At a simplified level, you can think of your Experimental Method as being like a recipe in a cookbook. Your procedure is like the instructions for how to bake a cake. The instructions will include things like the order to mix the ingredients, and the temperature to set the oven. Your Materials List is like the list of ingredients. A recipe that lists only flour, sugar and eggs would be nearly useless; you would need to know how much flour and sugar and how many eggs in order to bake a good cake.
Make sure you include everything you will need for your experiment in your materials list, including notebook and pen for recording.
What Materials do you think he needs for this experiment?
An experiment generally has three types: independent, dependent and controlled. When choosing your variables, keep in mind that good variables are usually those that you can measure with a number (e.g., concentrations of pollutants, time of day, temperature) or observe objectively (e.g., colors). Subjective qualities, like whether noise pollution makes local birds happy or sad, are not appropriate variables.
The independent variable is the one that you, as the scientist, change or manipulate. Your experiment should have only one independent variable. For your EnvironMentors project, possible independent variables could be time (e.g., testing the amount of pesticides in the water at the same site on different days) or location (e.g., measuring noise pollution at different locations at the same time of day). Time and location are just two examples of independent variables. You and your mentor should work together to determine the best independent variable for your project.
The dependent variable changes in a consistent manner in response to changes you make in the independent variable. In the examples above which used time and location as the independent variables, the dependent variables would be the amount of pesticides in the water, and the amount of noise pollution, respectively. Whereas there should only be one independent variable, the number of dependent variables can vary. For instance, if you were investigating water quality at the same site on different days, your independent variable would be time, and each different pesticide concentration you measure in the water would be a different dependent variable.
The controlled variables are those that you try to keep constant throughout your experiment. These are all variables that might affect your dependent variable. If you were measuring the concentrations of pesticides in water on different days, you would want to make sure that things like the weather and outside temperature remain relatively constant. You should keep track of your controlled variables as carefully as your other variables. Remember that it is important to try to keep your controlled variables as constant as possible. For instance, if you measured the noise pollution at two different traffic intersections in your city (independent variable = location; dependent variable = noise pollution) but made your measurements at different times of day, you wouldn’t be able to tell if changes in the amount of noise pollution were due to the different location or the different time of day. Most experiments will have more than one controlled variable.
Line graphs are used to show how changes in one variable affect changes in another variable. It is very common to create a line graph by plotting your independent variable on the x-axis (bottom) and your dependent variable on the y-axis (left). Line graphs can also be used to show how data change over time.
Example 2: Using a line chart to show the changes in river flowrate over time.