Unit 9 Retest

Which statement describes an action that most likely resulted in a chemical reaction?

• A. A pan of water was heated on a stove, and steam formed.

• B. A liquid was mixed with another liquid, and a precipitate formed.

• C. A liquid was sprayed into the air, and a sweet odor was smelled.

• D. A child blew through a wand filled with soap, and bubbles were produced.

Tags

NGSS.MS-PS1-2

Assuming the students did not make any careless errors, what likely explains these changes in mass?

• Procedure 1: All the reactants were liquids that evaporated. Procedure 2: A gas was formed as one product, and it escaped into the air.

• Procedure 1: One of the reactants was converted to thermal energy.

  Procedure 2: All the products were liquids.

• Procedure 1: The reactants were liquids with different densities. Procedure 2: The reactants were combined into only one product.

• Procedure 1: One of the products was a gas that escaped into the air. Procedure 2: A gas from the air reacted with one of the other reactants.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Two solutions are mixed and react to produce the solid precipitate AgCl. The chemical reaction is shown by the balanced chemical equation. What happens to the total mass as the reaction takes place?

• The mass increases

• The mass decreases

• The mass remains constant

• The mass first decreases and then increases

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

For a laboratory investigation, some students put a strip of shiny metal into a beaker of blue solution and then stored the beaker on a shelf overnight. The next morning, students recorded observations about the metal and the solution in the box below. Based on their observations, can the students correctly conclude that a chemical reaction occurred AND what evidence could be used to support the answer?

Tags

NGSS.MS-PS1-2

Which observation of this process provides evidence of a chemical reaction?

• Hot water heated the aluminum foil.

• The liquid solution changed color.

• The pan was lined with aluminum foil.

• The hot water cooled.

Tags

NGSS.MS-PS1-2

Nitrogen dioxide is a gas that can be generated by emissions from vehicles and factories. It can also be generated by natural sources, such as forest fires, lightning, and microbial activity in soil. The equation for producing nitrogen dioxide is shown below. 2NO + O₂ → 2NO₂ Colorless gas + Colorless gas → Brown gas Which of these provides evidence that a chemical reaction occurs?

• A gas is present.

• The total number of atoms remains unchanged.

• The state of matter remains the same.

• A brown gas is produced.

Tags

NGSS.MS-PS1-2

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Students performed a lab investigation on chemical reactions. The students put on goggles and plastic gloves and then followed these steps.

1. Pour 150 milliliters of vinegar into a beaker.

2. Place a thermometer in the vinegar and record measurements.

3. Add a piece of steel wool to the beaker.

4. Observe and record thermometer measurements.

5. Remove the steel wool from the beaker.

6. Use tweezers to pull strands of the steel wool apart and observe changes.

Which observation would indicate that a chemical reaction occurred?

• The vinegar took the shape of the container in step 1.

• The steel wool sank into the vinegar in step 3.

• The temperature of the vinegar increased during step 4.

• The steel wool changed shape during step 6.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-4

Some students in a chemistry lab conducted an investigation in which they added four different solid substances to separate beakers of water, stirred the mixtures for one minute and then recorded their observations in the table below. Which substance most likely caused a new substance to be formed when mixed with water?

• Substance 1

• Substance 2

• Substance 3

• Substance 4

Tags

NGSS.MS-PS1-2

Researchers are investigating processes that happen during digestion. Which answer choice describes only a physical change during digestion?

• Hydrochloric acid in the stomach breaks down proteins.

• Chewing in the mouth breaks food into small pieces.

• Enzymes in saliva start the digestion of starches before food is swallowed.

• Bacteria in the intestines convert dietary fiber into fats.

Students create a table that lists processes observed in nature. Which process describes only a physical change?

• Process 1

• Process 2

• Process 3

• Process 4