PLAYING WITH SANDWICHES AT THE “CHEMISTRY CAFÉ”

ONE CHEMISTRY LESSON USING A PHET SIMULATION

Chrysi Doulaki 3rd High School of Alex/polis

Introduction

Teachers many times need to incorporate in their lessons activities that

stimulate the interest of the pupils, make connections between everyday life and the

learning object and give students visual cues helping them

understand difficult concepts and phenomena

Especially in Science, activities such as experiments or simulations are often very useful in order to succeed the above pedagogical goals.

Today I will present you one chemistry lesson which incorporates a quite simple simulation from the internet recourses.In particular, I use one interactive simulation from a very known for science teachers site http://phet.colorado.eduThis site provide us with fun, interactive, research-based simulations of physical phenomena from the PhET™ project at the University of Colorado.

http://phet.colorado.edu

Reactants, Products, and Leftovers Activity

Lesson Plan

This is an introductory lesson to the stoichiometry unit My teaching is based on the

“prediction-check-discussion” schedule I use a worksheet guiding pupils on the above

schedule in every activity The lesson should be done in the computer lab. In this

case pupils could work in pairs or small groups working independently and filling in their worksheets

Another option is to use the worksheet with the whole class using a projector or the interactive boar

Learning goals

Relate the real-world example of making sandwiches to chemical reactions

Describe what “limiting reactant” means using examples of sandwiches and chemicals at a particle level.

Identify the limiting reactant in a chemical reaction

Description of the worksheetActivity 1st

2 Bd + Ch → Bd2Ch

a. b. c. d.

They have to choose the icon that matches to the above type of sandwich Then I give them another type of sandwich Bd2Ch2 and they have to match

again We discuss about coefficients and subscripts

We discuss that for the sandwich we can choose the ratio (double cheese …) but for the chemicals this is often fixed (for example for water H2O)

Activity 2nd

They have to predict (without using the sim) the number of cheese sandwiches (Bd2Ch), that someone can make with 10 pieces of bread and 8 slices of cheese and what should be remain.

We discuss about their thinking to get the answer.

Then, we use the sim to check their answers and make any corrections.

We continue with another prediction changing the type of sandwich to Bd2Ch2 and keeping the same 10 pieces of bread and 8 slices of cheese

We check their predictions using the sim We discuss again about their thinking and why did the number of sandwiches change even

though the amounts of ingredients were the same

Also we discuss about leftovers and here we introduce the concept of “limiting reactant”

Relate the model to Chemistry:

Activity 3rd They have to predict how many particles of water should be

shaped if we had 6 particles of H2 and 4 particles of O2 . Then we check their predictions using the sim. I ask them to find which is the limiting reactant here.

We proceed with more examples and we meet one limitation of the simulation which is that it stops at the particle level and some times we get leftovers of both ingredients.

So here we discuss with pupils that in reality, in a two-reactant synthesis reaction, usually one reactant gets entirely used up (and determines how much product is made).

The BEST PART: the game

We play the game and discuss strategies for best score

In conclusion

At the beginning I was afraid that it might not be such an interesting lesson for my pupils at the age of 16.

But I saw that not only enjoyed it but also they saw it very seriously and gave extensions that I didn’t expect.

The discussion helped them to analyze steps of their strategies and therefore to follow these steps more consciously.

Weak or disinterested pupils were attracted and they did very well with predictions while some good pupils found it difficult to make the predictions.