[Biological]

Humidifiers turn water into steam. If a humidifier is filled with hard water, a residue called "scale" made from calcium and magnesium deposits will form along the inside of the machine. Is this a chemical reaction?

This is what I gave as a response:

 I would suspect this to be a decomposition chemical reaction which starts off with hard water and decomposes into all the individual products including Calcium, Magnesium, and H20. 

But apparently this doesn't answer the question.  Help please?  Thank you.

[fledarmus]

What is hard water?

[Biological]

What is hard water?

I believe it's water that contains a high mineral content.  Esp. calcium and magnesium. 

[Arkcon]

What is hard water?

I believe it's water that contains a high mineral content.  Esp. calcium and magnesium. 

Good, so we start with water, and we lose steam, which is water vapor.  We start with calcium, magnesium ... what?  Free metals?  Calcium and magnesium ions ... by themselves?  Or with something else?

[Biological]

This is literally the entire question as it's been presented to me.  I'm also completely at a loss as to what she's asking for.  

I think the question may be asking if this is one of the 5 types of chemical reactions:  combination, decomposition, combustion, single replacement, double replacement.  

The teacher gave this response:  The water is not "pure" water but contains dissolved substances. Thus it is a solution. With this in mind, what happens?

[AWK]

Start reading from:
http://en.wikipedia.org/wiki/Hard_water

[Biological]

Is the fact that it's a solution make it so it's reversible and therefore not a chemical reaction?