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# Physical Properties ## Mass and Weight * Matter has mass. * Mass is the measure of the quantity of matter a body contains * The mass of a body does not vary as its position changes. * The weight of a body is the result of the mass and gravitational attraction. * The weight varies as the gravita...

# Physical Properties ## Mass and Weight * Matter has mass. * Mass is the measure of the quantity of matter a body contains * The mass of a body does not vary as its position changes. * The weight of a body is the result of the mass and gravitational attraction. * The weight varies as the gravitational attraction varies with the distance from the centre of the earth. * The mass of a body is more fundamental than its weight. * The basic unit of mass in the SI system is the kilogram (kg) * A fractional quantity called "gram" (g) is used for weighing small quantities of chemicals in the laboratories. ## Length * The atomic radius, bond length, wavelength of electromagnetic radiation are examples of properties that can be expressed using length * The SI unit of length is the metre (m) * Fractional units of the SI unit of length are used for small quantities, like nanometre (nm) and picometre (pm). ## Volume * Volume is the amount of space occupied by a three-dimensional object. * The SI unit of volume is expressed as (metre)³ or m³ * Litre (L) is commonly used for measuring volume of liquids and gases. # SI Units * Officially, the **International System of Units**, or **SI units**, was established in 1960 by the General Conference of Weights and Measures. * SI units are based on the metric system, which originated in France in the late eighteenth century. * SI units provide a common standard that makes communication in science easier. * The SI system has seven base units: | Quantity | Name | Symbol of the SI Unit | |---|---|---| | Length | metre | m | | Mass | Kilogram | kg | | Time | Second | s | | Electric Current | Ampere | A | | Thermodynamic Temperature | Kelvin | K | | Amount of Substance | Mole | mol | | Luminous Intensity | Candela | cd |