Igneous Rock Forming Processes

Earth Science Unit 4- Rock Forming Processes

Goal:

  1. Students will make and test out hypotheses about how the rate of cooling of a liquid affects the size of the crystals that form.
  2. Students will determine the relationship between cooling rates and size of crystal formation.
  3. E3.1d Explain how the crystal sizes of igneous rocks indicate the rate cooling and whether the rock is extrusive or intrusive.

Background

The rate of cooling of igneous rock determines the size of the crystals that form in igneous rock. The faster the rate of cooling the smaller the size of the crystals that will form. This information can be used to determine if an igneous rock is an intrusive or extrusive igneous rock. Small crystals would be found in an extrusive igneous rock since the cooling would occur faster than in an intrusive rodk.

Time Frame

20 minutes to set up on day one, 10 minutes to observe on day two.

Student Misconceptions

Vocabulary

Cooling

Crystallization

Extrusive

Intrusive

Igneous rock

Magma

Materials

Epsom Salt mixed with equal volume of water- each group needs about 60 ml of

the solution- you can either make a solution up for the whole class to use

or have students make their own Epson salt solution.

Test tubes

Ice or refrigerator

Warm water or an incubator

Beakers

Pipe cleaner

Goggles

Stir bars or spoons

Hot plate

Procedure

  1. Make a hypothesis about how temperature affects the size of the crystals that will form in a solution.
  2. Heat 100 ml of water in a 250 ml beaker until the water is boiling.
  3. Add Epson salt to the heated water and stir (you can take the beaker off the hot plate). Continue adding Epson salt until the water can no longer dissolve the salt.
  4. Put 20 ml of the Epsom salt/water solution in three different test tubes.
  5. Wrap a section of pipe cleaner (about 10 cm long) around a pencil to coil it and place the pipe cleaner in one of the test tubes. Repeat with 2 more pieces of pipe cleaner and put a piece in each of the test tubes.
  6. Place one test tube in a water bath with water at room temperature, one test tube in a warm water bath, and the 3rd test tube in a water bath filled with ice water and placed in a refrigerator. If an incubator is easily accessible, the incubator (set at a temperature warmer than room temp) could be where warm water bath sits until the next class.
  7. Let the test tubes sit in the water baths until the next class period.
  8. Examine the crystals that form in each test tube. Record your observations.
  9. Make a conclusion about how cooling rates affectthe size of the crystalsthat form.

Procedure for incorporating more inquiry

  1. Make a hypothesis about how temperature affects the size of crystals that will form in a solution.
  2. Design an experiment to test you hypothesis.
  3. Record your observations
  4. Make a conclusion about how cooling rates affect the size of the crystals that form.

Expected Results:

Students will observe that the crystals will be smaller in the solution that was placed in the refrigerator (cooler) than in any of the warmer conditions.

Igneous Rock Formation

Student Master

Name ______

  1. Make a hypothesis about how temperature affects the size of crystals that will form in a solution. Record your hypothesis in the space below:
  1. Heat 100 ml of water in a 250 ml beaker until the water is boiling.
  1. Add Epson salt to the heated water and stir. Continue adding Epson salt until the water can no longer dissolve the salt.
  1. Put 20 ml of the Epsom salt/water solution in three different test tubes.
  1. Wrap a section of pipe cleaner (about 10 cm long) around a pencil to coil it and place the pipe cleaner in one of the test tubes. Repeat with 2 more pieces of pipe cleaner and put a piece in each of the test tubes.
  1. Place one test tube in a water bath with water at room temperature, one test tube in a warm water bath, and the 3rd test tube in a water bath filled with ice water and placed in a refrigerator. If an incubator is easily accessible, the incubator (set at a temperature warmer than room temp) could be where warm water bath sits until the next class.
  1. Let the test tubes sit in the water baths until the next class period.
  1. Examine the crystals that form in each test tube. Record your observations. In the space below:
  1. Write a conclusion about how cooling rates affect the size of the crystals that form:
  1. Describe the crystals that would be found in an extrusive igneous rock.
  1. Describe the crystals that would be found in an intrusive igneous rock.