Conduction, convection, and radiation

Question 1

A student wants to keep a cup of cold water as cold as possible for several hours. Which of the following designs would best minimize thermal energy transfer from the surrounding room to the water?

Accepted Answer

A double‑walled container with a vacuum between the walls and a tight‑fitting lid.

Answer

A thin plastic bag with a loose‑fitting lid.

Answer

A cardboard box lined with a single layer of paper and a loosely tied flap.

Answer

A single‑walled metal cup with a thin lid.

Question 2

A 200 g piece of aluminum (specific heat = 0.900 J/g·°C) is heated from 25 °C to 75 °C. How much heat energy does it absorb?

Accepted Answer

9,000 J

Answer

2,250 J

Answer

4,500 J

Answer

13,500 J

Question 3

A student wants to keep a cup of hot chocolate warm for as long as possible. Which of the following design changes would best minimize thermal energy transfer from the hot chocolate to the surrounding air?

Accepted Answer

Add a double‑walled vacuum‑insulated sleeve around the cup.

Answer

Cover the cup with a thin plastic lid that has a small hole for a straw.

Answer

Replace the cup with a thin paper cup.

Answer

Wrap the cup in a metal spoon.

Try three questions

A student wants to keep a cup of cold water as cold as possible for several hours. Which of the following designs would best minimize thermal energy transfer from the surrounding room to the water?

A 200 g piece of aluminum (specific heat = 0.900 J/g·°C) is heated from 25 °C to 75 °C. How much heat energy does it absorb?

A student wants to keep a cup of hot chocolate warm for as long as possible. Which of the following design changes would best minimize thermal energy transfer from the hot chocolate to the surrounding air?

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