The Action |
An endothermic reaction will cause a flask to freeze to a block of wood. | ||
Grade Level |
Grade 6 - Chemicals and Reactions Grade 7 - Temperature and Heat Grade 8 - Energy Resources in Saskatchewan Grade 10 - Physical Science and Chemical Change |
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Materials |
32g barium hydroxide crystals, Ba(OH2)·8H2O 16g ammonium thiocynate, NH4SCN 150 mL flask Scale (digital) and 2 small beakers for weighing chemicals water pipette or eye dropper wood block oven mitt |
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Instructions |
Make a small pool of water (~1-2 mL) on top of the wood block. Add barium hydroxide and ammonium thiocynate in a 150 mL flask. Stopper the flask and shake vigorously until the crystals begin the liquefy. Place the flask on the pool of water on the wood block and allow to stand for a few minutes. Pick up the flask and the wood block will also be lifted because the water will have frozen the flask to the wood. |
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Safety |
Care should be taken with handling and disposing of the chemicals. Eye protection is suggested. The flask also becomes very cold to the touch as a result of the reaction so using the oven mitt is recommended to keep you're hand from getting too cold. | ||
Hints |
The barium hydroxide and ammonium thiocynate should be measured prior to the demonstration. Let the flask sit in the water on the block for at least 3 minutes prior to the demonstration. Let the flask sit in the water on the block for at least 3 minutes to ensure the water "freezes". | ||
Science Principle |
The water and crystals are initially at room temperature. Heat energy was transferred from the water to the materials in the flask, increasing their internal energy. This is therefore and example of an endothermic reaction. | ||
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