Scientific Method

The passage below describes an experiment. Read the passage and think about the variables that are described.

Kate was using steel to make rusted sculptures. After building each sculpture, she caused the steel in the sculpture to rust by placing it into a tub filled with salt water for eight hours. Kate wondered if steel would rust faster submerged in vinegar instead of salt water. To find out, Kate cut ten squares of steel sheet metal and split them into two equal groups. She put one group of squares into a tub filled with salt water and the other group of squares into a tub filled with vinegar. Once an hour for eight hours, Kate counted the number of rusted steel squares in each group.

Which of the following was an independent variable in this experiment?

Hint: An independent variable is a variable whose effect you are investigating. A dependent variable is a variable that you measure.

• the number of rusted steel squares

• the type of liquid used

The passage below describes an experiment. Read the passage and think about the variables that are described.

Simon heard that when it was cold outside, a sled would travel farther after it got to the bottom of a hill. To test this idea, Simon headed to the sledding hill near his house on a cold winter morning. When he got to the hill, the temperature outside was 16°F. Starting from the top of the hill, Simon rode straight down the hill three times. For each ride, he measured the distance he traveled across the flat field at the bottom of the hill. Then, Simon waited until mid-afternoon, when the temperature outside had increased to 43°F. He rode straight down the hill three more times and measured how far he traveled across the field.

Which of the following was an independent variable in this experiment?

Hint: An independent variable is a variable whose effect you are investigating. A dependent variable is a variable that you measure.

• the distance the sled traveled across the flat field

• the temperature at the hill

Tags

NGSS.MS-PS3-4

NGSS.MS-PS3-5

The passage below describes an experiment. Read the passage and think about the variables that are described.

Gordon was baking cupcakes for his stepfather's birthday. Gordon wondered whether the volume of a cupcake would be affected by the type of flour in the batter. Gordon bought three types of flour and made three batches of cupcakes. He followed the same recipe for each batch, except for the type of flour used. He made one batch using whole wheat flour, one batch using cake flour, and one batch using buckwheat flour. After all the batches had baked and cooled, Gordon measured the dimensions of each cupcake to calculate its volume.

Which of the following was an independent variable in this experiment?

• the volume of the cupcakes

• the type of flour

The passage below describes an experiment. Read the passage and think about the variables that are described.

Donald often saw woodpeckers perched in trees in his backyard, but he never saw them at his bird feeders. Donald usually filled his feeders with sunflower seeds. He wondered if he could attract woodpeckers by adding a different type of food to the feeders. To test this idea, Donald gathered eight identical bird feeders. He filled four with sunflower seeds. He filled the remaining four feeders with crushed peanuts. Donald then placed the bird feeders in his backyard. Over the next five days, he counted the number of woodpeckers that visited each bird feeder each morning.

Which of the following was an independent variable in this experiment?

• the type of food used in the bird feeders

• the number of woodpeckers who visited the feeders

Tags

NGSS.MS-LS2-1

The passage below describes an experiment. Read the passage and think about the variables that are described.

Raymond designed an electric circuit to test how well different types of metal conduct electricity. The circuit included a battery, a light bulb, wires, and clips that could be attached to a sheet of metal. If the metal conducted electricity poorly, the light bulb would appear dim. If the metal conducted electricity well, the light bulb would appear bright. Raymond collected nine equally sized sheets of metal: three sheets of copper, three sheets of iron, and three sheets of aluminum. He used the clips to attach each metal sheet, one sheet at a time, to the circuit. For each sheet, Raymond used a light meter to measure how much light the bulb produced.

Which of the following was a dependent variable in this experiment?

• the amount of light produced by the light bulb

• the type of metal sheet used in the circuit

Tags

NGSS.MS-PS1-2

The passage below describes an experiment. Read the passage and think about the variables that are described.

Harry's daughter complained that the apple slices in her lunchbox turned brown by lunchtime. Harry read that when apple slices are exposed to air, oxygen in the air reacts with the cut surface of the apple slices, turning them brown. Harry's favorite cooking website said that pouring lemon juice on the apple slices would slow down this chemical reaction. Harry cut an apple into ten slices. He put five of the slices into a bowl and poured two tablespoons of lemon juice over them. He put the other five slices into another bowl and did not add any lemon juice to them. After one hour, Harry counted the number of apple slices in each bowl that had turned brown.

Which of the following was an independent variable in this experiment?

• the amount of lemon juice added to the apple slices

• the number of apple slices that turned brown

Tags

NGSS.MS-PS1-2

The passage below describes an experiment. Read the passage and think about the variables that are described.

Giardia is a microscopic parasite that lives in water and can infect humans. Dr. Mueller designed a drinking straw that contained a filter to remove Giardia from water. Dr. Mueller wanted to know if a longer filtering straw would remove more Giardia. Dr. Mueller made six filtering straws: three that were five inches long and three that were ten inches long. She prepared six one-liter batches of water, each containing 10,000 Giardia. Then, Dr. Mueller passed one batch of water through each straw. After each batch passed through the straw, she used a microscope to count the number of Giardia that remained in a small sample of the water.

Which of the following was a dependent variable in this experiment?

• the number of Giardia that remain in the water

• the length of the filtering straw

Tags

NGSS.MS-ETS1-3

NGSS.MS-ETS1-4

The passage below describes an experiment. Read the passage and think about the variables that are described.

Dr. Vincent was the land manager for a prairie that had become overrun by unwanted grasses. These grasses crowded out other plants. Dr. Vincent thought that she could use fire to remove the unwanted grasses and allow other plants to grow. But she didn't know how often the prairie should be burned. Dr. Vincent marked off six plots within a large area of the prairie. She used carefully controlled fires to burn all of the plants in each plot. She burned three of the plots once a year for three years. She burned the other three plots twice a year for three years. A year after the last fire, Dr. Vincent counted the number of unwanted grasses in each of the six plots.

Which of the following was a dependent variable in this experiment?

• the number of times the plots were burned each year

• the number of unwanted grasses

The passage below describes an experiment. Read the passage and think about the variables that are described.

Garrett's grandmother suggested that soaking berries in hot water might help prevent the berries from getting moldy. To test this idea, Garrett harvested fresh blackberries and divided them evenly into eight bowls. He filled four of the bowls with room temperature water and the other four bowls with water heated to 125°F. Garrett let all of the berries soak in the water for 30 seconds. Then, he poured out the water and dried the berries. Garrett placed the two groups of bowls in the refrigerator, keeping each group separate. After five days, Garrett counted the number of moldy blackberries in each bowl.

Which of the following was an independent variable in this experiment?

• the number of moldy blackberries

• the temperature of the water

Tags

NGSS.MS-LS1-5

NGSS.MS-LS2-4

The passage below describes an experiment. Read the passage and then follow the instructions.

Bruce grew ten mint plants on his back porch. He grew each plant in its own pot, and each pot was the same size and shape. Bruce noticed that his plants did not grow many leaves, and he wanted to see if earthworms could help them grow more. To test this idea, Bruce divided his ten plants into two equal groups. For one group, he added three earthworms to the soil in each pot. He did not add any earthworms to pots in the other group. Two months later, Bruce counted the number of leaves on each of the ten plants. He compared the number of leaves on the plants in each group.

Complete the sentence.

In this experiment, the number of leaves was .

• a dependent variable

• an independent variable