We haven’t been doing much actual chemistry in class yet but today was Halloween so I decided to do a bunch of chemical reaction demonstrations and then have the kids make glow in the dark slime… complete with eye balls.
I found an interactive notebook lesson that we did at the beginning of class. The lesson is Signs of Chemical Change from Chemistry : Compounds, Bonding & RXNs by Stephanie Elkowitz and I bought it on teacherspayteachers.com. It has different test tubes that you cut out and each one has something like, odor, light, bubbles… things that can indicate a chemical reaction has taken place. They cut them out and make a pocket in their notebook to hold them. While they were cutting and putting it together I started talking about the different types of chemical reactions that can occur – basically a simpler version of the talk I gave for the high school class.
Then we did some chemistry. We started with burning some magnesium ribbon, which is a synthesis reaction – magnesium plus oxygen produces magnesium oxides. After watching the demonstration the students went back to their notebooks and described what they saw, including the clues that a chemical reaction had taken place, in this case a very bright light was produced and there was a color change.
The second reaction I showed them was the copper wire that we had put in silver nitrate last week during the high school class. The copper wire was completely covered in silver and many students guessed that it was a fish or a leaf inside the tube. I explained that it was a single displacement reaction, the copper displaces the silver in the silver nitrate solution and you end up with bits of silver forming on the copper wire. Then we dripped silver nitrate solution into salt water and watched the precipitate, silver chloride form and sink to the bottom. This reaction is a double displacement with the silver and sodium atoms switching places to form silver chloride (solid) and sodium nitrate in solution.
Next we made elephant toothpaste – the instructions I followed can be found here on Science Bob’s website. Steve Spangler also has videos and instructions on his website. I used about 15 ml of hydrogen peroxide (40 Volume bought at Sally Beauty Supplies – its a higher concentration of hydrogen peroxide than what you would buy in grocery store), a couple of squirts of dawn dish detergent, and dripped some food coloring down the side of the cylinder. Then put a tablespoon of yeast in warm water, stir a bit and pour into cylinder. If your ‘toothpaste’ is too runny try putting less water in with the yeast. This is an example of decomposition reaction because the hydrogen peroxide is breaking down into water and oxygen – the yeast acts as a catalyst – helping the reaction along.
Lastly, we did the black snake demonstration.
For this experiment I followed the instructions of the Crazy Russian Hacker.
Since today was Halloween I let the kids make glow in the dark slime for their own chemical reaction. The instructions are on the American Chemical Society’s website. I added some eyeballs that I found at the local halloween store.
No class next week, but we’l be back in two weeks with the kids presentations on the elements.