Energy Tokens: Act Out Melting and Boiling, Then Graph It

Investigation question: If energy is added to a pure substance at a steady rate, what happens to its particles' motion, its temperature and its state, and where does the energy go when the temperature stops rising?

Your role today

• Energy source (also particle A): Hands one token to every particle at the start of each round, keeps the running total of tokens added, and in the cooling run collects tokens into the cold-sink cup.
• Rule keeper (also particle B): Reads the rule card aloud each round, says whether tokens go onto chains or into a bank, and calls the state and how each particle should move.
• Thermometer reader (also particle C): After each freeze, counts the clips on every particle's chain and works out the model temperature, the average chain length.
• Recorder (also particle D): Writes each round's row in the group's data table and checks that the token accounting balances before the next round starts.

Safety

• This is a walking model: walk only, never run, push or touch. A 'collision' is a turn made at arm's length.
• Clear backpacks, chairs and cords from the floor area, press the tape flat so it is not a trip hazard, and pull it up afterward.
• Paper clips are small and have points. Keep them on chains or in cups, never in mouths, and pick up any that drop.
• Students who cannot move safely in a crowd, or prefer not to, run the tabletop version described under accessibility or take a non-moving role in another group.

Procedure

1. Set up: each particle wears a tag and starts with a chain of 1 paper clip, standing on an X mark. The substance is a solid. The energy-source cup holds the remaining clips and the bank cups are empty. Round 0 is already filled in on your table.
2. Read the heating rule card together. In this model the melting point is 3 and the boiling point is 6, measured in clips per chain.
3. Each round: (a) the energy source hands every particle one token; (b) the rule keeper reads the rule and says where each token goes, onto your chain or into a bank; (c) everyone moves for 15 seconds the way the rule card says for their state and chain length; (d) freeze.
4. After each freeze, the thermometer reader works out the model temperature (total clips on chains ÷ 4), the rule keeper counts the clips in each bank and how many particles are solid, liquid and gas, and the recorder writes the row. Check that the 4 starting clips plus the tokens added so far equal the clips on chains plus the clips in banks.
5. Run rounds 1 to 10. When the loosening bank reaches 4 clips, two particles leave their X marks and become liquid; at 8, all four are liquid. When the separating bank reaches 4, two particles leave the liquid strip as gas; at 8, all four are gas.
6. Plot the heating curve: model temperature against tokens added so far. Circle each flat step and label what the particles were doing during it. Answer q1 and q2.
7. Part C, the uneven round: reset to a liquid with a chain of 4 clips on every particle, 8 clips in the loosening bank and none in the separating bank. Read the uneven-round card, deal the 4 tokens as it says, record the chains and the liquid's temperature, then apply the escape rule and record again. Answer q3.
8. Return the clips to their cups, pull up the tape if the room is needed, and answer the analysis questions individually.
9. Optional session 2, cooling (about 30 minutes): rebuild the end of the heating run (all four particles gas with chains of 7, and 8 clips in each bank). Each round every particle gives one token to the cold-sink cup, following the cooling rule card. Run 10 rounds, fill in the cooling table, and plot the cooling curve on the same graph in a different color.

Record your observations

Lab 3 recording sheet: Energy tokens

Each student is one particle of a pure substance, and each paper clip is one unit of energy. Clips on your chain are motion energy: a longer chain means you move faster. Clips in a bank are energy that loosened the particles from their fixed spots (melting) or separated them completely (boiling). The model temperature is the average chain length: total clips on chains ÷ 4.

Uneven-round card. This round, the energy source deals the 4 tokens unevenly: 3 to particle A, 1 to particle B, none to C or D. All dealt tokens go onto chains. Escape rule: a liquid particle whose chain is 6 or longer may escape. It puts 2 clips into the separating bank and walks into the gas region. The liquid temperature is the average chain length of the particles still in the liquid.

Analysis questions