Even carbon dioxide can dissolve in the groundwater, causing the water to be naturally carbonated. This water is sometimes sold as mineral water. Groundwater can be heated by magma below the Earth's surface. The heated water can create hot springs, springs with water that is naturally hot (Figure 13.23). Some hot springs are used as natural hot tubs and are considered therapeutic and spiritual by some people. However, hot springs can be dangerous, too.
We used a level tablespoon of salt in a cup of water. The batteries we have shown here are more correctly called cells. An actual battery is made up of two or more cells. The zinc-air cell produces about three quarters of a volt.
The actual origin of the manufacturing process for Interstate Batteries is vague. The automotive, truck, and marine batteries are made by Johnson Controls which makes 65% of the automotive, truck, and marine batteries sold in the USA. Johnson Controls also makes the batteries for Wal-Mart and AutoZone. From Louisiana to Southern California the Interstate brand batteries are made by a Johnson Controls manufacturing plant in Monterrey, Mexico. In the other states, the batteries are made by Johnson Controls in the United States.