Grade 7 Science #3: MEASUREMENTS, The SI UNIT SYSTEM, SCIENTIFIC NOTATION, DIMENSIONAL ANALYSIS

Measuring involves ascertaining a material's property and expressing it in a defined, standard unit. The International System of Units (SI) was adopted in 1960 to provide a coherent and standardized unit system for common physical quantities like length (meters), mass (kilograms), time (seconds), electric current (amperes), temperature (Kelvin), and volume (cubic meters).

For extremely large or small numerical values, decimal multipliers are used. These are fractions or multiples of the base unit; for example, a kilogram equals 1000 grams, and a milligram equals one-thousandth of a gram. This allows appropriate unit selection, such as kilograms for a sack of rice and milligrams for a microchip.

For extremely large or small quantities, such as the number of atoms in a mole or the radius of a hydrogen atom, scientific notation is a more convenient way to express values. It is formatted as 'n times 10 raised to a', where 'n' is a numerical coefficient between 1 and 10, and 'a' is the power of 10 indicating how many times the coefficient is multiplied or divided by 10.

In science, converting between units of measurement is often necessary. This can be done using the factor-label method, also known as dimensional analysis. This approach uses valid conversion factors, which are equal to one, to transform an initial unit of measurement into a desired unit without changing the underlying value.