Chemistry questions about specific content rather than curriculum choices

[Kendall]

I am going to teach Chemistry next year to my rising 10th and 11th graders. My older kids did a self teaching text and I am wanting to move away from it. So the preparations begin... I am working through introductory Chemistry by Zumdahl and just finished Chapter 3.

 

I have a few questions.

 

This is a question from the text.

 

Consider three 10 g samples of water: one as ice, one as liquid, and one as vapor. How do the volumes compare with one another? How is this difference in volumes related to the physical state involved?

 

Unfortunately this is an odd numbered problem and the solutions guide has only even answers. This problem is listed as one students could do after reading section 3.1 which is very short and just describes the three states ad doesn’t talk specifically about water at all. The previous chapter had the density of liquid water and a discussion of the relationship between density, mass, and volume. I think I know the answer: smallest volume to largest- liquid, ice, vapor. Is this correct? Is there something in the text up to this point that should allow them to figure this out? Or if you don’t have the text,what information would they need?

 

I also don’t understand why element and compound are defined and molecule is used occasionally but not defined until 30 pages later. Do you have any thoughts on that? 

 

Thanks,

Kendall

[EKS]

Equal masses of a substance are usually most dense (and have the smallest volume) in the solid state and least dense (and have the greatest volume) in the gaseous state.  The liquid state would be somewhere in between.  But water is odd because its solid state is less dense than its liquid state.  This is the reason that ice floats on liquid water.

 

Both of my children and I found the Zumdahl text to be very clearly written, and I'm surprised that I missed these issues when we used it (though my degree is in biochemistry, so I may have just taught over any omissions without noticing).

[Kendall]

Thank you. I am glad to hear that you all found it to be clearly written. I bought 2 student texts and a solution guide and assignments so I want to stick with this. I'm sure there isn't going to be a text that is completely without a few issues! If I don't find these things myself this summer, my daughter who gets thrown by them will be asking.

 

I'm not finding where molecule is first used and defined, so I will just teach that when the book introduces elements and compounds.

[JanetC]

The 10g of water vapor will fill whatever container is holding it. The smaller the container the higher the pressure.

[Kendall]

I should have trusted myself because my first thought was that 20 g water vapor could go in various sized volume containers.