Reflections on Previous Experiments and Observations

You may talk over these questions with your lab partners, but write your responses in your own words.

1. Is it necessary to have the notion of density? Why not simply have the separate concepts of mass (weight) and volume? For example, what's wrong with simply saying that "zinc is lighter than copper" when explaining why new pennies are lighter than older ones? In tables of the properties of the metals, why not simply record the mass (weight) of each element rather than its density?

2. Do you think it would be possible to identify unknown pure metals by measuring their density carefully and comparing to the tables of the properties of the metals? In other words, if someone gave you a hunk of yellow metal and said it was gold, could your prove or disprove that claim by measuring the density of the hunk? What information would you need?

3. Reflecting on the demonstration you saw in the lab involving the "water aspirator" suction device and the flask of acetone ("nail polish remover"):

a. What is going on at the molecular level when a liquid boils?

b. How does your explanation of boiling account for the observed facts that, at high elevations, water boils at a temperature lower than 100 deg. C?

c. How does your explanation of boiling account for the observation that a pressure cooker cooks foods more rapidly that boiling water in an open container?

d. What exactly did you observe in the laboratory demonstration involving the "water aspirator" suction device and the flask of acetone?

e. What is going on at the molecular level that can explain the puzzling observations in that laboratory demonstration?

4. a. What are the two reference systems (hot and cold) that define the Celsius temperature scale and what are their temperatures on that scale?

b. What are the two reference systems (hot and cold) that define the Fahrenheit temperature scale and what are their temperatures on that scale?

5. What is the smallest and simplest molecule, containing only carbon, hydrogen and oxygen, that you can construct with your model kit that is chiral, i.e. has distinct non-superimposable left- and right-handed forms? It must be a "legal" molecule with no empty bond holes. Prove that it is chiral by constructing its mirror image. (Produce one pair for the whole class).

6. Describe one experiment or observation in this course that caused you to change a previously-held idea. Describe how you thought before, what experiment or observation you made, and how it caused you to change your mind.