Final answer:
An experiment tests a hypothesis by manipulating an independent variable and observing changes in a dependent variable while keeping control variables constant. In an example where a scientist investigates bacterial growth on two types of gel, the type of gel is the independent variable, bacterial growth is the dependent variable, and conditions like temperature must be controlled.
Step-by-step explanation:
An experiment is a type of scientific investigation performed under controlled conditions to test a hypothesis. The hypothesis often proposes that changes in an independent variable will cause changes in a dependent variable. A control variable is any factor that is held constant to prevent it from affecting the outcome of the experiment. It is essential to the experiment's validity because it eliminates alternative explanations of the experimental results.
Let's consider the experiment where a scientist wants to determine if bacteria grow faster on gel A or gel B. In this scientific experiment, the independent variable would be the type of gel (A or B) because that is what the scientist changes. The dependent variable would be the growth of the bacteria, which is what is being measured after 24 hours. Control variables could include factors such as temperature, pH levels, and the amount of light, as these need to remain constant to ensure that it is the type of gel that is affecting the bacterial growth.
The importance of control variables lies in their ability to ensure that only the independent variable is having an effect on the dependent variable. Thus, control variables enable scientists to draw more accurate conclusions from their experiments.