## A Physics Teacher’s Strongman Trick

Strongman tricks often involve seemingly impossible tasks like bending iron bars, lifting gigantic weights, or pulling trains with your teeth. This “teacher trick” doesn’t take great strength to impress. Using a clever arrangement of a mirror and a laser, students can see that steel girders, concrete block walls, and other seemingly immovable materials flex when a force is exerted on them, even a force as small as the force exerted by a wimpy pinkie finger.

Most people don’t think at all about how “rigid” objects exert forces on other objects (the force that teachers often term “normal” force”).  Early in a unit on Newton’s Laws, it would have been asserted that the downward force of the earth on an object is balanced by an upward force of a surface on the object when we observe that the object is at rest. The terminology that is often used for this situation is problematic. Following Newton, the force of a surface on an object is often called a “reaction force.” But how can a table “react?” What do we mean by reaction? This is an issue that is often raised by students. If they don’t bring it up, I pose the question myself. This trick supplies the answer and the explanation.

The script goes something like this:

“Students, suppose I place a book on a table, and then ask you: “With how much force does the table support the book?” You would have no problem stating that since the book is at rest, the table must produce an upward support force equivalent to the downward pull of the earth on the book (the “weight” of the book). But what happens when we replace the book with something else? Now suppose I put a watermelon on the table. The same logic tells us that the table supports the melon with a force equivalent to the weight of the melon. A garbanzo bean? A feather? A fifty-pound catfish. . . Hmm. That’s a clever table. It always knows what to do. How did the table get so smart?”

At this point, I would likely pause, ask them to talk to their neighbors about “smart tables.” We discuss a few of the ideas (typically, nobody has a complete answer, but everybody agrees that the question is ridiculous). –Of course tables aren’t smart. They just “react” to what you do.

“But how does a table “react?” Wouldn’t that be interesting to know? Maybe simple things are more mysterious than we realized?

I make a proposal. “Let’s make a model table and see if we can observe how it “reacts.” The model table is constructed of light wood strips or meter sticks and some books.

I place something light on the model table (a feather or a marshmallow, say). “Did anybody see it react?” -No. And yet, it must have “reacted,” whatever exactly we mean by that. Then I place something heavier on the table, say a large mass, or a big physics book. We might see a slight sag in the table at this point.

Next, something even heavier, until there is an unmistakable sag in the “table:”

I could continue, adding mass until the table breaks, but it’s easier on meter sticks to just suppose we put something really large on the table. Suppose an elephant came in and sat on the table. What would happen then?” -A normal table would break. Tables have limits.

“How does the model table know how much force to exert on the objects? ” -It sags. “Is it possible that the table or the floor sags when you put something on it?” –Maybe “Could you ever see it sag? –I doubt it. “What if I could somehow magnify the movement? Would you believe it then?” –Maybe. “Would you believe I can make a steel girder (or a concrete block wall) move by just pushing with my little finger?” –Nope.

At this point I set up the materials to show the movement of a girder, or concrete block wall:

The laser light is reflected off of the fragment-of-CD mirror so that a visible spot is seen on a wall or ceiling several meters away. A tiny movement of the girder moves the metal rod (“attached” to the girder or wall with a lump of modeling clay). Friction between the metal rod and the dowel rotates the dowel a tiny amount. This changes the angle of the CD, and the reflected spot of laser light moves. If you push on the girder  and then pull on it, you can see that the movement of the laser light changes direction. Here is a picture of one of my students getting ready to push the girder:

And here is a video of the laser spot moving. The motion is not so pronounced, but is usually still evident if you push and pull with a pinkie finger.

It’s even more impressive if you start out with the apparatus in a room connected to a concrete block wall, and then send someone outside to push from the other side.

At this point most students can explain that objects, no matter how rigid they seem, “exert” forces by deforming slightly. The greater the force, the more they deform.

When we go back into the room, I pull out the Pasco Matter Model:

The red plastic spheres represent simplified atoms/molecules, and the metal springs represent simplified bonds. This gives students a visual for what is going on when rigid materials exert forces. It is greatly simplified and quite a bit exaggerated, but also very memorable.

