This experiment can lead nicely into a social studies unit about the importance of water to human communities. It could also be used as a starting point for a discussion of how scarcity affects price.
Make sure to add taking measurements in metric units to this activity in order to fully meet the standard. This unit could be connected to a social studies unit on the plants that are important to the local community and humans in general.
The number of different properties that the teacher requires the students to observe can greatly affect the difficulty of this assignment. That offers a great opportunity for differentiation. This would probably be best as a long activity during a detailed unit.
While this activity does not cover a specific standard it does meet the requirement of teaching the design process. Make sure that students must design, test, and revise their design to make the activity authentic. A race would be a great final activity. Assessment could come from an oral presentation on what they did and why or a visual presentation, such as a poster.
Students who finish early could try drawing the structures of blood. If the teacher can obtain the materials, looking through a microscope at real slides of blood and draw that for a further extension.
This activity lets students create a simple and safe model of human blood. It provides a way to make something microscopic easier for children to understand.
I like this activity because it works well for a wide variety of students. For students who are easily overwhelmed reduce the number of scents to match. High level students could be asked to come up with an idea for another experiment like this one but for a different sense. Consider allergies when you plan this activity!
Students with high literacy skills can read more information about worms and share it with the class. Students with low literacy skills can be in charge of making drawings of their observations to keep a visual record of the worms' progress.