Chemical Reactions and Changes

What is a chemical change?

• A change in the composition and properties of a substance

• A change in the size of a substance

• A change in the temperature of a substance

• A change in the location of a substance

Which of the following is NOT a sign of a chemical change?

• Melting of ice

• Formation of a solid precipitate

• Release of gas bubbles

• A color change not due to mixing

What is the law of conservation of mass?

• Mass is neither created nor destroyed in a chemical reaction

• Mass is always increased in a chemical reaction

• Mass is always decreased in a chemical reaction

• Mass can be created from nothing

Which of the following is an example of a chemical reaction?

• Rust forming on iron

• Water boiling

• Ice melting

• Salt dissolving in water

What do chemical reactions involve at the atomic level?

• Rearrangement of atoms and molecules

• Movement of atoms to a new location

• Increase in the number of atoms

• Decrease in the number of atoms

Which of the following is a sign of a chemical change?

• Formation of a solid precipitate

• Evaporation of water

• Freezing of a liquid

• Condensation of steam

What is a chemical reaction?

• The transformation of reactants into new substances (products)

• The mixing of two substances without change

• The heating of a substance

• The cooling of a substance

Which of the following is NOT a concept related to chemical reactions?

• Physical properties

• Chemical change

• Law of conservation of mass

• Chemical properties

What is the main evidence that a chemical reaction has occurred?

• Appearance of products with different physical and chemical properties from the reactants

• Change in the shape of the substance

• Increase in the size of the substance

• Decrease in the temperature of the substance

What does the law of conservation of mass imply about atoms in a chemical reaction?

• Atoms are only rearranged, not gained or lost

• Atoms are destroyed

• Atoms are created

• Atoms disappear