Supplementary reading Text 1. Stored Energy and Batteries

Energy cannon be created or destroyed, but it can be saved in various forms. One way to store it is in the form of chemical energy in a battery. When connected in a circuit, a battery can produce electricity.

If you look at a battery, it will have two ends – a positive terminal and a negative one. If you connect the two terminals with a wire, a circuit is formed. Electrons will flow through the wire and a current of electricity is produced.

Inside the battery, a reaction between the chemicals takes place. But reaction takes place only if there is a flow of electrons. Batteries can be stored for a long time and still work because the chemical process doesn’t start until the electrons flow from the negative to the positive terminal through a circuit.

A very simple modern battery is the zinc-carbon battery, called the carbon battery. This battery contains acidic material within and a rod of zinc down the centre.

When zinc is inserted into an acid, the acid begins to “eat away” the zinc, releasing hydrogen gas and heat energy. The acid molecules break up into its components: usually hydrogen and other atoms. The process releases electrons from the zinc atoms that combine with hydrogen ions in the acid to create the hydrogen gas.

If a rod of carbon is inserted into the acid, the acid does nothing to it. But if you connect the carbon rod to the zinc rod with a wire, creating a circuit, electrons will begin to flow through the wire and combine with hydrogen on the carbon rod. This still releases a little bit of hydrogen gas but it makes less heat. Some of that heat energy is the energy that is flowing through the circuit.

The energy in that circuit can now light a light bulb in a flashlight or turn a small motor. Depending on the size of the battery, it can even start an automobile.

Eventually, the zinc rod is completely dissolved by the acid in the battery, and the battery can no longer be used.

Different types of batteries use different types of chemicals and chemical reactions. One of the more common types of batteries is an alkaline battery (Duracell and Energizer batteries). The electrodes are zinc and manganese-oxide.

Lithium batteries are used in cameras for the flash bulb. They are made with lithium, lithium-iodide and lead-iodide.

Lithium-ion batteries are found in laptop computers, cell phones and other portable equipment.

In a nickel-cadmium or NiCad battery the electrodes are nickel-hydrogen and cadmium. The electrolyte is potassium-hydroxide.

In a zinc-carbon or standard carbon battery the electrodes are made of zinc carbon with a paste of acidic materials between them serving as the electrolyte.

Batteries store energy in a chemical process, but there are other ways of storing energy. Food is another method of storing energy. Let’s consider the “food chain” on our planet.

Plants, like grass in a meadow, convert the sun’s energy through photosynthesis into chemical energy. This energy is stored in the plant cells used by the plant to grow and reproduce itself.

Cows and other animals use the energy stored in the grass or grain and convert that energy into stored energy in their bodies. When we eat animal meat products we store that energy in our own bodies.