a) at 8:00 am     Please get to class on time!
     b) at 8:05 am
     c) at 8:10 am
     d) at the time at least 25 students are present.

2. Which of the following statements is true?

     a) Matter takes up space.
     b) Matter has mass
     c) Matter and energy are closely related.
     d) all of the above.  See your lecture notes for definition of matter and the relationship between matter and energy

3. Which of the following cannot be classified as matter?

     a) chocolate
     b) smog
     c) heat  -- heat is classified as energy - How does heat move matter?
     d) genes

4.  Atoms, the smallest unit of matter, differ by

    a) mass
    b) volume
    c) reactivity
    d) all of the above  Atoms are distinct by size (and therefore mass and volume) and they are distinct by chemical behavior.

5. Review the lab exercise for this week and determine which has a greater mass, sodium (Na) or chlorine (Cl) ? 
Compare the average atomic mass of Na ( 22.99 amu ) with the average atomic mass of Cl (35.45 amu). 

6. Review the lab exercise for this week and determine which has a greater volume, sodium (Na) or chlorine (Cl) ?

Recall volume of a sphere = 4/3 p r ³  , and therefore, the larger the radius, the larger the volume.

Check out this web-site for an illustration of relative atom size: http://intro.chem.okstate.edu/1314F00/Lecture/Chapter7/Lec111300.html

7. Review the lab exercise for this week and determine which of the following atoms is not a component of ammonia.

     a) nitrogen atoms
     b) oxygen atoms  A molecule of ammonia is composed of  1 nitrogen atom and 3 hydrogen atoms  (NH₃)
     c) hydrogen atoms

8. Review the lab exercise for this week and determine which of the following compounds is the most abundant component of air:

     a) nitrogen gas
N₂,  is both an element and a compound and makes up about 79% of the mass of air. Oxygen makes up about 20%.
     b) oxygen gas
     c) hydrogen gas
     d) carbon dioxide gas

9. Which of the following terms best describes the molecular geometry of ammonia.

     a) linear
     b) trigonal planar
     c) tetrahedral
    d) trigonal pyramidal       

Explore this web-site and find a 3-D, rotatable,  model of ammonia (along with other molecules) : http://www.stolaf.edu/people/jackson/08-125/molshape/molshape.htm 

10. Which of the physical states of matter has indefinite volume and indefinite shape?

     a) gas 
     b) liquid
     c) solid

11. What is the physical state of ammonia at room temperature ( 20 ^oC) ?

     a) gas 
In your computer lab exercise, you discovered the boiling point of ammonia to be -33 ^oC, therefore, ammonia would be gaseous at 20 ^oC.
     b) liquid
     c) solid

12. The combustion of natural gas (methane) involves a reaction between methane and oxygen to produce carbon dioxide and water (steam). If the  combustion of 1000 g of methane leads the production of 2750 g of carbon dioxide and 2250 g of steam, how many grams of oxygen were consumed in the reaction?  

***Here's the key point:  The Law of Conservation of Mass:    Mass of reactants = Mass of products)

     a) 2000 g
     b) 3000 g
     c) 4000 g   mass of reactants = mass of products therefore, 1000 + x = 2750 + 2250   x = 4000
     d) 5000 g

 13. The process by which ice melts involves:

     a) a change in chemical composition
     b) a change in physical state:  solid to liquid
     c) a change in temperature  -  During a state change, the temperature remains constant.
     d) all of the above

14. The process by which ice freezes is:

     a) endothermic 
     b) exothermic   Heat  must be removed, from liquid to form solid and is therefore a product of the process.

15. Review the lab exercise for this week and determine which of the following describes the Haber reaction.

     a) ammonia and oxygen combine to make nitrogen dioxide
     b) nitrogen and oxygen react with each other to form ozone
     c) ammonia can be synthesized with a reaction between nitrogen and hydrogen. 
     d) hydrogen can be synthesized with a reaction between nitrogen and ammonia. 

16. Which of the following statements does not describe a physical property of a substance?

     a) Pure water is odorless.
     b) Ethanol is flammable. Flammability is a chemical property.
     c) Gold is shiny.
     d) Pure water is a poor conductor of electricity.

17. Which of the following statements describes an "extensive property" of a substance?

     a) Mercury is a liquid metal
     b) Water has a density of 1.00 g / mL
     c) A certain water sample has a mass of 10.0 g. Extensive properties describe a measurement of a particular sample.
     d) Water boils at 100 ^oC under conditions of normal atmospheric pressure.

18. As a spring is stretched

     a) its potential energy increases  -- What kind of energy do you have when you let go? -- kinetic energy.
     b) its potential energy decreases

19. Explain the terms "hypothesis" and "theory". A hypothesis is an explanation for a observation. A theory is an explanation that is supported by experimental evidence. Experimentation can promote a hypothesis to a theory. However, experimentation can never prove a theory.