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Crystal Size and Cooling Rate
http://www.rsc.org/Education/Teachers/Resources/jesei/cooling/index.htm
From DLESE Community Collection (DCC)
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This activity relates to the process of igneous rock formation by the cooling of magma. It can be used to illustrate how the rate at which molten rock cools affects the size of the crystals that form within the solid rock - rapid cooling producing small crystals, slower cooling producing larger ones. Hot, saturated solutions of lead iodide are cooled at different rates. The solution that cools faster produces smaller crystals. Students relate this to samples of rhyolite and granite and discover that the intrusive igneous rock (the granite) has cooled slowly from magma, and the rhyolite lava (extrusive igneous rock) has cooled very quickly. This leads to a fuller explanation of the terms intrusive and extrusive. The site also has an alternative demonstration in which melted Salol is placed on hot and cold glass slides with similar results.
Intended for grade levels:
  • Middle (6-8)
Type of resource:
  • For the classroom:
    • Lab activity
  • Text:
    • Glossary
Subject:
  • Geological Sciences:
    • Mineralogy or petrology
Technical requirements:
No specific technical requirements, just a browser required
Cost / Copyright:
No cost
Copyright is waived for original material published on this site if the material is required for use within the laboratory or classroom. The copyright of material reproduced by permission of other publishers rests with the originating publisher.
DLESE Catalog ID: DLESE-000-000-006-565
Educational standards:
  • National Science Education Standards (NSES):
    • 5-8:
      • Unifying concepts and processes:
        • Evidence, models, and explanation
      • A - Science as inquiry:
        • Abilities necessary to do scientific inquiry
      • B - Physical science:
        • Properties and changes of properties in matter
Resource contact / Creator / Publisher:
Publisher: Joint Earth Science Education Initiative (JESEI)