Question

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?”
1.2. write a research question, using the format suggested in the read this! box, for the experiments alka - seltzer® and vinegar — boiling points of alcohols —
1.3. 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:

Problem 1.3 Analysis:

To identify the variables in the experiment where a student wonders if changing the volume of alcohol affects its boiling point, we analyze each type of variable:

Independent Variable:

The independent variable is the factor that is intentionally changed by the experimenter. In this experiment, the student is changing the volume of alcohol. So, the independent variable is the volume of alcohol.

Dependent Variable:

The dependent variable is the factor that depends on the independent variable (it is measured or observed to see the effect of the independent variable). Here, the student is measuring the boiling point of the alcohol (to see how it changes with volume). So, the dependent variable is the boiling point of the alcohol.

Controlled Variables:

Controlled variables are factors that must be kept constant to ensure a fair test (so that only the independent variable affects the dependent variable). For a boiling point experiment with alcohol, examples of controlled variables include:

• The type of alcohol (e.g., ethanol concentration, purity) – different alcohols have different boiling points.
• The atmospheric pressure (boiling point depends on pressure; using a closed system or testing at the same altitude controls this).
• The heating method (e.g., same heat source, same rate of heating) – inconsistent heating could alter the boiling point measurement.

Final Answer:

• Independent Variable: Volume of alcohol
• Dependent Variable: Boiling point of the alcohol
• Controlled Variables: Type of alcohol, atmospheric pressure, heating method (and other factors kept constant to ensure a fair test)

Answer:

Problem 1.3 Analysis:

To identify the variables in the experiment where a student wonders if changing the volume of alcohol affects its boiling point, we analyze each type of variable:

Independent Variable:

The independent variable is the factor that is intentionally changed by the experimenter. In this experiment, the student is changing the volume of alcohol. So, the independent variable is the volume of alcohol.

Dependent Variable:

The dependent variable is the factor that depends on the independent variable (it is measured or observed to see the effect of the independent variable). Here, the student is measuring the boiling point of the alcohol (to see how it changes with volume). So, the dependent variable is the boiling point of the alcohol.

Controlled Variables:

Controlled variables are factors that must be kept constant to ensure a fair test (so that only the independent variable affects the dependent variable). For a boiling point experiment with alcohol, examples of controlled variables include:

• The type of alcohol (e.g., ethanol concentration, purity) – different alcohols have different boiling points.
• The atmospheric pressure (boiling point depends on pressure; using a closed system or testing at the same altitude controls this).
• The heating method (e.g., same heat source, same rate of heating) – inconsistent heating could alter the boiling point measurement.

Final Answer:

• Independent Variable: Volume of alcohol
• Dependent Variable: Boiling point of the alcohol
• Controlled Variables: Type of alcohol, atmospheric pressure, heating method (and other factors kept constant to ensure a fair test)