Understanding Evidence of Chemical Reactions

What is a combustion reaction?

• A combustion reaction occurs only in the absence of oxygen.
• A combustion reaction is a slow process that absorbs heat and light.
• A combustion reaction is a chemical change that produces only solid products.
• A combustion reaction is a rapid chemical reaction between a substance and oxygen that produces heat and light.

In the chemical equation 2H₂ + O₂ → 2H₂O, what are the reactants?

• H₂ and O
• H₂O and O₂
• 2H₂ and O₂
• 2H₂ and 2O₂

Indicate whether each statement is true or false.

A precipitate is a solid that forms from a solution during a chemical reaction.

• TRUE

• FALSE

Chemical equations must be balanced to reflect the law of conservation of mass.

• TRUE

• FALSE

What is a noticeable sign of a chemical reaction according to the passage?

• Color change

• Sound production

• Magnetic attraction

• Weight increase

Which of the following reactions is an example of an exothermic reaction?

• Combustion of wood

• Dissolving ammonium nitrate in water

• Mixing vinegar and baking soda

• Rusting of iron

What happens when vinegar and baking soda are combined?

• Gas is produced

• A solid precipitate forms

• The temperature decreases

• Light is emitted

What is an example of a reaction that absorbs heat?

• Dissolving ammonium nitrate in water

• Combustion of wood

• Rusting of iron

• Mixing vinegar and baking soda

What causes the smell of rotten eggs in a chemical reaction?

• Formation of hydrogen sulfide gas

• Release of carbon dioxide

• Emission of light

• Production of heat