Evidence of Chemical Reactions

A student places a piece of a potato into a container of hydrogen peroxide. One observation the student makes is that bubbles form around the potato. The presence of bubbles indicate the formation of a new substance because bubbles -

• show that a gas is forming

• always rise to the top of a liquid.

• are almost always perfectly spherical.

• usually burst after a few minutes.

Tags

NGSS.MS-PS1-2

Four students performed four different investigations by combining different substances. Their results are shown in the table provided. In which experiment are new substances being formed?

• Experiment 1
• Experiment 2
• Experiment 3
• Experiment 4

Tags

NGSS.MS-PS1-2

Which of the following is an example that includes evidence that a NEW substance was formed?

• A sample of zinc is placed in water and it settles to the bottom

• A solid block of ice is heated and it completely melts into a liquid.

• Sugar that is burned gives off an odor and turns brown and then black.

• A tomato is placed into a blender and chopped up into smaller pieces.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

In a container, a solid consisting of clear crystals is combined with a blue liquid and the following observations are obtained.
 How many of the listed observations indicate a new substance was formed?

• 1
• 2
• 3
• 4

Tags

NGSS.MS-PS1-2

For an investigation a student poured a blue solution of CuSO₄ into a beaker. The student placed a shiny, silver-colored strip of zinc metal in the solution and observed the changes.

The student inferred that a chemical reaction occurred. What evidence supports this inference from the picture?

• A dark solid, rust, formed on the zinc metal.

• The zinc metal remained silver-colored and shiny

• The CuSO₄ solution was blue when the zinc metal was added.

• None of these are correct

Tags

NGSS.MS-PS1-2

Two clear, colorless solutions were combined.

The student observed that the temperature changed from 25 •C to 23 •C when the solutions were combined, and that a white substance rapidly formed and settled to the bottom of the container. What most likely happened to produce these results?

• One of the original compounds came out of solution

• The solutions reacted chemically

• Some of the water froze into ice crystals

• Rapid evaporation of water occurred, leaving a solid

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-4

A scientist performed four investigations using eight different liquids. In each investigation, the scientist combined two of the liquids and recorded observations in the table shown. In which investigation is it least likely that the liquids reacted chemically?

• 1

• 2

• 3

• 4

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Copper pennies turning greenish after a few years is an example of a chemical change because...

• The pennies' texture became different.

• The pennies changed temperature.

• The pennies changed colors as they tarnished.

• This is NOT an example of a chemical change. It is a physical change.

Tags

NGSS.MS-PS1-2

A physical change occurs in the digestive system when —

• gastric juices in the stomach convert proteins into amino acids.
• saliva change complex carbohydrates into simple sugars.
• teeth break down and grind food particles into smaller pieces.
• pancreatic enzymes change fats into fatty acids and glycerol.

Which of the following is an example of a chemical change during digestion?

• Muscles in the esophagus move food toward the stomach.

• Protein changes into amino acids in the stomach.

• Water is absorbed into the blood stream in the large intestine.

• Teeth tear and grind food in the mouth into smaller pieces.

Tags

NGSS.MS-PS1-2

NGSS.MS-LS1-7