Physical Properties:
-Colourless
-Odourless
-Heavier than air
Combustable
-NO
Solubility in Water
-Soluble
Acidic / Basic
-Acid
Testing for Gas
-Limewater Test

Equations:
Acid + Carbonate -> H2O + Salt + CO2

Equation explaining the solubility of CO2 in water and the Acidic nature of CO2:
CO2+H2O -> H2CO3
Carbon Diocide + Water -> Carbonic Acid

The CO2 dissolves into the water creating Carbonic Acid (Hydrogen Carbonate)

Equation explaining the CO2 reaction with Limewater
Ca(OH)2 + CO2 -> CaCO3(s) + H2O
Calcium Hydroxide (Limewater) + Carbon Dioxide -> Calcium Carbonate + Water + CO2

The CO2 reacts with the Limewater to create Calcium Carbonate (salt) precipitate mixed in with water (hence the milky colour) There are also bubbles formed which contain CO2. Because of this reaction Limewater was used as building mortar before cement as the calcium carbonate precipitate eventually dries out, and hardens.

Equation explaining what happens when you breathe (and keep breathing) into Limewater
Ca(OH)2(aq) + CO2(g) -> CaCO3(s) + H2O
H2O + CO2 -> H2CO3(aq)
H2CO3(aq) + CaCO3(s) -> CaC(OH)2 (aq) + H2O + CO2(g)

This cycle of Limewater turning into water with calcium precipitate and then turning acidic and dissolving the calcium into the acid and starting again is caused by the continual reaction of CO2 and the other chemicals. It is a culmination of the same forumlae and equations used in the previous mini-experiments. It is an example of an Acid (Carbonic Acid) when added to a carbonate (calcium carbonate) creates a Salt (Calcium Hydroxide in aquios form) H2O and Carbon Dioxide.