chemical changes

Which scenarios involve a chemical change?

• baking a cake

• melting of ice

• brushing teeth with toothpaste

• rusting of nails

• photosynthesis in plants

Which statements illustrate a chemical reaction?

• Total mass of the atoms is conserved during the reaction.

• New substance is formed.

• Total number of atoms remained the same during the reaction.

• Most chemical changes cannot be reversed.

methane + oxygen -> carbon dioxide + water.

Which substances are the reactants in the reaction?

• methane

• oxygen

• carbon dioxide

• water

methane + oxygen -> carbon dioxide + water.

Which substances are the products in the reaction?

• methane

• oxygen

• carbon dioxide

• water

hydrochloric acid + magnesium metal -> magnesium chloride + hydrogen gas.

Which substances are reactants in the reaction?

• hydrochloric acid

• magnesium metal

• magnesium chloride

• hydrogen gas

hydrochloric acid + magnesium metal -> magnesium chloride + hydrogen gas.

Which substances are products in the reaction?

• hydrochloric acid

• magnesium metal

• magnesium chloride

• hydrogen gas

Where are the reactants found in a chemical equation?

• left side of the equation before the arrow.

• right side of the equation before the arrow.

Where are the products found in a chemical equation?

• left side of the equation before the arrow.

• right side of the equation before the arrow.