Chemical reactions: Section 4.1 answers to vocabulary

Chemical reaction Occurs when two or more substances combine to form new substances. Occurs when two or more substances combine to form new substances. Examples: Examples: Space shuttle Space shuttle Air bags Air bags Baking soda and vingar Baking soda and vingar Mentos and diet coke Mentos and diet coke

When a chemical reaction occurs, a new substance forms and evidence of the reaction may include one or more of the following: A color change A color change The formation of an odour The formation of an odour The formation of a solid or gas The formation of a solid or gas The release or absorption of heat The release or absorption of heat

Reactants The materials at the start of a reaction The materials at the start of a reaction The substance that reacts with another substance to create something new. The substance that reacts with another substance to create something new. Examples: Examples: Burning wood: the log and oxygen Burning wood: the log and oxygen Rocket science: Alka seltzer and vinegar Rocket science: Alka seltzer and vinegar

Products The new materials produced by a reaction. The new materials produced by a reaction. Examples: Examples: Burning wood: carbon dioxide, water, energy released Burning wood: carbon dioxide, water, energy released Rocket science: Rocket science: NaC 2 H 3 O 2(aq) + H 2 O (l) + CO 2(g)

Chemical word equation The reactants always appear on the left of the arrow The reactants always appear on the left of the arrow The products are always on the right of the arrow The products are always on the right of the arrow The arrow indicates the direction in which the reaction is most likely to occur. The arrow indicates the direction in which the reaction is most likely to occur. Example: Example: Log + oxygen  carbon dioxide + water + energy released Log + oxygen  carbon dioxide + water + energy released Alka seltzer + vinegar  Alka seltzer + vinegar  NaC 2 H 3 O 2(aq) + H 2 O (l) + CO 2(g)

Exothermic reaction A chemical reaction that RELEASES (or give off) heat energy A chemical reaction that RELEASES (or give off) heat energy Examples: Examples: Fire Fire When your body is metabolizing food When your body is metabolizing food Combustion reactions (considered the first chemical reaction used by humans.) Combustion reactions (considered the first chemical reaction used by humans.) Fireworks Fireworks Combustion engines Combustion engines

Endothermic reactions A chemical reaction in which heat energy is ABSORBED. A chemical reaction in which heat energy is ABSORBED. Examples: Examples: Chemical cold packs – energy is absorbed from the liquid in the bag, and the pack becomes very cold. Chemical cold packs – energy is absorbed from the liquid in the bag, and the pack becomes very cold. Baking soda and vinegar - temp decreases. Baking soda and vinegar - temp decreases.

Combustion A chemical reaction that occurs when oxygen reacts with a substance to form a new substance and gives off energy. A chemical reaction that occurs when oxygen reacts with a substance to form a new substance and gives off energy. Therefore, always exothermic (give off energy!) Therefore, always exothermic (give off energy!) Examples: Examples: Burning wood: Burning wood: Log + oxygen  carbon dioxide + water + energy released Internal combustion engine: Internal combustion engine: a fuel, such as gasoline, fills a chamber mixed with air (oxygen) and then is ignited by a spark plug, causing a small explosion (heat released) which generates work.

Corrosion The slow chemical change that occurs when oxygen in the air reacts with a metal. The slow chemical change that occurs when oxygen in the air reacts with a metal. Examples: Examples: Rust: Iron + oxygen  Iron oxide Rust: Iron + oxygen  Iron oxide Tarnished silver Tarnished silver

Cellular respiration A chemical reaction that takes place in the cells of your body. A chemical reaction that takes place in the cells of your body. Example: Example: In your cells In your cells Food + Oxygen  carbon dioxide + water + energy Food + Oxygen  carbon dioxide + water + energy