Comprises of length, area, volume, mass, density and time

Universal System of Units is called **system international d' unites** (International System of Units) - SI Units.

Below are the major SI Units

Below are the major SI Units

Basic Quantity | SI Unit | Symbol |

Length | Metre | m |

Mass | Kilogram | kg |

Time | Second | s |

Electric Current | Ampere | A |

Thermodynamic | Kelvin | K |

Luminous Intensity | Candela | Cd |

Amount of Substance | Mole | mol |

- The distance between two fixed points.

- The S.I Unit is**Metre (M)**

Derived units are shown below

*Estimating the length of a tree*

- The S.I Unit is

Derived units are shown below

Unit | Symbol | Equivalence in Metres |

Kilometre | Km | 1000 |

Hectometre | Hm | 100 |

Decametre | Dm | 10 |

Decimetre | dm | 0.1 |

Centimetre | Cm | 0.01 |

Millimetre | mm | 0.001 |

Micrometre | µm | 0.000001 |

- measures the surface area covered by a body

- Its unit is**m**^{2}.

#### Area of a regular body

#### Area of an irregular body

The squares must be 1cm^{2} each.

**Area**

Full Squares = .... cm^{2}

½ x Incomplete squares = .... cm^{2}

Area = Full Squares + (½ x Incomplete squares)

- Its unit is

Can you convert 15.5M^{2} to cm^{2}?

*Solution*

1m = 100 cm

1m^{2} = 100 cm x 100 cm = 10000 cm^{2}

15.5 m^{2} = 15.5 x 10000 cm^{2}

= 1550000 cm^{2}

1m = 100 cm

1m

15.5 m

= 1550000 cm

Full Squares = .... cm

½ x Incomplete squares = .... cm

Area = Full Squares + (½ x Incomplete squares)

- measures the amount of space occupied by a body

- Its unit is**m**^{3}.
#### Volume of a regular body

NB: Liquids can be measured by putting them into containers with sizes of graduated objects such as Graduate Cylinder, Syringe, Buret and others

#### Volume of an irregular body

It can be done using a **Measuring Cylinder** or a **Eureka Can**.

##### Measuring Cylinder

Volume = Q (V1) - P (V2)

##### Measuring Cylinder

Volume will be read on the measuring cylinder.

- Its unit is

Can you convert 4.5m^{3} to cm^{3} ?

Remember: 1m^{3} = 100cm x 100cm x 100cm = 1000000 cm^{3}

Remember: 1m

NB: Liquids can be measured by putting them into containers with sizes of graduated objects such as Graduate Cylinder, Syringe, Buret and others

Volume = Q (V1) - P (V2)

Volume will be read on the measuring cylinder.

- Quantity of matter in a body. SI units is Kilogrammes (Kg)

Mass can be measured using:-

Mass can be measured using:-

- Top Pan Balance
- Beam Balance
- Lever Balance

- Mass per unit volume. Its symbol is rho (ρ). Its SI Unit is Kilogramme per Cubic Metre (Kg/m^{3})

##### Density Using a Density Bottle

#### Relative Density

**Relative density** (RD) is the ratio of the density of a substance to the density of water. It is also known as **specific gravity** (SG).

- if the value is**less than 1**, it is less dense than water and would float

- if the value is**equals to 1**, it has the same density as water

- if the value is**greater than 1** it is more dense than water and would sink.

A block of stone has a mass of 140g and is 10cm long, 5 cm wide and 4 cm high. Calculate the density of the stone

*Solution*

The mass of a density bottle is 20g when empty and 45g when filled with water. When filled with liquid x, its mass is 400g. Calculate the density of liquid x. (density of water 1.0 g/cm^{3})

*Solution*

- if the value is

- if the value is

- if the value is