Observation Questions:

1. Which solution cooled the quickest? The solution in the freezer cooled the quickest it froze in 2 hours.
2. Which solution took the longest to cool? The solution on the counter cooled slowest but it took days for the crystals to form. The water had to evaporate and evaporation is a cooling process. Just think how you feel when you come out of the shower or bathtub and the water evaporates from your skin..cold.
3. Which crystal was the largest? There were fewer but larger crystals in the solution that took the longest to cool.
4. Which crystals were the smallest? The solution that cooled quickly formed many small crystals.

Analysis Questions:

1. How does the cooling rate relate to crystal size? The slower the cooling the larger the crystal.
2. How does this experiment relate to intrusive igneous rocks? Igneous rocks that cool inside the earth cool slowly so the crystals have a longer time to form and can be large. For example the crystals in granite
3. Which part to the experiment would describe extrusive igneous rocks? Igneous rock that cools on the surface of the earth like basalt and scoria has small crystals that require magnification to be seen. The freezer would be the closest model in this experiment.
4. How does this experiment relate to the texture of igneous rocks? Give examples. Texture has to do with crystal size in igneous rock. Large crystals have a phaneritic texture like granite or the Alum formed on the counter. The crystal was the size of a grain of rice or larger. Fine or small crystals have an aphantic texture like basalt. Many of the crystals in formed in the freezer were small you could see their shape under a magnifying glass.
5. Where would this process occur in nature? This could happen where igneous rock is cooling along convergent boundaries and subduction zones and divergent boundaries along spreading centers.
6. What other rock types could relate to this lab experiment. Explain why. Chemical sedimentary rocks are formed from minerals dissolved in water. Crystals form when the water evaporates or the minerals precipitate or fall out of the solution. The alum that was put in the freezer precipitated and ended up in the bottom of the glass. While the solution left on the counter evaporated to form alum crystals. Limestone can be formed in this way.