8.5E Chemical Reactions

Which of the following is NOT considered evidence for a chemical reaction?

• Formation of a precipitate.

• Temperature change in the surroundings.

• Change in state (e.g., melting or freezing).

• Emission of light or heat.

Tags

NGSS.MS-PS1-2

What distinguishes a chemical change from a physical change?

• Chemical changes only occur in liquids.

• Physical changes involve a change in temperature.

• Chemical changes alter the composition of substances.

• Physical changes are irreversible.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

In a laboratory experiment, students mix baking soda with vinegar. They notice that the mixture fizzes and produces bubbles. Which of the following statements best explains the observed phenomenon?

• The temperature of the mixture increased, causing it to bubble.

• The baking soda and vinegar underwent a physical change, resulting in the bubbles.

• A chemical reaction occurred, producing a gas that formed bubbles.

• The mixture became denser, causing bubbles to form.

Tags

NGSS.MS-PS1-2

A scientist mixes two clear liquids together and observes that the temperature of the mixture decreases. Which of the following conclusions is most likely?

• A chemical reaction occurred, releasing heat into the surroundings.

• The mixture underwent a physical change, causing a decrease in temperature.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-4

NGSS.MS-PS3-4

NGSS.MS-PS3-5

When iron nails are left in moist air for a long time, they gradually rust. Which of the following statements best describes the chemical change that occurs during rusting?

• Iron is converted into oxygen.

• Oxygen is converted into iron.

• Iron and oxygen combine to form a new substance.

• Iron and oxygen separate into different substances.

Tags

NGSS.MS-PS1-2

A student mixes together two clear liquids in a beaker and observes that a solid forms at the bottom of the beaker. Which of the following best describes what has happened?

• A physical change has occurred.

• A chemical change has occurred.

• The liquids have evaporated.

• The liquids have dissolved completely.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

When a piece of magnesium ribbon is burned in air, a bright white light is emitted. Which of the following best describes this observation?

• Physical change

• Chemical change

• Change in state

• Change in shape

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

In a chemical reaction between hydrochloric acid and calcium carbonate, carbon dioxide gas is produced. Which piece of evidence best supports the conclusion that a chemical reaction has occurred?

• The mixture turns cloudy.

• The temperature of the mixture decreases.

• Bubbles form in the mixture.

• The mixture changes color.

Tags

NGSS.MS-PS1-2

When iron filings are added to copper sulfate solution, the solution turns blue-green, and a brown solid forms. Which of the following best represents the change observed?

• Physical change

• Chemical change

• Change in state

• Change in shape

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

A student mixes two clear liquids and observes a color change and the formation of a precipitate. Which of the following best describes the evidence of a chemical reaction?

• The change in temperature of the mixture

• The change in volume of the mixture

• The formation of a new substance

• The change in density of the mixture

Tags

NGSS.MS-PS1-2