Maths for A Level Chemistry - updated edition

Graphs In chemistry and other subjects, we use graphs to display data graphically. If data is in a table it is hard to see patterns in it. When graphs are used, the patterns are much easier to see. When we conduct experiments in chemistry, we often need to test the relationships between variables and we can do this by drawing graphs. 4.1 Straight line graphs Straight line graphs are also called linear graphs and have an equation of the form y = mx + c Notice there is one y on the left-hand side of the equation. m is the gradient (i.e. the steepness of the line) and c is the intercept on the y- axis. It is important that in this equation there is only an x term, so there are no terms containing x 2 , x 3 , √ x , 1 x , etc. The following equation is an equation of a straight line. y = 2 x − 3 Comparing this equation with y = mx + c You can see that the gradient, m is 2 and intercept on the y- axis, c , is −3. Examples 1 Which of each of the following equations are equations of straight lines? a) y = 1.4 x + 7 b) y = 4 x 2 + 1 c) y = 2 x d) y = −4 x e) y = √ x f) 2 y = 8x + 6 g) 5 x + 2y = 3 h) y = 4 3 x − 2 Chapter 4 38