# Density

> How much mass fits in each cm³


## Objectives

- Define density as mass per unit volume: density = mass ÷ volume, in g/cm³.
- Calculate a density from a mass and a volume.
- Explain that more mass in the same volume means a higher density.

## 1. General properties: mass, radius and metallic property




## 2. Same size, different feel

Predict: what is different about the heavier ball?

- It takes up more space
- More mass is packed into the same volume ✓
- Gravity pulls only on that ball

The two balls have the same size, so the same volume, and gravity pulls on both. The heavier one has more mass packed into the same volume: it has a higher density.

[ar-EG] الكورتين في نفس الحجم، يعني نفس الـ volume، والجاذبية بتشد الاتنين. الأتقل فيهم محشور فيه mass أكتر في نفس الـ volume: يعني الـ density بتاعته أعلى.
## 3. Mass per unit volume

Density The mass of a unit volume of a substance. mass in g, volume in cm³, density in g/cm³ Example: an aluminum block has mass 27 g and volume 10 cm³. Its density is 27 ÷ 10 = 2.7 g/cm³.


## 4. Pack in more mass

Keep the volume at 10 cm³ and raise the mass. Then try changing the volume. mass volume density Same volume, more mass → higher density.


## 5. Your turn

Box A and box B are the same size. Each holds 100 marbles of the same size, but B's marbles are heavier. Which box has the greater density?

- A
- B ✓
- Equal: same number of marbles

Density = mass ÷ volume. The boxes have the same volume and the same number of marbles, but B's marbles are heavier, so B has more mass in the same volume and the greater density.

[ar-EG] الـ density = mass ÷ volume. الصندوقين ليهم نفس الـ volume ونفس عدد البلي، لكن البلي بتاع B أتقل، فـ B فيه mass أكتر في نفس الـ volume، والـ density بتاعه أكبر.
## 6. Summary

Density: the mass of a unit volume, in g/cm³ Density is the mass of a unit volume: density = mass ÷ volume, in g/cm³. Same volume, more mass → higher density. Next in Chapter 1: why the density of transition metals rises from Sc to Cu. Can you explain why two balls of the same size can have different densities?



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