Make a crystal snowflake using borax. This activity is a good cross-curricular lesson for elementary subjects. It can be used in a lesson about winter and weather. Borax is a naturally occurring mineral, sodium borate, used as a whitener in many detergents. It can be purchased in many grocery stores and pharmacies. Have the children twist pipe cleaners together into the shape of a snowflake or star. Attach a piece of string to one arm of the snowflake. Tie the other end of the string to a pencil. Fill a large jar with enough boiling water to cover your snowflake. For each cup of water in the jar, add 3 tbsps. of borax. Stir until the borax is dissolved. Add a few drops of blue food color. Lower the snowflake into the jar so that it is immersed in the water. Rest the pencil on top of the jar. Leave the snowflake in the jar and in one or two days it will be covered in blue-white crystals.
This project is a good way to introduce elementary school children to science basics, such as using a magnifying glass and observing shapes. Have the elementary children cut a piece of black construction paper to fit into the bottom of a disposable aluminum pie pan. Add 1 or 2 tbsps. of Epsom salts (available in most grocery stores and pharmacies) to 1/4 cup of hot water. Stir until the Epsom salt dissolves. Pour the water into the pie pan. Leave the pie pan in a warm place, such as the sun, or near a heater. The water will evaporate, leaving behind crystals of Epsom salt. The crystals will be shaped like small spikes, or needles.
This activity uses ammonia, so it is not suitable for children in younger grades at elementary school and you may want to reserve it for grades five and six. The children should place a few pieces of broken pottery, charcoal, cork or sponge in a disposable plastic bowl. Fill the bowl with water and let it sit for a few minutes. Drain off all the water. Drop a few drops of food coloring onto the material. Mix 4 tbsps. of non-iodized salt with 4 tbsps. of liquid bluing (a whitener made of Ferric Hexacyanoferrate found in the laundry section of most grocery stores), 4 tbsps. of ammonia and 4 tbsps. of water. Pour this mixture into the bowl and let it sit. You will see crystals begin to grow in about six hours.
This crystal experiment can be eaten and fits in well with elementary projects on nutrition and shapes. Heat 2 cups of water in a saucepan until it boils. Add 4 cups of sugar to the water, stirring with a wooden spoon until the sugar is completely dissolved. Pour the solution into a jar. Have each elementary child dip a string into the sugar solution, then lay it on a piece of waxed paper and let it dry for at least 24 hours. Repeat this step. Cover the jar with waxed paper or a lid when you are not dipping. Small crystals will form on the string, making seed crystals that will help larger crystals grow. Tie a pencil to one end of the string, remove the lid of the jar and suspend the string in the jar. After a few days, your rock candy will begin to form large crystals.