Crystal Growing Experiment

What to do: Design an experiment that tests how evaporation rate affects the size of hydrated crystals. (Extra Credit / Honors option) Develop a question that can be answered by doing an experiment about hydrated crystal growing. (not a yes or no question) Devise hypotheses and clearly state the reasons behind your thinking. (Use complete sentences.) Write a detailed procedure that identifies the changed variable, measured variable, control, constants, repetitions, equipment and timing of your experiment. Record results in an organized fashion, including time, dates, drawings, observations, charts or graphs. Analyze your results in the conclusion. Identify problems (uncontrolled variables) and areas for further study.

Extra Credit Examples Poor questions: Can I grow crystals? Will sodium chloride grow crystals? How big will my crystals be? Better questions: How does temperature affect crystal growth? Does mixing chemicals affect crystals? Good questions: How does solution temperature affect the size of hydrated alum crystals? How does the mixing of alum and sucrose affect the growth time of crystals made from these chemicals? (Changed and measured variable is identified in the question)

Materials and Chemicals Things I will have for you to use: Beakers, Bunsen burners, tongs, stirring rods, ring stands, balances, graduated cylinders, eye goggles. You must grow crystals in something disposable or that you bring from home. (Styrofoam cups provided) It also must be able to hold liquids that are close to boiling temperature. Chemicals: Sodium Chloride, Borax, Sucrose (sugar) Other chemicals found at the grocery store, drug store or Fleet Farm: Alum and Epsom Salts, Copper Sulphate

Before starting, your group must: Have a completed question, hypothesis, procedure, and materials list. (Use the sample procedure on the next slide if you are doing the basic experiment.) Have all measurements in your procedure converted to metric (grams, ml, etc.) and reduced to a useable volume. Try this link to help you convert. Know and have what your are growing your crystals in. Have all of your materials (chemicals) you need at school. Have signed lab safety contracts in.

Question: How does the evaporation rate affect the size of hydrated borax crystals? Changed Variable: Measured Variable: Hypothesis: If , then Procedure: 1. Create a super-saturated borax and water solution. 2. Measure 75 mLs of water and place in a beaker. Place the beaker on a ring-stand above a lit bunsen burner. Slowly add borax, 2-4 mLs at a time to the solution. Stir the solution until the borax dissolves completely. Repeat this process until no more borax will dissolve. 3. Pour equal amounts of the solution (25 mLs) into 3 different styrofoam cups. Cover one cup with a paper towel completely. Cover another with a paper towel and punch holes in the paper towel. Leave the last cup uncovered. Place all three cups in the cabinet and allow crystals to grow over a number of weeks. Compare crystal size when the solution has evaporated. Control test: Constants: Materials: Results: Conclusion: