formula

In chemistry, a representation of a molecule, radical, or ion, in which the component chemical elements are represented by their symbols. For example, the formula for carbon dioxide is CO₂, showing that a molecule of carbon dioxide consists of one atom of carbon (C) and two atoms of oxygen (O₂). An empirical formula indicates the simplest ratio of the elements in a compound, without indicating how many of them there are or how they are combined. A molecular formula gives the number of each type of element present in one molecule. A structural formula shows the relative positions of the atoms and the bonds between them. For example, for ethanoic (acetic) acid, the empirical formula is CH₂O, the molecular formula is C₂H₄O₂, and the structural formula is CH₃COOH.

Formula is also another name for chemical equation.

formula

In mathematics, a set of symbols and numbers that expresses a fact or rule. For example, A = πr² is the formula for calculating the area of a circle. E = mc² is Einstein's famous formula relating energy and mass. Other common formulae exist for density, mass, volume, and area.

Changing the subject of a formula Transforming a formula means rearranging to change the subject of the formula. For example:

S = D/T (speed = distance/time)

S stands alone on one side of the equation, so the subject of this formula is S. D or T can be made the subject of the formula:

D = S × T or T = D/S

The formula used to change temperatures in degrees Celsius into degrees Fahrenheit is:

F = 1.8C + 32

This formula can be rearranged to make C the subject of the formula:

F − 32 = 1.8C (F − 32)/1.8 = C

Substituting into a formula This is the process of substituting numbers into the letters in a formula. For example, using the temperature formula to convert the temperature 5°C to degrees Fahrenheit:

C = 5, so F = 1.8 × 5 + 32 so F = 9 + 32 = 41

The temperature conversion from 5°C to Fahrenheit is 41°F.

formula

In computing, an expression entered into a cell on a spreadsheet. The formula is displayed in the data entry line of the spreadsheet and the result is displayed in the cell. Formulae normally start with an equals (=) sign, which is followed by the expression. For example =SUM(A1:A6) would add up the contents of cells A1 to A6. Parentheses are also used to control the order of the calculation. For example =A1 + (B3−C3).