23-24 Q1 Review with Explanations

For the Science Fair, Alyssa designs an experiment to learn about erosion shown in the diagram below. Tray A is flat on the table. One end of tray B is raised 5 cm, and one end of tray C is raised 10 cm. Alyssa then slowly pours 200 mL of water onto the sand in each tray. Finally, she observes and measures how far sand is carried by the water.

What is the independent variable (test variable) in Alyssa's experiment?

• the volume of water she pours

• the speed she pours the water

• the height of the tray

• the amount of sand

Answer explanation

In Alyssa's experiment, the independent variable is 'the height of the tray'. This is because she is changing the heights (5 cm and 10 cm) of the trays (B and C) to observe the effect on how far the sand is carried by water. The other options are constants, they remain the same throughout the experiment.

The independent variable is the thing that is changed and tested!

Tags

NGSS.MS-ESS2-2

Jesse is designing an experiment to find out if objects of different masses fall at different rates, or speeds. She plans to drop four objects having a similar size and shape, but different masses (measured in grams), from the same height (measured in meters) of a staircase. Jesse plans to measure how long (measured in seconds) it takes each object to hit the floor. What is the dependent variable (outcome variable) in Jesse’s experiment?

• the shape of the objects

• the mass (grams) of each object

• 
  the time (seconds) it takes each object to fall

• the height (meters) of the staircase

Answer explanation

The dependent (outcome) variable is the variable that is measured. This is the data you collect!! The dependent variable depends on the independent.

Tags

NGSS.MS-PS2-2

A group of students plans to investigate marigold plants. They want to know if marigolds will grow larger flowers when given plant food. The students made this table for their investigation.

How can they improve the investigation to make their results more accurate?

• Plant 1 should receive 6 hours of light.

• Plant 1 should be a different type of plant.

• Plant 1 should receive 5 mL of plant food.

• Plant 1 should be removed from the investigation.

Answer explanation

The students are testing whether or not the plant food will affect the plant growth. Plant food is the independent variable, everything else will remain the same.

Remember, you only change one variable at a time. So in order to have accurate results, the only thing that is changing is the plant food. So, each plan should receive the same amount of light.

Tags

NGSS.MS-LS1-5

NGSS.MS-LS2-1

NGSS.MS-LS2-4

The table compares the average temperatures on three inner planets of the solar system.

Assume all three planets receive roughly the same amount of radiation from the Sun. Based on the data, which of the following is a reasonable conclusion?

• Earth’s temperature would be cooler without carbon dioxide in its atmosphere.

• More carbon dioxide would form in Earth’s atmosphere if it were warmer.

• Earth’s atmosphere would be thinner if it contained more carbon dioxide.

• Carbon dioxide prevents the Sun’s heat from reaching Earth’s surface.

Answer explanation

The question implies that all the three inner planets receive roughly the same amount of radiation from the Sun. Given this, the temperature of Earth would be cooler without carbon dioxide. This is because carbon dioxide is a greenhouse gas that traps heat and prevents it from escaping into space, thus warming the Earth.

Morgan puts some books under a ramp. She rolls a ball down the ramp and measures the distance the ball travels before it stops. She adds more books under the ramp and repeats the investigation.

What is the independent (test) variable in this investigation?

• the angle of the ramp

• the length of the ramp

• the speed the ball rolls

• the distance the ball travels

Answer explanation

In the question, Morgan is changing the number of books under the ramp, which changes the angle of the ramp. So, the independent variable is the thing that is deliberately changed, which in this case is 'the angle of the ramp'.

Tags

NGSS.MS-PS2-2

A state agency evaluates the safety of heavy metal concentrations in soil. The table lists the limits that are considered acceptable. Levels that are higher than the ones in the table could harm human health. So, land must be tested for heavy metals before houses are built. If any levels are too high, then a developer must clean up the soil before building.

A developer wants to build a neighborhood on a site where a car manufacturing plant used to be located. He takes a sample of soil from the site and has it tested. The results are shown in the table below.

Based on the results, the developer decided not to clean up the site before building. Do the data support this decision?

• Yes, because all levels are below the acceptable limits.

• Yes, because only one level is above the acceptable limit.

• No, because one level is above the acceptable limit.

• No, because two levels are above the acceptable limits.

Answer explanation

Lead is above the acceptable limit so they must clean up the site before building.

If you look on the first table, you'll see that the acceptable limit is 400. The second table shows that the level of concentration of lead is 500, so it is above.

Tags

NGSS.MS-PS1-2

A scientist is unsure about the accuracy of her experiment. She has checked her equipment and found it to be in good working order, checked her data and found it to be accurate, and reviewed her interpretation of the data, which she found to be logical. What should she do in addition to check the accuracy of her results?

• checking the hypothesis

• interpret the data

• make a different conclusion

• repeat the experiment

Answer explanation

The scientist should repeat the experiment. Despite having checked the equipment, data, and interpretation, repeating the experiment can help confirm the accuracy of the results. This would allow her to verify if the same results are consistently produced, which is an important aspect of scientific research.

All experiments must be repeated and replicated (by other scientists) in order to make sure it's valid and accurate!

Scientists have several ways for evaluating the validity of experimental results. Which of the following is a characteristic shared by all valid scientific investigations?

• The experiment must be long.

• The experiment must produce replicable results.

• The experiment must obtain the desired (wanted) results.

• The experiment must be complex.

Answer explanation

Every experiment must be repeated (multiple trials) and replicated. Replication is when other scientists repeat the experiments and get the same results. If that is not done, then the experiment is not valid or accepted by the scientific community.

Tags

NGSS.MS-PS1-2

Water evaporates from a lake into the air, forming clouds. The clouds eventually form rain and it falls to the ground. In which spheres does this cycle happen?

• geosphere and cryosphere

• cryosphere and hydrosphere

• hydrosphere and atmosphere

• thermosphere and atmosphere

Answer explanation

The water cycle described in the question happens primarily in the hydrosphere and atmosphere. The lake, which is part of the hydrosphere, sees the evaporation of water. The evaporated water forms clouds in the atmosphere, which eventually leads to rainfall, completing the cycle.

Tags

NGSS.MS-ESS2-4

Earth’s spheres interact in many ways. Which describes how the geosphere and atmosphere interact?

• A heavy snowfall adds mass to a glacier.

• Polluted air kills several animal species.

• Magma erupts and releases trapped gases.

• Ocean currents influence weather patterns.

Answer explanation

The geosphere and atmosphere interact when magma erupts and releases trapped gases. The geosphere, which includes the solid parts of the Earth like the crust and magma, influences the atmosphere by releasing gases. These gases can change the composition of the atmosphere, affecting weather and climate.

Tags

NGSS.MS-ESS2-4