Indicators of Chemical Reactions

In a chemical reaction, the reactants and products are separated by a _______.

• Comma
• Arrow
• Equal sign
• Triangle

The reactants are on the left side of the chemical equation.

• True
• False

Two clear colorless solutions were combined.
The student observed that the temperature changed from 25^oC to 17^oC 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-PS1-5

Two clear colorless solutions were combined.
The student observed that the temperature changed from 25^oC to 17^oC 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-PS1-5

Coal contains carbon and other elements. Carbon dioxide forms when coal burns in the presence of oxygen. Which of these is the best evidence that a chemical reaction occurs when coal burns?

• The shape of the coal changes
• Oxygen is present
• A new substance is produced
• Coal is made up of more than one element

Tags

NGSS.MS-PS1-2

Which of the following BEST describes a chemical reaction?

• A compound is crushed into a fine powder.
• Atoms break apart into even smaller particles.
• Existing electron bonds break and reattach to other atoms
• Molecules move faster until they fly apart from each other

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

When a scientist mixed two chemicals, an exothermic reaction takes place. Which of the following would be proof that the reaction was exothermic?

• a change of color
• a change of state
• a temperature decrease
• a temperature increase

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-4

NGSS.MS-PS3-4

A scientist combines chemicals and produces an exothermic reaction. What byproduct of this reaction would show that it is exothermic?

• heat
• coolness
• a precipitate
• gas bubbles

Tags

NGSS.MS-PS1-4

Which of the following is a chemical change?

• water freezes to form ice
• sugar dissolves in water
• gasoline burns in a car engine
• a piece of metal expands when it is heated

Tags

NGSS.MS-PS1-2

In the reaction methane + oxygen turns into carbon dioxide + water, the methane and oxygen are called _______________.

• reactants
• products
• neutrals
• energizers