HOW DO WE KNOW A CHEMICAL CHANGE/REACTION HAS OCCURRED?

let’s go to one of the old classics

BAKING SODA & VINEGAR (ACETIC ACID) REACTION NaHCO3 + HC2H3O2  NaC2H3O2 + H2O + CO2 BAKING SODA ACETIC ACID (VINEGAR) SODIUM ACETATE WATER CARBON DIOXIDE  REACTANTS PRODUCTS

BAKING SODA & VINEGAR (ACETIC ACID) REACTION What gas is produced? BAKING SODA & VINEGAR (ACETIC ACID) REACTION NaHCO3 + HC2H3O2  NaC2H3O2 + H2O + CO2 BAKING SODA VINEGAR SODIUM ACETATE WATER CARBON DIOXIDE  REACTANTS PRODUCTS

BAKING SODA & VINEGAR (ACETIC ACID) REACTION What gas is produced? CO2 BAKING SODA & VINEGAR (ACETIC ACID) REACTION NaHCO3 + HC2H3O2  NaC2H3O2 + H2O + CO2 BAKING SODA VINEGAR SODIUM ACETATE WATER CARBON DIOXIDE  REACTANTS PRODUCTS

does carbon dioxide fuel a fire? Does FIRE need CO2?

does carbon dioxide fuel a fire? Does FIRE need CO2? As a REACTANT? NO!!!

does carbon dioxide fuel a fire? Does FIRE need CO2? NO!!! OXYGEN FUELS A FIRE!

See how oxygen gas (O2) is a reactant in all of these… 4Fe + 3O2 à 2Fe2O3 C3N6H6O6 + O2  3 CO2 + 2 H2O + 3 N2 + H2 2CH2 + 3O2 à 2CO2 + 2H2O 2C4H10 + 13 O2 à 8CO2 + 10H2O COMBUSTION & CORROSION NEED OXYGEN AS A REACTANT– THEREFORE, WE CALL THESE OXIDATION REACTIONS

Which one is the rusting/corroding of iron? 4Fe + 3O2 à 2Fe2O3 C3N6H6O6 + O2  3 CO2 + 2 H2O + 3 N2 + H2 2CH2 + 3O2 à 2CO2 + 2H2O 2C4H10 + 13 O2 à 8CO2 + 10H2O COMBUSTION & CORROSION NEED OXYGEN AS A REACTANT– THEREFORE, WE CALL THESE OXIDATION REACTIONS

Which reaction seems to be the most sensitive/tempermental? 4Fe + 3O2 à 2Fe2O3 IRON RUSTING/CORRODING C3N6H6O6 + O2  3 CO2 + 2 H2O + 3 N2 + H2 2CH2 + 3O2 à 2CO2 + 2H2O 2C4H10 + 13 O2 à 8CO2 + 10H2O COMBUSTION & CORROSION NEED OXYGEN AS A REACTANT– THEREFORE, WE CALL THESE OXIDATION REACTIONS

Which one needs the least oxygen to make the most products? 4Fe + 3O2 à 2Fe2O3 IRON RUSTING/CORRODING C3N6H6O6 + O2  3 CO2 + 2 H2O + 3 N2 + H2 2CH2 + 3O2 à 2CO2 + 2H2O 2C4H10 + 13 O2 à 8CO2 + 10H2O COMBUSTION & CORROSION NEED OXYGEN AS A REACTANT– THEREFORE, WE CALL THESE OXIDATION REACTIONS

That second reaction is the combustion/explosion of c4!!! 4Fe + 3O2 à 2Fe2O3 IRON RUSTING/CORRODING C3N6H6O6 + O2  3 CO2 + 2 H2O + 3 N2 + H2 C4 EXPLOSION 2CH2 + 3O2 à 2CO2 + 2H2O 2C4H10 + 13 O2 à 8CO2 + 10H2O COMBUSTION & CORROSION NEED OXYGEN AS A REACTANT– THEREFORE, WE CALL THESE OXIDATION REACTIONS

