Chemical ReactionsChemical Reactions

Cornell Notes page 139Cornell Notes page 139

Chemical Chemical PropertiePropertiess

Characteristics of a Characteristics of a material that can material that can only be determined only be determined during a Chemical during a Chemical ReactionReaction– ReactivityReactivity– Flammability Flammability – pHpH– OxidationOxidation

Chemical Chemical ReactionReaction

ReactantsReactants

ProductsProducts

The process of The process of substances substances changing into new changing into new substances.substances.

Substances at start Substances at start of reaction that are of reaction that are changedchanged

New substances New substances made from the made from the reaction (end reaction (end results).results).

The Law of The Law of ConservatioConservation of Mattern of Matter

Matter is not Matter is not created or created or destroyed.destroyed.

mass of mass of reactants reactants should equal should equal mass of mass of products!products!

4 Signs of 4 Signs of a a Chemical Chemical ReactionReaction

Used to identify Used to identify when a reaction has when a reaction has occurredoccurred

Not definite- more Not definite- more signs increase signs increase confidence that a confidence that a reaction has reaction has occurred.occurred.

Best indicator is Best indicator is that substances that substances have new have new properties.properties.

4 Signs of 4 Signs of a a Chemical Chemical ReactionReaction

1. Formation of a Gas1. Formation of a Gas BubblesBubbles Least reliable signLeast reliable sign

Ex.) baking soda and Ex.) baking soda and vinegar; yeast and vinegar; yeast and hydrogen peroxide.hydrogen peroxide.

4 Signs of 4 Signs of a a Chemical Chemical ReactionReaction

2. Formation of a 2. Formation of a PrecipitatePrecipitate Solid is created Solid is created

when two liquids when two liquids are mixedare mixed

May look like small May look like small particles suspended particles suspended in a liquid.in a liquid.

4 Signs of 4 Signs of a a Chemical Chemical ReactionReaction

3. Unexpected Color 3. Unexpected Color ChangeChange When two When two

substances are substances are mixed and an mixed and an unexpected color unexpected color occurs.occurs.

Ex.) Bleach spilt on Ex.) Bleach spilt on colored clothes. colored clothes.

4 Signs of 4 Signs of a a Chemical Chemical ReactionReaction

4. Temperature 4. Temperature ChangeChange temperature temperature

changes as energy changes as energy is used or released is used or released from the reaction.from the reaction.

ExothermicExothermic- heat is - heat is released (gets released (gets warmer)warmer)

EndothermicEndothermic- heat - heat is absorbed (gets is absorbed (gets colder)colder)

What is a What is a Catalyst?Catalyst?

A substance that A substance that starts or speeds up starts or speeds up a chemical reaction a chemical reaction that is not used or that is not used or changed in the changed in the reaction.reaction.

lowers the amount lowers the amount of energy needed in of energy needed in a chemical reactiona chemical reaction

Oxidation Reactions

• Specific type of Chemical Reaction in which a substance reacts with oxygen

• Often results in a color change– Apples turn brown

– Many metals oxidize, such as iron turning red or copper turning green; we often call this rust.

• Oxygen reacts with iron to create rust.

• The new color is evidence that a chemical reaction has taken place.

• Oxygen reacts with apples to cause them to brown

• Adding citric acid prevents the oxidation reaction.

• Oxygen reacts with copper to create a green color called verdigris

• Many oxidation reactions take time to happen.

• Burning is an example of a rapid oxidation reaction.

• Oxygen is required for burning, the heat and light are evidence that a reaction is taking place.