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

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

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

In a chemical reaction, bonds are broken and new bonds are formed that create new substances. The bonds that are broken are called what?

• Reactants
• Products
• Atoms
• Catalysts

What type of reaction is shown in the image?

• exothermic reaction
• endothermic reaction
• synthesis reaction
• decomposition reaction

What type of reaction is shown in the image?

• exothermic reaction
• endothermic reaction
• single displacement reaction
• double displacement reaction

In an exothermic reaction, energy is ...

• released
• absorbed
• protons
• electrons

In an endothermic reaction, energy is...

• released
• absorbed
• protons
• neutrons