Crystals and disappointments

The Marrickville science class hasn’t gone as well as I had hoped. In our first session, we wasted a lot of time just setting up and getting into groups. Next time I think I’ll just tell the kids who they are sitting with. Secondly, truth be told, scratch tests don’t really make me say, “woo-hoo!” I’ve already noted for myself that it’s better to start with something I feel extremely passionate about.

I thought crystal growing might do the trick. We all love crystals, don’t we? I really hoped the second session would go well. It didn’t . Crucially, my lovingly prepared supersaturated solution of sodium carbonate failed to deliver any crystals within the time of our session. Furthermore, the behaviour of the children ranged from pure indifference (one of my offspring, I have to admit) to violent hyperactivity (another one of mine). There was little attention paid to the slow-forming crystals, and little chance for getting excited about science.

I had tried the experiment at home, . I really thought it would work . I suspect that I had not allowed it to cool down for long enough. I allowed five hours for it to get to room temperature. If I repeat the experiment I will either prepare the solution the night before, or try putting the solution in the fridge for a short while before seeding it.

Nevertheless, after the class had finished, some of the jars started to show some good crystals forming. If anyone’s interested in the instructions I can post them another time. Sodium carbonate is a good chemical to choose because it’s easy to get hold of and relatively safe. We wore disposable gloves and safety goggles but it’s only a minor irritant, not horribly caustic like sodium hydroxide. You can dispose of the crystals and the solution down the sink without worrying about neutralising it or any other special measures.

One additional property of sodium carbonate crystals is that as they crystallize they incorporate some of the water molecules into their crystal structure. This is called water of crystallization. The crystals we grew from solution had a very shiny, glassy appearance. Fairly soon after taking them out of the jars, they began to take on a dry, powdery appearance – the sodium carbonate was reverting to what we call it’s anhydrous state. (Anhydrous means “without water”.)

We also had a brief discussion introducing the terms solutesolvent and solution, talked about the difference between rocksminerals, and crystals, and looked at some pictures of unit cells.

So it wasn’t a complete let-down. But I’m definitely going to have to rejig the classes and rethink the way I present things.

Next session we are going to look at how rocks are formed and try to classify rocks into igneous, sedimentary and metamorphic. I think a few videos of volcanoes may be inspiring. We’re also thinking of separating the older and younger children.

Teaching this group of homeschoolers, with a range of ages and abilities and (sadly) different levels of enthusiasm, is very different to teaching adults for the Open University, or from teaching in a school with a set syllabus and a properly equipped lab. Undoubtedly there will be many activities I have to change, and some disappointments too.

It’s a steep learning curve for all of us and I will keep on going, making changes along the way in order to deliver a better experience, one that is inspiring for the children and satisfying for me.

3 thoughts on “Crystals and disappointments

  1. Jen in NSW 21 June, 2013 / 13:38


    I wonder if you could check out the samples for me. I checked out the 3rd book and it may actually be useful for your science class. I am also checking with some US friends if anyone could send it to me after I ship to them.

    Best wishes
    Jen in NSW

    • scimumsam 23 June, 2013 / 23:15

      Hi Jen. I’ve had a brief look and I like the questioning approach. I’ll have a more in-depth look and get back with some more detailed comments after I’ve finished our permanent residency application, which is keeping me very busy at the moment.
      Another good resource for primary aged kids is Building Foundations of Scientific Understanding by Bernie Nebel
      I have this book at home and I really think it encourages children to think about the scientific method at the same time as introducing them to key vocabulary and concepts.

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