My daughter has a science question

[lugeforlife]

As she slurps away at her maccys milkshake.

How come the top of her straw has gone so soggy she can't drink from it but the bottom which is actually in the milkshake is still robust? Does she have particularly acid saliva?

Not acid, more likely enzymes in the saliva. Also might be to do with her gripping that part of the straw in her mouth as she sucks so it's under more pressure

Plus if it's colder in the milkshake?

As above plus the equalising pressure of the high viscosity liquid holding the straw in a more stable position.

*holding the bottom of the straw in a more stable position

She'll be exerting pressure on the top of the straw with her lips and also from sucking, which the bottom of the straw won't be subjected to.

Because paper straws were made to piss people off! They disintegrate before you can finish the bloody drink 🙂

Also, the properties of the milkshake (thicker and colder) make suction of it more difficult thus the pressure will be both greater and applied for a longer time on the straw than if she was drinking something like coke.

We tend, as humans, associate behaviours, patterns and rituals with foods. The fact that the milkshake requires more effort/takes longer/has an annoying soggy straw top makes it stick in our mind more than, perhaps, the effortless imbibing of another drink: even if they both are transported from cup to gob via paper tube.

Ohhhh super, thanks everyone!

If you read her all my wittering explanations your DD will probably wish she hadn’t asked! 😂

The paper is waxed isn't it? So warm wax [mouth] versus cold wax [shake].