Explore changes in color by having the children look through colored glasses. Explore color combinations by having students look at a blue object while wearing red colored glasses. Alternatively, you can give them magnifying glasses and have them experiment with seeing small things in greater detail. Hanging a diagram of the parts of the eye and discussing them is also a good way to bring more science into the project.
Take paper lunch bags and fill them with different materials. Examples include jello, rocks, pom poms, or anything else you have on hand. Have the children reach inside the bags and touch the objects and try to guess what is in each bag. Alternatively, you can make a book or a poster board with samples of different textures.
Give the children tuning forks and show them how they work. Let them experiment with the vibrations and sounds. Kazoos are another way for them to understand the connection between vibration and sound. Fill some cans with different small objects and have the children shake them and try to guess what is inside.
This is frequently the children's favorite "sense" activity. Set up a taste testing for the students, with different flavors represented. You can use lemon for bitter, pretzels for salty, strawberries for sweet, and so on. Have the children taste each food and describe it.
Place cotton balls in small containers and sprinkle them with various things that smell. You can use essential oils or strongly scented foods, like garlic. Pass them around the class and have the children guess which scent is which. Alternatively, you can make two sets of the scent jars and have them try to match the scents.