Labs from Chicago, Fall 1993 :
Chemical Energy.

Dr. Rich Kron, Dr. Heidi Newberg, and Luisa Rebull
Labs written for the CARA Space Explorers, Fall 1993

This is meant to be handed out to the students.

I. Introduction

The Universe is made up of very tiny building blocks, sone of which we've discussed before. At a very tiny scale, all normal matter is composed of neutrons, protons, and electrons. The neutrons and protons are charged. The electrons have negative charge and the protons have positive charge. Atoms are made up of protons and neutrons very densely packed at the center, with electrons hovering in a big cloud around them. This central structure is called the nucleus of the atom. All neutral atoms have the same number of protons and electrons.

There are over 100 types of atoms (usually seen in the periodic table). The atoms are hydrogen, helium, lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine, neon, sodium, etc. The type of atom is determined by the number of protons in the nucleus, since this the chemical properties that the atom will have. Hydrogen, for example, is composed of one proton with one electron hovering over it. Oxygen is composed of 8 protons and 8 neutrons in the nucleus and 8 electrons hovering over it. Chemistry is the study of how atoms bind together. For example, two hydrogens and one oxygen like to bind together to make a water molecule. A molecule is formed when the electrons from one atom interact with another atom, making a bond between them. Sometimes electrons are shared between atoms. Sometimes an electron is transferred from one atom to another, and they are held together because now one atom is positively charged and one is negatively charged; opposite charges are attracted due to electrical fields.

These chemical bonds store energy. If we made hydrogen and burned it, the burning process would make heat. During burning, the hydrogen makes chemical bonds with oxygen atoms in the air to form water. Water is a lower energy state, so some energy is given off. When we burn gasoline in our cars, it produces heat which runs the car motor. When we eat food, we get energy to heat and move our bodies. Batteries convert chemical energy directly into electricity.

In this lab, we produce heat from a chemical reaction, and we will make our own batteries.

II. The Experiment

A. Start a chemical reaction that produces heat. Follow the instructions on the heat packs to produce heat. Flipping the metal disc starts the following reaction:

[equation missing; we're looking for it.]

Do you see which bonds are breaking and which ones are forming? How many bonds do carbons like to make? ________

How many bonds do oxygens like to make? ________

This is the reaction of an acid and a base to produce a salt plus water.

B. Use the batteries provided to light a diode, a light bulb, and to buzz a buzzer. Use the voltmeter to measure the voltage of one battery.

Voltage: ______________

Now, put the batteries so that the positive and negative surfaces are touching. What is the voltage of the combination?

Voltage: _______________

What happens if you put the positive sides together?

Voltage: _______________

Measure the maximum current from the batteries (THIS SHORTS IT OUT, SO DON'T KEEP THIS CIRCUIT CONNECTED VERY LONG!!!!!)

Maximum Current: ________________

C. Make your own batteries. To make a battery, you need two metals and a solution of ions. In our case, we will use acids of various types. Fill a beaker 2/3 full with lemon juice. Attach a buzzer to a copper rod on one side and a zinc rod on the other side. Place the rods in the lemon juice. You should hear a buzz. Does it matter how far the rods are in? _______ Does the sound change with time? _______ Does it matter where the rods are in the solution? _______

Measure the Voltage and the maximum current from your battery.

voltage: ___________ Maximum current: ____________

Which direction is the current flowing, from the copper to the zinc or from the zinc to the copper? ___________

Electrons come out of the anode of the battery and are deposited at the cathode.

Now try different metals, different numbers of rods of each metal, and different acids.

# Metal 1    # Metal 2    acid    anode V    Max. I

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III. Possible quiz questions

1. If you have four 1.5 V batteries, how would you light a light bulb that requires 6 volts?

2. If the maximum current that your batteries will supply is 0.01 amps, how can you light a light bulb that requires at least 0.015 amps?

3. What is an atom?

4. What is a chemical bond?

5. How do batteries work?

Important Disclaimers and Caveats

Go back to the Chicago Fall 1993 Energy home page.