The indicators tells us the given substances are acidic or basic in nature by changing the colour and olfactory indicators change their smell or odour when they come in contact with an acid or base.
Aim of activity
To observe the changes in odour of cloth strips soaked in onion, vanilla essence and clove oil after exposure to acidic and basic solutions.
Materials used in the activity
- Finely chopped onions
- Clean cloth strips
- Plastic bags
- Fridge
- Dilute hydrochloric acid
- Dilute sodium hydroxide
- Vanilla essence
- Clove oil
- Test tubes
- water
Procedure
1.Preparation of Onion infused cloth strips
We take some finely chopped onions in a plastic bag along with some strips of clean cloth and tie up the bag tightly and leave overnight in the fridge. The cloth strips can now be used to test for acids and bases.
2.Testing odour with acids and base
Now we take two of these cloth strips and check their odour so we keep them on a clean surface and put a few drops of dilute HCI solution on one strip and few drops of dilute NaOH solution on the other. Note the observation in the table.
Now rinse both the cloth strips and smell again.
3.Testing of vanilla and clove oil
We take some amount of vanilla essence and clove oil in separate test tubes and add dilute HCl in both test tubes.
We take some amount of vanilla essence and clove oil in separate test tubes and add dilute NaOH in both test tubes.
| Sample | Initial odour | After adding HCl | After adding NaOH |
| Onion infused cloth strips | Strong onion smell | Odour remains | Odour fades |
| Vanilla essence | Sweet smell | Odour fades | Odour remains |
| Clove oil | Distinct clove aroma | Odour remains | Odour fades |
Onion : Smell of onion diminishes in a base and remains as it is in an acid.
Vanilla essence : The odour of vanilla essence disappears when it is added to a base. The odour of vanilla essence persists when it is added to an acid.
Clove Oil: In bases its characteristic smell cannot be detected.
Conclusion
The olfactory indicators change the odour in acidic and basic medium. So through this activity, we can easily identify and distinguish between acidic and basic substanes.
FAQs
- What is the aim of this activity?
Ans- To observe the change in odour of cloth strips soaked in onion,vanilla and clove oil when they come in touch with acid and basic solutions
- What are olfactory indicators?
Ans – The olfactory indicators are the substances whose smell changes when exposed to acidic or basic solutions.
- Why does the odour changes in acidic and basic solutions?
Ans – The change in odour occurs due to the chemical interactions of olfactory indicators with acids and bases.
- What is the chemical formula of hydrochloric acid?
Ans- HCl
- What is the chemical name of NaOH?
Ans – sodium hydroxide