Learning target: I can graph and calculate from data to show how cooling time controls crystal size, and I can use a tally from a rock-cycle game to judge what the game models well and poorly.
Both datasets on this sheet are teaching datasets: the numbers were invented to be realistic, not measured in a real laboratory. Part A is about a classroom melt that grows crystals as it cools. Part B is a tally from a rock-cycle dice game played by a class. Graph with a ruler, show every calculation with units, and answer in complete sentences when a question asks you to explain.
You will need: This worksheet, Pencil, Ruler, Calculator (optional)
A science class melted a safe, low-melting-point solid in a warm water bath and let samples cool for different lengths of time before the crystals stopped growing. Students measured the ten largest crystals in each sample under a hand lens and recorded the average length. Two trials were run for every cooling time. The melt is a stand-in for magma: it is not rock, but its crystals grow by the same rule.
| Cooling time (hours) | Trial 1: average crystal length (mm) | Trial 2: average crystal length (mm) |
|---|---|---|
| 2 | 0.6 | 0.5 |
| 4 | 1.1 | 1.2 |
| 6 | 1.8 | 1.6 |
| 8 | 2.3 | 2.2 |
| 10 | 2.7 | 2.9 |
| 12 | 3.4 | 3.3 |
| Mean of the two trials (mm) |
|---|
| 2 hours |
| 4 hours |
| 6 hours |
| 8 hours |
| 10 hours |
| 12 hours |
| Texture name | Typical crystal size | Usual meaning |
|---|---|---|
| Glassy | No crystals large enough to see; mostly glass | Cooled almost instantly, as in an explosive eruption |
| Fine-grained | Crystals smaller than about 1 mm | Cooled quickly at or near the surface (extrusive) |
| Medium-grained | About 1 mm to 5 mm | Cooled at a moderate rate, often in a shallow intrusion |
| Coarse-grained | Larger than about 5 mm | Cooled slowly, deep underground (intrusive) |
A class of 24 students played a rock-cycle game. Each student started at a station (magma, igneous rock, sediment, sedimentary rock or metamorphic rock), rolled a die, and followed a rule card that said whether to stay or which station to move to. Every student rolled ten times, for 240 rolls in total. The tally below records what happened at each station.
| Station | Rolls made there | Stayed | Moved to magma | Moved to igneous | Moved to sediment | Moved to sedimentary | Moved to metamorphic |
|---|---|---|---|---|---|---|---|
| Magma | 40 | 20 | 0 | 20 | 0 | 0 | 0 |
| Igneous rock | 48 | 24 | 4 | 0 | 5 | 0 | 15 |
| Sediment | 44 | 22 | 0 | 0 | 0 | 22 | 0 |
| Sedimentary rock | 48 | 24 | 4 | 0 | 3 | 0 | 17 |
| Metamorphic rock | 60 | 30 | 13 | 0 | 17 | 0 | 0 |
A rate is a change divided by the time it took. Step 1: subtract to find the change (for q2, the mean at 12 hours minus the mean at 2 hours). Step 2: divide by the time between them (12 − 2 = 10 hours). The unit is millimeters per hour. For a percentage (q9), divide the part by the whole and multiply by 100: part ÷ 240 × 100. For q7, you are asking 'how many hours at this rate make 5 mm?', so divide 5 mm by the rate.
Rewrite the rule card for the sediment station so that it includes two routes the current game lacks: dissolved material crystallizing straight into rock (chemical sedimentation) and sediment being carried farther before it is deposited. Decide what die rolls trigger each route and write a one-sentence justification for each probability you chose. Then predict how your new card would change the 'stayed' percentage for the sediment station after 44 rolls, and explain whether that change makes the model more or less realistic.