Signs of Chemical Reactions

What happens to atoms during a chemical reaction?

• They are destroyed

• They are rearranged to form new substances

• They remain unchanged

• They are duplicated

What is an exothermic reaction?

• A reaction that absorbs heat

• A reaction that occurs at extreme temperatures

• A reaction that releases heat

• A reaction that only occurs in the cold

Why does a change in color indicate a chemical reaction?

• Because it's easier to see

• Because the temperature changes color

• Because the reaction is reversible

• Because the light absorption properties change

What does the formation of bubbles usually suggest?

• The substance is freezing

• The substance is boiling

• A chemical reaction is taking place

• A physical change

What is a precipitate?

• A gas released during a reaction

• A type of bubble

• A solid that dissolves in liquid

• A solid that forms and falls to the bottom in a chemical reaction

What sign of a chemical reaction is observed when burning substances?

• Decrease in temperature

• Emission of light

• Formation of a solid

• Change in smell

What does not count as a sign of a chemical reaction?

• Change in temperature

• Boiling of water

• Formation of a precipitate

• Emission of light

How can a change in smell indicate a chemical reaction?

• It indicates the presence of water

• It means the reaction is reversible

• It signifies a new substance with different properties has formed

• It shows a physical change

Why is it difficult to reverse a chemical reaction?

• Because new substances with different properties are formed

• Because it requires a lot of energy

• Because the original substances are destroyed

• Because it's legally prohibited

What is true about the substances before and after a chemical reaction?

• They can easily change back to their original form

• They have the same chemical properties

• They have different chemical and physical properties

• They are in the same physical state