GRAPHING TECHNIQUES

The Experiment Various amounts of table salt are added to 100 grams of water. The boiling point of the solution is measured with a thermometer.

The Data Data for Mass of NaCl and Temperature of Solution Grams of NaCl _Boiling Point 0g100.0 o C 2g103.1 o C 4g107.0 o C 6g107.9 o C 8g108.7 o C 10g109.5 o C

1. Assign Variables To The Proper Axis (See our class page at school fusion for printable graph paper.)  Use graph paper. Draw the axes with a ruler, covering at least ¾ of the page. Leave room on the left & bottom for labeling.  A graph relates two variables from an experiment. One of the variables is changed in order to study how it affects the other variable.  The variable that is manipulated by the experimenter is called the independent variable. It’s values are plotted on the ‘x’ or horizontal axis.  The variable whose values are the results of the experiment is called the dependent variable (responding) and is plotted on the ‘y’ or vertical axis.

The Graph Mass of NaCl Temperature 1. Assign variables to the proper axis.

2. Set-up the scales  Each axis must have a numbered scale to show the values of each variable.  The scale should begin with a number slightly less than the lowest value and extend to a number slightly more than the greatest value, and be designed to occupy the majority of the paper.  The numbered scale (intervals) must be uniform. Each block on the axis must represent the same amount as any other block.  Scales do not necessarily need to begin at zero.  The two scales do not necessarily need to match.

2.Set-up the axes and intervals (scale). The Graph Temperature Mass of NaCl

3. Label Each Axis  Each axis must have a label which states the variable which is plotted on the axis.  Each axis must indicate the unit, usually in symbol form, used to measure the variable.  Determine whether or not a legend is necessary. If the graph will contain more than one line displayed in differing colors, or the slope or other value needs to be given, these will be shown in the legend.

Label each axis with the quantity and unit. Mass of NaCl (g) Temperature ( o C) The Graph

4. Plot And Circle The Points  Use a small uniform dot to plot each point in it’s proper position.  A small circle is drawn around each dot. The purpose of the circle is to represent the uncertainty in the measurements of that set of data.  In more advanced classes you may be asked to calculate the uncertainty of the measurements and to draw a circle that precisely represents that uncertainty.

4. Plot and circle the points. The Graph Mass of NaCl (g) Temperature ( o C)

5. Connect The Points  The points on the graph should be neatly connected to show the trend in the data. How the points are connected depends upon what kind of data was collected.  Discrete data (counted items) are connected point- to-point by straight lines.  Continuous data (measured quantities) are connected by a smooth line which may be straight or curved. This is called a “best-fit-curve”. The line does not need to touch each point or circle. It only shows the trend in the data.

The Graph 5. Connect the points. Mass of NaCl (g) Temperature ( o C)

6. Title & Summary Statement  Each graph should have a title placed in a clear area near the top of the paper.  The title should be informative. It should relate to the reader information about the experiment to help the reader understand the graph.  Below the graph, write one sentence (or two) summarizing the data trend(s) [or relationship between the variables] shown on the graph.

The Graph 6. Title the graph and write the summary. The Boiling Point of Salt Solutions Mass of NaCl (g) Temperature ( o C) At first, as the mass of the NaCl increases, the boiling temperature of the salt solution steadily increases. A point is reached where, as the mass of NaCl added continues to increase, the rise in temperature is not increasing as rapidly.