Question

read this!
a well - written research question states the independent and dependent variables for an experiment. for example, a student investigated the effect of the deicer, magnesium chloride, on vegetation on the sides of highways. her research question was, “what is the effect of magnesium chloride solution concentration on the growth of rye grass?”

1. write a research question, using the format suggested in the read this! box, for the experiments in models 2 and 3.

alka - seltzer® and vinegar —
boiling points of alcohols —

1. a student wonders, “will changing the volume of alcohol in a boiling point experiment change the boiling point of the liquid?” identify the variables that should be considered in this experiment.

independent
dependent
controlled

Explanation:

For Question 13:

• Independent Variable: The independent variable is the one that is manipulated or changed in an experiment. Here, the student is changing the volume of alcohol, so the volume of alcohol is the independent variable.
• Dependent Variable: The dependent variable is the one that is measured or observed to see the effect of the independent variable. The boiling point of the liquid (alcohol solution or pure alcohol, depending on the setup) is what is being measured as the volume of alcohol changes, so the boiling point of the liquid is the dependent variable.
• Controlled Variables: Controlled variables are factors that are kept constant to ensure a fair test. Some examples could be the type of alcohol (e.g., ethanol), the atmospheric pressure (since boiling point depends on pressure), the type of container used for boiling, the heat source and its intensity (to ensure consistent heating), etc. These need to be kept the same throughout the experiment so that any change in the boiling point can be attributed to the change in the volume of alcohol.

• For formulating the research question, we follow the format from the example: stating the independent variable (the factor we change) and the dependent variable (the factor we measure/observe the effect on). For the "Boiling Points of Alcohols" experiment, the independent variable can be the type of alcohol (e.g., methanol, ethanol, isopropanol) and the dependent variable is the boiling point. For the "Alka - Seltzer and Vinegar" experiment, the independent variable can be the amount of Alka - Seltzer and the dependent variable is the rate of gas (like CO₂) production.

Answer:

• Independent: Volume of alcohol
• Dependent: Boiling point of the liquid
• Controlled: Type of alcohol, atmospheric pressure, type of container, heat source intensity (and other relevant constant factors)

For Question 12 (assuming it's about formulating a research question for the given experiments like "Alka - Seltzer and Vinegar" and "Boiling Points of Alcohols"):

Let's take the "Boiling Points of Alcohols" experiment as an example. A research question in the suggested format (stating independent and dependent variables) could be: "What is the effect of the type of alcohol (independent variable) on its boiling point (dependent variable)?"

For the "Alka - Seltzer and Vinegar" experiment, a research question could be: "What is the effect of the amount of Alka - Seltzer (independent variable) on the rate of gas production (dependent variable) when reacted with vinegar?"