermal energy creation is accidental. Landfill sites, with trash buried, can create very high temperatures within them and even combust.
Thermal energy itself is a naturally occurring part of our world, but it can harm the environment.
When Was Thermal Energy First Discovered?
English physicist James Prescott Joule stood on the shoulders of previous scientists with his work on thermal energy. A brewer’s son, he had no official schooling, yet his experiments became the cornerstone of the First Law of Thermodynamics.
Joule understood mechanical actions and movements created heat energy. He measured the amount of thermal energy in a physical system by taking a moving object, in this case, a paddle, and moving it continuously through the water.
The water displayed different temperatures depending on the mechanical energy used. Joule presented his work to the Royal Society of London in June 1849, stating that the water temperature increases were thermal energy.
The work was important. According to the law of the conservation of energy, the energy of a system cannot be destroyed. Energy can only be transformed from one form of energy into another.
Joule showed that thermal energy is part of the conservation of energy. His experiments showed that a system’s internal energy change equals the heat absorbed minus work carried out.
Thermal Energy, Heat, and Temperature: A Review
Thermal energy surrounds every aspect of our life, from warming someone up with a hug to burning our fingers on a hot object.
Thermal energy is the transfer of heat from one object to another, a flow of energy. In contrast, a snapshot of something’s heat is its temperature.
One of the most pressing questions facing the world is global warming. We have a vital choice to make about our interactions with thermal energy. Do we keep transferring thermal energy from fossil fuels to power society, or do we harness the sun’s free energy?
Fortunately, there is something you can do now. Contact your electricity company and ask about green energy packages so you can enjoy your lifestyle while doing your part to save the planet.
Brought to you by amigoenergy
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