Dry+Ice+Properties

Formula
CO2

Appearance
Appearance at SATP - Colourless, odourless gas Appearance below -78.5ºC (at atmospheric pressure) - white solid, much like frozen water

Density
1.4 g/mL - 1.6 g/mL (solid) @ -78.5ºC 1.9 g/L (gas) @ 0ºC

Melting/ BoilingPoint
-78.5ºC (sublimates directly from solid to gas)

Solubility In Water
1.45 g/L@ 25ºC and 100 kPa

Importance of Properties For Lab
The properties of dry ice are crucial for this lab. Carbon Dioxide has a low melting point, which means that in its solid form, it is very cold. This low temperature would allow it to quickly reduce the temperature of many things. It is much colder than regular ice, and much more dense, meaning the same amount of dry ice has significantly more cooling power than regular ice. it has much less cooling power than liquid nitrogen however, due to it's poor thermal contact with objects to be cooled. A solid touches another solid at only a small portion of it's surface area, whereas a liquid can cover the complete surface area of the solid to be frozen, cooling it much more quickly, and therefore freezing it more quickly. Since dry ice is never found in liquid form under normal conditions (it sublimates directly to a gas), to allow the dry ice to use its full potential speed when freezing an object, you must first use it cool a liquid to as near its temperature as possible. If you attempted this with water, it would simply freeze and be more ineffiient as dry ice. However by using isopropyl alcohol, which has a very low melting point, you can create a very cold liquid that is nearly as effective at freezing objects as liquid nitrogen.