Heat and Temperature
Grade 3 · Science · Study Guide
Learn the difference between heat and temperature and how heat moves.
Heat and temperature are related, but they're not the same thing! Temperature measures how hot or cold something is — we measure it in degrees using a thermometer. Heat is actually a form of energy that flows from warmer objects to cooler ones.
Think about what happens when you drop an ice cube into warm water. Heat energy flows from the water (warmer) into the ice (cooler) until they reach the same temperature — this is called thermal equilibrium. Heat always flows from hot to cold, never the other way around.
Heat can move in three ways. Conduction happens when heat travels through a material by direct contact — a metal spoon left in hot soup conducts heat to your hand. Convection happens in fluids (liquids and gases) when warmer, less dense material rises while cooler material sinks, creating a cycle — this is how a pot of water heats up evenly. Radiation is heat traveling as waves through empty space — the warmth you feel from the Sun is radiated energy that traveled 93 million miles through the vacuum of space!
Different materials conduct heat differently. Metals are excellent conductors — that's why metal feels cold to touch. Wood and plastic are insulators — they slow down heat transfer. Insulation in your home keeps warm air inside in winter and outside in summer.
Key terms
- temperature
- A measure of how hot or cold something is, measured in degrees
- heat
- Thermal energy that flows from warmer objects to cooler objects
- conduction
- Heat transfer through direct contact between objects or particles
- convection
- Heat transfer through the movement of fluids (liquids or gases)
- radiation
- Heat transfer through waves, even through empty space
Flashcards
- temperature
- How hot or cold an object is, measured with a thermometer in degrees
- heat
- Thermal energy that transfers from warmer objects to cooler ones
- conduction
- Heat transfer through direct contact
- convection
- Heat transfer through fluid movement (warm rises, cool sinks)
- radiation
- Heat transfer through electromagnetic waves, including through empty space
- insulator
- A material that slows heat transfer, like wood or rubber
Practice questions
What happens when heat energy is added to ice?
- The ice gets heavier
- The temperature decreases
- The ice melts and temperature may rise
- Nothing changes
Show answer
Answer: The ice melts and temperature may rise
When heat is added to ice, the energy breaks apart the water molecules' rigid structure. Ice melts into liquid water, and then the water temperature rises as more heat is added.
Heat always flows from cooler objects to warmer objects.
Show answer
Answer: False
Heat always flows from regions of higher temperature to regions of lower temperature — from hot to cold. This is a fundamental law of thermodynamics.
Heat transfer through direct contact between objects is called ___.
Show answer
Answer: conduction
Conduction occurs when heat is transferred directly between materials in contact. Metal conducts heat well because its loosely held electrons can carry thermal energy quickly.
How does the Sun's warmth reach Earth through the vacuum of space?
- Conduction
- Convection
- Radiation
- Insulation
Show answer
Answer: Radiation
Radiation transfers heat as electromagnetic waves — mainly infrared radiation. It's the only type that can travel through the vacuum of space, which is why we feel sunlight's warmth.
Metals are good conductors of heat.
Show answer
Answer: True
Metals are excellent heat conductors because of their molecular structure. This is why a metal spoon in hot soup quickly becomes hot to touch.
Fun facts
- A thermos bottle keeps liquids hot or cold by using a vacuum layer — heat cannot travel through empty space by conduction or convection!
- Your body temperature stays at about 98.6°F (37°C), and even a 2-degree rise means you have a fever.
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