2nd 9 wks review

Which of the following observations results in a chemical change?

• Burning wood

• Boiling water

• Melting ice

• Breaking glass

Answer explanation

Burning wood is a chemical change because it transforms the wood into ash, smoke, and gases through combustion, altering its chemical structure. In contrast, boiling water, melting ice, and breaking glass are physical changes.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Which of the following is evidence of a chemical change?

• Change from gas to liquid

• Change in color

• Change in odor

• Change in shape

Answer explanation

A change in color indicates a chemical change, as it often signifies the formation of new substances. In contrast, changes in state (gas to liquid), shape, or odor may not necessarily indicate a chemical change.

Tags

NGSS.MS-PS1-2

Which of the following is NOT an indicator of a chemical change?

• Change in color

• Change in shape

• Formation of precipitate

• Production of gas

Answer explanation

Change in shape is a physical change, not a chemical one. Chemical changes are indicated by color change, gas production, or precipitate formation, which involve alterations in the substance's chemical structure.

Tags

NGSS.MS-PS1-2

During a laboratory experiment, a student mixed two colorless and odorless solutions. The new product became a white solid formation. What can be concluded?

• It is a physical change because the temperature was absorbed.

• It is a chemical change because heat was absorbed and the temperature changed.

• It is a chemical change because a new substance was formed.

• It is a chemical change because the temperature did not change.

Answer explanation

The formation of a white solid from two colorless solutions indicates a chemical change, as a new substance was created during the reaction.

Tags

NGSS.MS-PS1-2

A student is investigating the reaction between baking soda and vinegar. Which of the following observations would provide evidence of a chemical change? Select ALL that apply.

• Appearance of bubbles

• Baking soda dissolving

• Increase in temperature

• Production of gas

Answer explanation

The appearance of bubbles and production of gas indicate a chemical change, as they suggest a reaction is occurring. Baking soda dissolving and an increase in temperature may not necessarily indicate a chemical change.

Tags

NGSS.MS-PS1-2

Describe an example of a chemical change that involves a change in thermal energy.

• Melting ice

• Burning wood

• Freezing water

• Dissolving sugar

Answer explanation

Burning wood is a chemical change that releases thermal energy as it transforms into ash and gases. This process involves combustion, which is an exothermic reaction, unlike melting ice or freezing water, which are physical changes.

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

The formation of rust when iron reacts with oxygen and water is considered a chemical change because:

• It changes color

• It melts

• It dissolves

• It remains the same

Answer explanation

The formation of rust involves a chemical reaction where iron reacts with oxygen and water, resulting in a new substance with different properties, including a change in color, indicating a chemical change.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

What does a wave transfer from one place to another?

• Matter

• Energy

• Heat

• Water

Answer explanation

A wave transfers energy from one place to another, not matter, heat, or water. While waves can carry energy through various mediums, they do not transport the medium itself.

Tags

NGSS.MS-PS4-1

What are the two main types of mechanical waves?

• Microwaves and sound waves

• Radio waves and sound waves

• Transverse waves and longitudinal waves

• Ultraviolet waves and longitudinal waves

Answer explanation

The two main types of mechanical waves are transverse waves, which move perpendicular to the direction of energy transfer, and longitudinal waves, which move parallel to the direction of energy transfer. Thus, the correct answer is transverse waves and longitudinal waves.

Which set of terms are used to describe parts of a transverse wave?

• Crest and compression

• Trough and refraction

• Crest and trough

• Compression and refraction

Answer explanation

In a transverse wave, the highest point is called the crest and the lowest point is called the trough. Therefore, the correct terms to describe parts of a transverse wave are 'crest and trough'.