1. Grow your own Crystals An investigative activity by Jenny Douglas, Janet Troy and Vanessa Keenan-Boldt

2. Introduction

3. VELS VELS progression points (2.25): Science: Science knowledge and understanding –Awareness of similarities and differences between materials in a group –Knowledge of everyday changes related to matter… Science at work –Recoding of observations made during teacher directed experiments involving measurement in the collection and recording of data –Recognition of simple patterns evident in collected data –Awareness of safety procedures undertaken during experiments

4. Purpose To see if we can grow our own crystals – is it possible?

5. Hypothesis That mixing salt and boiling water will result in crystals forming That crystals can be grown in the classroom in a short period of time

6. Materials A glass jar A measuring cup 1 cup of boiling water ½ cup of salt A pencil Cotton string A spoon A paperclip Paper towel To add extra variables, we also used: 1 cup of water (room temperature) 1 cup of cold water (refrigerated for six hours) Food colouring

7. Method 1 Tie the paperclip to one end of the cotton string, and the pencil to the other end. Place the pencil on the top of the jar so that the paperclip is just touching the bottom of the jar. Remove from jar and set aside for later. Boil the water. Pour the boiling water into the jar Add the salt very slowly, about 1tsp at a time, stirring between additions until completely dissolved. When you find that the salt stops dissolving, you have added enough and your mixture is supersaturated. Lower the paperclip and sting into the water and rest the pencil across the top of the jar. Cover the jar with the paper towel. Place the jar where it won’t be disturbed for a couple of days After about 12 hours you should be able to see small crystals forming at the bottom of the jar, on the paperclip and on the string. After 24 hours there will be more crystals

8. 12 Hours later – Method 1 Crystals beginning to form on the string in the “boiling” glass. Crystal-like substance forming around the glass at the top of the water – evident on all samples, more so on the “boiling glass”, with the “cold” glass having the least amount.

9. 24 Hours later – Method 1 Crystals formed on string of “boiling” glass. Crystal-like substance more evident on all glasses Thin crystal formation on “room temperature” and “cold” glasses.

10. 24 Hours Later Crystals formed in “boiling” glass 24 Hours later – Method 1

11. 48 Hours later – Method 1 Foggy substance around glass is more pronounced on all samples. Dry part of string has formed thick salty substance on all samples. Tiny square crystals beginning to form on string that is in “cold water” and “room temperature” water samples.

12. Method 2 To produce another variable we decided to try our crystal experiment with a food colouring additive. We followed the same method in our previous example and added food colouring to boiling water, room temperature water and cold water.

13. 12 Hours later – Method 2 Foggy substance forming around top of glass. Salt at bottom of glass taking on pink colouring. Small vein-like sticks protruding from string. Random lumpy bits floating in glass.

14. 48 Hours later – Method 2 Vein-like sticks protruding from string are more prominent. Foggy substance around glass is more pronounced. Dry part of string has formed thick salty substance. Tiny square crystals beginning to form on string that is in water.

15. More results Left picture contains room temperature water and Right picture contains cold water after 48 hours. Both showed little change except for a crusty salt residue around the dry part of the string. The cold water started and remained quite bubbly.

16. More crystals were formed in the “boiling” glass than any other. Crystals were formed in all samples tested however significantly more crystals developed in the “boiling” water that had no food colouring. Adding food colouring appeared to decrease the amount of crystals formed in all water temperatures. More results

17. Discussion This investigation supported our hypothesis that mixing salt and boiling water will result in crystals forming. Our findings also supported the hypothesis that crystals can be grown in the classroom in a short period of time – within just twelve hours we were able to observe some crystal formation, and after 24 hours the crystals had clearly formed.

18. Conclusion

19. Delegation of Activity