I could have pulled out the model from the start and said “Today I’m going to show you how matter behaves.” But, that wouldn’t be very dramatic, would it?

##### Physics Teacher Notes Below

This activity aligns with the College Board’s AP Physics 1 Learning Objectives 3.C.4.1 and 3.C.4.2:

 3.C.4.1: The student is able to make claims about various contact forces between objects based on the microscopic cause of those forces. [SP 6.1]
 3.C.4.2: The student is able to explain contact forces (tension, friction, normal, buoyant, spring) as arising from interatomic electric forces and that they therefore have certain directions. [SP 6.2]

I usually schedule this activity two or three meetings into the force unit. In class we would not have done much more than mention Newton’s Laws. The students would have learned how to name forces (using agent-object notation), and how to draw force diagrams.

I first learned of this demonstration from a fellow participant named Steve Brehmer (a physics teacher from Minnesota) at the Project PHYSLAB teacher workshop in Portland, Oregon. The format of the activity itself was inspired by the book Preconception in Mechanics by Charles Camp and John Clement, published by American Association of Physics Teachers. The 2nd edition is available in print from the AAPT Store or as a download from American Modeling Teachers Association when you join and gain access to their curriculum repository. If you buy the book, you’ll see that they have a more detailed strategy than I outline here.

If you would like to know exactly how much your wall (or girder) moves, I recommend this article from The Physics Teacher, “Demonstrating and Measuring the Flexure of a Masonry Wall: by Daniel MacIsaac and Michael Nordstrand.

## WHITEBOARDING TECHNIQUES (To promote a good classroom environment and possibly, inquiry)

I have about 10 – 20 large whiteboards in the classroom. These are made from “tile board” purchased at building supply stores. This material is “Masonite” coated with a smooth white surface on side. It is intended for inexpensive bathroom remodeling. Tile board comes in 4΄ x 8΄ sheets. I have them cut it down the middle of the long dimension, and then make two cuts across the short dimension, so that I have six boards from one sheet. Each board is approximately 24″x 32″. Students write on these with dry erase markers, and erase them with rags. Blue and black erase most easily. Other colors and writing left for a long time may discolor the boards. Whiteboard cleaners will help remove the leftover writing, but rubbing alcohol also works.

PRESENTATION OF LAB RESULTS

Labs are a big part of the physics classroom. In my classroom students generally share their lab results by presenting them on a whiteboard. If everybody has done the same lab, then I usually only pick one or a few groups with good or interestingly poor results to present. More often, each group has investigated a different dependent variable, and everybody presents. The students below are showing lab results from a pendulum lab.

They investigated period and starting angle (the angular displacement from the rest position). Notice how they have graphed it two ways. On the left is a “zoomed in” version, based on what their graphing calculator showed them when commanded to set the window to zoom in on the data. On the right is a view that makes more sense, the “zoomed out” view. The zoomed in view emphasizes the variation in the data. When discussing their results with me before the presentation, the students recognized that the variation in the data was very small, and agreed that the calculator view was not a fair representation of their data. I asked them to show both graphs, which led to an interesting whole-class discussion of how the representation of the data influences what people think about it.

WHITEBOARD PROBLEM SETS

This is a technique I first learned from Jeff Steinert and Jamie Vesenka at a Physics Modeling workshop at the University of New England in Maine. More about modeling workshops here.

Students are given a set of problems, often as a worksheet. They work through the problems in their groups, and then share their answers with the class using the whiteboards. This technique works best if all students have attempted all problems, so you may want to schedule the group presentations on a different day from the group work. The problems may be conceptual, mathematical, or data-based, but I prefer a mix, rather than all one type in a session. The biggest gains in understanding come when the problems are on closely-related topics, and when at least some of the problems highlight misconceptions.

Rules that I use for presentations (which I generally do not grade):

All group members should

• participate equally in the preparation of the presentation.
• participate in the presentation by speaking.
• be prepared to answer questions that extend the ideas in the presentation.

