Chemical Reactions

What are some signs that a chemical reaction might have occurred?

• Change in color, formation of a gas, temperature change, or formation of a precipitate

• Increase in mass only

• No change in appearance

• Only a change in shape

What happens to atoms during a chemical reaction?

• Atoms are destroyed.

• Atoms are created.

• Atoms are rearranged.

• Atoms disappear.

What happens to the total mass in a chemical reaction?

• It increases

• It decreases

• It remains the same

• It doubles

Define: chemical reaction.

• A process in which substances combine or break apart to form new substances.

• A process in which energy is only absorbed but no new substances are formed.

• A process where substances are mixed but retain their original properties.

• A process in which only physical changes occur without forming new substances.

Define: chemical equation.

• A representation of a chemical reaction using symbols of the elements and formulas of compounds.

• A list of all the elements found in nature.

• A mathematical formula used to calculate mass.

• A chart showing the periodic table of elements.

Define: reactant.

• A substance that takes part in and undergoes change during a reaction.

• A product formed after a reaction is complete.

• A catalyst that speeds up a reaction without being consumed.

• A solvent used to dissolve other substances in a reaction.

Define: product.

• A substance that is formed as the result of a chemical reaction.

• A tool used to measure temperature.

• A type of energy released during combustion.

• A device used to separate mixtures.

Define: law of conservation of mass.

• The principle that the total mass of substances does not change during a chemical reaction.

• The principle that energy is always created during a chemical reaction.

• The principle that the volume of substances always increases during a chemical reaction.

• The principle that the temperature of substances always decreases during a chemical reaction.

Define: coefficient (in a chemical equation).

• A number placed in front of a chemical formula in an equation that indicates how many molecules or atoms of each reactant and product are involved in a reaction.

• A symbol used to represent an element in a chemical equation.

• The total mass of all reactants in a chemical reaction.

• A type of bond formed between atoms in a molecule.

According to the passage, fireflies produce light by:

• burning fuel in their bodies

• a chemical reaction in their bodies

• absorbing sunlight and glowing at night

• using electricity stored in their bodies