The right proportion
Concentration: how much solute in how much solvent.
Not just any sugar and salt
Oral Rehydration Solution (ORS) is made by adding specified amounts of salt and sugar to a fixed amount of water. A child makes a drink with the same salt and sugar but double the water.
Is it still ORS?
What this lesson covers
The idea
The concentration of a solution is the amount of solute (the substance dissolved) in a given amount of solvent (the substance that dissolves it) or of solution; the right proportion is always essential when preparing a solution.
Not just any sugar and salt
Oral Rehydration Solution (ORS) is made by adding specified amounts of salt and sugar to a fixed amount of water. A child makes a drink with the same salt and sugar but double the water.
Is it still ORS?
- No. The proportion is different
- Yes, it has the same salt and sugar
- Yes, more water is always better
Spray the crop
Mix pesticide into the tank. The label gives the right proportion. Try two tank sizes.
Concentration
The amount of solute dissolved in a given amount of solvent or solution is the concentration of the solution. The right proportion is always essential when preparing a solution.
Farmers must mix the right amount of pesticide with a fixed amount of water. Too little may not protect the crops. Too much can damage crops, soil and the environment.
Concentration matters in medicine, agriculture, food, cosmetics, and even a cup of tea. Not all sugary drinks are ORS.
Notes
Concentration is the amount of solute in a given amount of solvent or solution. The right proportion is always essential.
Check yourself
What is the concentration of a solution?
A farmer sprays a solution with too much pesticide. What can happen?
The label says 1 mL of pesticide for every 100 mL of spray. How many mL of pesticide are needed for 300 mL of spray?
Answer: 3 mL
3 mL: 1 mL for each 100 mL.
Why is a sugary drink from the market not always ORS?
- The colour of the solution. Colour does not define concentration.
- The temperature of the solution. Temperature is not concentration.
- The amount of solute dissolved in a given amount of solvent or solution — correct. Yes.
- It can damage the crops, soil and environment — correct. Yes.
- Nothing; more is always safer. Too much pesticide is harmful.
- The crop is protected better and nothing else happens. Too much can damage the crop, soil and environment.
- ORS has no sugar at all. ORS has specified amounts of salt and sugar.
- ORS needs specified amounts of salt and sugar in a fixed amount of water — correct. Yes. The proportion must be right.
- Any sugary drink has exactly the same proportions. Other drinks do not have the ORS proportions.