Raven lays a table from a chemistry text on the Bench. "Specific heats," she says. "How much energy it takes to warm one gram by one degree."
Rocket runs his finger down the list. "Water, 4.18. Iron, 0.449. Aluminum, 0.897. Water is way higher."
"So what do you notice?" Raven asks. "Think about your warm water and the foil."
"The water holds a lot of energy per degree," Rocket says. "The foil barely holds any. It is not storing heat, it is just a wall."
Nova hovers over the rebuilt cup, now with an air gap and a paper lid. "The table explains the water," she says. "Your test explains the wall."
Rocket grins. "Second test. Same water, same room. One change." The grown-up pours. "Start."
The table below comes from an introductory chemistry text hosted by a university library. Specific heat is the energy needed to raise 1 gram of a substance by 1 degree Celsius.
The unit is joules per gram per degree Celsius. A higher number means the substance needs more energy for the same warming, and gives up more as it cools.
| Substance | Specific heat (joules per gram per degree Celsius) |
|---|---|
| Water, liquid | 4.18 |
| Water, solid (ice) | 2.06 |
| Water, gas (steam) | 1.87 |
| Aluminum, solid | 0.897 |
| Carbon as graphite, solid | 0.709 |
| Iron, solid | 0.449 |
| Copper, solid | 0.385 |
| Silver, solid | 0.233 |
| Gold, solid | 0.129 |
Water has a very high specific heat compared with most substances. The text notes that water is used as a coolant for machinery because it can absorb large amounts of heat.
For your cup, this means the water itself is a big store of energy. Every degree it drops means a lot of energy left through the cup walls and the top.
Metals are low on the table. The foil in your wrap is not storing much energy. Its job, if it helps, is as a layer the heat must cross.
Now the second half of the standard. Identify what performed best in your first test, keep it, and change one weak spot.
The standards say that testing the most promising solutions and modifying them based on results leads to a better design.
Run the exact same fair test with the exact same control. Record amount, time and temperature in a new row labeled Prototype 2.
| Test | Amount used | Time | Temperature or distance | Best on this test? |
|---|---|---|---|---|
| Control | ||||
| Prototype 1 | ||||
| Prototype 2 |
| Improving | True or false? |
|---|---|
| You should keep the parts of the design that performed best. | ? |
| Changing one thing lets you know what caused the difference. | ? |
| The second test can use a different amount of water than the first. | ? |
| Modifying a design based on test results leads to a better design. | ? |
Two rounds of testing done. Tomorrow you write the Matter Lab report that ties the whole course together.