# Concentrated and dilute solutions

> Same acid, different amounts


## Objectives

- Describe a concentrated and a dilute solution by the amount of solute in a given volume.
- Explain that a dilute and a concentrated acid are the same substance with different amounts of water.

## 1. Concentrated and dilute solutions: from zero




## 2. Same formula, two labels

Predict: what is the difference between dilute and concentrated sulphuric acid?

- The dilute one has fewer H atoms in its formula.
- Same acid; the concentrated one has much more acid in each volume. ✓
- They are two different compounds.

Dilute and concentrated sulphuric acid are the same compound, $\ce{H2SO4}$; the concentrated one has much more acid in each volume. Diluting adds water and does not change the formula.

[ar-EG] الـ dilute والـ concentrated sulphuric acid هما نفس الـ compound، $\ce{H2SO4}$؛ الـ concentrated فيه acid أكتر بكتير في كل حجم. التخفيف بيزوّد مية ومش بيغيّر الـ formula.
## 3. Concentrated solution

A solution has a dissolved substance, the solute, spread through a solvent such as water. Concentrated solution A solution with a large amount of solute in a given volume. Same volume of solution: many solute particles vs few


## 4. Dilute solution: add water

Dilute solution A solution with a small amount of solute in a given volume. Keep the same solute. Add water to raise the volume. Watch the particles spread out. Volume of solution Solute particles in each 100 mL


## 5. Which is more concentrated?

Beaker A: 5 g of sugar in 50 mL of solution. Beaker B: 10 g of sugar in 500 mL. Which is more concentrated?

- They are equally concentrated
- A ✓
- B, because it holds more sugar

Beaker A is more concentrated: it has $5 \div 50 = 0.1$ g of sugar in each mL, while B has $10 \div 500 = 0.02$ g in each mL. Concentration compares the solute in each volume, not the total amount.

[ar-EG] الـ beaker A هو الأكتر concentrated: فيه $5 \div 50 = 0.1$ g سكر في كل mL، أما B فيه $10 \div 500 = 0.02$ g في كل mL. الـ concentration بتقارن الـ solute اللي في كل حجم، مش الكمية الكلية.
## 6. Summary

Concentrated: a large amount of solute in a given volume. Dilute: a small amount of solute in the same volume. Adding water dilutes a solution. The solute itself does not change. In Chapter 1, iron gives different products with dilute and with hot concentrated sulphuric acid. Can you explain why 10 g of sugar can be dilute while 5 g is concentrated? Concentration compares the solute in each volume, not the total amount. 10 g of sugar in 500 mL is $10 \div 500 = 0.02$ g in each mL (dilute), while 5 g in 50 mL is $5 \div 50 = 0.1$ g in each mL (concentrated).



Chapter: Transition Elements (https://yaani.ai/en/learn/chemistry/chem-s3-en.ch1)
Source: https://yaani.ai/en/lesson/chem-s3-en.lesson-chem.solution-concentration