OBSERVATIONS AND DATA COLLECTION Solutions Color on pH

indicator pH value Acid/Base

Water Lemon Juice

Salt Liquid Soap

Vinegar

QUESTIONS

1. What material was a base and what was an acid?

2. Do you think the pH level would change if you added more lemon juice to the water?

3. How could you change your acidic solution to a neutral solution?

4. Was your water perfectly neutral? If it wasn’t neutral what might be some reasons why?

BATTERY LAB

BACKGROUND INFORMATION

Batteries have three main components: a cathode (positive electrode), an electrolyte, and an anode (negative electrode). An electrode is usually a type of metal such as copper or zinc, and an electrolyte is a chemical such as lime juice or saltwater. Chemical reactions between the

electrodes and the electrolyte cause a voltage to appear across the two electrodes. The cathode has a positive voltage with respect to the anode, which means current will flow through the battery from the anode to the cathode when a circuit is made.

LEDs are a member of the family of electrical components called diodes. Diodes only allow a current to flow in one direction. Like batteries, diodes have a cathode and an anode and, like batteries, current flows from the anode to the cathode. Current cannot flow from the cathode to the anode of a diode. Light-emitting diodes, called LEDs for short, emit light when enough

current flows through them. Because of the

way diodes resist current flow, LEDs usually

emit light when around 0.7 volts are applied

to them.

Current only flows when a circuit is made. In our circuit we had two components: the battery and the LED. When we connected the wires to the LED and the two ends of the battery, we

completed the circuit and current could flow. However, if we connected the diode backwards, no current could flow.

Part 1: Lime Battery

MATERIALS LIST

• Limes (4 Per Group)

• 4 Strips of Copper or Equivalent copper coins

• 4 Strips of Zinc or Galvanized Nails

• Aluminum Foil

• Tape

• light-emitting diodes (LEDs) PROCEDURES

1. Place the copper strip/coin into one side of the lime.

2. Place the zinc strip/galvanized nail into the other side.

Note: Make sure the zinc and copper do not touch inside the lime!!

3. Attempt to light up a light-emitting diode by attaching the + side of the LED (the one with the longer wire) should be connected to a copper strip or coin, and the aluminum attached to the zinc to the – side.

4. Repeat steps 1-2 with the limes, so you have 4 lime batteries.

5. Connect the copper on one lime to the zinc on the other lime by using the aluminum foil to link them together. Use tape if necessary. Leave the limes at the end unconnected but with long strips of aluminum foil attached.

6. Now connect the two strips of aluminum foil to that of the LED. The + side of the LED (the one with the longer wire) should be connected to a copper strip or coin, and the aluminum attached to the zinc to the – side. Observe and record what happens.

7. Connect the LED backwards, so that copper goes to – and zinc to +. Observe and record what happens.

8. Remove the aluminum foil and metal pieces so you can use them in the next part of the experiment

Part 2: Salt Water Battery

MATERIALS LIST

• 4 x 50mL Beakers

• Water

• Salt

• 4 Strips of Copper or Equivalent copper coins

• 4 Strips of Zinc or Galvanized Nails

• Aluminum Foil

• Tape

• light-emitting diodes (LEDs) PROCEDURES

1. Add water to the four 50mL beakers until they are almost covered.

2. Add a large amount of salt into the solution and stir.

3. Fold the metal strips into half.

4. Place the copper strip/coin onto one side of the beaker.

5. Place the zinc strip/galvanized nail into the other side.

Note: Make sure the zinc and copper do not touch inside the beaker!!

6. Repeat steps 1-2 until you have 4 salt water batteries.

7. Connect the copper on one beaker to the zinc on the other beaker by using the aluminum foil to link them together. Use tape if necessary. Leave the beakers at the end

unconnected but with long strips of aluminum foil attached.

8. Now connect the two strips of aluminum foil to that of the LED. The + side of the LED (the one with the longer wire) should be connected to a copper strip or coin, and the aluminum attached to the zinc to the – side. Observe and record what happens.

9. Connect the LED backwards, so that copper goes to – and zinc to +. Observe and record what happens.

QUESTIONS

1. In part 1, what material was the cathode made out of? What material was the anode?

What was the electrolyte? What about in part 2?

Hint: Electrolytes are usually a liquid chemical, and electrodes are usually metals.

2. Why did we have to use four lime batteries in series to light the LED? Did the lime batteries generate voltages on their own?

Hint: Voltage is always generated when an electrolyte is placed between an anode and a cathode.

3. Based on your answer to question 2, what can you say about voltage sources (such as lemon batteries) in series?

4. In step 13, why didn’t the LED light up?

Hint: Was current flowing? Why or why not?

5. If you have three batteries which are 1.5 volts each, what do you have to do to get a voltage of 4.5 volts out of them?

Hint: How should you connect them together?