Justin B. Believes that the temperature lowering during the fall months is what causes the color of the leaves to change. He set up an experiment wherein he placed some plants in 80 degrees rooms and some in 60 degree rooms. He observed the color of the leaves for a total of 1 month. At the end of the month Justin observed that 3/4 of the plants in the 60 degree temperature had begun to change colors and only 1/4 of the plants in the 80 degree temperature began to change colors.

This question is incomplete, the remaining part of the question is:

What is the control group, independent variable and dependent variable?

Control group: Plants placed in 80 degree rooms

Independent variable: Change in temperature

Dependent variable: Change in color of leaves

Explanation:

The independent variable in a scientific experiment is the variable that the experimenter controls or manipulates in order to bring about a change in the dependent variable. In this experiment, the variable manipulated by Justin B is the TEMPERATURE CHANGE.

On the other hand, a variable is said to be dependent if it is the variable that responds to a change made to the independent variable or rather it is the outcome. In this experiment, Justin B is trying to see the outcome on the color change in leaves when exposed to a low temperature, hence, COLOR CHANGE IN LEAVES is the dependent variable.

Control group of an experiment is the group that receives no experimental treatment. It is the group the experimenter considers normal and hence is comparing with his experimental group. In this experiment, Justin B believes the leaves change color in a low temperature, hence, he placed some plants in a lower temperature (60 degree) in order to compare them with when the plants are placed in a higher temperature (80 degree). As far as this experiment is concerned, the plants placed in 80 degrees temperature are believed by Justin B not to undergo color change, hence, they are the CONTROL GROUP while the group he placed in 60 degrees temperature are what he is interested in, making them the EXPERIMENTAL GROUP

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.