11. Conservation of Mass,       Charge, and Energy   Previous PageNext Page

1. What is a conservation principle? Why is it useful in chemistry?

2. Which of the following properties of reactants and products are always conserved during a chemical reaction?
(a) colour ; (b) temperature ; (c) number of atoms ; (d) number of bonds ;
(e) kinds of bonds: ionic, covalent etc. ; (f) energy ; (g) molecular shape ;
(h) mass ; (i) electrical conductivity ; (j) dipole moment ; (k) oxidation
number ; (l) total of mass and energy

3. In what way does a zero net change in oxidation number for all participants in a reaction represent conservation of electrons?

4. What is the hidden assumption when we use conservation of mass as being equivalent to the conservation of the number of each kind of atom?

5. What is the difference between weight and mass? Which would change and which would stay the same on going from the Earth to the moon? Would the one that changes be greater, or less, on the moon?

6. How can we use the weighing operation to tell how many atoms are present in a sample of material, although the direct counting of atoms is impossible?

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