Category: Chemistry

Density Lab Challenge

At the end of modeling and practicing density I provided my chemistry classes with the following Lab Challenge (this idea took shape for me after seeing a Flinn email about how to make measurement interesting).  I’m not sure this makes it interesting, but at least there is some motivation behind the measuring, not just doing it for nothing.

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1) Pick any 10 items from the front tables and rank them in order of most dense to least dense.
2) Identify the chemical makeup (specific substance type) of the 10 items you measure.


Students spent the first class period making measurements on the different items.  Some chose to use water displacement for volume, others used rulers for the regular shaped items.  One of my big goals of this activity was to see how well students would remember all of the measurement rules and techniques we’ve already practices.  (On their first mass vs. volume lab many failed to estimate a digit in their measurements)  I also wanted students to show me they can organize a data table that contained ALL of their measurements (i.e. initial and final volumes) not just the actual volume they calculated.  This is my Lab Goal #1 LAB.1 – I can recognize the precision of a measuring instrument, and record data in an appropriate, organized manner.

The second Lab Goal I assessed the students on was LAB.2 – I can design and/or follow an experimental procedure that tests a hypothesis, investigates a phenomenon, or solves a problem.

After the first class period most groups had their measurements made and densities calculated.  Good start.

On day 2 I had the students finish their measurements and then begin searching online for densities of the various items.  I did not provide any lists or other resources for them, just told them to start searching.  As tech savvy as the students are when it comes to searching for real, relevant information they have a long way to go.  Some were fine, but others were just lost.  Part of my reason for this part of the challenge was to allow them to struggle a little bit in finding this information.

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Finally on the 3rd day I gave the class the task to sort all of the items from the front table from largest to smallest density.  Since each group only measured about half of the objects this took some class collaboration and problem solving as to how to handle this.  This task proved to be an interesting study in class dynamics.  Of my 3 classes each went about this in a different way.  One class had each small group put a post-it note on each item and then were able to sort them that way.  Another class had each small group put their sorted list of objects on the front whiteboard.  That class proceed to find the overall largest, and if there were multiple measurements of the same item took the average.  The final class had one representative from each group work together and started with the largest (kind of like class 2, but without writing everything on the front board).

As you can imagine there were definite challenges the group had.  But as I talked about with each class was that this was a good simulation of what “real world science” looks like.  Multiple small groups set out to solve the same problem.  Those small groups then need to come together and collaborate and agree on something.  They need to rely on each other and their data, and at the same time solve discrepancies that arrive between the sets of data.

Eventually the final product looked like this:

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I would have liked to have their predictions as to what each substance was made out of on the board here as well, but we had a tough enough time just getting things lined up.  Maybe we’ll discuss that the next day, but maybe I won’t worry about it.  I talked with most individual groups as they were using the internet and searching densities anyways, so we might not need that large group time to discuss that.

Overall I really liked this challenge activity as a way to conclude Unit 1.  This activity contained everything from experimental design, measurement, mass, volume, and density.  If there is one thing I would change for next year it would be that on Day 2 I would have the class begin the process of organizing all of the materials right away since the groups have the densities.  I would then have the students do the searching as homework or at the same time as the objects are being organized.  I think that might be a more efficient use of time and would save us a class hour.  But then again maybe not.  Can you really rush good science?


Modeling Acids and Bases Lab

As my paradigm lab for Acids and Bases in Chemistry 2 we do a very simple classifying lab.  My lab handout is here: Classifying Lab

Basically what this entails is that I give the students 7 substances.  HCl, H2SO4, HNO3, NaOH, KOH, Ba(OH)2, and H2O.  They know the formulas and proper names, but NOT acid names (i.e. Nitric Acid).  I have each group do some qualitative tests in well plates using various indicators and other chemicals.  They take observation data in the table provided.

After all test are complete the students are to group the 7 substances into as many or few categories as they need.  They just need to justify their groupings.  After a little staring at the data most lab groups are able to see the pattern that emerges.  They almost always create 3 groups.  One contains HCl, H2SO4, HNO3, One has NaOH, KOH, Ba(OH) and H2O is by itself.

