Important annoucement - Chemistry

Dear 3E2,

See you guys for extra lesson on 5 May (Wed) 2.30pm.

Jia you in your exam preparation!

Eat well and sleep well too!

Cheers,
Mrs. Yeoh

Thursday, April 22, 2010

3) Onions



When we cut the onion, we cut through the cells, releasing their contents. Amino acid sulfoxides to form sulfenic acid. Enzymes that were kept seperated now are free to mix with sulfenic acid to form a volatile sulfur that reacts with your tears to form sulfuric acid, making your eyes "cry". The chemicals are amino acid, sulfenic acid, propanethiol sulfuric-oxide and sulfuric acid.
First, we can chop the onions in cold water so that the volative sulfured compound will react with the water but not our eyes. Second, we can freeze the onion for 10mins before cutting. It will slow down the chemical reaction of the volatile sulfured compounds.

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