Even the brightest student may struggle to visualize chemical changes where they really happen-- at the molecular level. Graphic organizers help students grasp and remember abstract concepts pertaining to chemical change by organizing vocabulary, pictures and concrete examples in visual maps, graphs and foldable notes.
Chemical vs. Physical Changes
You can find a wealth of free examples of graphic organizers online, including at Freeology.com, or you can create your own. To help students differentiate between chemical and physical changes, have them fold a paper into three sections. In the center, place the picture and name of a familiar material. Draw an arrow pointing left to a picture of a physical change and to the right a chemical change. For example: Chop<------------- WOOD---------->Burn Bend<--------------IRON-----------> Rust Boil<---------------WATER--------->Electrolysis The main questions to ask are, "If you burn wood, is it still wood? If you chop wood, is it still wood?" The pictures will help students to see how chemical changes are irreversible and change the actual makeup of the material.
Signs of a Chemical Change
Students can create a foldable chart, such as a five-door book, to organize information about the main signs of a chemical change. Fold paper in a hotdog fold leaving about a half inch overlap to write the heading, "Signs of a Chemical Change." Glue the uncut side into a notebook or sturdy paper. With the paper folded, write one of the five signs per section: precipitate, unexpected color change, change in chemical property, temperature change and gas formed. Open the paper, add a definition and description on the left and a drawing of an example of this change on the right.
Rate of Chemical Reaction
The speed, or rate of chemical reaction, is affected by many factors such as concentration, temperature, surface area, a catalyst and pressure. You can use a square web map, with a pentagon in the center of the page and a box attached by a line to each corner. In each box write the factor, definition, example and draw a picture to represent the factor. Reference any experiments or demonstrations you have done in class as concrete examples.
Endothermic and Exothermic Reactions
A main indicator that a chemical change has occurred is the change in temperature. Exothermic reactions release heat and feel hot, and endothermic reactions absorb heat from their environment, which results in a decrease in temperature. In this case, a simple graph of time versus temperature is the best way to graphically represent the difference. When reactants change into products and heat is released, the temperature will go up, as will the slope of the line. For an endothermic reaction, the temperature and the slope both go down. You can have the students record what is going on in the reaction right on the graph.
- BananaStock/BananaStock/Getty Images