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
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
