Circuits

Day 91: Real Life Circuits & Energy in Equilibrium

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Physics: Real Life Circuits

Continuing the circuit patterns set of labs from the PUM curriculum, students used power supplies and resistors to build series circuits and test the patterns they found in the simulation yesterday. Class ended with each group summarizing their rules on a whiteboard. Several groups used proportions to come up with a rule for how much potential difference goes to each resistor; for next year, I want to think about the questions I’m asking to try and get more groups to take a similar leap.

 

Chemistry: Energy in Equilibrium

Students did a short reading from the book to look at the role energy plays in chemical equilibrium and to help explain some of the results in yesterday’s lab. It also ended up being a nice set-up for the reaction rates lab we’ll be doing tomorrow.

Day 90: Circuit Patterns & Disturbing Equilibrium

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Physics: Circuit Patterns

Today, students started working on a series of labs based on the circuit patterns activities from the PUM curriculum. Today, students built series circuits in PhET’s circuit construction kit, measured the current and potential difference at each element, and started looking for patterns in their results. When using the voltmeter, I was pleased by how many students went back to a lab we’d done moving the ground wire of the multimeter to help explain why some voltages were negative, along with what that negative voltage means. Tomorrow, we’ll pull out the power supplies and resistors to see if their patterns work in the real world.

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Chemistry: Disturbing Equilibrium

Students played with moving a reversible reaction out of equilibrium. After mixing Fe(NO3)3 and KSCN solutions in several different test tubes. Once the reaction was in equilibrium, they tried something different, such as changing the concentration or putting the test tube into a water bath, to and observed the results.

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Day 89: Cost Effectiveness of Light Bulbs & Vocab Intro

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Physics: Cost Effectiveness of Light Bulbs

After a brief introduction to electric power, I tasked students with figuring out which of several light bulbs is the most cost effective. I provided them with the cost and estimated lifetime for each bulb and the current rate the local electric company is charging, along with some Kill-A-Watts they could use to take some measurements.

Calculated costs to run for 15,000 hours
Calculated costs per day

Chemistry: Reversible Reactions

After a quiz on limiting reactants, students used the textbook to start defining reversible reaction and equilibrium.

Day 88: Ohm’s Law & Limiting Reactants

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Physics: Ohm’s Law

Students wrapped up using the PhET circuit construction kit to develop Ohm’s Law. Students were able to pretty easily reason out the formula based on their graphs. Looking back, I wish I’d had students put their experimental conditions and equations on the boards, as well. I usually try to keep the boards pretty simple since I have some big classes, but I think that information would have added a lot of value to the conversation in this case.

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Chemistry: Limiting Reactant Practice

Today, students did some limiting reactant problems where the given and desired information is in grams, rather than moles. I was really pleased at how easily most of them worked through the problems. A lot of my students were struggling to connect ideas between different days earlier in the trimester, so it was great to see how many readily pulled out earlier skills and problem solving strategies to help today. I also saw a big jump in the quality of the questions I’m getting from my students; one student in particular was really focusing on the why when she was talking to me, when in the past she seemed most interested in getting something to write down. I’ve been having a lot of conversations with this class about how learning works and sharing why I do things the way I do, and I’m hoping I can get students to continue with the things I saw today.

Day 87: Ohm’s Law & Limiting Reactants

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Physics: Ohm’s Law

Students used PhET’s circuit construction kit to do a short activity based on the PUM materials to help orient them to the sim, then started looking for a relationship between current and potential difference. I loved it when, during the orientation activity, several groups got curious about the mysterious resistors in the kit, and immediately tried adding them to a circuit to see what they do, without any prompting or intervention on my part. There was also some great discussion and debate in one class about what exactly the blue dots represent. There were also many attempts to electrocute the dog.

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Chemistry: Limiting Reactants

After a short percent yield quiz, we had some class discussion to formalize what students found in yesterday’s PhET sim on limiting reactants. I picked some reactant quantities for one of the reactions in the simulation, then had students get into groups and try to predict what they would produce and what the leftovers would be. Before students went to their groups, we had some conversation about what I was looking for. I tried to emphasize that I wasn’t after right answers; instead, I wanted them to share different approaches so we could decide on some useful ways to think about this kind of problem. There was a nice mix of students who focused on the equation given for the reaction and students who sketched diagrams.