The last 2 are the combustion reactions for wax and butane. 4Fe + 3O2 à 2Fe2O3 IRON RUSTING/CORRODING C3N6H6O6 + O2  3 CO2 + 2 H2O + 3 N2 + H2 C4 EXPLOSION 2CH2 + 3O2 à 2CO2 + 2H2O CANDLE WAX BURNING 2C4H10 + 13 O2 à 8CO2 + 10H2O BUTANE LIGHTER COMBUSTION & CORROSION NEED OXYGEN AS A REACTANT– THEREFORE, WE CALL THESE OXIDATION REACTIONS

COMBUSTION & CORROSION NEED If were on a submarine undersea, and you had only candles and butane to keep you warm, which would you use? 4Fe + 3O2 à 2Fe2O3 IRON RUSTING/CORRODING C3N6H6O6 + O2  3 CO2 + 2 H2O + 3 N2 + H2 C4 EXPLOSION 2CH2 + 3O2 à 2CO2 + 2H2O CANDLE WAX BURNING 2C4H10 + 13 O2 à 8CO2 + 10H2O BUTANE LIGHTER COMBUSTION & CORROSION NEED OXYGEN AS A REACTANT– THEREFORE, WE CALL THESE OXIDATION REACTIONS

COMBUSTION & CORROSION NEED If we’re on a submarine undersea, candles uses up less oxygen in its reaction. 4Fe + 3O2 à 2Fe2O3 IRON RUSTING/CORRODING C3N6H6O6 + O2  3 CO2 + 2 H2O + 3 N2 + H2 C4 EXPLOSION 2CH2 + 3O2 à 2CO2 + 2H2O CANDLE WAX BURNING 2C4H10 + 13 O2 à 8CO2 + 10H2O BUTANE LIGHTER COMBUSTION & CORROSION NEED OXYGEN AS A REACTANT– THEREFORE, WE CALL THESE OXIDATION REACTIONS

oxygen helps rust, combust, fire-up & explode!!! 4Fe + 3O2 à 2Fe2O3 IRON RUSTING C3N6H6O6 + O2  3 CO2 + 2 H2O + 3 N2 + H2 C4 EXPLOSION 2CH2 + 3O2 à 2CO2 + 2H2O CANDLE WAX BURNING 2C4H10 + 13 O2 à 8CO2 + 10H2O BUTANE LIGHTER COMBUSTION & CORROSION NEED OXYGEN AS A REACTANT– THEREFORE, WE CALL THESE OXIDATION REACTIONS

DUMB QUESTION: ARE OXIDATION REACTIONS EXO OR ENDOTHERMIC?

COMBUSTION & CORROSION NEED oxygen helps rust, combust, fire-up & explode! OXIDATION REACTIONS ARE EXOTHERMIC 4Fe + 3O2 à 2Fe2O3 IRON RUSTING C3N6H6O6 + O2  3 CO2 + 2 H2O + 3 N2 + H2 C4 EXPLOSION 2CH2 + 3O2 à 2CO2 + 2H2O CANDLE WAX BURNING 2C4H10 + 13 O2 à 8CO2 + 10H2O BUTANE LIGHTER COMBUSTION & CORROSION NEED OXYGEN AS A REACTANT– THEREFORE, WE CALL THESE OXIDATION REACTIONS

To stop oxidation/combustion reactions, we shut off the supply of ________ gas reactant. Fire extinguishers either release water or carbon dioxide foam. Blanket or covering a fire stops the oxygen from reaching the flame.

To stop oxidation/combustion reactions, we shut off the supply of oxygen gas reactant. Fire extinguishers either release water or carbon dioxide foam. Blanket or covering a fire stops the oxygen from reaching the flame.

COMBUSTION & CORROSION NEED reactant, the whole reaction STOPS! oxygen helps rust, combust, fire-up & explode! OXIDATION REACTIONS ARE EXOTHERMIC 4Fe + 3O2 à 2Fe2O3 IRON RUSTING C3N6H6O6 + O2  3 CO2 + 2 H2O + 3 N2 + H2 C4 EXPLOSION 2CH2 + 3O2 à 2CO2 + 2H2O CANDLE WAX BURNING 2C4H10 + 13 O2 à 8CO2 + 10H2O BUTANE LIGHTER COMBUSTION & CORROSION NEED OXYGEN without oxygen gas as a reactant, the whole reaction STOPS!