All audience members should

• listen carefully throughout the presentation.
• hold all questions until the end.

No Comments or Applause until the group is dismissed.

The best advice I think I ever got on moderating whiteboard presentations in the classroom was “Allow Only Questions.”  In other words, students cannot comment positively or negatively. Positive comments tend to shut off conversation from both the audience and the presenters. Negative comments tend to embarrass presenters and destroy their ability to engage in a constructive dialogue. If mistakes are made in the presentation, the students in the audience are challenged to find a polite question that causes the presenters to realize the mistake. “Could you explain your assumptions in part (b)?” “Does your answer seem about the right size?”

HOMEWORK ATTEMPTS

Individual (or pairs or groups) of students present their attempts at homework solutions. An attempt, at a minimum constitutes a picture or diagram, summary of given info, summary of definitions, and (hopefully) an attempt at a solution. They transfer them to the whiteboard and make a brief presentation of their work.  If they are really struggling, they may present only their narrative of what they think they would try OR what they don’t understand that’s keeping them from solving the problem. Grades (if assessed) are based on how well they explain their attempt, either successful or “failed”.

CIRCLE WHITEBOARDING

This technique works particularly well for quick conceptual questions which can be answered with a graph or diagram (the students at left are working on Free-Body Diagrams, for instance). Students sit in a circle facing inward. It’s best if you really make them scoot in, so they are all in the circle. Either pairs or individuals have a whiteboard. Small “slate-sized” whiteboards may work better than the large ones, particularly if the group is small, the questions are not very involved, and you want to go quickly. The students complete a single question on a whiteboard, keeping their response hidden from the others. When the instructor, who is outside the circle, says “Go”, they hold up their whiteboards and examine them for differences and similarities. The teacher and students lead a discussion. Students must be gently persuaded by questioning to change their whiteboards until all agree on the best answer and every white board reflects the discussion. Only at this time should the teacher give the signal to go onto the next question. The goals are to quickly reach agreement for good physics reasons and move through a lot of conceptual material quickly. Sometimes the teacher sits in the group and marks their own answer on the slate with a strategic mistake.

WHITEBOARD GALLERY

This is a good way to mix it up a little. Students or student groups complete their whiteboards and then arrange then around the room in a gallery display. After the boards are complete, everyone strolls around the room and carefully examines the work in the boards. If they agree with the physics on the boards, they put a smiley face on the board. If they think the board has problems, they put a frowny face on the board. After everyone has finished rating the boards, a class discussion about the work and the ratings happens.

WHITEBOARD SPEED-DATING

This is a technique I learned about from Kelly O’Shea’s blog:

https://kellyoshea.blog/2012/01/22/whiteboard-speed-dating/

I think she invented it. (BTW, if you are a physics teacher and you have not spent some time reading her blog posts, I suggest you do that. Lots of great information, thoughtfully and creatively presented.) I have only used “speed-dating” a few times, but students thought it was fun. Students are given a problem or problems. They have a short time to work on the problem on the whiteboard, and then they have to change to a different whiteboard. In Kelly’s blog post, she had the whiteboards stay in place while some students rotate clockwise and others rotate counterclockwise. See Kelly’s pic below (Definitely read her blog post to get the full story):

I have also tried having pairs of kids move around to different whiteboards. The problems need to be fairly deep, or on a topic new to the students, otherwise some kids will solve them so quickly that there is nothing left to do when the next students get there. It’s definitely worth trying if whiteboarding is getting stale.

THE MISTAKE GAME

Another Kelly O’Shea innovation (at least she is the person I think I heard about it from). Kelly does this a lot. In fact, in this blog post, she recommends doing it nearly all the time, in order to build a classroom climate that I call “constructive failure.” I do this when whiteboarding problems is getting a little stale. I instruct students to put an intentional mistake on their whiteboards. The teacher should walk around and ask students what mistakes they are putting on the board. Most groups will probably put something pretty trivial on the board, like a mistake in units, or significant figures. The teacher will want some of the groups to highlight misconceptions, such as “the force of motion” that persists for a long time in spite of determined instruction.

