Chemical Reactions Test Review

How can particles of a new substance be formed out of the particles of an old substance?

• The new substances form from the gas.

• The new particles break apart from old particles.

• The particles of the old substances might break apart and/or stick together to form new combinations of particles.

How can a new substance be produced and the total mass of the closed system not change?

• The mass does change, the mass decreases.

• The mass does change, the mass increases.

• The amount of matter at the beginning (in the reactants) is the same amount of matter at the end of the reaction (in the products). This is because all of the atoms we started with are still there. No new atoms can appear that weren’t there to start with.

How can you determine if a new substance is produced and thus a chemical reaction occured?

• Testing properties of the substances can help identify whether it is a new substance or not. Properties for a substance do not change therefore if the properties change, it is a new substance.

• Change in color of substance.

• Change in temperature of substance.

How do the molecules of old substances (reactants) react to form new substances (products)?

• Old molecules slow down, spread apart, and make new molecules.

• In a chemical reaction, new molecules are made from the atoms that make up the old substances. If certain atoms are in the reactants of the reaction, those atoms can break apart and rearrange to make new substances.

• Old molecules speed up, come together, and make new molecules.

The Law of Conservation of Mass (Matter) can be followed by knowing the ​reactants' mass should be ​ to the mass of the products.

What is physical change?

• Atoms are rearranged creating new molecules & new substances with new properties.

• Molecules stay the same and the substance(s) remains the same with the same physical properties.

What is a chemical change?

• Atoms are rearranged creating new molecules & new substances with new properties.

• Molecules stay the same and the substance(s) remains the same with the same physical properties.