Check for understanding…

Which gas can STOP combustion? OXYGEN GAS (O2) CARBON DIOXIDE (CO2)

Which gas can STOP combustion? CARBON DIOXIDE (CO2) OXYGEN GAS (O2) OMG…this STARTS the whole thing!!!

What’s a heavier molecule: CO2 or O2? Which has more atomic mass?

What’s a heavier molecule: CO2 or O2? Use your periodic tables!!!

COMPARE MOLECULAR MASS! CARBON DIOXIDE OXYGEN GAS 16+12+16 16+16

Carbon dioxide CO2 is a heavier molecule! OXYGEN GAS 16+12+16 = 44 16+16 = 32

Anyways…

Let’s compare Compare reactions: Vinegar & baking soda reaction NaHCO3 + HC2H3O2  NaC2H3O2 + H2O + CO2 Candle wax burning reaction 2CH2 + 3O2 à 2CO2 + 2H2O

What if I replaced the O2 reactant in the candle burning reaction with CO2? Vinegar & baking soda reaction NaHCO3 + HC2H3O2  NaC2H3O2 + H2O + CO2 Candle wax burning reaction 2CH2 + 3O2 à 2CO2 + 2H2O

What if I replaced the O2 reactant in the candle burning reaction with CO2? Vinegar & baking soda reaction NaHCO3 + HC2H3O2  NaC2H3O2 + H2O + CO2 Candle wax burning reaction 2CH2 + 3O2 à 2CO2 + 2H2O The reaction would stop & the flame would go out!

Where can I get a whole lot of carbon dioxide to find out! That old classic reaction that’s where!

BAKING SODA & VINEGAR (ACETIC ACID) REACTION YES!!! BAKING SODA & VINEGAR (ACETIC ACID) REACTION NaHCO3 + HC2H3O2  NaC2H3O2 + H2O + CO2 BAKING SODA VINEGAR SODIUM ACETATE WATER CARBON DIOXIDE  REACTANTS PRODUCTS

And we Know now that CO2 is a heavier gas compared to O2! That old classic reaction that’s where!

CO2 pours into the beaker & replaces the O2 reactant in the candle reaction. Vinegar & baking soda reaction NaHCO3 + HC2H3O2  NaC2H3O2 + H2O + CO2 Candle wax burning reaction 2CH2 + 3O2 à 2CO2 + 2H2O The reaction stops & the flame goes out!

CO2 pours into the beaker & replaces the O2 reactant in the candle reaction. Vinegar & baking soda reaction NaHCO3 + HC2H3O2  NaC2H3O2 + H2O + CO2 Candle wax burning reaction 2CH2 + 3O2 à 2CO2 + 2H2O The reaction stops & the flame goes out!

replace the O2 reactant WITH HEAVIER CO2 SHUTS DOWN THE REACTION!. Vinegar & baking soda reaction NaHCO3 + HC2H3O2  NaC2H3O2 + H2O + CO2 Candle wax burning reaction 2CH2 + 3O2 à 2CO2 + 2H2O The reaction stops & the flame goes out!

How did we know the baking soda reacted with the vinegar?

EVIDENCE of a CHEMICAL REACTION (aka a CHEMICAL CHANGE) 1. 2. a. b. 3. 4.

EVIDENCE of a CHEMICAL REACTION (aka a CHEMICAL CHANGE) a GAS is produced (fizzes up)

How did we know the candle burning was a combustion chemical reaction?

