Cream Soda Physics & Diving

[Mako Mark]

The pressure on the bottom of the lake is one of the reasons the ice forms on the top.

The pressure has nothing to do with it dude.

 

[Mako Mark]

Ecch. I hate cream soda.

Thats OK sue, it works with beer too.
.

 

[WJL]

For your further education on supercooling and the effects of bubbles on liquids near the freezing point, clink this link.

 

[DepartureDiver]

How would this be true in a moving body of water that freezes, such as a river which is more or less always mixing? I think C Mark is correct in that the cold air freezes the water and therefore the surface gets colder first.

You need to start with water that is not near freezing such as 50 degrees. As the surface gets colder due to being in contact with the air, it starts increasing its density and then descends ... and the process then starts with the new water that just hit the surface. eventually as the water is cold, it's density starts decreasing and this less dense water is in contact with the surface and then it freezes. As to your example ... try this experiment. Place an ice cube in freezing water. Of course it will float. So did the water (all at the same temperature from the mixing) freeze at the surface from being in contact with the air or below from nucleating activity and then rise? Also, once a layer of ice forms, water can not come into contact with the air, so it is the water below the ice that is freezing ... which is not from any air contact.

 

[Mako Mark]

Once a layer of ice forms, water can not come into contact with the air, so it is the water below the ice that is freezing ... which is not from any air contact.

good point, this would be freezing by conduction.

 

[Scubakevdm]

There is a fundemental relationship between volume, temperature and pressure. This is demonstrated by Boyle's Law, Charle's law and the General Gas Law.

BOYLE'S LAW states that the volume of any dry gas varies inversely with its absolute pressure, provided the temperature remains constant. This law may also be expressed as the formula wherein V1 is the original volume of the gas, P1 is its original absolute pressure, V2 is its new volume, and P2 is its new absolute pressure.

V1*P1 = V2*P2

CHARLES'S LAW states that the volume of a gas is directly proportional to its absolute temperature, provided the pressure is kept constant. The equation for Charles's law is:

V1 * T2 = V2 * T1

The GENERAL GAS EQUATION combines Boyle's law and Charles's law. It expresses the interrelationship of the volume, the absolute pressure, and the absolute temperature of gases. The general gas law is expressed by the formula:

P1 * V1 = P2 * V2
....T1......... T2
(sorry about the dots, it wouldn't let me space it right without 'em)

1. When TEMPERATURE is held constant, increasing the pressure on a gas causes a proportional decrease in volume. Decreasing the pressure causes a proportional increase in volume.

2. When PRESSURE is held constant, increasing the temperature of a gas causes a proportional increase in volume. Decreasing the temperature causes a proportional decrease in volume.

3. When the VOLUME is held constant, increasing the temperature of a gas causes a proportional increase in pressure. Decreasing the temperature causes a proportional decrease in pressure.

In discussing the effects of pressure on a gas, we should point out that the volume and the temperature of gas are different AFTER the pressure has been changed. It is important to note, however, that a temperature change normally occurs in a gas WHILE the pressure is being changed. Compressing a gas raises its temperature; allowing a gas to expand lowers its temperature.

Therefore by chilling the cream soda, and the disolved gas inside to near freezing, and then reducing pressure by opening the bottle, you are allowing the gas to expand and its temperature to drop which removes heat from the solution it's disolved in from the inside out. Since you have already chilled the soda to near freezing the drop in temperature caused by the expanding gas is enough to put it over the edge.

 

[SueMermaid]

My brain hurts. Chemistry gives me hives. But Kevin's right.

 

[Scubakevdm]

My brain hurts. Chemistry gives me hives. But Kevin's right.

Not me, Boyle and Charles.

 

[Hank49]

You need to start with water that is not near freezing such as 50 degrees. As the surface gets colder due to being in contact with the air, it starts increasing its density and then descends ... and the process then starts with the new water that just hit the surface. eventually as the water is cold, it's density starts decreasing and this less dense water is in contact with the surface and then it freezes. As to your example ... try this experiment. Place an ice cube in freezing water. Of course it will float. So did the water (all at the same temperature from the mixing) freeze at the surface from being in contact with the air or below from nucleating activity and then rise? Also, once a layer of ice forms, water can not come into contact with the air, so it is the water below the ice that is freezing ... which is not from any air contact.

True the air is not in contact with the water under the ice...but in very cold conditions (-25 F) the temperature of the ice goes well below 32F also. So wouldn't the very cold ice start freezing the water underneath as it comes into contact with it?

 

[DepartureDiver]

Therefore by chilling the cream soda, and the disolved gas inside to near freezing, and then reducing pressure by opening the bottle, you are allowing the gas to expand and its temperature to drop which removes heat from the solution it's disolved in from the inside out. Since you have already chilled the soda to near freezing the drop in temperature caused by the expanding gas is enough to put it over the edge.

good points and physics in your post ... but in this situation, a supercooled liquid's temperature is already below freezing, so it is not the temperature drop that does it ... it was the seeding from the nuclei (in this gas the CO2 coming out of solution).