We got a test tube containing a white solid chemical called salol.
We placed it in a beaker of boiling water and the solid melted to form a clear and colourless liquid.
Then we poured the liquid onto two microscope slides. One had been in the freezer until just before the experiment and was noticeably cold. The other microscope slide had been in a warm oven. It took about 5 minutes for the liquid to solidify and form crystals on the cold slide. It took 45 minutes to solidify on the warm slide. In the picture below, the cold slide is on the left and the warm slide is on the right.
The crystals on the cold slide are smaller because they solidified first and did not have as much time to grow. The crystals on the warm slide are bigger because it took a long time to solidify so the crystals had more time to grow. Rocks that solidify from hot molten liquid are called IGNEOUS ROCKS. If the molten rock reaches the surface by coming out of a volcano, we call it LAVA. If it gets trapped underground and cools we call it MAGMA. In the picture below, GRANITE on the left forms when molten magma underground cools very slowly to form large crystals. BASALT on the right forms when lava comes out of a volcano in the air or water which cools it really quickly so it has tiny crystals that are really hard to see.
All igneous rocks have randomly arranged interlocking crystals. There are no layers or any obvious structure. The basalt is called an EXTRUSIVE igneous rock because the molten lava came out onto the surface of the Earth through the EXit of a volcano. The granite is an INTRUSIVE igneous rock because it never escaped from the inside of the Earth and was kept IN the Earth to solidify.
