It is common knowledge that oil and water don't mix. However, for a fun twist on the reaction, direct students to freeze an oil and water mixture. Use a plastic container with water in it. Add cooking oil and watch it float to the water's surface. Explain about the properties of oil and those of water, emphasizing how water in its liquid state is more dense than oil. Place the container in the freezer for a few hours and then remove it. The oil will be underneath the water because water expands and becomes solid when it freezes, thus making it less dense than the oil.
When water turns into steam, it can literally disappear as the steam molecules disperse and mix with air molecules. Direct students to boil water in a beaker or sauce pan. Then, instruct them to hypothesize about how heat transforms water and at what temperature the transformation occurs. To make the activity more complex, students can add table salt or sugar to the water before boiling. Adding salt causes the water to boil faster by lowering its boiling point. Adding sugar to water elevates the boiling point by increasing the water's viscosity or thickening its consistency.
Condensation is an interesting process, because it is not only the temperature of the water that causes condensation. To demonstrate this, place cold water in a glass, then warm the air around the glass with a hair dryer. Give students an observation sheet and ask them to observe what happens inside the glass as well as environmental conditions that might create condensation. Direct students to measure the water level before and after creating condensation. Then, hypothesize whether the water literally moved from inside the glass to the outside, or water molecules collected on the outside of the glass from the surrounding air.
Place a small droplet of water on a strip of white paper and place it under a heat lamp or direct sunlight. From there, the evaporation process will result in small trace amounts of minerals left behind on the paper. Distribute the paper to students so that when they look under a microscope, they can record physical observations. It is also important to note the hours it takes to evaporate a drop of water under varying degrees of heat. To answer the question, "Where did the water go?" instruct the students to collect water molecules in the air (using a small plastic container with a lid) and watch them condense to find the answer.
Use plastic wrap to seal off a small container or tub with moist dirt in the bottom. If the exterior environment is hot, students will see moisture from the air condense onto the plastic wrap then accumulate and fall as "rain" would. In this way, students get to observe and create a mini water cycle and gain understanding of our planet's geological systems that involve water.