Vapor Pressure and Making Pasta

[jgalt42]

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Hey Guys,

I guess there is a technique when you put salt into a pot of water before you boil pasta. When you do that, because NaCl is nonvolatile, it lowers the vapor pressure. I've heard that it makes water boil faster, but seeing that you lower vapor pressure, and because vapor pressure needs to get up to atmospheric pressure in order to boil, doesn't it take longer to boil when you put salt into a pot of water?

 

[capn jazz]

Adding salt to water makes it take longer to boil by raising the boiling point, but due to the raised BP, once it does boil, it's at a higher temperature and the pasta cooks faster.

 

[matth87]

Adding salt to water makes it take longer to boil by raising the boiling point, but due to the raised BP, once it does boil, it's at a higher temperature and the pasta cooks faster.

Yup

 

[Seraph 84]

I was reading in TBR chem that adding salt doesn't help that much.

 

[boaz]

Hey Guys,

I guess there is a technique when you put salt into a pot of water before you boil pasta. When you do that, because NaCl is nonvolatile, it lowers the vapor pressure. I've heard that it makes water boil faster, but seeing that you lower vapor pressure, and because vapor pressure needs to get up to atmospheric pressure in order to boil, doesn't it take longer to boil when you put salt into a pot of water?

I thought so too for a long time, but then I realized that time until boiling and boiling point have little to do with each other. This is especially in the case of boiling water for pasta since the amount of salt is so small that the change in b.p. is a small fraction of a degree. The salt may actually increase the heat conductivity and thus allow for quicker boiling. I keep telling myself I'll do an experiment one of these days ... but I'm kinda lazy.

If you really want a foolproof way to decrease boiling time, shake the pot every half-minute or so. Think about why ...

 

[dragon529]

TBR explains that you add salt when cooking pasta to increase the osmolarity. Since salt is added, the water will be less likely to go into the pasta, therefore your pasta won't be soggy and nasty

 

[loveoforganic]

TBR explains that you add salt when cooking pasta to increase the osmolarity. Since salt is added, the water will be less likely to go into the pasta, therefore your pasta won't be soggy and nasty

This. It would take an enormous amount of salt to significantly effect the boiling point and thus the cooking time of the pasta.