I have a physics assignment to do on Aerosol Cans !?

Here are a some questions to get you thinking about aerosols and aerosol cans. I could give you the answers, but better that I give you some ideas that you can go learn about. I've included a couple of web sites that you might find helpful. I'll bet you never thought there were so many questions you could ask about aerosols and spray cans, good luck!

What makes an aerosol? Can any liquid be an aerosol or only certain ones? How does temperature come into play, can a liquid be an aerosol at room temperature but not at a hot or cold one?

What are the conditions that create an aerosol? Pressure difference through a nozzle, anything else? Is there anything special about the shape of a nozzle that is needed to create an aerosol from a spray can, or will any nozzle shape work? Why does the liquid break up into tiny droplets instead of squirting out in a stream? Does surface tension of the liquid come into play?

What affects the size of the droplets, surface tension, density, temperature? How does the ambient environment affect the aerosol? That is, if you spray a spray can into an air environment at standard pressure and temperature, you get an aerosol. What happens if you spray into a pure nitrogen, or other gaseous atmosphere?

How does an aerosol can work? There's a certain amount of gas inside that pressurized the can and squirts the fluid out. What properties are important in the gas? Would you want a poisonous gas used in a whipped cream can for example? How does temperature affect the pressure inside the can? There are always warnings on aerosol cans about not throwing it into a fire, why not?

Most aerosol cans on the supermarket shelf are roughly the same shape and size. WHy? Is it just marketing, or is there some physical reason why they are that size. How much pressurized gas needs to be in the can to squirt out all of the liquid at exactly the same time that the gas runs out? You only have so much volume in the can, so too much liquid means too little gas, and some liquid gets left in the can. Or, too little liquid means too much gas, and there's plenty of gas left over after the can is empty.

Why does an aerosol can get cold when you spray it for awhile?

How are aerosol cans made, what is the process? Since the can is pressurized, how is the nozzle designed so that it won't leak the gas? What material is the can made out of? Any special things to think about to make sure the can is strong enough to withstand the pressure inside?

What's the history of the aerosol can? Who invented it, and why? What kinds of thigs are aerosol cans used for?

Advantages: portability, ease of use, disposable

Disadvantages:

One time use, you can't refill an aerosol can

You can't spray upside down

Safety issue, it can explode

Propellent gas must be compatible with the liquid inside - imposes limitations on what can be sprayed

Hope this helps,

-Guru