Introduction to Physical Quantities

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Students will be able to make connections between physical quantities and everyday life.

Big Idea

All measured quantities in physics can be described through a combination of the basic units of distance, time, and mass.

Setting the Stage

At the beginning of the school year, I spend the first few weeks getting to know my students so that I can determine better ways to help them access physics content and develop logical ways of addressing challenges. This year I notice that many of my students enjoy playing card games and spend lots of time trading cards for games like Yu-Gi-Oh!.

Many of my students find physics content to be complex and sometimes are intimidated by the vocabulary and logical skills required for learning and doing physics. One of the most common student responses to being confronted with new material in physics class appears to be rote memorization and surface level recognition. With this in mind, I create this lesson because I want students to layer their understanding of units and move beyond memorizing letters and phrases. I used the trading card game format because it is one that many students were already familiar with and because using a non-linguistic representation in the form of magic cards to understand fundamental physics concepts is just plain fun.

One of the common challenges students share in terms of content knowledge is a lack of understanding of the idea of units. In fact, many students began focusing on metric prefixes instead of units during an earlier lesson. This year I saw a student explanation with a conversion between km (kilometers) to cg (centigrams).   This lesson asks students to create character cards similar to those found in magic trading card games. The character cards students create either represent units of measurement or measured quantities in physics. In this section of the lesson, students determine whether each card corresponds to fundamental or derived units of measurement. Students identify physical quantities based on units and make note of any connections between units and measured quantities in their lab notebooks. I want students to use their understanding of trading card game dynamics to use mathematical operations on units correctly.


5 minutes

This part of the lesson begins with this routine to help students focus on the goals of the lesson.  I ask students to write the objective and the BIG IDEA in their notebooks. I ask my students that, instead of relying on a set of instructions, they focus on constructing an explanation using tools that are familiar to them and their understanding of physical quantities.

Today's piece of additional information is a Big Idea which states that all measured quantities in physics can be described through a combination of basic units of distance, time and mass. The objective of the Bellringer is to give students a clear understanding of the focus of today's lesson. In this lesson, I want students to focus on the ideas that units do matter and that measured quantities have units of distance, time, mass or some combination of the three. 

An overview of this lesson can be found below:

Classwork On Basic Physical Quantities

10 minutes

After students have completed the bell-ringer activity, I distribute a set of handouts for students to complete. Each handout asks students to use their understanding of orders of magnitude to compare relative values of known fundamental quantities of lengthtime and mass.

During this activity students use resources like our digital textbook, class notes and their common knowledge to determine which order of magnitude corresponds to a specific measurement of length, time, and mass on the handout. Students write the correct order of magnitude next to the quantity in the provided box. I use this activity because students have recently completed the physics according to you task and have some previous background research on the basic SI units that are useful in physics. After five minutes elapse, I collect the handouts and ask a series of questions in order to tease out the idea that understanding the manner by which certain physical quantities are measured or derived is useful in studying and learning physics. After I collect and grade these handouts, I return them to students so that they can staple the handouts to their lab notebooks. 

Then I ask students to spend five minutes creating a Mind Map. The phrase students write down and then circle is either "physical quantities" or "units". I ask students to include physical quantities, SI units, diagrams and equations in the mind maps they create in their notebooks. Student work (here as well) demonstrates how students are able to communicate their ideas on physical quantities. One shows a summary mind-map and the other shows a mind-map on mass. After students complete their mind maps, I ask students from each lab station to complete a summary mind map on the interactive whiteboard at the front of the room. I take their work and create a representative mind map so that students will have multiple viewpoints on this topic and have a chance to share their thoughts on the topic as a class.

To follow up with this activity, in the next section I ask students to create a set of game cards that classify units as either being derived or fundamental units.

Student Visuals on Physical Quantities

45 minutes

Within this section of the lesson, I ask students to describe a trading card game that they play with their friends. I summarize the most popular one of the interactive whiteboard. I then lead a whole class discussion on the idea of creating a physics based trading card game that is related to physical quantities and their units which I assess according to this Rubric

I ask students to create cards that will unlock abilities like in the magic trading card game Yu-Gi-Oh!. I project a Physical Quantity Card Template Example on the interactive whiteboard for students to discuss with their peers. Students understand the complex rules of the trading game that allows them to use "ability chains" in order to win each dueling match they enter. I use this type of template so that students associate strategy with physical quantities and their units. For our physical quantity card trading game, each card has a set of abilities associated with it that can be used to win a duel. An "ability chain" helps students make connections between units and corresponding quantities within equations. A student can use the card game to learn that the volume of a cube has units of cubic meters. First the student can create a card that lists the symbol m for "meter", identify "length" as the measured quantity. A student unlocks the "volume ability" by multiplying three units of length by one another. During the game, a player who unlocks the "volume ability" will win a duel against an opponent who unlocks the "area ability" or an opponent who plays single "length" card. I ask students to discuss the units and physical quantities they want to use  to design cards with their elbow partners.

While students are discussing the template with their table mates, I distribute an SI Units Summary Sheet and set of Physical Quantity Card Templates for students to use as resources for this activity. Students use the handouts to create a minimum of 8 cards that represent a set of connected fundamental and derived units. After I distribute the handouts, I ask team resource managers to gather materials from the resource bins in the front of the room for their teams. I remind students to also use credible sources like those posted on our class website to help design their ability cards.  I conduct a quick check-in with the class to make sure everyone understands the task and to clear up any puzzles students may have.  After students create a set of cards, I circulate and ask questions based on the cards they develop. For example, I ask students to invert a time card to unlock the frequency ability. Students now have an alternative representation of converting from seconds to hertz that they can utilize during more complex assignments.

After 45 minutes, I collect the cards. I assess them based on the correct symbol, classification and ability chain. After I grade the cards, I return them and give students a week to create more accurate cards that I laminate and add to student binders that remain in our classroom. We use the cards on review days to practice using units to help set up problems or check solutions.


10 minutes

To wrap up the lesson, I distribute an Exit Slip that I  collect at the end of the lesson to be graded and returned to students during the first 5 minutes of the tomorrow's class. This exit slip has set of choices in which students compare and contrast key ideas and illustrate their understanding of the concepts associated with today's topic.

I use this routine because it helps me to visualize the underlying challenges behind gaps in student understanding of physical quantities and their units.  I find that while computation is taught at several points during students' academic careers, performing mathematical operations using units remains a challenging task to students regardless of their overall proficiency level. At the end of this lesson, I remind students to read section 2-1 on 1-D Kinematics as independent study; we will return to this content later on in this unit.