Graphical+Techniques

Another very important skill especially when doing your practical is drawing graphs. A graph shows the relationship between two variables. usually a dependent variable is always draw on the y-axis while an independent variable is always shown on the x-axis. If a graph is a straight line through the origin, then the two variable are directly proportional to each other. If the graphs look like a hyperbola then the two variables are inversely proportional to each other. 


 * HOW TO DRAW A GRAPH **

For example you are required to plot a graph for the following data:


 * Temp/ o C || 20.0 || 30.0 || 40.0 || 50.0 || 60.0 ||
 * Volume of gas cm 3 || 60.0 || 62.0 || 64.0 || 66.0 || 68.0 ||


 * 1) <span style="font-family: 'Tahoma','sans-serif'; font-size: 18.6667px;">When drawing a graph, choose appropriate scales and decide which variable goes on the x-axis and y-axis. (hence temperature is independent since as the temperature is varied the volume of the gas changes. So temperature is independent while volume is dependent. So temperature goes on the x-axis while volume goes on the y-axis.
 * 2) <span style="font-family: 'Tahoma','sans-serif'; font-size: 18.6667px;">Now choose and appropriate scale. For x-axis a scale of 10 would be good since it can be easily subdivided and also is big enough for all the values up to 50 cm3 to fit. For the y-axis, the values do not start from zero but from 60. So you can decide to start the graph from 59 and have scale of 2 cm3.
 * 3) <span style="font-family: 'Tahoma','sans-serif'; font-size: 18.6667px;">Plot the points.
 * 4) <span style="font-family: 'Tahoma','sans-serif'; font-size: 18.6667px;">Draw a line of best fit- this is a line/curvet that passes through most of the plotted points.

//<span style="font-family: Tahoma,sans-serif; font-size: 19px; line-height: 28px;">The graph looks as follows: //

<span style="font-family: 'Tahoma','sans-serif'; font-size: 18.6667px;">If you would like to read a value from the graph all you have to do is draw a dotted line to find the other variable. Eg: finding the volume when temperature is 35 o <span style="font-family: 'Tahoma','sans-serif'; font-size: 18.6667px;">C. Draw a line from the x-axis where the temperature is 35 o <span style="font-family: 'Tahoma','sans-serif'; font-size: 18.6667px;">C, so that it meets the curve/line. Draw a horizontal line from this point and thus find the value of the volume of the gas from the graph.

<span style="font-family: 'Tahoma','sans-serif'; font-size: 18.6667px;"> <span style="font-family: 'Tahoma','sans-serif'; font-size: 18.6667px;">So at 35 o <span style="font-family: 'Tahoma','sans-serif'; font-size: 18.6667px;">C the volume of gas is 63 cm 3 <span style="font-family: 'Tahoma','sans-serif'; font-size: 18.6667px;">.

NEXT UP- NOTHING!!! CONGRATULATIONS YOU ARE DONE WITH THE CORE PART OF THE SYLLABUS!!
 * By the end of this lesson you should be able to: **
 * ** Know from the shape of the graph whether the variables are directly proportional or inversely proportional **
 * ** Draw graphs for a given set of data (table of values) **
 * ** Draw lines of best fit through points on a graph **
 * ** Read values from a graph **
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