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.
In our increasingly mobile world, batteries serve quite a purpose. They power our cars, portable electronics and items we use every day. Batteries can even be made out of vegetables. Batteries are identified by the product they're used for (car battery, cell phone battery, etc.) or its size (9V, button cell).But for scientific purposes, batteries' names are based on the metals they contain.atteries are identified by the product they're used for (car battery, cell phone battery, etc.) or its size (9V, button cell). But for scientific purposes, batteries' names are based on the metals they contain.