Lesson 7: Quiz/Dalton's Law of Partial Pressures

Figure F.22 - Collecting a gas over water

Ptotal = Pgas + PH2O

  • Hook: Demonstration – a large graduated cylinder with a gas collecting tube will be used to demonstrate gas collection over water. Using this demonstration, students will understand that gas can be collected by displacing water. The gas collected will exert a certain amount of pressure but the water vapour pressure of water should also be considered when calculating the pressure. This will aid students in visualizing the rest of the lesson and can be referred to throughout. The basis of this demonstration will be done in an experiment the following day.
  • Action: Students will answer questions based on Dalton’s Law of Partial Pressures using on the board. This provides students with proper practice before moving on to their homework. The first example can be done as a class, the second can be done by a student volunteer and the third will be done individually and the method and answer will be taken up. This follows the gradual release method.
  • Debrief: Snowball fight – students will list three things on they learned about Dalton’s Law of Partial Pressures or collecting gases over water on three separate sheets of paper and throw them around the class, the students will then pick up three separate snowballs and read them individually. This activity allows students to recall what they have learned from the lesson through what they write down themselves and what they read from their classmates' notes.