For the first day of this lesson, we began with a review of dimensional analysis by way of also reviewing phase changes. The diagram below illustrates the connection between the three phases of matter commonly encountered on Earth, and the vocabulary associated with changing phase. Click on the image to learn a whole lot more about the science of phase change.
To help students visualize the least familiar of the phase change reactions (the solid-to-gas and gas-to-solid phase changes), we watched a brief video below, complete with spooky soundtrack:
Next, we investigated the concept of number density by learning about the densities of different phases of water. We calculated how much mass would be in a given volume of sample of each phase of water, appreciating the effect of phase on mass. We then asked the question: how can we calculate the mass of a given amount of any particles of a substance? To help answer that, we watched the Crash Course video below:
To end class, we learned how to use the periodic table to calculate mass of one mole of various molecules.
For homework, students received the Lesson 64 Worksheet to work this evening in preparation for class tomorrow.
For the second lesson of the Gas Laws mini-unit, students worked with dry ice and watched a couple of teacher demonstrations involving dry ice. To begin class, students worked in small groups to measure the mass of a small amount of dry ice, quickly transfer the dry ice into a balloon, and then quickly tie off the balloon to trap the sublimated carbon dioxide gas. Students then measured and recorded the mass of the dry ice added to the balloon at the beginning and at the end of the experiment, then measured the volume of the bag after the dry ice finished sublimating in order to calculate the density of carbon dioxide gas.
While waiting for the dry ice to sublimate, students hypothesized about what they might observe when water ice and dry ice were heated on a hot plate, and also what would happen when water and dry ice were added to liquid water or vegetable oil (pictured below).
Students then observed the outcomes and recorded their observations on the Lesson 56 Worksheet. Students also recorded the definitions of sublimation and evaporation, both of which are included in the Lesson 56 PowerPoint.
Note: For students who missed class due to testing today, please watch the videos below as a substitute for participating in the lab.
For the final day of this lesson, students need to write a lab report (Google Doc, shared with Mr. Swart) detailing their results from the dry ice in a balloon experiment. The lab report must include the following clearly labeled sections:
- Introduction: One paragraph explaining the lab concept. Explain how dry ice (frozen carbon dioxide) sublimation connected with the Ideal Gas Law.
- Procedure: A clearly written explanation of exactly what was done in the experiment. Must be detailed enough that a random stranger could read the instructions and repeat exactly what you did.
- Results: Must include the following:
- initial mass of the dry ice
- use the initial mass of dry ice to calculate the number of moles of dry ice
- initial mass of the dry ice and balloon
- final mass of the dry ice and balloon
- final volume of the balloon
- use Ideal Gas Law (PV=nRT) to solve for n
- include pictures if you have any!
- Conclusion: Compare the calculated number of moles of dry ice to the value of n that you solved for using the Ideal Gas Law. Explain why the numbers are different. Suggest at least two possible sources of experimental error.