Physical and Chemical Changes

Front

A change in which no new substances are formed is called a __________ change.

Back

physical

Front

In a chemical reaction, the substances that react with each other are called the _____ . The new substances that are formed are called the _____ .

Back

reactants; products

Front

Which of the following statements about all chemical reactions is true?

• Atoms are lost in a chemical reaction.
• Atoms are formed in a chemical reaction.
• A chemical reaction involves the rearrangement of atoms to form products.
• Mass is not conserved in a chemical reaction.

Back

A chemical reaction involves the rearrangement of atoms to form products.

Answer explanation

During a chemical reaction, atoms of the reactants rearrange themselves and combine chemically to form products. No atoms are lost or formed in a chemical reaction. Thus, the mass of the reactants is equal to the mass of the products. Mass is conserved during a chemical reaction.

Front

Which of the following statements correctly describes combustion?

• Combustion is a chemical change in which a substance is heated in the presence of carbon dioxide.
• Combustion is a physical change in which a substance is heated in the presence of carbon dioxide.
• Combustion is a chemical change in which a substance is heated in the presence of oxygen.
• Combustion is a physical change in which a substance is heated in the presence of oxygen.

Back

Combustion is a chemical change in which a substance is heated in the presence of oxygen.

Answer explanation

Combustion is a chemical change in which a substance is heated in the presence of oxygen.