During our whiteboard discussion each group explains their reasons for putting certain things together.  Sometimes they talk about only one indicator but most groups see the patterns emerge across all the tests.  After we have an agreed upon grouping system I then pose the question, “Now look at your groups what do each of the substances have in common within a group?”  Obviously you always get a variety of answers but the initial responses usually revolve around how one group has begins with Hydrogen and the other ends with Hydrogen.  I remind them about what is significant about the order compounds are written in, and also what is significant about the Conductivity test we did.  They realize we are dealing with ionic compounds, and the first ion is positive, while the second is negative.  They also see the Hydrogen “on the end” always comes with an Oxygen, and we have hydroxide.  Someone usually also realizes that water is really just HOH, thus a combination of both of these groups.

My class this year is quite bright and it didn’t take them long to verbalize these patterns.  Within only a couple of seconds of this “light bulb” going off one young lady exclaimed.  “Can we make this a Vin diagram!?”  “Why not?” I said, “that would be a great way to model this!”

How perfect!  Never a mention of the words Acid or Base, and we have Arrhenius’s Model!  Concept before name!

Naturally the next day I challenged them by testing NH3.

To which a young man exclaimed.  “Here we go again, we create a Model one day, and the next day we prove it wrong!”

I said, “Don’t shoot the messenger, that’s the way the world works.”

He then added, “in English they call it an exception to the rule, but in Science we create a new rule!  That is why science rocks!”

Holy cow, have I done my job here?  At least it made me feel good that I’m getting through to a few kids!

Whiteboard Peer Review

I’m always looking for news ways to change up the whiteboard process I use (almost daily) in my class.  Whiteboarding is amazing, it gets and keeps everyone involved in the process of scientific thinking and problem solving.  However, early on each year I struggle with getting the students involved in the questioning and discussion process during WB presentations.

My theory is that it is an intimidation factor.  Students have a hard time adjusting to being able to questions their peers in front of a larger group of peers.  Usually in my Chemistry classes it is the first time students have been exposed to “low pressure”/”conversations starting” presentations such whiteboards.  Most have experienced the dreaded report presentation but that is it.

This year I tried something different to get the conversation started while my Chemistry students were whiteboarding the Modeling Chemistry worksheet on density.

I split the class into groups and gave each one problem to work on (students were to work on all of these problems individually before they came to class).  The problems on this WS consist of a mass vs. volume graph and several questions relating to that particular graph.  I gave the groups about 8-10 minutes to work on their problems.

As groups finished up working on their problems I rotated the boards themselves so that each group was looking at someone else work on a different problem than what they just did.  I gave them the following instructions:

  • Do NOT change any of the work on the board.
  • Write at least 1 relevant chemistry question about something that was on the board (Not why did you spell this wrong?)
  • Even if  you agree with everything on the board you need to write 1 question you would like to ask the group about why or how they did something.

I believe this process is similar to a “Whiteboard Museum,” but my classroom is not set up well for that at all, and I’ve never seen that done where students actually write questions right on the boards.

Here are a couple of examples of the boards I got.  (These aren’t the best ones I had all day, but I forgot to take pictures during my first couple of classes):

Overall I really liked the  way this whiteboard modification turned out.  There were a couple of benefits my students gained from this WB modification.

  • It gave everyone a sense of what I am looking for during the “questioning” phase of whiteboarding.  The whole idea of asking a question even if the answer is correct and they agree with the answer is foreign to them.  This forced their hand a little bit, to understand I’m more interested in the overall process of them “getting” a problem.
  • It allowed the shy students that have a lot of great questions and insights a chance to ask a question without asking in front of everyone else.
  • As groups presented the boards we were able to skip them explaining some of the WS problems they had been assigned.  Since all groups already looked over the boards and didn’t have an questions on a particular problem we saved that time.
  • As the groups presented they were able to focus their explanations based on the questions written on the board.  It gave them a sense of “direction” for their presentation.

I don’t think I will do this every time I whiteboard (especially not for labs), but when WBing a set of worksheet problems it seems as if it could be an effective way to change things up.

I would be interested to hear your thoughts and comments about this.  Have you done something similar?  What could I do better?  Different?  Please post below!

