Basically the cumilative volume and weight of the bottle doesnt change at all. This is what happens.
As you pour your boiling water into the bottle it releases heat energy into the plastic that of course causes the plastic to turn into fluid... now the laws of physics... cant remember which one... anyway a body that has mass is always trying to change its shape to form a sphere assuming its left in a vacuum.
 
only thing is solids find it quite hard to do that but fluids would find it easier as their molecules are not tightly bound together. so basically thats what the bottle is trying to do as it starts melting.
 
Now the bottle is also finding it hard to do it properly coz for one as the water loses its energy the temperature drops and as there is no more energy to keep the plastic melted it solidifies halfway during the process of trying to  become a sphere... now at this point the bottle may look bent out of shape and smaller in size but if you look closely you will notice that in some areas the bottle is thicker and more irregular than others this has compensated for the height lost.
 
Finally the atmospheric pressure... as pressure inside the bottle drops coz the temperature has dropped, the bottle ends up being sucked inwards to balance it out with the external pressure. That is what is then responsible for the final shape of the bottle once it solidifies.

Steve Obbayi, 


 

From: skunkworks-bounces@lists.my.co.ke [mailto:skunkworks-bounces@lists.my.co.ke] On Behalf Of Peter Karunyu
Sent: Friday, June 05, 2009 9:38 AM
To: Skunkworks forum
Subject: Re: [Skunkworks] Of shrinking bottles

Look at this way, if you put a plastic bottle in fire, it will totally melt and turn to liquid (sort of) thus structurally look totally different from the original bottle. When you put the hot water, you start this melting process, but the hot water cools down probably because of contact with air and the process is halted.

Like Shiro said, it must be the Highlands bottle uses a different type of plastic from the others, maybe one with a lower melting point.

On Fri, Jun 5, 2009 at 9:23 AM, Shiro Njagi <sheeroh@gmail.com> wrote:
plastic melts in high temperatures.
I guess the Highlands bottle uses a type of plastic that is less
resistant to heat than the other bottles.
that's my take.

On 6/5/09, Tech List Kenya <techlistkenya@gmail.com> wrote:
> I have a question:
> The other day I put hot - as in boiling - water into a plastic bottle
> and it shrunk to almost half the size.
> This happens especially with Highlands juice bottles, av tested with
> Quencher and empty Coke 2ltr bottle but they are not affected much.
> I mean a 1ltr bottle literally shrunk to 500ml. Where did the rest of
> the bottle go?
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