GOALLESS PROBLEMS

Students are given a diagram or a written situation, but they aren’t given a specific problem to solve. Instead they try to model everything they can about the situation, using whatever physics they have learned in that unit, or multiple units, if you wish. For instance, you could give your students this diagram,

###### (copyright Pearson, from the Knight textbook Physics for Scientists and Engineers: A Strategic Approach)

with a brief description, i.e., “a suitcase is being towed 100 m on a level surface by a force T, at a 45 degree angle.” I can see several ways I might use this picture as the source of a goalless problem.

Near the end of the study of forces, it would be a useful review problem. The command might be, “Tell me everything you can about this situation, using the physics that you have learned. I expect to see diagrams, graphs, equations, and words that describe the physics of the situation.” The students could address this goalless problem again after studying energy, and use techniques that they have learned in the energy unit to model the situation in a new way.

I usually give all groups the entire sheet of problems, but each group only presents one of the problems on the sheet. I walk around and help or ask questions.  It can take a while to work through the situations and then a fair amount of time to present the whiteboards, so we don’t always finish all of the problems.

A subset of goalless problems is the “Model a Story” whiteboard. I’ve only done this when we were studying motion, but it worked very well then. Students were instructed to invent a story, and then illustrate the story using the representations from the constant velocity and constant acceleration units. The results are often funny, as the students outdo themselves trying to be creative. The whiteboard on the left had something to do with squirrels and acorns. The one on the right has to do with speeding cars.

SEEDING

The idea here is that students often respond better to a question or comment from a student than from the teacher. Teachers walk around to different groups or students and suggest questions for them to ask of the presenters.

If you have suggestions for things I ought to try, please post in comments below.

Frank Noschese wrote this post some years ago, which got a lot of attention and is an excellent overview of the reasons why physics teachers love whiteboards so much.

## Pinterest Boards for Teachers

Last year, inspired by my oldest daughter’s obsession with Pinterest, I started making Pinterest boards for high school physics teaching. Pinterest is a website that allows you to create “bulletin boards” of images (with a snippet of text) “pinned” from websites. The boards are themed, and viewers can click on the images to visit the websites that they come from. Pinterest itself feeds you pins that it thinks you may be interested in, and there is a social media aspect to the whole thing. Users are encouraged to follow each other, sharing boards and pins. A lot of boards are themed around fashion, accessories, food, home furnishings, and luxury objects. Mine are themed around science books and lab equipment (insert nerd emoji here).

Okay, so maybe this is a dumb idea, but unlike most of my dumb ideas, I’m not alone on this one:

I currently have boards on AP Physics Essential Books:

AP Physics 1 and Physics C Mechanics Lab Equipment:

Electricity and Magnetism Lab Equipment:

AP Physics 2 Labs:

I have a couple more science teaching boards in progress, but they don’t have enough pins yet to count as much. I’m not a huge fan of Pinterest. Like most of the Web, it seems to exist mostly to get you to consume more. But, for the purpose of sharing teaching ideas, it has some advantages:

• The search and social media aspects make it easy to see what other teachers are doing (although there don’t seem to be a lot of HS physics teachers using Pinterest right now).
• The images make it more useful and more appealing than my old “Useful Links” page.

If you are a science teacher with a board for teaching, please share with me.

## Racism and the past

Last summer I drove through the delta from Searcy, Arkansas to Pine Bluff, Arkansas. It’s a pleasant drive. The land is mostly farmland, dedicated to cotton, soybeans, and rice. The delta is an area of rich soils, plentiful water, and productive farms. Arkansas is the largest producer of rice in the country. Rice fields are particularly beautiful. The rice is a vivid green, planted in sinuous curves, and the fields are often flooded, the water reflecting sky and earth.

