Saltwater buzzer: Test the current!

Author: Maddie Van Beek

Most of you probably know that electricity is able to travel through some materials, but doesn’t travel through others. For example, electricity can easily travel through metal such as copper, but it does not travel well through plastic. If electricity can easily be transmitted through a certain material, that material has good conductivity. Another word for conduct is transmit or transfer. If electricity cannot travel well through a material, that material has poor conductivity. 




Example: Wood has poor conductivity. Most metals have good conductivity. 

http://www.online-sciences.com/wp-content/uploads/2015/03/conductors-2.png

Check out the link below to learn more about conductivity: 

Conductivity

Look at the photos below. Which items are conductive? Which are not? 

http://cdn.omg-facts.com/2012/6/8/dddbcc1f839f0246c9167667026f7c2f

http://obidotoys.com/images/westcott_shatterproof_12_ruler.jpg

https://www.fantasyjewelrybox.com/Images/ProductFull/19775-4727/unisex-plain-sterling-silver-wedding-band-ring-6mm.jpg

http://shard4.1stdibs.us.com/archivesE/jewelry/1stdibs/071913/WimpoleJWL_LON_LB_CC//09/x.jpg

http://www.meiselrockproducts.com/wp-content/uploads/2014/07/rocks-323419_640.jpg

http://images.fineartamerica.com/images-medium-large-5/crushed-plastic-bottle-daniel-sanchez-blasco.jpg

Today, you are going to be using electricity to test water for its saltiness. What?! How could electricity tell you whether water is salty or not? Well, when salt is dissolved in water, the salt atoms break apart and become ions, which contain a positive or negative charge. Atoms become ions when they gain or lose electrons. Remember, electrons are negatively charged, so if an atom gains an electron, that atom becomes a negative ion. If an atom loses an electron, that atom becomes a positive ion. 

Remember when we learned about atoms and ions when we bent a stream of water with static electricity?

Believe it or not, salt water will conduct electricity! Lets try it out. 




YOU WILL NEED:

• Glass
• Distilled water (must be distilled, not tap or drinking water)
• Salt
• Buzzer (a.k.a piezo transducer/buzzer.  You can find this online at a variety of vendors.  Click here for examples. Be sure to get one with a black and a red wire!)
• 9-volt battery
• 2 wooden craft sticks (or Popsicle sticks)
• Aluminum foil
• Electrician’s tape

Here’s what to do! 

1. First, wrap each craft stick with aluminum foil. 
2. Use the electrician’s tape to attach the red wire of the buzzer to the positive end of the 9-volt battery. The positive end of the battery will have a plus sign on it (+). 
3. Tape one of the foil-covered craft sticks to the negative end of the battery. The negative end will have a minus sign on it (-). 
4. Tape the second foil-covered stick to the black wire of the buzzer. 
5. Now, test out your circuit. Touch the tips of the two foil-covered craft sticks together. BUZZ!!! When the circuit is complete, your buzzer should have gone off. If the buzzer did not sound, go back and check your connections to make sure everything is in place. If this does not work, try a new buzzer. 
6. Fill a glass with one cup of water. 
7. Place both ends of the foil sticks in the cup of water so they are about one inch apart. Does anything happen? Record results. Is plain water conductive or not? How do you know?
8. Remove the foil sticks from the glass. Mix one tablespoon of salt into the glass of water. Stir in the salt until it fully dissolves. 
9. Once again, place the ends of both foil sticks into the glass of water so they are about one inch apart. What happens? Record your results. Did salt water conduct electricity? How could you tell? 

Follow-up Questions:

1. Did the buzzer sound in plain water? Why or why not? 

2. Did your results change when you added salt to the water? Why would salt make a difference? 


3. How is saltwater able to conduct electricity? 



Extensions: Try using sugar water instead of salt water. Do you get the same results? What if you try using Gatorade or milk? Will other liquids conduct electricity? Try it out! 




References

http://www.education.com/activity/article/Experiment_with_Salt_Water/

http://pbskids.org/zoom/activities/sci/saltwatertester.html

https://en.wikipedia.org/wiki/Ion

http://www.physics4kids.com/files/elec_conduct.html