Monday
Monday: Hot, Cold and In Between
Rocket sets two ice cubes on two plates. One plate goes on the sunny windowsill, the other in the shade at the Bench.
"Race," he says, and starts a timer. Ten minutes later, the sunny cube is a puddle with a sliver in the middle.
The shaded cube has only a wet ring. "What do you notice?" Raven asks, pencil ready.
"The sun cube melted faster," Rocket says. "The sun heated it."
Nova hovers between the plates, her light soft. "Heated it how?" she asks. "Think about the water particles. What are they doing differently in the sun?"
Rocket frowns, then grins. "Moving faster. Jiggling until they break loose."
Raven writes a new heading in the Bench Log: Temperature, Heat and Melting.
What temperature really measures
Temperature is a measure of how hot or cold an object is. In the particle model it means something precise.
Temperature is a measure of the average kinetic energy of the particles in matter. Kinetic energy is the energy of motion.
In a hot gas, the molecules move faster than in a cold gas. The particles have the same mass, but more kinetic energy, so the temperature is higher.
When a substance is heated, some of the energy increases the motion of its particles. You see that as a rise in temperature.
The motion of the atoms or molecules within a substance is called its thermal energy.
What heat really means
In everyday talk, "heat" can mean the thermal energy inside something or the energy moving from one thing to another.
In science, heat has only the second meaning. Heat is energy transferred from one object to another because of a difference in temperature.
Heat always flows from the object at the higher temperature to the object at the lower temperature.
The flow continues until the two objects are at the same temperature. Then they are in thermal equilibrium.
That is why the sunny ice cube melted first. Warm air and sunlight transferred thermal energy to the cold ice.
- Read the question.
- Tap your answer.
| Statement | True or false? |
|---|---|
| In a hot gas, the molecules move faster than in a cold gas. | ? |
| Heat flows from a colder object to a warmer object. | ? |
| Thermal energy is the motion of atoms or molecules within a substance. | ? |
| Two objects at the same temperature keep exchanging heat. | ? |
| Kinetic energy is the energy of motion. | ? |
- Tap a card.
- Then tap its spot.
Which spoon transferred heat to you, and which took heat from you? Write it in your Bench Log.
A grown-up handles any kettle, stove or microwave, and hot water hotter than the tap.
The facts this week come from NASA Glenn, the Next Generation Science Standards, the United States Geological Survey and LibreTexts chemistry.
Clear thinking. Tomorrow you will meet the thermometer and the three scales that put numbers on hot and cold.