Hypothesis, Controls, Variables, Constants

A student places elodea plants in water at different temperatures and counts the number of oxygen bubbles produced per minute. What is the independent variable?

• Type of plant

• Number of bubbles produced

• Temperature of the water

• Time of day

Tags

NGSS.MS-LS2-1

NGSS.MS-LS2-3

A scientist provides yeast with different sugar types and measures the amount of CO₂ gas released over 30 minutes. What is the dependent variable?

• Amount of CO₂ released

• Type of sugar

• Amount of yeast used

• Volume of solution

A student investigates enzyme activity by testing the breakdown of hydrogen peroxide with catalase at different pH levels. Which of the following is a constant?

• pH of solution

• Temperature of solution

• Reaction rate

• Amount of product formed

A class tests the effect of fertilizer concentration on bean plant height after 4 weeks. What is the best control setup for this experiment?

• Plants with no fertilizer added

• Plants watered twice a day

• Plants grown in shade

• Plants with different soil types

Tags

NGSS.MS-LS1-5

NGSS.MS-LS2-1

A group of students investigates how light color affects photosynthesis in algae. Which of the following is a valid hypothesis?

• If algae are exposed to different colors of light, then the growth rate will differ.

• Algae require oxygen for respiration.

• Photosynthesis increases with temperature.

• If algae are placed in dark, they will not survive.

Tags

NGSS.HS-LS1-5

The null hypothesis in a study on how light color affects the growth rate of algae is:

• Light color has no effect on the growth rate of algae.

• Light color increases the growth rate of algae.

• Light color decreases the growth rate of algae.

• Light color changes the color of algae.

A student tests how temperature affects the activity of catalase by measuring the height of foam produced when hydrogen peroxide breaks down. What is the independent variable?

• Temperature

• Amount of foam produced

• Amount of enzyme used

• Concentration of hydrogen peroxide

Tags

NGSS.HS-PS1-5

A researcher investigates how enzyme concentration affects the breakdown of starch by measuring the time required for the iodine test to remain negative. What is the dependent variable?

• Enzyme concentration

• Time for starch to disappear

• Temperature of solution

• Type of starch used

A student examines the effect of pH on enzyme activity by measuring reaction rate. Which condition must be kept constant?

• Enzyme concentration

• Reaction rate

• Type of pH buffer

• Amount of substrate remaining

A student tests enzyme activity by comparing test tubes containing starch with and without amylase. Which test tube represents the control setup?

• Tube with starch but no amylase

• Tube with starch and amylase

• Tube heated to high temperature

• Tube with added salt solution