### Theory:

Mass is the quantity of matter contained in a body.

Mass is a basic property of matter. The mass of each substance is in a solid, liquid or gaseous state.

**Key takeaways:**

**1.**All the matters contain mass; that is why it is known as base quantity.

**2.**Mass is a scalar quantity. That is mass only has a numerical (magnitude) value.

**3.**The mass of an object is a constant value and, it does not vary by the changes of gravity, place, temperature or pressure.

**4.**In the International System of Units, the basic unit of mass is the kilogram (kg).

**5**. One kilogram is the mass of a particular international prototype cylinder made of platinum-iridium alloy, kept at the International Bureau of Weights and Measures at Sevres, France.

The units gram (g) and milligram (mg) are the submultiples of ten (1/10) of the unit kg. Similarly, quintal and metric tonne are multiples of ten (× 10) of the unit kg.

**Atomic mass unit**:

Mass of a proton, neutron and electron can be determined using an atomic mass unit (amu).

$1\phantom{\rule{0.147em}{0ex}}\mathit{amu}\phantom{\rule{0.147em}{0ex}}=\phantom{\rule{0.147em}{0ex}}{\left(\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$12$}\right.\right)}^{\mathit{th}}\phantom{\rule{0.147em}{0ex}}\mathit{of}\mathit{the}\mathit{mass}\mathit{of}{C}^{12}\mathit{atom}.$

**In our daily life, do we use the word mass?**

For example, we would not ask, what your mass is? But, we would ask, what your weight is?

So, what is the difference between mass and weight? Now let us see the difference between these two terms.

S.No | Differentiating property | Mass | Weight |

1 | What it is? | Mass is the quantity of matter contained in a body. | The weight of an object is relevant to the force acting on the object. The force can be either gravity or a reaction force that holds it in place. |

2 | Is it changeable? | The mass of an object is a constant value, and it does not vary by the changes of gravity and place. | Weight has the capability to change from place to place. |

3 | Quantity | The mass is the fundamental quantity. | The weight is the derived quantity. |

4 | Scalar/Vector | The mass is the scalar quantity | Weight is the vector quantity |

5 | How can you measure it? | The mass is measured by the physical balance instrument. | Weight is measured using a spring balance instrument |

6 | Unit | Kilogram | Newton |

**Mass measuring methods:**

We know that, the SI unit of mass is kilogram; in our day to day, life we generally use the term ‘weight’ that represents ‘mass’. Many things are measured in terms of ‘mass’ in the commercial world.

Using the below instruments, we can determine the mass of an object: