Making a plastic bag biome is a great way to teach students what plant-life needs in order to grow effectively. To make a plastic bag biome, cut off the top from a 2-liter soda bottle. Fill the bottom of the bottle with small rocks and stones. Cover the stones with potting soil or compost. Plant seeds in the soil, covering them with more soil. Water the soil until it starts to drain into the stones. Place the entire bottle into a gallon-sized plastic bag, sealing it tightly. The water in the bottle will circulate back into the bottle, and the plants will grow without needing to be watered.
Salt water cannot be ingested, but you can show your students how to take salt water and transform it into fresh water using a solar distiller. Pour 1/2 cup of water into a bowl and add 4 tbsp. of salt to it. Place a short glass into the bowl. Make sure that the glass is shorter than the bowl, yet above the water line. Cover the entire bowl with plastic wrap, sealing it tightly. Place a round stone in the middle of the plastic wrap so that it pushes the plastic into the center of the glass. Place the bowl in the sun outdoors. The water will evaporate and condense on the top of the plastic wrap, leaving the salt in the bowl. The fresh water will drop down into the glass.
A thermometer measures the temperature of your environment, which can be demonstrated to students by creating a homemade thermometer out of materials found around a kitchen. Start by filling a plastic water bottle to the top with water, and add in around 10 drops of food coloring, any color. Insert a clear drinking straw around one-third of the way into the bottle. Wrap duct tape around the top of the bottle and the straw to hold everything in place. Mark where the water level is in the straw. Place the entire bottle into ice water. The level of water inside the straw will drop as the temperature of the water lowers.