Chemical Chemical reactions: reactions:

Section 4.1Section 4.1answers to vocabularyanswers to vocabulary

Chemical reactionChemical reaction Occurs when two or more Occurs when two or more

substances combine to substances combine to form new substances.form new substances.

Examples:Examples: Space shuttleSpace shuttle Air bagsAir bags Baking soda and vingarBaking soda and vingar Mentos and diet cokeMentos and diet coke

When a chemical reaction When a chemical reaction occurs, a new substance occurs, a new substance

forms and evidence of the forms and evidence of the reaction may include one or reaction may include one or

more of the following:more of the following:

A color changeA color change The formation of an odourThe formation of an odour The formation of a solid or The formation of a solid or

gasgas The release or absorption of The release or absorption of

heatheat

ReactantsReactants The materials at the start of a The materials at the start of a

reactionreaction The substance that reacts with The substance that reacts with

another substance to create another substance to create something new.something new.

Examples:Examples: Burning wood: the log and oxygenBurning wood: the log and oxygen Rocket science: Alka seltzer and vinegar Rocket science: Alka seltzer and vinegar

ProductsProducts The new materials produced by a The new materials produced by a

reaction.reaction.

Examples:Examples: Burning wood: carbon dioxide, Burning wood: carbon dioxide,

water, energy releasedwater, energy released Rocket science: Rocket science:

NaC2H3O2(aq) + H2O(l) + CO2(g)

Chemical word Chemical word equationequation

The reactants always appear on the left of The reactants always appear on the left of the arrowthe arrow

The products are always on the right of the The products are always on the right of the arrowarrow

The arrow indicates the direction in which The arrow indicates the direction in which the reaction is most likely to occur.the reaction is most likely to occur.

Example: Example: Log + oxygen Log + oxygen carbon dioxide + water + energy carbon dioxide + water + energy

releasedreleased Alka seltzer + vinegar Alka seltzer + vinegar NaC2H3O2(aq) + H2O(l) + CO2(g)

Exothermic reactionExothermic reaction A chemical reaction that RELEASES A chemical reaction that RELEASES

(or give off) heat energy(or give off) heat energy

Examples:Examples: FireFire When your body is metabolizing foodWhen your body is metabolizing food Combustion reactions (considered the Combustion reactions (considered the

first chemical reaction used by first chemical reaction used by humans.)humans.)FireworksFireworksCombustion enginesCombustion engines

Endothermic Endothermic reactionsreactions

A chemical reaction in which heat A chemical reaction in which heat energy is ABSORBED.energy is ABSORBED.

Examples:Examples: Chemical cold packs – energy is Chemical cold packs – energy is

absorbed from the liquid in the bag, absorbed from the liquid in the bag, and the pack becomes very cold.and the pack becomes very cold.

Baking soda and vinegar - temp Baking soda and vinegar - temp decreases.decreases.

CombustionCombustion A chemical reaction that occurs when oxygen A chemical reaction that occurs when oxygen

reacts with a substance to form a new reacts with a substance to form a new substance and gives off energy.substance and gives off energy. Therefore, always exothermic (give off Therefore, always exothermic (give off

energy!)energy!) Examples:Examples:

Burning wood:Burning wood:Log + Log + oxygenoxygen carbon dioxide + water + carbon dioxide + water + energy releasedenergy released

Internal combustion engine:Internal combustion engine:a fuel, such as gasoline, fills a chamber mixed with air a fuel, such as gasoline, fills a chamber mixed with air (oxygen) and then is ignited by a spark plug, causing a small (oxygen) and then is ignited by a spark plug, causing a small explosion (heat released) which generates work. explosion (heat released) which generates work.

CorrosionCorrosion The slow chemical change that The slow chemical change that

occurs when oxygen in the air reacts occurs when oxygen in the air reacts with a metal.with a metal.

Examples:Examples:Rust: Iron + oxygen Rust: Iron + oxygen Iron oxide Iron oxideTarnished silverTarnished silver

Cellular respirationCellular respiration A chemical reaction that takes A chemical reaction that takes

place in the cells of your body.place in the cells of your body.

Example:Example: In your cellsIn your cells

Food + Oxygen Food + Oxygen carbon carbon dioxide + dioxide + water + water + energyenergy