My Way to Make Measurement Make Sense

To me measurement is one of those topics that doesn’t seem like is should be a challenge.  BUT every year and every teacher I talk to finds that measurement is a HUGE PROBLEM with students.  I’ll let you form your own theories as to why this is the case.  This post is to describe the process I use to “reteach” students how to measure correctly, with the emphasis being on using a system of 10 divisions.

Nerd Rulers

I personally treat this activity as a lab, but it can be done any number of ways.  Here is the handout I use: How Many Nerds Lab.  The lab begins with me giving each student a ruler that looks like this:
They are asked, what do you notice about this ruler?  Things such as “no markings,” “a 0 and a 10,” “10 inches,” and many other things come up.  First thing I tell them is that this is NOT 10 inches or any other unit of measurement they have ever used.  So I have given the units a name: NERDS!  I tell them that since I’m kind of nerdy I wanted a unit of my own.

In reality the credit for this name and the rulers goes to Mr. Ryan Peterson of Brillion High School.  Any unit name you see fit can work.

From there I ask: “What is this ruler good for.”  The usual response is “not much.”  I usually have to hold something up and say “really, you can’t tell me anything about the length of this object?”  Someone usually realizes they can tell the object it either shorter or longer than 10 nerds.  “Ok, so what should I do to report the length of the object?”  “Guess” seems to be a popular response, but I quickly say guessing is random, like how many Jelly Beans are in a Jar.  Someone will finally say “Estimate.”

“Ok, now go and measure 8 things around the room.  Try to get at least 2 or 3 things that are longer than 10 nerds.”

I give them about 5 minutes to make their 8 measurements.  Then I hand out this ruler:
After a very brief discussion revolving around the fact that this ruler has the whole numbers marked, and that in science WE DO NOT USE FRACTIONS, I send students to remeasure the same 8 objects.

Finally comes the gold ruler:

They are off to remeasure the same 8 objects they have already measured.

Before I explain my discussion, here is how these rulers were created.  Again credit for the original Excel file goes to Ryan Peterson.

Nerds Rulers.  This Excel file contains 3 tabs, each containing 6 rulers on each tab.  Print from each tab.  I then copied enough sheets to make a class set of ruler on colored paper.  Finally I sent the pages through the laminater and cut out each ruler.  The set I made 5 years ago is still going strong.  The only real issue I’ve had is kids fold the blue ruler in half.

Back to the lab.

Once all measurements are made the students see a pattern of increased precision with each ruler (they don’t call it precision, but that’s what it is).  We quickly discuss things such as which ruler is best for measuring different objects, what makes a measurement “correct,” and how to handle measurements that we right on a marking.  The next thing is to have small groups discuss and whiteboard a rule or rules for using a ruler.

I give groups about 10 minutes to discuss some things and come up with what they think we should consider as “rules.”  Most groups come up with things like:

  • Start at zero
  • Measure the same object
  • Measure twice

I tell them that those are good and true and all, but how do make sure we are using a ruler correctly?  I sometimes have to give them the hint about what they did with the 3 different color rulers.  Most of the time that helps them realize that they ESTIMATED something in the answer.  Ultimately, after all groups have shared their rules I want the class to agree that we should:


This usually makes sense to the class, and they agree this the #1 rule.  PERFECT!

I extend the discussion with what that estimated number means.  I show them how the number they estimated is really reporting a range of numbers.  So for example a measurement of 3 is likes saying somewhere between 2 and 4.  A measurement of 3.6 is the range of 3.5 to 3.7.  Reporting 3.65 is something like 3.64 to 3.66 (this range might be a bit larger depending on the ruler).  Something I don’t stress at this point.

Metric Rulers

The next step is to introduce our more typical units of measurement: METERS!  Students know it is coming but they grumble and complain, and raise a fit over why we can’t just do it the “easy” way (inches, feet, etc.)  I then proceed to ask them something like; “so what increment comes after 7/32?”  Someone says 8/32.  “Ok, but I’m not going to find a wrench marked that.”   4/16, 2/8. oh 1/4.  “Congrats that just took you 1 minute to figure out.”  “What wrench comes after 7 mm?”  8mm.  “1 second, nice job, now which way is easier?”  I will then of course have the discussion about english vs. metric.

