EasyPhysicsHigh School (11–12)Heat & Thermodynamics › Temperature and Thermal ExpansionConceptualBoard Exam
Answer, and give a reason. A bath of water and a cup of water are both at 40 °C…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Answer, and give a reason.
- A bath of water and a cup of water are both at . Which has the higher temperature? Which can give out more heat as it cools to room temperature?
- Why does a thermometer need a moment in your mouth before it reads correctly?
- Why is the kelvin scale the one used in the gas laws?
Need a reminder? The key ideaShow
Heat flows from hot to cold; temperature decides the direction. and . A thermometer's readings between its ice point and steam point are scaled to the true degrees.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) Neither is hotter: same temperature. The bath, with far more water, gives out far more heat as it cools.
Step 2. (b) It must reach thermal equilibrium with your mouth; until then heat is still flowing into it.
Step 3. (c) Its zero is absolute zero, where a gas's pressure and volume would vanish, so and are in proportion to the kelvin temperature.
Answer: (a) Same temperature; the bath. (b) Equilibrium. (c) A true zero.
Watch out. 'Hotter' means a higher temperature, not more heat.
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