In this lesson students continue their learning about gas laws through reviewing Boyle's Law, Charles Law, Gay Lussac's Law, and The Combined Gas Laws and then learning about the Ideal Gas Law and Dalton's Law of Partial Pressures.
For this lesson I have students do a review activity using matching cards. I print them on regular paper but you could also make them on cardstock to improve their longevity.
To begin this lesson I have students spend some time reviewing what they have already learned in the first four lessons of the unit through performing a gas laws matching activity.
After students have completed their introductory activity I then have them do a quick mid-unit quiz.
When students have completed their quizzes, I then let them know that we are going to be learning two more gas laws.
- I stress that this is the only gas law that has one of each variable at the SAME TIME!
- I also tell students that there are multiple "R" values, but that for this class we will only be using 0.0821 so our units for volume are always in Liters, temperature in Kelvin, moles in mol, and pressure in atm.
- I make sure that students use the problem solving technique of underlining what they know, circling what they want, labeling, writing down the equation, isolating their variable, and then solving for the answer.
- In the first example students have to first convert mL to L. I have them do this to review this type of conversion.
- In the second example students need to first convert grams to moles using molar mass. I give them the hint that they will need their periodic tables for this.
- For the first practice question students need to convert between pressure units.
- For the second practice question students get confused if they do not read the question carefully because they are solving for one of the partial pressures, not the total pressure.
To complete the lesson I have students perform practice homework questions on the Unit 7 lecture 4 homework paper.
I have students begin the homework in class and then finish at home.
I stamp their papers for completion at the next class period and go over the answer using the answer key.
Here is one example of a student's completed homework.
The biggest mistakes that students make are when they have to first perform a conversion before plugging into the equations. For example in question 2 where they first need to convert pressure to atm, and in question 3 where they need to first solve for moles and then convert to grams.