"H2O is hot water, and CO2 is cold water"

“Define H2-O and CO-2. H2-O is hot water and CO-2 is cold water” (supposedly from a student exam paper) was printed in The Lamar Democrat (Vernon, AL) on November 9, 1932. “Coach: ‘Define H-2-O and CO-2.’ Annie D. ‘H-2-O is hot water, and CO-2 is cold water’” was printed in the Opelousas (LA) Herald on February 6, 1942. “H2O is hot water, and CO2 is cold water” was printed in the book Anguished English (1987) by Richard Lederer. This is incorrect, of course.

“Herb’s definition of H2O, CO2 and CH2O. ‘H2O is hot water; CO2 is cold water and CH2O is sea water’” was printed in the Ferndale High School - Reflector Yearbook (Johnstown, PA), Class of 1942. “If H2O is hot water, then CO2 is cold water and CH2O is sea water” was printed in the book A Treasury of Science Jokes (1986) by Morris Goran. “CH2O” sounds like “sea H2O,” but it’s actually formaldehyde.

Wikipedia: Water
Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth’s hydrosphere and the fluids of all known living organisms (in which it acts as a solvent). It is vital for all known forms of life, even though it provides no calories or organic nutrients. Its chemical formula H2O, indicates that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds.

Wikipedia: Carbon dioxide
Carbon dioxide (chemical formula CO2) is an acidic colorless gas with a density about 53% higher than that of dry air.

Wikipedia: Formaldehyde
Formaldehyde (/fərˈmældəhaɪd/ fer-mal-duh-hahyd, also /fɔːrˈmældəhaɪd/ for-) (systematic name methanal) is a naturally occurring organic compound with the formula CH2O (H−CHO).

Newspapers.com
9 November 1932, The Lamar Democrat (Vernon, AL), “Boners,” pg. 6, col. 5:
BONERS are actual humorous tidbits found in examination papers, essays etc., by teachers.
Define H2-O and CO-2.
H2-O is hot water and CO-2 is cold water.

Newspapers.com
6 February 1942, Opelousas (LA) Herald, pg. 4, col. 6:
Coach: “Define H-2-O and CO-2.”
Annie D. “H-2-O is hot water, and CO-2 is cold water.”

E-Yearbook.com
Ferndale High School - Reflector Yearbook (Johnstown, PA) - Class of 1942
Pg. 81:
Herb’s definition of H2O, CO2 and CH2O. “H2O is hot water; CO2 is cold water and CH2O is sea water.”

Google Books
A Treasury of Science Jokes
By Morris Goran
Springfield, IL: Lincoln-Herndon Press
1986
Pg. 60:
If H2O is hot water, then CO2 is cold water and CH2O is sea water.

Google Books
Anguished English
By Richard Lederer
New York, NY: Dell Publishing
1987
Pg. 7:
H2O is hot water, and CO2 is cold water.

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Google Groups: misc.education.language.english
Seeking language anecdotes, quotes
kevin giansante
Mar 24, 1996, 3:00:00 AM
Here’s one for you, from an actual student paper:
“H2O is hot water. CO2 is cold water.”

Twitter
Celebrity Paycut
@celebritypaycut
Just Located: Al Gore’s Answers to His Science Class Final Exam: 1. H2O is hot water and CO2 is cold water. 2. T.. http://tinyurl.com/6vsme3
1:36 AM · Jan 18, 2009·Twitter Web Client

Google Groups: jokes-n-toons
March 3rd Jokes-N-Toons
SJ JNT
Mar 3, 2009, 5:57:14 AM
(...)
Science Definitions from Kids

H2O is hot water, and CO2 is cold water.

Twitter
Tweepak
@DeePakao
Water is composed of two gins - Oxygin & Hydrogin. Oxygin is pure gin. Hydrogin is gin and water! H20 is hot water, CO2 is cold water! 😉
10:21 AM · May 26, 2009·Twitter Web Client

Google Books
Title H2o Is Hot Water Co2 Is Cold Water: Lined A5 Notebook for Scientist
Author Science Publishing
Publisher Independently Published, 2019
ISBN 1711751375, 9781711751375
Length 122 pages

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WSⱯꓛꓤⱯS ꓨNIꓥIꓶ
@SarcasmLiving
H2O is hot water, and CO2 is cold water.
8:54 AM · Jan 24, 2020·Twitter for Android

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B̸̪̏́ͅḧ̵͓̼e̸̥͍̚ň̵̡ṫ̷̨̫a̵̱̥̓ ̴
@Babe_A_Roo
H2O is hot water and CO2 is cold water
3:02 PM · Mar 23, 2021·Twitter Web App