1. Introduction
Bases are substances commonly found in soaps, baking soda, detergents, and cleaning solutions. They have characteristic physical properties that help us identify them easily.
These properties describe how bases feel, taste, look, and behave when dissolved in water.
2. Main Physical Properties of Bases
Bases show several observable properties. Below are the most important ones explained in simple terms.
2.1. Bitter Taste
Bases taste bitter. For example, baking soda solution has a mild bitter taste.
Important: Never taste bases in laboratory conditions. This property is mentioned only for natural, safe bases found in food or household items.
2.2. Slippery or Soapy Touch
Bases feel slippery or soapy when touched. This happens because bases react with the natural oils on our skin to form soap-like substances.
This is why soap solution feels slippery.
2.3. Effect on Litmus Paper
Bases turn red litmus paper blue. This is a simple test to identify whether a substance is basic.
2.4. State and Appearance
- Many bases are solids (e.g., sodium hydroxide pellets, washing soda crystals).
- Some are liquids (e.g., ammonium hydroxide solution).
- Most bases are colourless when dissolved in water, though some may form white or coloured crystals.
2.5. Solubility in Water
Some bases dissolve in water, and these soluble bases are called alkalis.
Examples of alkalis include:
- Sodium hydroxide (NaOH)
- Potassium hydroxide (KOH)
- Ammonium hydroxide (NH4OH)
Other bases like copper oxide (CuO) or iron(III) hydroxide (Fe(OH)3) are not soluble in water.
2.6. Electrical Conductivity
Bases conduct electricity in aqueous solution because they release ions such as:
\( \text{OH}^- \) and \( \text{Na}^+ \)
These ions allow electric current to pass through the solution.
2.7. Corrosive Nature
Strong bases like sodium hydroxide and potassium hydroxide are corrosive. They can burn skin, damage fabrics, and react strongly with certain materials.
Because of this, they must be handled carefully.
2.8. Odour
Most bases do not have a strong smell. However, some like ammonium hydroxide have a sharp, pungent odour.
3. Summary of Physical Properties
To remember easily, bases generally have the following physical properties:
- Bitter taste
- Slippery or soapy feel
- Turn red litmus paper blue
- Often solid in form
- Some bases dissolve in water (alkalis)
- Conduct electricity when dissolved
- Strong bases are corrosive
- Some may have a pungent smell
These properties help us identify bases in daily life as well as in laboratory experiments.