Graphing makes up an important skill-set for students and can be taught with simple activities. One teaching idea is to pass out 5 gummy worms to each student. Have them note the colors of their worms. Tell the students to create a basic bar graph by creating columns for the different colors and then make the bars match the number of worms of each color that they possess. This finishes the first graph. For the second graph, have them take the number of worms for each color, divide by 5 (the total), and then multiply by 100. This will give them each color's percentage. Have the students create a pie graph based on the percentages.
Although supply and demand might be initially thought of as a more advanced concept, learning the basics is incredibly simple and can be made fun and creative as well. Supply the classroom with drinks, such as cold soda, hot chocolate, or other assorted beverages. Over the course of a set period of time, ranging from several days to weeks, each day have the students rate how much they'd be willing to pay for each type of drink. If performed during periods of weather fluxes, then the curve should vary based on changes in weather, which shows how demand curves are affected by their environment.
Another fun and creative economics concept that can be taught to older elementary school kids is marginal utility. The game begins by asking a class to rate their well-being on a given scale. Afterwards, give them chocolate, candy, or another object that will increase their rate of happiness. After providing this, then ask them to re-rate their scale. Do the same thing several times over and there should be a general shift in the increase of happiness after each subsequent turn. Have the students graph the curve afterwards.
Density can be a tricky concept to understand, but an easy one to visualize for kids. Invisible density can be made visible by preparing a container. Fill the container half full with water and salt. Next fill the rest of the container with water that is unsalted. Then place an egg in the water. If performed correctly, the egg should drop through the unsalted water---due to being more dense---while floating within the salted water, due to being less dense.