PLAYING WITH SANDWICHES AT THE “CHEMISTRY CAFÉ” ONE CHEMISTRY LESSON USING A PHET SIMULATION Chrysi Doulaki 3 rd 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 This site provide us with fun, interactive, research- based simulations of physical phenomena from the PhET™ project at the University of Colorado.research- based

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 worksheet Activity 1st 2 Bd + Ch → Bd 2 Ch 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 Bd 2 Ch 2 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 H 2 O)

Activity 2nd  They have to p redict (without using the sim) t h e number of cheese sa ndwiches (Bd 2 Ch), 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 Bd 2 Ch 2 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 H 2 and 4 particles of O 2.  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.