Grade 8 Science

1.

1 point

Scientists perform experiments to test hypotheses.

How do scientist try to remain objective during experiments?

They analyze all results.

They use safety precautions.

They conduct experiments once.

They change at least two variables.

2.

1 point

A teacher asks her students the following question: How does the air pressure inside a soccer ball affect the distance the Which statement below is the best hypothesis for this investigation?

If a soccer ball has 0.5 atmospheres of internal pressure, then the ball will travel slower than a ball with .8 atmospheres of internal pressure.

If a soccer ball has a high internal air pressure, then the ball will travel a farther distance than a soccer ball with the less internal air pressure.

If a soccer ball is large, then the soccer ball will travel a farther distance than a small soccer ball.

If a soccer ball travels a distance of 15 meters, then the ball is traveling faster than a soccer ball that travels a distance of 20 meters.

3.

1 point

Which conclusion is supported by the data from the investigation?

Water is the main ingredient in many cleaning supplies.

A substance changes from a gas to a liquid as the temperature of the substance increases.

Cleaning solutions with a weak odor are acids.

Many cleaning supplies are soluble in water.

4.

1 point

Biologists conduct investigations to learn about living organisms.

Obtaining other opinions concerning what should happen during the investigation.

Limiting the amount of background research before the investigation.

Designing an investigation with repeated trails during the investigation.

Developing a hypothesis after collecting data in the investigation

5.

1 point

The period of rotation for Earth is

13 weeks

1 year

24 hours

28 days

6.

1 point

Which of the following statements best explains why the tilt of Earth on its axis causes summer to be warmer than winter in the Northern Hemisphere?

The rays of the Sun strike the Northern Hemisphere more directly in the summer.

The Northern Hemisphere is closer to the Sun in the summer.

The warm ocean currents flow from the tropics to the Northern Hemisphere in the summer.

The greenhouse effect increases in the Northern Hemisphere in the summer.

7.

1 point

The two factors that combine to keep Earth and the moon in their orbits are

Gravity and orbital speed

Gravity and inertia

Mass and orbital speed

Mass and inertia

8.

1 point

What does the drop in barometric pressure from 1003 millibars to 926 millibars tell you about a hurricane?

It became weaker.

It became disorganized.

It became colder.

It became stronger.

9.

1 point

Tornadoes can occur in spring and early summer when the afternoon sun has heated the Earth's surface and a

cold, dry air mass meets a cold, humid air mass

warm, dry air mass meets a cold, moist air mass

warm, humid air mass meets a cold, dry air mass

warm, dry air mass meets a warm, humid air mass

10.

1 point

Based on the temperatures shown in the diagram, what is the relative humidity of air?

73 percent

69 percent

45 percent

63 percent

11.

1 point

Plants transform some of the electromagnetic energy from the sun (sunlight) into

visible light released by leaves

chemical energy stored in sugars

chlorophyll stored in leaves

nuclear energy stored in sugar

12.

1 point

A researcher places part of a plant in a beaker of water. She observes that the plant's leaves release bubbles of gas when she shines a light on the beaker. The leaves do not release gas when the beaker is placed in the dark. Based on her observations when the plant is exposed to light, which of the following is the most logical inference?

The plant is breathing.

Light is breaking down molecules of air.

The plant is undergoing photosynthesis.

The plant is undergoing cellular respiration.

13.

1 point

A scientist performed an experiment to determine the effect of temperature on the length of the cell cycle. On the basis of the data in the table above, how long would you expect the cell cycle to be at 5 degrees Celsius?

about 20 hours

between 29.8 hours and 54.6 hours

more than 54.6 hours

less than 12.3 hours

14.

1 point

Siberian tigers originated in the far northern continent of Asia. The climate is extremely cold, since much of the land is within the Arctic Circle. They were forced south over time and now reside in Southeast Asia, such as India, Thailand and Cambodia. They still have thick fur. Unlike other cats, wild or domestic, they soak in water to cool their bodies.

genetics

structure

physiology

behavior

15.

1 point

How do the elements magnesium (Mg) and fluorine (F2) produce the compound magnesium fluoride (MgF2)?

by nuclear connection

by magnetic connection

by physically combining

by chemically combining

16.

1 point

When 1 gram of water is evaporated, the volume of the water vapor increases but the mass remains constant.

Why does the mass of the water remain constant?

The temperature of the water remains constant.

The number of atoms in the water remains constant.

The pressure acting on the water remains constant.

The distance between water molecules remains constant.

17.

1 point

Which of the following is produced when two or more elements combine in a chemical reaction?

mixture

atom

compound

solution

18.

1 point

The masses of the reactants are 24 grams of carbon and 32 grams of oxygen. What is the mass of the product, CO2?

24 grams

56 grams

44 grams

32 grams