Stoichiometry

Day 138: Doppler Effect & Percent Yield

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Physics: Doppler Effect

I introduced the equation for the Doppler effect, then students worked through some problems. A few students used a lot of color coding to keep track of all the different variables.

Chemistry: Percent Yield

Students reacted hydrocholoric acid and sodium carbonate to make sodium chloride, then calculated their percent yield. Students really liked the lab and saw the value in the calculations, which reminded me that I need to keep working on getting more true chemistry labs into this course.

Day 137: Doppler Effect & Limiting Reactants

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Physics: Doppler Effect

I tried something new to introduce the Doppler effect today. Students slid transparencies along a grid and sketched wavefronts to get a sense of how a moving source changes the frequency a stationary observer would hear.

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Chemistry: Limiting Reactants

Students worked on some problems to identify limiting reactants. I shared a strategy one of my students came up with last tri to use reaction diagrams to help think through the problems, which seemed to help students wrap their heads around what the different numbers represent.

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Day 136: Longitudinal Waves & Leftovers

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Physics: Longitudinal Waves

We had some discussion about a high-speed video of a glass breaking due to sound waves to establish that sound is a new type of wave. Afterwards, students made longitudinal waves on slinkys to explore what aspects of our models for mechanical waves so far apply to longitudinal waves.IMG_1806

Chemistry: Leftovers Sim

I was gone on Thursday and Friday and it turns out that on Thursday, while I planned for my students to work on PhET’s Reactants, Products, & Leftovers simulation,  the school’s wi-fi went out. We did that lab today, instead. Students were pretty successful applying ideas from Friday’s lab to the simulation and seemed to build some nice bridges to the more abstract chemical reactions.

Day 133: Closed Pipes & Percent Yield

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Physics: Closed Pipes

Students whiteboarded and discussed their results from yesterday’s lab on closed pipe resonators. They pretty easily recognized that, since the graphs of tube length vs. wavelength consistently have a slope near 0.25, 1/4 of the wave must have “fit” into the tube to produce a standing wave. This lab is traditionally used to find the speed of sound, but I always ended up just giving them length = wavelength/4, which bugged me. By having students use the lab to find that relationship, they only needed to use relationship between speed, wavelength, and frequency they found using snakey springs and the speed of sound, which they found using both a Direct Measurement Video and a Vernier microphone.

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Chemistry: Percent Yield

Students continued working on their percent yield problems today. We spent some time discussing the physical meaning of the numbers they were using, especially the numbers in the balanced chemical equation and the molar masses since confusion about what those represent lead to a lot of the struggles students had on yesterday’s quiz.

Day 132: Closed Pipes & Percent Yield

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Physics: Closed Pipes

Students whiteboarded their results from yesterday’s lab and we discussed the results. Afterward, students started working on finding a relationship between wavelength and the length of an air column needed for a standing wave, using the speed of sound from the video to get the wavelength of a tuning fork.

Chemistry: Percent Yield

I introduced the concept of percent yield and students started working through some problems. They also took a quiz on stoichiometry, which didn’t go as well as I hoped. Looking at their work, I think a lot of students lost track of what all the different numbers mean, so I’m tweaking some lessons for later this week to try and get back to the physical meaning of the numbers they are using.

Day 131: Speed of Sound & Speed Dating

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Physics: Speed of Sound

After some time playing with the wave generator to confirm Thursday’s lab results, students used a Direct Measurement Video to produce a position vs. time graph and find the speed of sound. Tomorrow, they’ll put that speed to use in closed pipe resonators.

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Chemistry: Speed Dating

Students needed just a little more practice to firm up their stoichiometry skills, so we did some whiteboard speed dating with problems similar to what will be on tomorrow’s quiz. I was really pleased at the number of groups who were really talking through problems , taking turns with the marker, and taking other steps to ensure that both students really understood what was going on.

Day 130: Standing Waves & Stoich Practice

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Physics: Standing Waves

Students used a Direct Measurement Video to look for patterns in the wavelengths and frequencies that can produce a standing wave on a string. I’d set up the wave driver this morning to try some ideas for Monday, and several students asked if they could try it to answer some questions the videos raised for them, but didn’t have a great way to answer.

Chemistry: Stoich Practice

Students finished up their stoichiometry practice problems today. I’m trying to really focus conceptually on what the math means, so we spent some time drawing repeated reaction diagrams to better connect the math to the lab they did a few days ago.

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Day 129: Wave Superposition & Stoich

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Physics: Wave Superposition

We spent some time discussing the observations students had made about wave superposition yesterday. There was some good debate about whether pulses were reflecting off each other or passing through each other. Students then practiced sketching superpositions based on the original waves.

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Chemistry: Stoich

We spent some time discussing the lab students did yesterday and really focused on how they knew when and what to multiply or divide. We also spent some time explicitly discussing what the hardware represented and how what they were doing was similar to a chemical reaction. Afterwards, I gave students some more traditional problems using actual chemical reactions.

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