I passed through the tiny town of Des Arc, and spotted the Lower White River Museum State Park. The museum is in an unassuming tan metal building, only a few years old. It is spotlessly clean and little worn. There was a young woman in uniform, serving the state as museum staff. She told me that she grew up in Northeast Arkansas, near the Black River, a tributary of the White, and we chatted briefly about the exhibits. The few artifacts were largely quotidian, related to life near the river, but there were a lot of photographs, including many of riverboats, evocative of the era of Mark Twain. Exhibits highlighted the fishing, inland shipping, and mussel harvesting by which many subsisted off of the river in the past. The mussels were made into buttons. I discovered the origin of some odd mussel shells with holes drilled out of them that my father had owned. And there were works of contemporary art related to the river. It was a pleasant enough thirty minutes.

As I drove away, one thing bothered me. Look at the diorama below.

You are looking at the only purposeful mention or depiction of African-Americans in the entire museum. The only thing  clearly communicated by this mannequin is his inferior status. Poorly dressed compared to his white companions. Seated on a barrel looking up deferentially at the riverboat captain, while the white surveyor surveys and the white lady does whatever the exhibitor thought white ladies did by the side of the river.

Kids come into this museum, with their parents or with school groups. Kids of all races. As an educator, and a person who once worked in a history museum, it bothers me that there are no exhibits or words about the Arkansas African-Americans who played an important role in the history of the Lower White River. As they still do.

I wish I had thought to ask the young woman what her take on the exhibit was, and why there wasn’t more about African-Americans. But, I didn’t. It troubles me that a state museum would completely avoid the issue of race in Arkansas’s history but it doesn’t surprise me. If you’re the museum staff, it’s safer to avoid sticking your neck out. Often visitors come to museums to feel nostalgia. Museum staff don’t want to kill the nostalgia buzz. Those kids who come into the museum are going to learn a bit about Arkansas’s history. But the issue of racism, a problem that still holds us back nearly 200 years after we became a state, well, that’s just too tough.

I’ll leave you with an admittedly preachy quote from a writer my father was fond of, George Santayana:

Progress, far from consisting in change, depends on retentiveness. When change is absolute there remains no being to improve and no direction is set for possible improvement: and when experience is not retained, as among savages, infancy is perpetual. Those who cannot remember the past are condemned to repeat it.”

## The First Day of School: Marshmallows and Spaghetti

I have used this as a first-day activity for several years. Students walk in, and sit in groups of three or four assigned for them. The groups are given a large marshmallow, 20 sticks of spaghetti, about a meter of masking tape, the same length of string, and a scissors.

chrisgagne.com

In 18 minutes, each group is to use these materials to build a structure that supports the marshmallow. The highest structure wins. Below  are a couple of groups working on their structure.

The marshmallow must remain whole, and the structure may only be connected to the tabletop. That’s it. That’s the whole activity, almost. I project a countdown timer, walk around saying encouraging words, and call out the measurements at the end. We talk about what they did that worked, about how important it is for a group to work together, and how they might do better next time, knowing what they know now.  A successful structure looks like this:

Most of these kids have never built any kind of structure, or even thought about what it takes to build a structure.  Building a stable structure out of spaghetti is tough in 18 minutes, but the marshmallow adds another dimension. Once you place the marshmallow on top, most of the structures don’t stand, or they lean over until they are barely above the tabletop. It’s fun, it’s exciting, and there are lessons to be learned from it.

I pitch it to the kids as a “model” of what they will be doing in this class:

• they will collaborate in groups, often groups not of their choosing
• the groups will be given unfamiliar problems to solve with familiar tools
• failure is expected along the path to solving unfamiliar problems
• failing publicly is expected during class
• I expect them to learn from failure
• trying is valued, not just success
• success comes when you jump right in, apply what you know, and work together.

I didn’t invent this activity.There exists at least one website, devoted to it. In the TED talk posted on the website, Tom Wujec emphasizes how the including the marshmallow from the start leads to success. This is worth stressing to students in the physics classroom, as well.

Afterwards, we usually do something more traditional, a spring lab, or a pendulum lab. Talking about rules and procedures can wait until later. Getting right to work is more important.

