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Cards In This Set
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What is a graph?
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A graph is simply a visual representation isllustrating how one variable changes with another variable or it is a tool used to isslustrate the relationship between two variables
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A simplest way to represent this relationship between the two variables is to
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draw a picture
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Drawing such a picture is also the simplest way for the human mind to
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correlate, remember, interpolate, and extrapolate from the perfect or real data
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An additional advantage is that it ( the graph) enables
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An experimenter to average out small deviations in experimental results ( non-perfect or real data) from the perfect data
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Simply looking at columns X and Y (Real), it may be difficult to see the relationship between two variables. However, looking at the graph, the relationship between the two variables becomes apparent
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Y vs xif there is a unit you must put itSee slide 9
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There fore, a graph is a great aid to
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clear thinking
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It is important to note that for every graph relating two variables,
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there is an equation and conversely, for every equation there is a graph
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Plotting the graph from an equation is comparatively simple.
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The reverse process of finding an equation to fit the graph drawn from the experimental data is more difficult, except in the case of a straight line
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Certain conventions have been adopted to plot the set of data
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to a graphical representation
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The "y" variable, known as the dependent variable,
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is always depicted on the vertical axis (ie: ordinate); while the "X" variable (Independent variable) is on the horizontal axis (abscissa).
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It is said that "Y" varies with respect to 'X' and not the other way around.
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In other word change in the values of the'Y' variable is the consequence of change in the values of the 'X' variable. Therefore, 'Y' is a depedent variable
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See slide 13
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Dependent variable, Y (unit) vs Independent variable, X (unit)
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A decision as to which of the two variables is dependent can only be made by
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considering the nature of the experiment
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For example, the equilibrium solubility of a solute depends on the solution temperature (T);
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the temperature does not depend on the solubility of a solute
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Therefore, solubility would be depicted on the 'Y' axis (ie: ordinate) and
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temperature on the 'X' axis (ie: abscissa)
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