Air Pressure Curriculum

Section 3—Lesson 5: Contrasting Linear and Relational Causality in Explaining Air Pressure Phenomena

Background Information

Relational Causality

In relational causality, a relationship between two variables accounts for an outcome. Therefore, it is not enough to consider one variable or the other, both must be considered in relation or in comparison to each other. For example, two girls can be sisters but neither girl alone is the "cause" of being sisters. It is the relationship between the two that "causes" them to be sisters. You can make comparisons about the relationship. For example, you can say that one sister is older and one is younger, but this only makes sense in terms of their relationship, and in comparison to each other.

In science phenomena, relational causality often applies when two amounts of something are being compared, such as the densities of two liquids, or amounts of pressure. Typically, the outcome is due to balance or imbalance between two variables.

Reducing Relational Causality to Linear Causality

Students often reduce instances of relational causality to simple linear causality. For instance, when explaining why liquid rises when drinking from a straw, they may say something like, "Suction makes liquid go up the straw." It is also common for students to use token explanations where words common in the everyday world of science (such as 'static electricity', 'air pressure', or 'vacuum') are given as an agent or mechanism, as in "air pressure makes it happen." When pushed, students rarely have deep understanding that they can use to elaborate on the statement. Listen for instances when students give simple linear explanations or use token explanations in assigning cause in air pressure situations. Press them for their understanding of the words they use, and steer them towards a more thoughtful, reflective causal model to explain their observations.

To fully understand the effects of air pressure on an object, the air pressure inside an object must be compared and contrasted with the air pressure outside the object. Often, students focus solely on the air pressure inside the object or outside of the object, rather than considering the interaction or relationship between the two. When students only consider one side of the relationship, they lose important aspects of the causal story, which can limit their understanding of air pressure and pressure-related events.