Applications of Acids and Bases

Flame Tests

One of the more interesting parts of the salts produced by neutralisation reactions is that when the salt is burned in a flame, they turn the flame different colours. Each different salt gives a different coloured flame, depending on the metal it contains.

The image below shows the colour change of a Bunsen Burner flame when metal salts are heated in a flame:-

The colour changes are useful as they allow a scientist to figure out which Elements are present in an unknown sample. Also it is these salts that are present in fireworks to the the explosions their distinctive colours.

Note - Also makes the Bunsen look like tiny Lightsabers, which is always good!

Teeth and Acid Erosion

Acid found within food and drink over time will cause damage to teeth. This is because the hard enamel that covers teeth is made of a mineral that can be dissolved by Acid.

The diagram below shows the main parts of a tooth:-

Image result for tooth diagram for kids
  1. Enamel - Hard white substance made of Calcium Phosphate. Enamel is the hardest substance in the body, and protects the rest of the tooth.

  2. Dentine - Hard yellow substance, again made of Calcium Phosphate. Dentine is softer than enamel, but acts to support the enamel.

  3. Nerve/Pulp - The living part of the tooth, containing the nerve. If the nerve is damaged, pain occurs.

When you eat and drink anything, Acids within the food and drink can remain in the mouth for several hours, causing damage to the teeth:-

As can be seen from the diagram above, over the course of a day there are several points after meals or snacks which the pH within the mouth is below pH 5.5, at which point the teeth are being damaged. This is why snacking can lead to further Acid erosion, by keeping the mouth below pH 5.5 for longer.

The diagram below shows the effect of Acid erosion on a tooth:-

Acids in food and drinks can cause Acid erosion of teeth. This damage can eventually can lead to pain and tooth loss. Acid erosion occurs when the pH of the mouth is below pH 5.5, which happens after meals or snacks.

Ways to reduce Acid erosion are:-

  1. Don't snack, only eat at mealtimes.

  2. Brush teeth twice a day, for approximately 2 minutes each time.

  3. Drink only water or milk.

  4. Don't brush teeth straight away after eating, the enamel will be too soft at this point.

  5. Visit a Dentist every 6 months.

Acid Rain

As can be seen above on teeth, Acid can cause substances to erode. Another example of this is the effects of Acid rain on buildings, lakes and trees.

The diagram below shows how Acid rain occurs:-

  1. Sulphur Dioxide and Nitrogen Oxides are released from burning fossil fuels within power stations and vehicles.

  2. These gases dissolve into water droplets within clouds, forming weak Sulphuric and Nitric Acids.

  3. These Acids fall to Earth through Precipitation.

  4. Living things such as trees or marine life are damaged by these Acids, as well as certain buildings.

Acid rain occurs when Sulphur Dioxide and Nitrogen Oxides from burning fossil fuels dissolves in water in the atmosphere to form weak Acids. This then falls to ground, where it damages trees, marine life and buildings.

The effects of Acid rain can be reduced by:-

  1. Use renewable energy types as they don't give out Sulphur Dioxide or Nitrogen Oxides.

  2. Use cars with a catalytic converter, which removes some of the Nitrogen Oxides from the exhaust.

  3. Use cars that give out less exhaust emissions, eg electric cars powered using renewable energy sources.

  4. Adding Lime (an Alkali) to lakes can restore the lake to the correct pH, but this is very expensive and doesn't fix the problem long term.

Acid Indigestion

Hydrochloric Acid is found naturally within our stomachs. This Acid helps with the breakdown of food into smaller soluble parts before they are passed into the small intestine. The Acid also assists in preventing infections, by killing most microorganisms within the food. The stomach is protected from this Acid by a layer of mucus.

The diagram shows the main parts of the stomach:-

Parts of the stomach:-

  1. Esophagus - Muscular Tube which connects the Stomach to the Mouth

      • Stomach - Large Muscular chamber containing Stomach Acid.

      • Diaphragm - Flat Muscle that assists with Breathing.

      • Esophageal Sphincter - Valve which opens to allow Food to enter the Stomach

      • Pylorus - Valve which opens to allow Food to enter the Small Intestine.

When the stomach is working normally, the two valves work together to keep the Acid within the stomach. If the esophageal sphincter does not close properly, however, it can allow stomach Acid to enter the esophagus, causing a burning sensation. This is normally known as Acid indigestion, or Acid reflux.

We can treat the effects of indigestion easily at home by taking a indigestion remedy such as Milk of Magnesia or Gaviscon. These indigestion remedies are bases.

When the indigestion tablet is taken, it releases a base into the stomach Acid, neutralising the Acid. This reduces the effect of the Acid indigestion.