Student who are ready can learn to read a thermometer or a barometer as well as a part of this activity. Make sure to encourage careful record keeping and not accurate predictions. Students should be made aware that one does not "win" science by making correct predictions.
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.
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.