Science Buddies: "Ask an Expert"

Does the amount of sodium in a drink affect the time it takes to freeze?
I am looking for resources concerning this topic to write my research paper on the topic above.

Hi Linda,

Sodium does affect the freezing point in a drink. Sodium, the solute, depresses or lowers the freezing point of a solvent, which in this case would probably be water. I would assume that the time it takes for a salt water (let's use this term and pretend its the drink with more sodium) to freeze would be longer compared to the water (or the drink with less sodium) because the salt water would need more time to freeze since it must reach a lower freezing point than water. So, since water freezes at 0 degrees Celsius, the salt water would need to freeze at -15 degrees Celsius, and assuming that both solutions lower the same amount of degrees in temperature, it would take longer for the salt water to achieve its freezing point than pure water.

You can try these websites to familiarize yourself with the concept of freezing point depression of liquids:
http://hyperphysics.phy-astr.gsu.edu/hb ... eltpt.html
http://www.chemteam.info/Solutions/BP-E ... Lower.html

Hope this helps!

Hi Linda,

You have already gotten some great advice from grai. One thing I wanted to add is that freezing point depression depends on the number of particles dissolved in the liquid, not the type. Thus, other solutes including sugar will also affect the freezing point in a drink. You will want to account for all of your solutes when examining freezing point depression.

Make sure to use plain (preferably distilled) water as a control!

I hope this helps. Please post again (in this same thread) if you have more questions.

Heather