__Density__**Introduction-**

**Which one is more heavy? 1 kg of cotton or 1 kg of iron.Answer is both equal. Next which is more dense 1kg of cotton or 1 kg of iron? Now answer is Iron. To understand this let's learn a term Density . Density is the measure of how much matter is in a given amount of space.**

**ðŸŒˆ Mindmap Density **

**● Definition**** - Mass per unit volume.**

**● Formula****- Density = Mass÷ Volume**

**● Factors****- 1. directly proportional to Mass**

** 2. Inversely proportional to volume **

**●Units****- S.I - kg/ m³**

** C.G.S- g/cm³**

**● 1 g/ cm³ = 1000 kg/ m³**

**● Regular bodies**** - mass is found out using balance and volume by using formula **

**● Irregular bodies****- mass is found out using balance and volume by water displacement method **

**ðŸŒˆ Rainbow mindmap Relative density **

**● Definition- Relative density of a substance is the ratio of density of a substance to the density of water**

**● Relative Density of a substance = Density of a substance ÷ Density of water**

**● Relative density of a substance = Mass of a substance of certain volume ÷ Mass of same volume of water..**

**● R.D has no unit.**

**● Density = R.D g/cm³ **

** = R.D'x1000 kg / m³**

**● Relative density of water is 1 .**

**● If R.D of a body is more than 1, it will sink in water.**

** If R.D of a body is less than 1 , it will float in water. **

__Activities__

**Activity 1**

**To find Area of a irregular surface by using graph paper**

**Activity 2**

**To find volume of irregular body by water displacement method.**

**Activity 3**

**To find volume of cube.**

**Activity 4**

**To grind volume of cylinder**

**Activity 5-**

**To find volume of a cubiod.**

**Activity 6**

**To study Hydrometer**

__Solution- Essential Physics ICSE class 7 ch - Physical Quantities and measurements__

**Check your knowledge**

### What is Relative density of water?

Relative density of water is 1

### What is the density of water at 4 degree centigrade?

The density of water at 4 degree centigrade is 1000 kg per meter cube.

### Body will float or sink if density of body is equal to density of water?

Body will float just below the surface of water.

### What is the S.I. unit of weight of the body?

newton

### What is the weight of the body at the center of the earth

Weight of the body at the center of the earth is zero.