Raven draws two columns in the Bench Log: Plain Cup and My Cup. "Every device needs something to beat," she says.
"The plain cup is the control," Rocket says. "Same water, same start, no wrapping."
Nova hovers over the thermometer. "And how will you know a change came from your design?" she asks. "Not from the room?"
"Same room, same time, same amount of water," Rocket says. "Change one thing: the cup."
Raven nods. "What do you notice about a fair test? It is mostly about what you keep the same."
"And I measure at the same minutes," Rocket adds. "Zero, five and ten."
"Then tomorrow," Raven says, "we find out if three layers beats one."
Insulated cup: when two objects at different temperatures touch, heat moves from the warmer one to the cooler one. They end at the same temperature. That is thermal equilibrium.
The bigger the temperature difference, the more heat moves. Your cup cannot stop this, but layers and trapped air can slow it.
Chemistry students build a simple heat tool from two nested foam cups and a cover. Well-insulated containers all but prevent heat moving in or out.
Cold pack: when a reaction absorbs heat, the heat comes from the thermal energy of the liquid, so its temperature drops. The standard suggests changing the type and the concentration of the substance.
Fizzing boat: baking soda and vinegar react and make carbon dioxide gas. In a closed bottle that gas builds pressure until a cork shoots out, which is why your boat stays open.
A fair test changes one thing and keeps everything else the same. Same water amount, same starting temperature, same room, same timing.
The thing you change is your design. The thing you compare against is the control: a plain cup, a cup of plain vinegar, or a boat with no fizz.
The standard limits testing to three measurements: amount, time and temperature. Your data table needs those three columns.
| Device | Keep the same | Change | Control |
|---|---|---|---|
| Insulated cup | Water amount, start temperature, room, timing | The wrapping and layers | A plain single cup |
| Cold pack | Liquid amount, start temperature, bag type | Amount of baking soda or strength of the liquid | Liquid with no baking soda |
| Fizzing boat | Pan of water, boat shape, start position | Amount of vinegar and baking soda | The boat with water instead of vinegar |
| Statement | True or false? |
|---|---|
| The bigger the temperature difference, the more heat moves. | ? |
| An insulated cup can make warm water warmer. | ? |
| A cold pack reaction takes heat from the thermal energy of the liquid. | ? |
| A fizzing boat should be sealed so the gas stays inside. | ? |
Plan complete. Tomorrow is Bench Lab: build your prototype, run the fair test and record real numbers.