# What is it a student should be able to do and explain? How do we find that out???

### What is the evidence?

A perfect storm starts to form. We are on the concept of moles and I have some students who are struggling mathematically. It is a rough time of year to get kids excited. Many students are struggling with ACT and SAT prep and as a teacher, I am tired of test...test...test. Also, I had about two dozen 2 liter bottle "pre forms" that I needed to find something to do with.

I made up four sets of bottles, each containing different amounts of elements in each one, one type of element per bottle. Should a student select a bottle from the first two sets (numbers 1-12), they must get the mass, subtract out the mass of the bottle (which I provide) and calculate either the moles of the element in the bottle or the number of atoms in the bottle. If they get a bottle from one of the second two sets (numbers 13-24) then they are provided either the number of atoms of the element in the bottle or the moles of element and they need to calculate the total mass (including the mass of the bottle which I provide). They then compare their written answer with what they get when they place the bottle on the scale that I control.

All students must perform three tasks. First, they must physically do something besides just write answers on a piece of paper. All students have to collect some data that involves the mass and know what to do with it. Second, they have to be able to communicate their problem solving capabilities on paper. Having an answer, even if it is the correct answer, is not enough. They have to demonstrate a reasonable thought process. Finally, they need to get a correct answer. The closer they get to the correct answer, the better the grade.

Sure, this took awhile to set up. I have 24 different bottles. There are four sets with 6 different elements in each set and there are no two bottles that are the same overall mass. All data has been entered into a master spreadsheet so when a student provides an answer, I can check, provide immediate feedback within seconds and say, "Nice job" or "Try again". Most students generally make the mistake of forgeting about the mass of the bottle. Copying is virtually impossible. No two bottles are exactly the same. Students have three tries and I grade the best two. Also, they are up and moving around which tends to wake them up. Is this as good as a traditional "test"? That depends on the question..."What is it that we really want a student to be able to do and explain?"

This is a tough time of year to teach. Here is a thought...try to plan something this week in which your students will see you having fun, something you are passionate about, or both. As for me....I am kind of excited about trying to find a better way to see if students can explain the concept of moles....hopefully it will work.

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## NGSS

Students who demonstrate understanding can use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.

*More information about all DCI for HS-PS1 can be found at https://www.nextgenscience.org/dci-arrangement/hs-ps1-matter-and-its-interactions and further resources at https://www.nextgenscience.org.

Summary:

Students who demonstrate understanding can use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.

Assessment Boundary:

Assessment does not include complex chemical reactions.

Clarification:

Emphasis is on using mathematical ideas to communicate the proportional relationships between masses of atoms in the reactants and the products, and the translation of these relationships to the macroscopic scale using the mole as the conversion from the atomic to the macroscopic scale. Emphasis is on assessing students’ use of mathematical thinking and not on memorization and rote application of problem - solving techniques.

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## Comments 3

### Performance Assessments

Chad Bridle | Mon, 03/07/2016 - 05:40

I have ventured to try a "performance assessment" piece on as many of my unit assessments this year as possible. The results have been really intriguing. There's been a significant portion of my students who struggle on the more traditional part of the test, but they can go into the lab and do chemistry. It has really pushed the "What should students be able to do?" question to the front of my mind. It changes how I think about instruction during the unit. It changes how the students think about their preparedness for the assessment.

### Do you only put elements in

Shannon Bowen | Wed, 03/09/2016 - 10:13

Do you only put elements in the preforms? or some compounds, as well?  [I, too, have some preforms that need a purpose!]

### Compounds would work also...

Chad Husting | Wed, 03/09/2016 - 19:10

I put in elements but you could certainly put in compounds as well.  I did elements because we were just getting started with the mole.  You could do items like salt, water, glucose....Flinn has a great version of this in the "e-learning" series (https://elearning.flinnsci.com/) in which students actually are provided problems like, "provide your teacher with .15 moles of sodium chloride" etc.  First they have to solve the problems and then weigh it out.  Great activity, I just did not have the time in class so I tried to adapt it for what I had.  That being said...by all means...toss in some compounds...