## TESS has no meat on her bones

There are structural and cultural problems with the Arkansas Department of Education’s newish Teacher Excellence and Support System (TESS), the system by which teachers are evaluated. TESS is not really going to change anything.

TESS is based on Charlotte Danielson’s “The Framework for Teaching” which attempts to break teaching down into a bunch of separate components that can be assessed by evaluators, i.e. school principals.TESS replaces “some type of checklist” that most Arkansas districts were using with a purportedly clear but pretty complicated rubric. As far as I know, all Arkansas principals and teachers have received training and a copy of Danielson’s book. I don’t have any major problems with the book or the rubric. Really, I thought they were okay, with some reservations.

But student learning is going to be improved by giving everybody a new rubric? Really?

The main structural problem with TESS is that it doesn’t fundamentally change who does what, and how they go about it. Teachers are evaluated by principals. Principals have an interest in making sure their school is orderly, their “customers” are happy, and that the school appears successful (School Report Cards and word-of-mouth). Principals are busy. They deal with lots of phone calls, hundreds of emails, cantankerous students, parents, and staff. It’s not a job I would want.Principals evaluate classrooms to make sure the teacher has established procedures, the students are compliant and understand their roles, and that the education process appears to be moving at a reasonable pace for the level of the students. Principals rarely have an interest in the depth of learning that goes on in the classroom. It’s not their fault. As I said, they are very busy. And the chances that they come into a particular teacher’s classroom up to speed on the content depend on what they taught and how long ago they taught it. Principals are likely not even the person who should be evaluating this area of learning. I teach physics. I have never had a principal evaluate me who wanted to discuss the details of how students learn physics content. Twenty-plus years of teaching and a principal has never discussed with me how students learn the content. The depth of student understanding is the important part. This is the part that bears deep thought and consideration. Not whether or not students know how they are supposed to ask to go to the bathroom. Okay, so I’ve never been particularly great at the rules and procedures part of teaching. And I concede that it makes everyone’s life easier when the rules and procedures run smoothly. But the impact on depth of understanding? Not so sure. This is a cultural problem. If the classroom appears orderly and students “engaged,” then the culture assumes that learning is happening. But deep learning is a tricky thing. I think all of us who went to school can relate to forgetting everything you studied immediately after the test. That is not the kind of learning I am after. Deep learning requires thought on the part of the teacher. This is where another viewpoint would be helpful.

Another structural problem is the “classroom cul-de-sac.” Teachers have no way to move up without getting out. Teaching is teaching whether it’s your fifth year or your thirtieth year. The only promotion is to become an administrator, and then you are no longer a teacher. Teaching can be a lot of fun, and a lot of us don’t want to give up that part. After a few years of teaching, if you’ve worked your way into an assignment that you like and a nice classroom, that is probably where you will be at retirement (caught in that cul-de-sac).

Assuming you are deemed competent, there are no institutional incentives for improvement in teaching skills, monetary or other (is this structural, cultural, or both?). There are personal incentives, of course, and many teachers work hard to improve even after long years of teaching, for no reason other than to gain greater job satisfaction. But teachers generally don’t get paid more or recognized in any way for doing a better job.  Sure, teachers are rated by principals, but those evaluations are private, don’t impact salary and promotions, and rarely result in a concerted, cooperative effort to improve a teacher’s skills, particularly if that teacher is already a veteran teacher.

Teachers should evaluate each other. Peer evaluation could accomplish at least two things: 1. Teachers would  be more likely to get direct, practical feedback on their lessons. 2. Instead of having the same job for an entire career, experienced teachers would encounter new challenges and feel that their expertise was benefitting greater numbers of students.