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Day 86: Intro to Circuits & Limiting Reactants

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Physics: Intro to Circuits

I gave each group a bag with a mix of various items and asked them to use those items to try and light up an LED. In the past, I’ve told students their task is to light up the bulb, but they should keep track of what doesn’t work. This year, I was more conscious of stating the goal was simply to document what does and does not work so we could look for patterns, and I was much happier with how the exploration went. This was also the first time I used LEDs for this lab, instead of miniature incandescent light bulbs, and I liked the opportunity to reinforce that current has a direction. As an added bonus, the LEDs I have required two AA batteries, which gave the students more options to try. We wrapped up by watching a short excerpt from from the Private Universe series of MIT and Harvard grads trying a similar task.

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Chemistry: Limiting Reactants

Students worked through PhET’s Reactants, Products, and Leftovers simulation to introduce the idea of limiting reactants. I found a lot of students were looking for confirmation that their answers were right, even when the simulation showed the answer. When I talk to many of them, it sounds like they’ve gotten into the habit of assuming they are wrong in school. I need to continue to work on building a culture where my students feel like their ideas have value and to work on strategies to help students analyze their answers, right or wrong.

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Day 37: Kirchoff’s Rules & Vector Addition Diagrams

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Physical Science: Kirchoff’s Rules

With my 9th graders, I’ve always done series and parallel circuits pretty superficially where they try a few things in the lab, then memorize a couple of key behaviors. This year, my students have been thinking about the energy in circuits in some interesting ways that seem useful for getting at Kirchoff’s Rules, so I decided to give it a go. Today, students used PhET’s circuit kit to compare the voltage and current in different parts of each type of circuit. Students were able to articulate very nicely their own versions of Kirchoff’s Rules based on the energy in the circuit.

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Physics: Vector Addition Diagrams

Today, students took their first look at forces in 2D and drew some vector addition diagrams to scale. The problems, lifted from Kelly O’Shea, were all on a grid to keep things straightforward. This gave students the opportunity to practice drawing vector addition diagrams and start thinking about what they mean without getting bogged down in the math. Tomorrow, we’ll start crunching numbers with the diagrams.

Day 36: Electric Power & Unbalanced Force Problems

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Physical Science: Electric Power

Students plugged several different light bulbs into Kill A Watt meters to find the power used by each, then calculated how much you’d pay for the electricity to use each one for a year. This is the first year I’ve done energy before electricity with my 9th graders, so I decided to have them sketch energy bar charts for each light bulb, using thermal energy and light as the energy types. For the first time, my students had an easy time articulating in a meaningful way why the low wattage LED was just as bright as the high wattage incandescent.

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Physics: Unbalanced Force Problems

Students worked on some problems that combined Newton’s 2nd Law with constant acceleration calculations. I was a little nervous, because they just got Fnet = ma yesterday and many are still mastering net force, so I wasn’t sure how they’d do with using multiple models on a single problem. However, a lot of pieces seemed to really click today. By the end of the hour, several students who’ve been struggling with constant acceleration declared today’s problems easy, including the portions where they had to do constant acceleration calculations.

Day 35: Series vs. Parallel Circuits & Board Meeting

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Physical Science: Series vs. Parallel Circuits

Students used PhET’s circuit construction kit to explore the differences between series and parallel circuits. When I’ve used batteries and bulbs, students really struggle to see (let alone articulate) what’s going on with the current, so the visible “electrons” in the simulation were a huge help in getting students to understand why certain changes happened.

Physics: Board Meeting

We discussed as a class the results of the Newton’s 2nd Law lab. I need to have students practice talking about the slope more; they were able to get to “The force needed to accelerate 1 m/s2“, but it took some pushing on my part; I think the issue is just lack of practice. I was pleased by the discussion; students are doing more articulating of the big ideas. I was really excited by the discussion students had about the intercept. I’d planned to declare the intercept zero and move on, but in both sections students seemed interested in talking about it. They decided it would be reasonable to have a non-zero intercept on this experiment and it would be equal to the amount of friction you have to overcome to start the cart moving.

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Day 33: Ohm’s Law & Interactions

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Physical Science: Ohm’s Law

I gave students some batteries, some light bulbs, and some wires and asked them to find a qualitative relationship between resistance and current. Groups that had some extra time decided to experiment with voltage, as well.

Physics: Interactions

Students worked through some questions that reinforce the idea of forces as interactions between two objects from the Modeling Instruction curriculum. I was out of the classroom for a field trip, so I’ll find out how it went tomorrow when we discuss some of the answers.