Raven spreads a printed table across the Bench. "These are measurements from a college chemistry text," she says.
"Same tool as ours?" Rocket asks. "Two cups and a lid?"
"Nearly. Theirs is a foam cup calorimeter too." Raven taps a row. "What do you notice about the ammonium nitrate numbers?"
Rocket reads. "Start 24.9. End 20.3. It fell almost five degrees. That is the cold pack stuff!"
Nova brightens a little. "Now find a row that went the other way," she says. "Before you decide what it means."
"The acid and base row climbed," Rocket says. "Exothermic. Our vinegar test was the opposite of that."
Raven writes a question in the log: "Why would two changes move heat in different directions?"
The table below comes from a general chemistry textbook hosted by a university library. Each row is one test in a foam cup calorimeter.
Read each row the way you read your own Bench Log: start, end, change, direction.
The text treats the water in the cup as the surroundings of the reacting particles, just as you did yesterday.
| Change tested | Amounts | Start (degrees C) | End (degrees C) | Change |
|---|---|---|---|---|
| Solid ammonium nitrate dissolving in water | 3.21 grams in 50.0 grams of water | 24.9 | 20.3 | |
| Solid potassium chloride dissolving in water | 3.00 grams in 300 grams of water | not given | not given | down 1.05 |
| An acid solution and a base solution mixed | 50.0 milliliters of each | 22.0 | 28.9 | |
| Two solutions mixed, a new solid forms | 100 milliliters of each | 21.9 | 23.5 |
Two of the rows are blank in the Change column on purpose. You will fill them in below.
The text also reports that the ammonium nitrate test absorbed heat, and it names the acid and base test exothermic.
| Statement | True or false? |
|---|---|
| The ammonium nitrate test ended colder than it started. | ? |
| The acid and base test was endothermic. | ? |
| A small temperature change can still mean heat moved. | ? |
| The amount of water in the cup can affect how far the reading moves. | ? |
The same text explains that well-insulated calorimeters all but prevent heat moving between the cup and the room.
Student calorimeters made from foam cups let more heat leak, so their numbers are less exact. That is why yours were rough too.
Next week you will see where materials like foam, paper and metal come from. In week 12 you will use them to build.
Excellent data reading. Tomorrow you will connect energy changes to burning, food and the weather outside your window.