Which of the following best defines a base in chemistry?

In chemistry, a base is best defined as a substance that accepts protons or donates hydroxide ions. This definition aligns with the Brønsted-Lowry theory, which describes bases as proton acceptors, and the Arrhenius definition, which characterizes bases as substances that increase the concentration of hydroxide ions (OH⁻) in solution.

When considering this definition in the context of acid-base reactions, bases typically react with acids to form water and a salt, which illustrates their role as proton acceptors. The ability to donate hydroxide ions also plays a crucial part in neutralizing acidic solutions, further solidifying the role of bases in various chemical processes. This concept is fundamental in understanding acid-base chemistry and is applicable in a wide range of scientific and practical situations.

The other options do not accurately convey this essential aspect of what characterizes a base. For example, increasing the temperature of a solution does not define a base's chemical nature. Similarly, while some bases can be proton donors in specific reactions, this behavior does not encompass the broader definition of a base. Lastly, while bases can react to form salts, this is not a defining characteristic, as many other compounds can also form salts through various reactions.