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Crystal Snowflake

A snowflake shaped crystal made from white pipe cleaners with small crystals attached.

Dreaming of a white Christmas? Use Epsom salt and water to grow your own "snowflake" decoration and observe how crystals form.

Australian Curriculum links

  • Science > Chemical Sciences > Year 6 > ACSSU095
  • Science > Chemical Sciences > Year 7 > ACSSU113

You'll need

  • Three white pipe cleaners
  • Scissors
  • Shallow container e.g. a plate
  • Ruler
  • Cotton string/twine
  • Heatproof container e.g. coffee mug
  • Boiling water (ask an adult to boil water for you)
  • One 375g carton of Epsom salt (Magnesium Sulfate)
  • Spoon
  • Microwave
  • Spatula

Try this

Safety: This experiment requires adult supervision. Epsom salt is an inedible salt, so be sure to wash your hands after handling it and do not taste or swallow any. This experiment uses boiling water and a microwave. Please make sure you get help from an adult for these steps.

  1. Twist three pipe cleaners into a snowflake shape that will fit into the shallow container. You might need to cut the pipe cleaners to fit.
  2. Cut a 20 cm length of string and tie it to the end of one of the pipe cleaners.
  3. Half fill the heatproof container with boiling water.
  4. Pour a small amount of Epsom salt into the container and stir until it completely dissolves. Continue stirring and adding Epsom salt until no more will dissolve.
  5. Microwave the solution for 3 minutes on a high setting.
  6. Add more Epsom salt and stir until dissolved. Keep adding Epsom salt until no more will dissolve.
  7. Lay your snowflake in the shallow container, making sure the end of the cotton string hangs over the edge.
  8. Pour the liquid solution into the container until the snowflake is completely covered.
  9. Place the container somewhere it will not be disturbed.
  10. Leave the container for 1-2 weeks until most of the water has evaporated. Check each day to see crystals forming.
  11. When finished, pick up the snowflake by the cotton string. You may need to carefully slide the spatula under the snowflake and use it to help lift. Hang it somewhere it won’t be disturbed as it dries.
  12. When dry the snowflake is less fragile. You might like to hang it on your Christmas Tree.

Further investigation

Try making different crystals by using other salts or other materials to grow them on. Which salts make the best crystals? Which materials work best for growing crystals?

What's happening?

Crystals form when little bits of a substance (in this case: magnesium sulfate ions) arrange themselves in a regular pattern. Heating the water allows more Epsom salt to dissolve than could have in cold water. When the water cools, this extra salt is able to turn back into solid crystals. The pipe cleaner provides a location from which the crystals can start to grow.

When you add a small amount of Epsom salt to water, the salt dissolves. If you continue to add salt to the solution, you will reach a point where no more salt will dissolve. This is called the “saturation point”. Warmer liquids have a higher saturation point, so heating the water lets you dissolve more salt than you could in cold water. When the solution cools down again, there is extra salt dissolved in the water beyond the saturation point. At this point, the extra salt can start to form tiny solid salt crystals. As time goes by, more of the extra dissolved salt attaches to the growing salt crystals until the original saturation point is reached again.

After the hot salt solution is poured over the pipe cleaners, the water evaporates as it cools. This means that there is less water in the container, and the solution can hold even less dissolved salt than before. This allows even more salt crystals to form on the pipe cleaners and inside the container. As the water continues to evaporate, the crystals continue to grow.

However, there is a catch. Crystals need somewhere to start growing. It is very difficult for a salt crystal to form in a liquid; they usually need something solid to start growing on. This starting point is called a “nucleation site”. The tiny bristles on the pipe cleaner act as very good nucleation sites, as do tiny cracks or scratches in the surface of the plate.

Different salts make different shaped crystals. Epsom salt crystals usually form long spikes. If the crystals form quickly, you will have lots of small spikes forming on your snowflake. If the crystals form slowly, you may find longer and larger crystals forming.

Real world links

We come across crystals countless times every day. You may have even eaten one already today! Table salt, sugar and ice are all types of edible crystals. Quartz is a common inedible crystal used in jewellery and in clocks to help keep time. Diamonds are valuable crystals made from Carbon. Carbon can also form a different kind of crystal called graphite, which is the "lead" inside lead pencils. You even have tiny calcium carbonate crystals in your ears that help you keep balanced.