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.
Laptops are powered by several different types of batteries. These batteries provide direct-current power to your laptop. Lithium-ion: This is the type of battery you want to have in your laptop. This type is lightweight and performs better than the other types of batteries. Unlike NiCad or NiMH batteries, lithium-ion batteries donât have the dreaded âmemory effect.â