Air Pressure Curriculum

Section 3—Lesson 8: What is Charles' Law and How Does it Involve Relational Causality?

Understanding Goals

This lesson draws students' attention to how temperature is related to air pressure and introduces students to Charles' Law through the lens of relational causality.

Subject Matter

• Charles' Law can be used to predict what will happen to the volume of a fluid when the temperature is changed (at constant pressure). The law predicts that if the temperature of a fluid increases, the volume also increases, in order to maintain the same pressure. Similarly, if the temperature of a fluid decreases, the volume also decreases in order to maintain the same pressure.

Note to Teacher: It is important not to substitute the word 'changes' for 'differences' here. If both sides of the relationship change in proportion to each other, then it will still be at equilibrium.

• When the air pressure within an object and the outside air pressure are equal or balanced, it is difficult to notice the effects of air pressure. When the air pressure within an object and the outside air pressure are unequal or unbalanced, we are more likely to notice the effects of air pressure.

Causality

• A relational causal model can be used to understand Charles' Law.
• Considering multiple relationships at various levels within pressure phenomena can be a mentally challenging task, especially when the relationships are dynamic, as is the case with pressure-related phenomena.