Chemistry 3B

Objectives

Physical vs Chemical Change

• StudyJams

Physical Change

• The appearance of a substance may have changed, but the bonds holding the atoms together have not been broken and no new bonds have been made.

• Ex: Chocolate left in the sun

• Ex: Ice turning to liquid water

Physical Change Examples

• Change of state (melting, evaporation, condensation, freezing)

• Dissolving

• Cutting

***Process is Reversible

Chemical Change

• Produces new substances with new properties, which may or may not be noticeable.

• New bonds are formed while other bonds are broken.

• Elements are conserved during chemical change but compounds are not.

Reactants & Products

• Reactants - are the substances you start with that are going to react with each other.

• Product - is the new substances produced

Law of Conservation of Mass

• In a chemical reaction, the mass of the reactants is equal to the mass of the product.

Hydrogen + Oxygen -> Water

20g + 10g 30g

Are Atoms created or destroyed in a chemical reaction?

No

There are the same number of each type of atom on the reactant side as there are on the product side of the chemical equation.

Determine the number of Atoms on the reactant and product sides

Chemical equation for water

2H2 + O2 -> 2H2O

Reactant side: 4 hydrogen, 2 Oxygen. Product side: 4 hydrogen, 2 oxygen

x x

x

Determine the number of carbon, hydrogen, and oxygen’s on the

reactant and product side.

• CH4 + 2O2 CO2 + 2H2O

• Product side: 1 carbon, 4 Hydrogen, 4 Oxygen

• Reactant side: 1 carbon, 4 hydrogen, 4 oxygen

x x

x

• The atoms in the products come from the atoms in the reactants. In a chemical reaction, bonds between atoms in the reactants are broken and the atoms rearrange and form new bonds to make the products.

Evidence of a Chemical Change

• Color change

• Heat is produced or absorbed

• Gas is produced (Bubbles form)

• A precipitate forms

***Process is difficult to reverse

Precipitate

is the creation of a solid in a solution or inside another solid during a chemical reaction. The solid formed is called the 'precipitate'.

Worksheet

• Physical vs Chemical Changes

Bill Nye “ Chemical Reactions”

https://www.youtube.com/watch?v=Rtcf6Pjahec

Chemical Change Examples

1. Combustion (burning) – involves a substance combining with oxygen coupled with the release of energy.

Ex: liquid hydrogen fuel reacting with liquid oxygen within the shuttles rockets.

2. Corrosion – process by which metals combine with oxygen (oxidation).

Ex: NL Ferries undergo a rusting process when the iron reacts with the oxygenated water.

What may speed up the rusting process for the NL ferries?

What could be done to help protect the ship from corroding?

Textbook Page 90

• Parliament buildings roofs in Ottawa? Explain the color change.

Fruit Ripening Textbook Page 89

• Explain why one bad apple in a bag of apples should be removed immediately?

STSE

• Plastics & Modern Life

• Video’s

• Plastic Chart

• Article

• Plastic Milk Lab

• Video: Ocean of plastics

• Recycling Plastics (worksheet at this address) http://recycle-bowl.org/wp-content/uploads/15-Plastics-by-the-Numbers-numberless-done.pdf