We are finishing strong with our month long Science Celebration. Today Tatiana from The Musings of Mum is sharing a great hands-on exploration of the conductivity of liquids. Don’t let that intimidate you. The kids get to use a buzzer- how fun is that? Keep reading for instructions for a salt water conductivity experiment.
Why a Salt Water Conductivity Experiment?
My high school science class memories have absolutely nothing to do with science. Both my biology and chemistry teachers were known for incessant lectures and assigning endless research. Therefore I often caught up on sleep (yes, I know that’s bad) and occasionally caught up on homework during this time.
I’m a visual and kinesthetic learner, doing, is crucial when I’m learning something new. I’m sad to say that since we hardly ever did any hands-on learning, science class was the last place I wanted to be.
I look back on high school science class, and I want to a) kick myself on the behind for napping in class, and b) make it a point to make science fun and relevant for my students.
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Does salt water conduct electricity?
Earlier this year the kids that salt water does conduct electricity. Electricity and water are not two things you typically want to pair-up; however adding salt to the mix makes this experiment interesting.
Before seeing how it all works, let’s learn a little more about electricity and salt water.
What is Electricity?
Electricity is a form of energy resulting from the existence of charged particles (such as electrons or protons), either statically as an accumulation of charge or dynamically as a current. The following video does a great job of explaining how it works.
I suggest covering simple circuits before this activity. Paper circuits are a great way to begin exploring these ideas.
Why does salt water conduct electricity?
Salt is an ionic compound which is made up of sodium ions and chlorine ions. An ion is an atom or molecule with a net electric charge due to the loss or gain of one or more electrons.
When table salt (NaCl) is dissolved in water, the water molecules pull the sodium (Na) and chlorine (Cl) ions apart. As the ions float freely, they carry electricity through the water, making the water conducive.
To test the conductivity of salt water vs fresh water we can perform a simple, and fun experiment.
What You’ll Need to Experiment with the Conductivity of Salt Water.
- 2 popsicle sticks
- aluminum foil
- table salt
- 9-volt battery
- 2 cups of water
Let’s Get To it
- Add salt to one of the cups of water, you don’t need a lot, 3 spoons will do. Mix well.
- Wrap the popsicle sticks in foil.
- Tape the red wire lead of the buzzer to the positive (+) end of the battery.
- Next, Tape the black wire lead of the buzzer to one of the popsicle sticks.
- Finally, Tape the other popsicle stick to the negative (-) end of the battery.
Touch the ends of the popsicle sticks together:
You should hear the buzzer go off. If you can’t hear it, review steps 3 to 5 and make sure everything is correct.
Now dip the ends of the popsicle sticks in the salt water, make sure the ends are not touching each other. You should hear the buzzer go off, this is because the sodium and chlorine ions are carrying electricity as they float freely in the salt water.
Try this again in the fresh water.
What Does This Mean?
Since there are no sodium and chlorine ions floating around in fresh water, the buzzer will not go off unless you touch the ends of the popsicle sticks together (which will complete the circuit). The water only becomes conducive after adding salt.
Just for fun, we dipped the popsicle sticks in sugar water, cold coffee and milk; and you guessed it, there was no “BUZZ”.
More Electricity Ideas:
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