Alkali

Some things feel slippery like soap. These things can mix well with water. They are called alkalis.

When they touch your skin, they feel very slick. Some can even cause burns. This happens because they change the fats on your skin.

Alkalis can be found in the ground. Some soil is alkaline. Certain plants like to grow in this soil.

They can also be found in lakes. These are called alkali lakes. They have many salts in them.

It is neat to see them in nature!

An alkali is a type of base. A base is a substance that can change other things. Alkalis are special because they dissolve in water. They have a pH level higher than 7.0. This number helps scientists measure how strong they are.

When you touch an alkali, it feels slippery. This happens because it changes the fats on your skin. This change is called saponification. Some alkalis are very strong. They can cause chemical burns. These strong parts are called caustic.

We find alkalis in many places. Some soil is alkaline. This means the soil has alkali salts in it. Some plants, like cabbage, like this soil. Other plants might have trouble growing there. You can also find them in alkali lakes. In these lakes, water dries up. This leaves behind many salts. This makes the lake very salty. These lakes are also called soda lakes. Examples are Mono Lake and Bear Lake.

An alkali is a special kind of base. In chemistry, a base is a substance that can change other things. An alkali is a base that can dissolve in water. These substances have a pH level higher than 7.0. This number helps scientists measure how strong a solution is. Most alkalis are salts made from alkali metals or alkaline earth metals. Because they are so common, people often use the words alkali and base to mean the same thing.

There is a specific way that alkalis work in water. They are called Arrhenius bases. When you put them in water, they form hydroxide ions. This process changes how the liquid behaves. If a solution is strong, it can turn a liquid called phenolphthalein from colorless to pink. Some solutions are very strong and are called caustic. This means they can cause chemical burns if they touch you.

The word alkali comes from the Arabic word al qalīy. This word refers to the original source of these substances. Long ago, people used burned plant ashes to make a mild alkali called potash. This potash was mostly potassium carbonate. People also found that heating potash with calcium hydroxide made a stronger substance. This was called caustic potash, or potassium hydroxide. This substance was used to make soft soaps from animal fats.

Scientists use many different names for alkali salts. Sodium hydroxide is often called caustic soda. Potassium hydroxide is called caustic potash. You might also hear the name lye. Lye is a general name for these salts or a mixture of them. Another example is calcium hydroxide, which is a solution known as limewater. Magnesium hydroxide is also an alkali, but it is different. It does not dissolve in water very easily.

We can find alkalis in nature all around us. Some soils are alkaline if their pH is higher than 7.3. This happens when alkali salts are in the dirt. Some plants like cabbage enjoy this type of soil. However, many other plants prefer slightly acidic soil to grow well. You can also find alkali lakes, which are sometimes called soda lakes. In these lakes, water evaporates and leaves behind many salts. Examples include Mono Lake in California and Bear Lake on the Utah-Idaho border.

In chemistry, an alkali is a specific type of base. A base is a substance that can change the chemical properties of other materials. An alkali is defined as a base that can dissolve in water. These substances are characterized by having a pH level greater than 7.0. Most alkalis are basic salts made from alkali metals or alkaline earth metals. Because they are so common, people often use the terms "base" and "alkali" interchangeably. However, scientists often treat alkali as a smaller subset of the broader group of bases.

To understand how they work, we look at the Arrhenius definition of a base. An alkali is an Arrhenius base, which means it forms hydroxide ions (OH−) when it is dissolved in water. This chemical process changes the behavior of the liquid. For example, moderately concentrated solutions can have a pH of 10 or higher. Such solutions will turn a chemical called phenolphthalein from colorless to pink. Highly concentrated solutions are described as caustic. This means they are strong enough to cause chemical burns on living tissue. You might notice that alkaline solutions feel slippery or soapy. This feeling happens because of saponification, which is a process that turns the fatty substances on your skin into soap.

There are different ways to categorize these substances. One common definition of an alkali is a basic salt of an alkali metal or an alkaline earth metal. This definition includes magnesium hydroxide but excludes ammonia. Another way to define an alkali is any base that is soluble in water and forms hydroxide ions. This second definition is broader and includes ammonia. Most alkalis are water-soluble, but there are exceptions. For instance, barium carbonate is only soluble when it reacts with an acidic aqueous solution.

Many different alkali salts exist with specific names and uses. Sodium hydroxide is a common salt often called "caustic soda." Potassium hydroxide is another important salt known as "caustic potash." You may also hear the generic term "lye" used to describe these salts or a mixture of them. Calcium hydroxide is a saturated solution that is commonly known as "limewater." Magnesium hydroxide is considered an atypical alkali. While it is a strong base because its ions dissociate completely, it has very low solubility in water.

The history of these substances is tied to ancient practices. The word "alkali" comes from the Arabic word "al qalīy." This term refers to the original source of these alkaline substances. Historically, people used a water extract from burned plant ashes. This substance was called potash and was mostly made of potassium carbonate. When people heated potash with calcium hydroxide, also known as slaked lime, they created a much stronger substance. This was caustic potash, or potassium hydroxide. This substance was used with animal fats to make soft soaps through saponification. This process has been known since antiquity. The name for the element potassium actually comes from this plant potash. Even the chemical symbol K comes from the German name for potassium, which traces back to the word alkali.

We can observe the effects of alkalis in the natural environment. Soil is defined as alkaline if its pH value is higher than 7.3. This usually occurs naturally due to the presence of alkali salts in the ground. Different plants react to these levels in different ways. For example, vegetables like cabbage and fodder like buffalo grass prefer slightly basic soil. However, most plants actually prefer mildly acidic soil, with pH levels between 6.0 and 6.8. Very alkaline soils can cause growth problems for many plant species.

Another natural phenomenon is the existence of alkali lakes, which are also called soda lakes. These lakes form when evaporation concentrates naturally occurring carbonate salts. This process creates a lake that is both alkaline and often saline. There are many famous examples of these lakes around the world. In the United States, you can find Alkali Lake in Oregon and Mono Lake in California. Bear Lake, located on the Utah–Idaho border, is another example. Globally, you can find Lake Magadi and Lake Turkana in Kenya. Other examples include Redberry Lake and Tramping Lake in Saskatchewan, as well as Summer Lake in Oregon.