A couple of experienced teachers in each department /school could be given an extra planning period and designated evaluators, They could do the grunt work of evaluating their colleagues, and a principal could review their work and sign off on it. Certainly the principal could observe and evaluate the team themselves, as well. At least one of the teacher/evaluators should teach the same or a closely-related subject.Better if both did. The evaluation could be a collaborative process, focused on student learning. Ideally, it would be something like the Japanese education system’s Lesson Study. In a lesson study, groups of teachers watch each other teach the same subject in different ways. The group collaboratively develops a lesson that helps students understand a complex topic. Evaluators and evaluated could grow together and improve instruction, so that students develop the deep understanding of a subject that leads to success. And an evaluation instrument exists that could help teachers evaluate each other. It’s called the Reformed Teaching Observation Protocol. It’s not a replacement for TESS as an all-around evaluation, but it does look at whether what goes on in a classroom has the characteristics that have been shown to get students thinking more deeply.

Here’s another take on Danielson’s evaluation system.

## What should a kid get out of high school science?

Some friends asked me this question recently, and I gave a bad answer. In my bad answer I said something like “They should know some things. Some big ideas.” And I listed a few that came to mind, like conservation of energy. I don’t think there’s anything too terribly wrong with that idea, I just don’t think it’s enough. Students should know some “big ideas”, but also they should be able to do some science. This post is an attempt to give a better answer.

First, about the big ideas kids (and everybody) should know.  I’ve always liked the book Science Matters: Achieving Scientific Literacy by Hazen and Trefil. It’s still in print,25 years after I first read it, and still relevant.  It’s written for everybody. It’s engaging, and the prose has a sense of style. And it relays a good summary of the basic science concepts in every discipline; the big ideas a person should understand after a basic course in science  like astronomy, biology, chemistry, or physics. So read the book, or this one you can download for free, if you are really interested.

That said, here are a few big ideas I hope students leave school conversant in:

1. atoms , since somebody else said it better, I quote: “all things are made of atoms—little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another.” R.P. Feynman Lectures on Physics
2. some things we can calculate (“quantities”) are conserved. in a closed system, the amount never changes: matter, energy, momentum, angular momentum, charge
3. the universe, galaxies, solar systems, stars, planets are continuously changing in ways that are both understood and mysterious
4. the earth is the only living system known, and it is a system of interconnected parts, both living and non-living
5. organisms evolve, and their evolution can be understood both through fossils and observing living things; there is a common chemical basis for all life
6. at different scales (of space, time, and energy), different methods of investigation and description are needed
7. scientific understanding is constantly changing. a community of scientists works together to create the current best understanding. there are still many unanswered questions and huge gaps in our understanding

Now, about the science students should do (influenced by/condensed from modeling instruction and by the College Board’s Advanced Placement Science Practices):

Scientists make observations. Observations in science are usually measurements. No measurement is perfect; there is a limit to what can be known by measurement. The limits keep changing as technology improves, but there will always be a limit. Students should be able to make accurate measurements with classroom equipment, and be able to describe the limits of those measurements. Experiments are situations we create in order to make very specific observations.

Students should be able to create an experiment, or critique the flaws in somebody else’s experiment. They should understand the limitations of an experiment and also recognize when an experiment could be performed to find an answer, or at least the beginnings of an answer to a scientific question.

Observations/measurements are described by patterns. This is one of the deepest big ideas in science: there are recognizable patterns in nature. Some patterns are easier to observe, some more difficult. Patterns can be described by mathematics. When we know enough about a pattern, we use math, words, graphs to describe a conceptual model that encapsulates what we know about the pattern. Students should be able to describe the patterns in measurements using mathematics. They should be able to generalize these descriptions to describe conceptual models about nature.

Scientists make claims that are evaluated on the basis of evidence. Students should be able to make and evaluate scientific claims.

What’s the balance here between learning ideas and doing science? Ideally, students would learn science by doing science, as in methods like Modeling instruction, Process-Oriented Guided Inquiry Learning, Problem-Based Learning, and other inquiry instruction.

This is a very idealistic discussion. Being science literate depends on having a good understanding of these concepts and practices. Most students, those who just go through the motions in school as we know it, are not going to have that understanding. This discussion also leaves out engineering practices and applications, something important in the Next Generation Science Standards (and likely the to-be-released Arkansas High School Frameworks). So, I think this is a better answer, but not THE answer. Comments?