Group and Discussion Activities
- What evidence can be observed to indicate that a chemical change has occurred? [Color change, change in physical state, energy absorbed or released.]
- Why is it useful to be able to classify chemical reactions? [Classification enables us to organize information and ultimately to predict the results of similar types of changes.]
- Is there only one type of classification that might be used for chemical reactions? [No, there are many different ways to classify reactions. Many of these will be used as knowledge of chemistry increases. It is always necessary to state the criteria used for the classification.]
- What future classification schemes are suggested by this study? [Is energy absorbed or released? How fast is the reaction? What kind of products are produced? What kind of process is involved in the change?]
|a. Elements ||c. Gases ||e. Precipitates ||g. Solid Elements
|b. Solids ||d. Compounds ||f. Gaseous Elements ||h. Liquid Elements
Formulas, Equations, Conservation of Mass
- Zip-closure sandwich-size plastic bags
- Paper clips-jumbo, regular, small, assorted colors (at least four different types are needed); use at least six clips of each kind.
- Have students work in groups of two or three. Instructions can be both verbal and written on the board, as the activity progresses. Give bag of clips to each group.
- Use symbols J for jumbo, R for regular, Sm for small, and appropriate symbols for colored clips-Bl for blue; Wh for white; Rd for red (or any other designations you find satisfactory).
- Give directions for the activity by having one student in each group make a particular model. Then instruct the other student to look at it to see if it is what would be expected. If not, have them agree on a structure and explain verbally to each other why it is like it is. The class can give feedback when groups do not agree.
- Start with instructions to show an atom of an element-R, for example.
- Proceed to more complex examples, e.g., a diatomic molecule J 2 , multiples of an element, 4 J, and then work into compounds, RBl, JWh 2 , J 2 (BlRd)3 .
- Invite students to carry out chemical reactions involving a 1:1 mole ratio:
R + Bl ---> RBl
R + JWh---> J + RWh
JBl + RWh---> JWh + RBl
- To show the necessity for conservation of mass, proceed to:
2R + Wh 2 ---> 2RWh
2J + 2RRd ---> R 2 + 2JRd