Can saltwater, water, alcohol, and shampoo be stacked? This is a very simple student inquiry activty (and one of my students' favorites) that can be done in class (download handout).
What happens to hot and cold water when placed in room temperature water? What if the water is colored? Watch the video for a simple demonstration of the properties of hot and cold water.
The Styrofoam cup. It seems like a simple unitasker, one that holds liquids and is a good insulator. Why is it a good insulator and so light? Styrofoam is the the brand name that Dow Chemical uses for its version of polystyrene. Polystyrene is a polymer, which is a substance that is made up of repeated units, monomers, bonded together. What makes Styrofoam special is the process in which it is made. During the process, gas is blown into the polystyrene causing the material to be mostly empty space. The Styrofoam is very low in density becuase the mass of the polystyrene is contained in a larger area. It is a good insulator because the air spaces that make up the foam deters heat energy flow. The above video demo shows what happens when the polystyrene is dissolved in acetone. The polystyrene structure basically collapses and condenses, leaving a hardened, more dense mass.
Indicators are chemicals that show what type of chemical reaction occurred. I decided to have some fun with some pH indicators--chemicals that signify if a solution is acidic or basic. In the video, 3 different pH indicators, bromothymol blue, phenol red, and phenolphthalein (and ammonia) are used. The solutions are in long plastic pipes whereupon Alka Seltzer tablets are dropped. The Alka Seltzer tablets react with the water to produce carbon dioxide gas. The carbon dioxide dissolves in water creating carbonic acid and thus making the solution more acidic. The color of the solution changes as a result. Later ammonia, a base, is added to show how the color changes when the solution turns basic.