Why does a sealed bag expand in the freezer

[Nutz]

I'm a confused Nutz.
Recently I've been putting sealed bags of toffee from Woolies straight into the freezer (I like them like that because they're nicer to eat cold)
I know that if you were to climb to an certain altitude with them they would expand and eventually pop, something to do with air pressure inside the bag..
I think if you heat air up it expands too? ......so why are the bags ready to pop in da freezer.
I'm missing something here??

 

[Twizzle]

The bag pops with an increase in altitude because the air is less dense as altitude increases so the air in the bag will expand, assuming temperature is reasonably constant.

The only thing that expands as it gets below freezing point is water, everything else contracts, hence why ice floats.

The air pressure in the bag should get lower as the temperature gets lower, so the only logical explanation that I can think of is that there is moisture in the bag or leaching from the frozen toffees which is expanding as it freezes.

Would need to be a reasonable amount of moisture though.

 

[SpaceMonkey]

It’s because water crystallises when it freezes and the rigid crystalline structure of the water molecules takes up more space than water in a liquid state where the molecules all slide around against each other.

 

[Nutz]

It’s because water crystallises when it freezes and the rigid crystalline structure of the water molecules takes up more space than water in a liquid state where the molecules all slide around against each other.

Cheers. I didn't know you guys replied so I googled it. The question I posed was the first hit I saw in google, we're famous Do you think the bags swell because the bags of sealed toffee is near the freezer seal and when the freezer opens and closes the compartment sucks in air as it seals?
I guess your theory about ice crystals forming might be right because when I open the bag the toffee is moist.
You solve the worlds problems Space Monkey and I'm going to coach the Wests Tigers...I couldn't do worse than Sheens or Benji.

 

[Nutz]

The bag pops with an increase in altitude because the air is less dense as altitude increases so the air in the bag will expand, assuming temperature is reasonably constant.

The only thing that expands as it gets below freezing point is water, everything else contracts, hence why ice floats.

The air pressure in the bag should get lower as the temperature gets lower, so the only logical explanation that I can think of is that there is moisture in the bag or leaching from the frozen toffees which is expanding as it freezes.

Would need to be a reasonable amount of moisture though.

Yep I think your right mate. The toffees are wet after I opened them so I think the moisture trapped in them when packaged/sealed froze. The were probably packed in a humid sea level factory too.
I googled it and you guys are on the money.
On a side note, I remember buying potato chips at 34⁰ Port Moresby and flew in a helicopter to Mt Hagan (7000ft) and when we landed I went eat my chips and the bag was ready to burst....cool.

 

[Mr Angry]

Chemistry is cool and you can put other things in freezer and blow it up.

Water our life force comes in solid, liquid and gas.

I still love there is an element called Thorium...

 

[Nutz]

Chemistry is cool and you can put other things in freezer and blow it up.

Water our life force comes in solid, liquid and gas.

I still love there is an element called Thorium...

Oh great, another thing I have to google. Please explain Mr Angry....said in a screachy Pauline Hanson voice.