Heat
Did you know that even a freezing cold block of ice contains heat? Join Bill Nye the Science Guy as we explore the invisible energy that keeps us warm, cooks our food, and drives the entire universe!
What is heat, really?
We feel it every day, but heat isn't a fluid or a solid object you can hold in your hand. So what exactly is it?
They zip around like crazy! Heat is simply energy that can do work. When things get hot, their tiny molecules move much faster and spread further apart. That spreading out is exactly what makes a hot air balloon expand and float!
Yes! Because a glacier is made of molecules, and those molecules are still moving (just very slowly), it still contains heat energy. In fact, everything in the entire universe has at least a little bit of heat!
Put Your Instincts to the Test
Test your instincts before we dive into the science of heat transfer. Pick an answer for each scenario.
The ice swan! Even though it is much colder, the massive ice swan has billions more molecules than the tiny match. Because heat energy depends on the amount of matter, more molecules mean more total heat energy.
The metal knife! Metal is an excellent conductor. The fast-moving hot water molecules bump into the metal molecules, passing the heat energy right up the handle.
It travels as invisible light waves! This is called radiation. Because space is a vacuum (meaning it has almost no molecules), heat cannot travel by conduction or convection. It must travel as radiant infrared waves.
Understanding the Science
Let us break down exactly how heat moves around the universe and why molecules are the secret to understanding temperature.
Key Concepts
Conduction
Tap to learn moreThe transfer of heat directly from one object to another when they are physically touching. Fast-moving molecules bump into slower ones, passing the energy along. Example: A pancake cooking on a hot metal griddle.
Convection
Tap to learn moreThe transfer of heat by currents moving through a liquid or a gas. As air or water heats up, the molecules spread out, become lighter, and rise. Cooler, heavier fluid sinks to replace it, creating a loop. Example: Hot air rising from a toaster to spin a paper snake.
Radiation
Tap to learn moreHeat energy travelling as invisible infrared waves through space. It does not need molecules to travel, which is why it can move through a vacuum. Example: The warmth you feel on your skin from a campfire, even if the wind is blowing cold air toward you.
Molecules & Speed
Tap to learn moreEverything is made of tiny particles called molecules. The temperature of an object is just a measurement of how fast its molecules are moving. More heat = faster molecules.
Try It: Energy Forms and Changes
Explore how heating and cooling iron, brick, water, and olive oil adds or removes energy. See how energy is transferred between objects in real time!
Apply Your Knowledge
Let us see if you can connect what you have learned about heat transfer to the real world.
Match the Scenario to the Heat Transfer Type
Click an object to select it, then click the matching description to place it.
Real-World Challenge
You are an engineer designing a brand new winter coat for explorers in Antarctica. Based on what Bill Nye the Science Guy taught us about trapping "puffy pillows of air", explain how your coat will prevent the explorer's body heat from conducting away into the freezing environment.
What Has Changed Since This Episode Aired
This episode aired in 1994. While the laws of thermodynamics have not changed, our technology definitely has!
Updated: Today, modern "cold climate heat pumps" use highly advanced refrigerants and variable-speed compressors. They can efficiently extract heat from the outside air even when temperatures drop down to -20 degrees Celsius! They are now a crucial tool in fighting global climate change because they do not burn fossil fuels.
Updated: Thermal imaging technology has shrunk drastically. Today, you can buy a tiny infrared camera attachment that plugs directly into the bottom of a standard smartphone. Firefighters use modern, highly portable versions built right into their helmets to see through smoke and find people in burning buildings.
Test Your Understanding
Answer these questions and get instant feedback. How many can you get right?
Results
Your score:
The iceberg and the match analogy is such a classic science brain-teaser from this episode. I’ve built an interactive lesson to go along with it, including a model where you can control the molecules yourself. Did you get a chance to try it out and test your knowledge yet?