I usually like to get on my soapbox a little bit and complain about how “the US is the greatest country in the world, and by gosh we aren’t going to change our ways for anybody.”  I play that angle up a little bit, and we get to the point that metric is easier to work with, just not as common for us in America, but they hopefully see the point.

I now show the class a dowel that is marked as 1 meter long, but that is it.  Kind of like the blue ruler from above.  I then discuss and demonstrate how you can split a meter into 10 equal sections called decimeters, show them a ruler with only dm marks.  Each decimeter into 10 centimeters, show a cm ruler, and finally centimeters into 10 millimeters, show a typical meter stick with mm markings.

My lab hand out is here:  How Many Meters

Basically, I have a set of different metric rulers, and whatever the smallest markings are on the ruler is the “type” of ruler it is.  So a standard metric ruler is a mm ruler even though the numbers are cm.  This is just another complication in the process we have to deal with.  I have each student measure the same stuff with the same type of ruler so that we can compare results.

This is all for practice, and the whiteboard discussion is pretty minimal.  I usually focus on the different prefixes used in the SI system.  Why it is called SI and why it is important we have a standard unit of measurement for scientists.

Uncertainty of Measurement Activity

The questions I usually get about all this emphasis on measuring is “Why is this important?”  To me this activity nails it and relates why estimating measurements is so important as well as demonstrating exactly why significant figures work the way they do.

Uncertainty in Measurement

I distribute a index card and blue ruler to each student.   (something smaller than 10 nerds is a must, otherwise the uncertainty becomes too great.)  Each student measure the length and width of the card.  They then calculate the area, and I instruct them to write down exactly what the calculator says.

They remeasure with the pink ruler and again calculate and record area exactly as is displayed.  Finally they measure a third time with the gold ruler.

After all measurements and calculations are made I have each student list their calculated areas on the board.  One column for each ruler.  I forgot to take a picture of the entire set of class data, but it was something like this:

Notice how sweet this data is!  The discussion revolves around where the uncertainty in each calculation shows up.  For the Blue ruler it is in the tens place.  The Pink ruler the ones place, and the Gold ruler is in the tenths place.  Coincidence?!  I don’t think so.

Because of our “rule for using a ruler” the significant figure in each measurement comes out to be where our uncertainty shows up in our calculations!  Amazing!

Bottom line is the blue ruler gives us calculations that are uncertain plus or minus 10, thus we can only report an answer that is rounded in the tens place, which just so happens to coincide with 1 sig fig!

The pink ruler is uncertain plus or minus 1, thus rounded to the 1s place; 2 sig figs!

The gold ruler is uncertain plus or minus 0.1, thus rounded to the tenths place; 3 sig figs!

I think it is really cool how nicely the data comes out for students to “see” significant figures really work out.  In all actuality I not huge on make significant figures a huge issue as the year goes on, but I tell students, you better never ask me: “Where do I round?”  That is one of the biggest pet peeves I have and when the do I’m going to tell them to look at sig figs.

WOW!  That is a lot of information in one post.  Please use it for your benefit, and as always, if you have any questions or comments please leave them below.


My SBG Story

My journey towards Standards Based Grading started about a year ago (Fall 2011).  It just so happens that is when I discovered the Physics Education Blog world.  As I have stated in previous posts I give a lot of credit to Frank Noschese and Kelly O’Shea for many things I’ve picked up in the last year.  In terms of SBG I give these two ALL the credit!  I started reading their blog posts and ideas about what SBG is, how it works, and most importantly how to implement it.

2011-12 School Year
By about November last year I was convinced.  This is the way I needed to go.  The problem was of course changing “in-year.”  However, I am lucky because I just so happen to teach a Physics 2 class which is only 2nd semester.  My roster for this class was entirely seniors.  So I decided to experiment.  I presented the grading system to my 13 students as just that, and experiment.  My principal supported my idea without needing much convincing.  He just warned that I had a well documented plan to have on file.  Their wasn’t really any initial backlash from students or parents, so I considered that a victory.

I did run into some initial struggles, but nothing too major.  Our school has really pushed student and parent involvement through monitoring grades online,  so when I didn’t have a good way for that to happen I had some issues.  I ended up printing paper copies for each student ever couple of weeks.  I used ActiveGrade from the beginning to monitor and track students progress for myself, but I never explored it enough to figure out all the details (like how to allow students to login).  This is something that I have since resolved.

