South Dakota Science HS-PS3-4

ScienceGrades 9–12Physical Science

The Standard

Plan and carry out an investigation to provide evidence for the Second Law of Thermodynamics. (SEP: 3; DCI: PS3.B, PS3.D; CCC: Systems)

South Dakota Science Standards (2024) · Energy

Teacher's field guide

What Students Need to Do: Students plan and run a test using warm and cool water. They measure temperatures before and after mixing, then use the results to explain which way heat moves.
What Mastery Looks Like: A student measures equal amounts of water, records both starting temperatures, and predicts a final temperature between them. They explain that the mixed water will not separate back into hot and cold water on its own.
Common Misconceptions: Some students think the hot water will keep the mixture near its starting temperature, even when the amounts are equal. Others think heat disappears when water cools or that mixed water can separate back into hot and cold parts by itself.
How to Assess It: Exit ticket: Two 100 mL samples of water start at 40°C and 20°C. What would you measure before and after mixing them in a covered cup, what final temperature do you predict, and what would that result show?

Lesson moves

Mix 100 mL of 40°C water with 100 mL of 20°C water in a covered cup, then record the final temperature.
Ask students why mixed water settles near 30°C instead of separating back into hot and cold water.
Give pairs cards showing two touching objects and their temperatures; have them draw heat-flow arrows and predict what happens next.
Measure a mug of warm water and the room air, then check both again after five minutes and discuss where heat moved.

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