Controls and Variables (1) - Chemistry Controls and...

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Objective You will distinguish between variable and controlled parameters in various experiments. Activities Read the information below and answer the questions that follow. Have you ever performed an experiment? If so, you probably changed some of the factors in the experiment while keeping other factors the same. When you complete a scientific experiment, always keep some of the factors the same so that you can compare the effects of your changes against a standard. Otherwise, you cannot measure the effects of the changes that you make. The factors in an experiment that remain unchanged are called controls , which are any factor(s) of an experiment that are not tested or changed. Controls are used to compare the effects of changes to other factors in the experiment. In contrast, the factors in an experiment that are changed, or varied, are called variables . There are two different kinds of variables. Independent variables are any part of a scientific experiment that is changed by the scientist, and dependent variables are any part of an experiment that responds to a change made to an independent variable. For example, you wanted to investigate how adding different amounts of salt to the same amount of water affects the time until it boils. You might boil three samples of water: water without salt, water with two tablespoons of salt, and water with four tablespoons of salt. You would then measure the amount of time that it takes for the three samples to start to boil. In this
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