Acids

• Acids tend to have a sour taste

• Acids react strongly with metals to produce hydrogen

• Acids are corrosive, which means that they can eat away at the surfaces of different materials.

• Acids in your everyday lives include lemon juice, vinegar, hydrochloric acid in your stomach and ascorbic acid (Vitamin C).

Bases

• Bases tend to taste bitter and are usually slimy or slippery.

• Another word for base is alkali.

• Like acids, bases are corrosive. When talking about bases however, we instead use the word caustic.

• Bases include soap, baking soda, antacids and bleach.

pH Scale

• The pH scale measures how acidic or basic a substance is.

• pH stands for 'Potential of hydrogen'. It measures the concentration of hydrogen ions.

• The higher the concentration of hydrogen ions, the lower the pH.

• Acids have more hydrogen ions (H⁺).

• Bases have more hydroxide ions (OH^-).

pH Scale

• Substances with a pH below 7 are considered acidic.

• Substances with a pH above 7 are considered basic.

• Substances with a pH of 7 are considered neutral.

Strength of Acids

Strength of Bases

• A small amount of acid or base dissolved in a large volume of water.

• To dilute a solution, water is added to the substance.

• Diluting a solution makes it more neutral.
  

Concentrated Solutions

Concentrated and Dilute Solutions

Dilute Solutions

• A large amount of acid or base dissolved in a small volume of water.

• To make a concentrated solution, more acid or base can be added.
  

Indicators

• Indicators are chemicals that change colour depending on the pH of their environment.

• We can use these indicators to determine the pH of solution

• There are several different types of indicators

  • Red cabbage indicator

  • Universal indicator

  • Litmus paper

Neutralisation Reactions

• When acids are added to a base or vice versa, the pH becomes neutral. This is known as a neutralisation reaction.

• Neutralisation reactions produce a salt (metal and non-metal bonded together), and water.

Neutralisation Reaction Example

• When you brush your teeth, the bases inside the toothpaste help to neutralise the acids produced by plaque on your teeth.