Praxis Middle School Science

Which of the following best explains how metamorphic rocks are formed?

• Molten magma cools and hardens inside the Earth.

• Weathered rock is eroded, deposited, and cemented to form new rock.

• Hot lava cools and hardens outside the Earth.

• Rocks are changed by heat, with or without high pressure, deep inside the Earth.

Answer explanation

Metamorphic rock forms deep inside the Earth. Contact metamorphic rock forms under high temperatures. Regional metamorphic rock forms under high heat and pressure.

As the Pacific Plate and the North American Plate bump past one another, energy is built and stored as potential energy. When that energy is released, what event is most likely to occur?

• volcanic eruption

• an earthquake

• trench formation

• 
  mountain formation

Answer explanation

Energy stored as the result of a plate bumping into another is released as an earthquake

Tags

NGSS.MS-ESS3-2

a horseshoe-shaped region around the Pacific Ocean that's characterized by frequent earthquakes and volcanic eruptions

result of plate tectonics, where tectonic plates meet, collide, or move past each other

• Ring of Fire

• Mid-Atlantic Ridge

• Himalayan Belt

• Great Rift Valley

Tags

NGSS.MS-ESS3-2

A (a)   is a protein that DNA wraps around to form a more compact structure called a (b)   ; essentially, a histone is a building block protein that makes up a chromosome, which is the larger, thread-like structure containing the (c)   itself

• histone

• chromosome

• DNA

A teacher would like to assess students' understanding of the similarities and differences between mitosis and meiosis. Which of the following would be the most effective way to do this?

• Show a video about mitosis, followed immediately by a video about mitosis, then ask students to state the differences.

• Have students partner up and create a Venn diagram for mitosis and meiosis.

• Make a model of the cell and show students where the chromosomes are at each stage of mitosis and meiosis.

• Ask each student to create a pipe cleaner model of a different stage of cell division.

Which TWO of the following describes a positive feedback loop? Select all answers that apply.

• Increasing numbers of chlorofluorocarbons in the atmosphere break down more ozone in the stratosphere and allow more harmful radiation from the Sun to strike the Earth.

• While a car is idling on a hot day, the passenger turns on the air conditioning. The engine works harder, further heating the car. In response, the passenger increases the amount of air conditioning.

• The Earth warms as atmospheric carbon dioxide increases and glaciers melt, exposing more soil to the Sun. Increasing temperature in the soil promotes soil microbes to decompose more vegetation and release more carbon dioxide.

• Overgrazing increases as the deer population in an area increases, leaving less food for the deer. In response, the deer population decreases.

Answer explanation

first option does not represent a feedback loop because an increase in harmful radiation at Earth's surface does not release more chlorofluorocarbons.

The Earth warms as atmospheric carbon dioxide increases and glaciers melt, exposing more soil to the Sun. Increasing temperature in the soil promotes soil microbes to decompose more vegetation and release more carbon dioxide.

Tags

NGSS.MS-LS2-3

A system model can illustrate the flows of energy and matter into and out of a system. Which of the following lists contains the appropriate inputs if the system under study is a living mouse?

• blood, bones, muscles

• jumping, running, squeaking

• food, water, air

• fur, eyes, tail

Answer explanation

Food, water, and air are a few of the energy and matter inputs for a living mouse. Inputs come from the surroundings, outside of the boundary of the system.

Tags

NGSS.MS-LS2-3

Which of the following physical properties is a measure of the force exerted by a fluid on a given area?

• viscosity

• pressure

• buoyancy

• density

Answer explanation

A fluid exerts pressure on the walls of its container. The pressure equals the force exerted by the fluid divided by the area of contact.

Viscosity is the resistance of a fluid (liquid or gas) to a change in shape or movement of neighbouring portions relative to one another

buoyancy- the ability or tendency to float in water or air or some other fluid.

The gravitational force from the sun extends:

• to infinity.

• only to the edge of the Solar System.

• only to the edge of the Milky Way Galaxy.

• only to the core of the Earth.

Answer explanation

The gravitational force from any object extends to infinity. The strength of the force decreases with distance, but the force never decreases to zero. This means every object in the Universe is pulled by every other object in the Universe.

Tags

NGSS.MS-ESS1-2

NGSS.MS-PS2-4

A block of ice of mass m slides down a frictionless ramp inclined 15° from the horizontal. Which of the following is the correct expression for the magnitude of the acceleration of the box?

• 
  g sin 15°

• mg sin 15°

• mg cos 15°

• 
  g cos 15°

Answer explanation

Two forces act on the ramp: the force of gravity, F_g = mg, and the normal force F_n, which points upward, perpendicular to the ramp. The component of gravity that points parallel to the ramp is mg sin 15°. From Newton's second law, the force along the ramp divided by mass equals the acceleration along the ramp. The acceleration is g sin 15°.

Tags

NGSS.HS-PS2-1

NGSS.HS-PS2-4