Today's interactive Google Doodle takes you back to freshman year chemistry class to celebrate S.P.L. Sørensen, the Danish chemist who invented the pH scale.
If you spent more time passing notes under your desk than you did paying attention to what was happening on the chalkboard, this quick refresher should help. A substance's pH is a useful way of indicating how acidic or basic (i.e. alkaline) it is. The pH scale ranges from zero to 14: Anything less than seven is acidic, seven is neutral, and anything greater than seven is basic.
When you hit play on today's Doodle, you'll see an illustration of Sørensen in the middle and a rainbow pH scale along the top. In front of Sørensen is a card with an icon: For each icon, you'll be asked to identify where it lands on the pH scale, by tapping the lefthand arrow (to indicate it has a pH of less than seven and is acidic), or the righthand arrow (to indicate it has a pH of greater than seven and is basic).
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While we won't give you the answers — that would be too easy — some common examples of acidic solutions include battery acid, lemon juice, and tomato juice. At the basic end of the spectrum are sea water, baking soda, and bleach.
Sorensen created the measurement method in 1909. The scientist headed up Copenhagen's well-known Carlsberg Laboratory with his wife, Margrethe Høyrup Sørensen. He died on February 12, 1939.
Head to Google today to test your pH knowledge.