FUSE Spring 2016 - Page 5

egg-emistry ActiVities! iSCIENCE ese trY tHM At Ho e! a magic egg-ct! Can you make an eggshell 'disappear' using only vinegar? 1. 2. 3. Yes! Vinegar is about 4% acetic acid (chemical formula; CH3COOH) and the rest is water (H2O). Eggshell (calcium carbonate, CaCO3) reacts to acetic acid. If you soak an egg in vinegar, the carbonate (CO3) in the shell steals hydrogen (H) from the acetic acid. They join to make carbonic acid (H2CO3). 4. You might see bubbles! -This carbonic acid shortly 5. Meanwhile, the calcium from the eggshell 6. 7. 8. breaks down and swaps its oxygen (O) around, making water and carbon dioxide (CO2) instead. This is written as H2CO3 => H2O + CO2. C H ALLE NG E : F ol l o w t h is story ab out change ! hooks up with the acetate to form calcium acetate, Ca(CH3COO)2. Interestingly, all acetates dissolve in H2O! (Yes, that's the water!) You are left with just a translucent membrane holding together a spooky-looking egg! Oh and don't forget the buzz from understanding CaCO3 + 2 CH3COOH => H2O + CO2 + Ca(CH3COO)2...! you’re a rotten egg! Use science to test if an uncooked (raw) egg is fresh! 1. 2. 3. Place undamaged egg gently into glass bowl of cold water. (Deep enough for egg to turn in any direction underwater.) If raw egg SINKS to bottom of water it is FRESH! On its side? Super fresh! Standing upright on one end? Older (although probably fine to eat). If raw egg FLOATS it is NOT fresh! It may be 'off ' and rotten or in fact still safe to eat, just not at its best. CHECK OUT: • QUIZ & WONDER WALL • ACTIVITY MIX • COOL WEBLINKS CHALLENGE: Why does this work? (See Answer – iScience next to the Quiz, p 17.) FUSE 5