This lab activity will guarantee a snow day! Teach solutions and crystallization while making snowflake decorations for your classroom.
Looking for an activity to do that will guarantee a snow day? Help your students learn about solutions and crystallization while making snowflake decorations for your classroom.
Borax is the common name for sodium tetraborate decahydrate, Na2B4O7 – 10H2O, also called sodium borate. Borax occurs naturally and is used in laundry and cleaning products. It is a mineral sediment formed after repeated evaporation of seasonal lakes. Borax is the salt of a strong base and a weak acid. When added to water, borax forms the borate ion.
A typical solution is one in which a solid is dissolved in a liquid. The amount of solid a liquid is capable of dissolving is limited. However, sometimes a solution can be manipulated so that it becomes supersaturated, that is, it contains a greater amount of dissolved solid than at its saturation point.
Increasing the temperature of the solution in this activity causes more borax to dissolve than at room temperature. As the temperature falls, the solution that was saturated at the higher temperature becomes a supersaturated solution. The excess solid does not remain in the solution indefinitely, and some of the dissolved chemical (borax) precipitates out to form new solid material (the crystals). This crystalline solid is deposited on a solid surface (the pipe cleaner), forming crystals. For an edible version of this activity, try making rock candy.
Topics covered: solutions, solubility, crystallization, crystal structure
Additional Reading: Crystallization Investigation
Materials (per student)
- Borax, 65 g
- Beaker, 600 mL
- Stirring Rod
- Graduated Cylinder, 500 mL
- Craft Stick
- String, 30 cm
- Scissors
- Pipe Cleaner
- Paper Towel
- Water
- Balance (can be shared)
- Hot Plate (can be shared)
Procedure
- Create a shape using a pipe cleaner. This shape needs to fit into the beaker without touching the sides, and it should be only half as tall as your beaker. If you wish to make a basic snowflake shape:
- Cut the pipe cleaner into 3 equal lengths.
- Twist 2 of the pipe cleaner pieces together at their centers forming an “X” shape. This does not have to be done tightly, just enough to hold them together.
- Place the 3rd pipe cleaner piece on top of the X shape so that the center of the X and the center of the 3rd piece are aligned. Holding the center of the X and the center of the 3rd pipe cleaner piece together, wrap the ends of the3rd pipe cleaner piece around the center of the X. This should form a basic snowflake shape with 6 branches.
- Trim the ends to ensure that all of the snowflake branches are about the same length.
- Cut a piece of string about 30 cm in length.
- Tie an end of the string around your pipe cleaner shape. If you have made a snowflake shape, tie the string around the center, where all of the pipe cleaner’s pieces intersect.
- Tie the other end of the string to the middle of the craft stick.
- Place the pipe cleaner shape in the beaker and rest the craft stick on top of the beaker. Rotate the craft stick, winding the string around it, until the pipe cleaner shape is suspended.
- Remove the craft stick and shape from the beaker, making sure not to unwind the string.
- Place 475 mL of water into the beaker.
- Heat the water on the hot plate until it is boiling. Using heat protection, remove the beaker from the heat.
- Add 65 g of borax to the water, and stir until the borax is mostly dissolved.
- Place the pipe cleaner shape into the borax solution, again resting the craft stick on top of the beaker. Ensure that the pipe cleaner shape is completely submerged and not touching the sides or bottom of the beaker. If it is, adjust the string by manipulating the craft stick.
- Allow the pipe cleaner shape to remain undisturbed for at least 24 hours.
- Remove the pipe cleaner shape from the solution and place it on a paper towel to dry.
Additional Reading: Rock Candy: An Edible Study of Crystallization
