Science 8 STAAR Practice 7

A sledgehammer has a mass of 3.5 kilograms. What net force, to the nearest whole newton, will a person need to apply to accelerate the sledgehammer at a rate of 4.0 m/s2 ? Record your answer and fill in the bubbles on your answer document. Be sure to use the correct place value.

Answer explanation

The force was obtained by multiplying 3.5 kg x 4.0 m/s2 using the formula: F = ma F = (3.5 kg) x (4.0 m/s2) F = 14 N

Tags

NGSS.MS-PS2-2

Which element has the same number of energy levels as lithium?

• Beryllium

• Sodium

• Magnesium

• Potassium

Answer explanation

Beryllium is in the same period as lithium. Elements in the same period have the same number of energy levels.

Which answer choice best describes the weather at location X on Day 1 and Day 2?

• Day 1: warm and rainy Day 2: cool with more rain

• Day 1: warm and windy Day 2: cloudy and cold

• Day 1: clear and cool Day 2: warm and rainy

• Day 1: cold and rainy Day 2: clear and sunny

Answer explanation

A cold front results in cold, rainy weather. Location X is on a cold front on Day 1. On Day 2, once the cold front has passed, the weather is clear and sunny. A high pressure (H) area, as shown behind the front on the map, is typically associated with clear and settled weather.

Tags

NGSS.MS-ESS2-5

Oxygen and oxygen-containing compounds are involved in many different reactions. Which balanced equation represents a reaction that involves 14 atoms of oxygen?

• NH 4Cl + KOH → NH 3 + H 2O + KCl

• 2Na + 2 H 2O → 2NaOH + H 2

• 2 C 2H 6 + 7 O 2 → 4 CO 2 + 6 H 2O

• 4Fe + 3 O 2 → 2 Fe2O 3

Answer explanation

There are 14 atoms of oxygen balanced on each side of this equation.

Tags

NGSS.MS-PS1-5

Which statement best explains a difference between Plant 1 and Plant 2?

• Plant 1 obtains more water from the soil because of its root surface area and root depth.

• Plant 1 obtains more sunlight because of its root surface area and root depth.

• Plant 2 obtains more water from the soil because of its root surface area and root depth.

• Plant 2 obtains more sunlight because of its root surface area and root depth.

Answer explanation

Plant 1 has a larger root system than Plant 2 and will therefore be able to absorb a greater amount of water from the soil.

Tags

NGSS.MS-LS2-1

Which statement best describes the flow of energy through this pyramid?

• The trophic level represented by catfish and gobies receives energy directly from the producers.

• The trophic level represented by shrimp and copepods receives energy directly from the tertiary consumers.

• The trophic level represented by redfish and flounder receives energy directly from the secondary consumers.

• The trophic level represented by wire grass and phytoplankton receives energy directly from the primary consumers.

Answer explanation

An energy pyramid represents feeding relationships in a community by showing the amount of energy transferred from one feeding position in a food web (trophic level) to the next. The efficiency of energy transfer typically decreases from the base (bottom) of the pyramid (producers) to the top of the pyramid (top consumers). In this energy pyramid, the secondary consumers are the catfish and gobies, which are below the redfish and flounder. Therefore, the redfish and flounder receive energy directly from them.

Tags

NGSS.MS-LS2-3

A student is building a model of a solar eclipse. Solar eclipses occur only during a new moon phase. Which motion best demonstrates a solar eclipse?

• The moon moves between the sun and Earth, casting a shadow of the moon on Earth.

• The sun moves between the moon and Earth, casting a shadow of the sun on Earth

• Earth moves between the sun and the moon, casting a shadow of Earth on the moon.

• Earth moves between the sun and the moon, casting a shadow of the moon on the sun.

Answer explanation

A solar eclipse occurs when the moon moves between the sun and Earth and casts a shadow of the moon on Earth.

Tags

NGSS.MS-ESS1-1

What function do both cell membranes and cell walls perform?

• Producing energy for cellular processes

• Allowing water to move into and out of cells

• Synthesizing genetic material

• Directing the reproduction of the cell

Answer explanation

Both cell membranes and cell walls allow water to move into and out of cells.

Tags

NGSS.MS-LS1-2

Which of these observations is an indication that a chemical reaction has occurred?

• Steam forms above boiling water.

• A solid forms when a clear solution is frozen

• A solid forms when two clear solutions are mixed.

• Sugar crystals form on the sides of a boiling pot of sugar water.

Answer explanation

The formation of a solid or precipitate by mixing two clear solutions indicates that a chemical (nonreversible) change has occurred.

Tags

NGSS.MS-PS1-2

Which statement best explains why the sun appears brighter to people on Earth than any other star?

• Sunlight reaches Earth’s atmosphere at an angle that causes the sun’s light rays to intensify.

• Unique chemical reactions in the sun’s core produce a high-energy wavelength of light.

• The sun burns at a higher temperature than any other star.

• The sun is closer to Earth than any other star.

Answer explanation

The sun is a closer distance to Earth than any other star, which results in it appearing brighter to people on Earth.