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Matter Lab 6-8 / Week 10 / Bench Day
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Week 10 · Reactions Give or Take Energy

Bench Day

Bench Day: Warm and cool hunt
// Some changes warm their surroundings, and some cool them
⏱ about 20 min

Bench Day: Warm and Cool Hunt

Saturday at the Bench starts with a thermometer and a family. Rocket hands out slips of paper labeled Warm and Cool.

"Every change we find today gets a slip," he says. "Ice melting, a mug cooling, a pack of frozen peas thawing."

Raven writes the rule on the Bench Log cover: "Measure before you label."

Nova drifts to the sink. "A thermometer in running tap water," she hints. "Then the same thermometer in a cup left out for an hour."

"Both water," Rocket says, "but different readings. So the cup is moving heat with the room!"

Raven adds a slip. "What do you notice? Nothing new formed, but heat still moved. Good find."

  1. The system is the matter being studied. The surroundings are everything else. Energy moves between them and is never created or destroyed.
  2. Exothermic changes release heat, so the surroundings warm up. Endothermic changes absorb heat, so the surroundings cool down.
  3. Instant cold packs use ammonium nitrate dissolving in water, which absorbs heat. Hand warmers use iron reacting with oxygen, which releases heat.
  4. Two nested foam cups with a lid make a simple calorimeter that slows heat leaking while you measure.
  5. One calorie warms 1 gram of water by 1 degree Celsius and equals 4.184 joules.
◇ FAMILY WARM AND COOL HUNT
Together, pick four things at home that are changing temperature. Try an ice cube on a plate, a warm drink cooling, tap water and a sunny windowsill.
Take turns: one person measures with the kitchen thermometer, one records in the Bench Log. Swap after each reading.
For each, decide together: is heat moving into the thing or out of it? Is any new substance forming, or is it only heat moving?
Finish by repeating Wednesday's salt in water test as a family. Does everyone read the same change?
For a grown-up
The student handles only room temperature or cool items. A grown-up pours anything hotter than tap water and keeps it out of reach.
No packs are opened today. Cold packs and hand warmers are discussed, not cut open.
The energy facts this week come from chemistry texts hosted on chem.libretexts.org, which you can read yourself.
Safety first
Nothing is tasted or smelled up close, even salt water.
Never seal a fizzing mixture in a closed container.
A grown-up handles anything hotter than tap water. Wash hands when the hunt ends.
THINK IT THROUGH
  • Read the question.
  • Tap your answer.
An ice cube on a plate slowly melts. Which way is heat moving?
A warm drink cools on the table. Is a new substance forming?
A change that absorbs heat from its surroundings is called what? Type one word.
WHY THIS EXERCISEBy now this word should come as fast as the thermometer reading does.
Bench Day checkTrue or false?
Measuring comes before labeling a change warm or cool.?
A fizzing mixture should be sealed tightly to keep the heat in.?
Heat can move without any new substance forming.?
WHY THIS EXERCISESafe, measured observations make your Bench Log worth comparing with real data.
Draw your home as a map and mark each warm or cool change you found. Use an arrow pointing in for endothermic and out for exothermic.
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