The other problem I had was creating well worded and good standards for units on Light and Waves.  I found plenty of good examples for mechanics, but not these.  I ended up relying mostly on the “Unit Goals” from the Modeling curriculum.  I did this in-semester rather than planning ahead, and that proved to be a challenge.  This will be much better this year, as I have my goals written going in.

Overall, my 13 seniors liked the idea of NO HOMEWORK and a weekly quiz for me to see where they were at.  They realized the quizzes were low pressure, but still worked to do well and get mastery scores.  I didn’t do official “reassessment requests” each week, but a couple of time during the semester I gave the class larger assessments, where all the problems were optional.  Students opted to complete only the questions that were relevant to the goals they hadn’t mastered yet.  I also did a reassessment assignment that included students video taping themselves working through a problem.  Only a few took me up on this offer, but those that did did a nice job of explaining what they knew.  I was able to tell if the truly “get it” or exactly where their conceptual breakdown occurred.

By the end of the semester students saw my grading system in a positive light, and I never had to defend it once to an enraged parent!

2012-13 School Year
This fall I have expanded my use of SBG to my Physics 1 class.  This class is a year long and consists entirely of Modeling Mechanics.  A lot of work has been done by other already to establish a system and standards for the Modeling Mechanics material, so naturally I relied heavily on that.  Below I have links to my Student/Parent Handout as well as my Goals for each mechanics unit.

If all goes well this school year I am planning to make the total change over to SBG next year, expanding to Chemistry as well.  I plan to continue to post idea, questions, and thoughts as they come up this year.

Learning Goals Based Grading

Physics 1 Learning Goals

2013-14 School Year 
I have again expanded my use of SBG to my Chemistry 1 classes in addition to Physics 1 and 2.  I’m really excited about using SBG in chemistry this year as well.  I saw how much it helped and focused my physics students last year, so to see that extend to chemistry will be good. 

The one big change I’ve made in my system is that I’m going to a 3 point scale for feedback purposes as opposed to using a 2 point scale.  The scale is defined as:

3 (Green) = Mastery has been demonstrated

2 (Yellow) = Developing Mastery – This indicates you are missing a minor piece of conceptual understanding, and/or that you have made a minor error in your reasoning process.

1 (Red) = Minimal Mastery – This indicated you are missing a major piece of conceptual understanding and/or you have made a major error in your reasoning process.

0 (Black) = No Data/Attempt

I’m going to use the colors on students quizzes and other assessments to try to get away from the “points-system” altogether.  The point values will simply be for ease in entering scores into ActiveGrade.  Although the scale changes students will still need to reach the “green” level for me to count the goal as mastered.  The yellow and red levels will better help me provide feedback for my students.  Giving them a more quantitative measurement of if they are close or far away from mastering the goal.  Last year I used the Yes/No scale and No was everything from minor mistakes or thinking to complete lack of understanding.  I wanted a better way to help students know exactly where they stand.  We’ll see how it goes.

I’m also attaching my revised document explaining Learning Goals Based Grading to my students and parents, and my Goals for Chemistry 1.

Chemisrty I Learning Goals

Learning Goals Based Grading – Explained

Chemistry Safety Posters

To deal with the boredom of Chemistry safety rules I allow my students some time to be creative and artistic with them.

The other day I presented my classes with my safety expectations.  Because of PBIS being an initiative in my school we were asked to fit our rules into an matrix that includes; Be Respectful, Be Responsible, and Be Safe…it’s the Blackhawk Way.  So I did.  It took me a little time to alter the wording of some the rules, but in the end it wasn’t actually that bad to fit into Respectful, Responsible, and Safe.  Here is my safety document:

Safety in the Chem Lab

The assignment I give students is to take a rule (or two or three) and create a Poster that depicts that particular rule.  I do allow students to work together as a group, but however many people they choose in their group is the number of rules they need to show on their poster.  I allow each group/person to choose whatever rule they want, so I do get some that are doubled up, but I’m okay with that.  I don’t like assigning rules to each person, because some of them are pretty tough to create a poster with.

After each group presents their posters we hang them around the room to serve as a reminder for the remainder of the year.  Here is a couple examples of what was hung around my room today:

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