Acrostic: dihydrogen monoxide

d
i
h
y
d
r
g
e
n

m
o
n
o
x
i
d
e

D - Dangerous substance
I - It's colorless and odorless
H - Harmful to people and property
Y - You can't taste it
D - Disrupts cell membranes
R - Reactive Hydroxyl Radical
G - Gene and DNA mutations
E - Explosive compounds
N - Neurotransmitters can be critically altered

M - Most people don't know what it its
O - Only people who look into it will find out
N - Nothing can survive without it
O - Otherwise safe
X - X marks the spot, you can find it on many maps
I - Included in everything
D - Drinkable, it's safe
E - Especially because it's WATER, H2O

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Yes it would be a physical change.