To begin this oil and water experiment, all you need is a clear plastic bottle (16- or 20-oz. bottles work well), some water, your favorite cooking oil and some food coloring. Pour the water and the oil into the clear plastic bottle. You can use any ratio of oil and water you would like. Add several drops of food coloring to the mixture. Replace the cap on the end of the bottle and give the bottle a good hard shaking. Observe what happens as the water and oil begin to settle again. The food coloring will only adhere to the water molecules and not to the oil as the oil begins to separate and settle on top of the water. This occurs because of the different densities and molecular structures of oil and water.
Pour water and oil into a clear plastic bottle again, using any ratio you desire. Make sure to leave some air space in the bottle (this will be important for the results). Allow the oil to rise to the top, and then place the bottle in the freezer for several hours. Observe how the densities of the oil and water change when the temperature is lowered. Remove the bottle from the freezer and observe how the frozen water is now above the oil. This is because water changes density as it passes from a solid to liquid state. Water also expands as it freezes, which is why you should leave some airspace in the bottle: to prevent overflow from freezing.
Pour water and oil into a clear plastic bottle at any ratio you choose. Add several drops of your favorite food coloring, secure the end, and shake. Again observe how the liquids react to each other. Once the liquids have settled, add several drops of dish washing detergent to the mixture. Secure the end again and shake. Now observe the changes in the experiment once the detergent is added. The mixture begins to emulsify because the dish detergent changes the molecular structures of oil and water, making them more adhesive to each other.
Pour cooking oil into the bottle so that the oil fills about 3/4 of the bottle, then fill the rest of the bottle with water. Add several drops of your favorite food coloring into the mixture. Take 1/8 of an effervescent antacid tablet, drop it into the mixture and observe the reaction of the tablet on the mixture. The colored water will bubble up through the oil and sink back down, creating a lava-lamp-like effect. The effervescent tablets introduce carbon dioxide gas into the colored water mixture, creating the rising effect. As the bubbles burst, the colored water sinks again.