warm up 5.4: determine if a chemical or physical change

1. An ice cube is placed in the sun. Later there is a puddle of water and then the puddle is gone.

2. Two chemical are mixed together and a gas is produce.3. A bicycle changes color as it rusts. 4. A solid is crushed to a powder. 5. Two substances are mixed and light is produced. 6. Mixing salt and pepper.7. Chocolate syrup is dissolved in milk.8. A marshmallow is burned over a campfire.

9. A marshmallow is cut in half.

Warm Up 5.4: Determine if a Chemical or Physical Change

PC

C

P

PP

P

C

C

Physical change effects….• Size• Shape • Color• State of matterAdditionally….• Reversible• No energy

Chemical Change effects…

• Composition Additionally…• Energy involved• New substance formed• Atoms rearranged

Signs of Chemical Change1. Color change2. Energy:

– Light– Heat– Fire– Electricity

3. Gas production: – Bubbles– Fizzing– Smoke– Odor change

4. Precipitate

Basics

Reactant

one or more substances

Change into New one or more substances

Product

Law of Conservation of Matter/Mass

• Matter is not created nor destroyed– Just rearranged

• Total mass of reactants = total mass of products

Symbols used in equationsAfter a chemical formula:(s) or ¯ : solid Cu(s) CaCo3 ¯(g) or : gas H2 (g) O2

(l) : liquid H2O(l)

(aq) : aqueous solution CaCl2 (aq)

dissolved in H2O

Other Symbols• or heat :heat supplied to rxn

• Chemical formula : catalyst

All chemical rxns have…. a change in energy

Ea: activation energy: Energy needed to start reactant collisions thus starting the rxnActivated Complex: “top of the hill” reactants’ atoms rearrange due to collisions.

H: Enthalpy: change in heat: products – reactants

Collision Theory ( 1:17 min)

Set up your paperEndothermic Exothermic

Sign Need 1 line

Descriptive words Need at least 2 lines

Drawingneed at least 6 lines

Reaction placementNeed 3 lines

Reaction path diagrams Need at least 10 lines

Endothermic ExothermicSign

Descriptive Words

Drawing

system heat

surroundings

system heat

surroundings

“ Into”, absorb, heat added; heat needed

Given off; heat produced; exit

EndothermicA + B + heat C orA + B C H= + kJ

ExothermicA + B C + heat orA + B C H= - kJ

Reaction placement

“ Endothermic Exothermic

Rxn Path diagram

Endothermic Exothermic

Reactants

ReactantsProducts

Products

Activated complex Activated complex

Ea Ea

H= + heat added

H= - heat given off

REACTIONS RATES

Catalyst

• speeds up rxn w/o being used • Less activation energy is needed• Lowers the activated complex

Other factors that effect rxn rate

• Increase Temperature• Increase Pressure • Increase Concentration – amount of a substance per area– Bigger M = more concentration • Which will cause a faster reaction: 3M or 0.4M 3M will make the rxn faster