Energy Conversion
The main ideas we are trying to get across in this presentation are different forms of energy, how energy is interconverted, scientific observations and hypotheses, proper recording of scientific data and inquiry-based experimentation.
The kids will all have a copy of THIS assignment sheet.
Introduce Yourself!
Tell the kids your name(s), what you are studying, why you are studying. Why you wanted to go to college, what you plan to do when you leave college, why you like college. Try to minimize questions about college life at this point (this shouldn't be difficult, they will probably be shy at the start), and return to this at the end.
Setup
This demo requires some setup. The light > electricity > sound demo and the chemiluminescence demo need a few minutes of prep time.
First the light > sound demo.
This is pretty straightforward, They have already seen this one on the field trip, this is to reinforce and remind them of the ideas from then and get them thinking in the right direction.
Next, lightbulb.
First connect the lightbulb to the battery. The point here is that the energy conversions stop this time at the battery. This time we have energy STORAGE, which differentiates this from the last demo. In the generator version, the energy is stored inside you, of course, in the form of chemcial energy.
Next, chemiluminescence.
The 2 beakers should be primed with a little rhodamine 6G and fluorescein to make the blue glow turn into red and green. Pour the solutions together into the spiral and listen to the kids saying "cool!" The obvious example of where they will have seen this before is glow sticks. If they try hard they will come up with luminescent deep-sea fish, fireflies and the sun as a really good example that one kid came up with!
Next, their turn.
Divide them into 2's. Each should have a luminol solution and a peroxide solution, measuring cups, a waste container and a small paper towel in case of spills. Each kid should be wearing goggles. The first and most important part is to get them to define the variables (the two volumes and the time). Get them to put the correct headings on the chart. Start them all with 5mL and 5mL. Someone needs to time the glows. After that, they can make up their own volumes, but don't let them use more than 10 mL of either solution. Make sure they empty the solutions into the waste and that the waste is has a lid at all times. After 4 - 5 experimeents, get them all to do the "best" one. For best results, make sure that they use a different measuring cup for the blue luminol solution.
Finish as usual.
Make sure they know that all energy comes from the sun, and that it is stored in the sun in form of chemical energy.
The solutions
The Luminol Solution
4 g sodium carbonate
0.2 g luminol
24 g sodium bicarbonate
0.5 g ammonium carbonate
0.4 g copper(II) sulfate pentahydrate
1L water
The solutes dissolve slowly!
The Peroxide Solution
20 mL 30% hydrogen peroxide in 1L water