EVIDENCE of a CHEMICAL REACTION (aka a CHEMICAL CHANGE) a GAS is produced a TEMPERATURE change

Some chemical reactions RELEASE heat! W_ _ m pack, butane l_ _ _ter, c_ _dle, f_ _ewor_ _,

Some chemical reactions RELEASE heat! Warm pack, butane lighter, candle, fireworks,

SIGNS of a CHEMICAL REACTION (aka a CHEMICAL CHANGE) a GAS is produced a TEMPERATURE change temp heat EXITS reaction--EXOTHERMIC

Heat is released during EXOTHERMIC chemical reactions. Candle wax burning reaction 2CH2 + 3O2 à 2CO2 + 2H2O + HEAT Hand warmers 4Fe + 3O2  2Fe2O3 + heat Potassium permagneate & glycerin 14 KMnO4 + 4 C3H5(OH)3  7K2CO3 + 7Mn2O3 + 5CO2 + 16H2O + HEAT

How about PHOTOSYNTHESIS How about PHOTOSYNTHESIS? Do phytoplankton and trees release OR absorb heat?

With PHOTOSYNTHESIS, phytoplankton and trees ABSORB the SUN’s heat

That’s partly why its cooler to lay on your lawn than on your driveway during the summer!

trees absorb heat when doing photosynthesis That’s why its cooler to walk through the shaded forest than a shaded garage. trees absorb heat when doing photosynthesis

SIGNS of a CHEMICAL REACTION (aka a CHEMICAL CHANGE) a GAS is created as a product a TEMPERATURE change temp heat EXITS reaction—EXOTHERMIC temp heat ENTERS reaction-ENDOthermic

Can you think of any ENDOthermic reactions that cool thing down in your home?

FRIDGES & AIR CONDITIONERS USE ENDOTHERMIC REACTIONS.

Check out this ENDOthermic reaction! Barium hydroxide (Ba(OH)2) mixed with ammonium chloride (NH4Cl)… HEAT + Ba(OH)2 + 8 H2O + 2 NH4Cl → 2 NH3 + 10 H2O + BaCl2 http://www.youtube.com/watch?v=5RJLvQXce4A

Some reactions ABSORB heat! Barium hydroxide (Ba(OH)2) mixed with ammonium chloride (NH4Cl)… HEAT + Ba(OH)2 + 8 H2O + 2 NH4Cl → 2 NH3 + 10 H2O + BaCl2 http://www.youtube.com/watch?v=5RJLvQXce4A COLD PACK! REFRIDGERATORS! PHOTOSYNTHESIS!!!

what other signs do we have that a chemical reaction/change has occurred????

SIGNS of a CHEMICAL REACTION (aka a CHEMICAL CHANGE) a GAS is created as a product a TEMPERATURE change temp heat EXITS reaction—EXOTHERMIC temp heat ENTERS reaction-ENDOthermic A ??????????????change

A BIG _ _ _ _ _ change is an OBVIOUS sign of chemical reaction & change. _ _ _ _ _ change indicates a new substances has been formed… first 1:14 of http://www.youtube.com/watch?v=ti_E2ZKZpC4 then 7:25-8:10

SIGNS of a CHEMICAL REACTION (aka a CHEMICAL CHANGE) a GAS is created as a product a TEMPERATURE change temp heat EXITS reaction—EXOTHERMIC temp heat ENTERS reaction-ENDOthermic a DRAMATIC COLOR change

Sulfuric acid helps oxidizing sugar shows all 4 signs of a chemical change…BUT ESPECIALLY COLOR CHANGE! http://www.youtube.com/watch?v=kcDSngXldB0 C12H22O11 + 4 O2 4 CO2 + 8 C + 11 H2O H2SO4

Sulfuric acid helps oxidizing sugar shows all 4 signs of a chemical change…BUT ESPECIALLY COLOR CHANGE! What role does sulfuric acid H2SO4 play in this chemical reaction? C12H22O11 + 4 O2 4 CO2 + 8 C + 11 H2O H2SO4

Sulfuric acid helps oxidizing sugar shows all 4 signs of a chemical change…BUT ESPECIALLY COLOR CHANGE! What role does sulfuric acid H2SO4 play in this chemical reaction? C12H22O11 + 4 O2 4 CO2 + 8 C + 11 H2O CATALYST H2SO4

Behold the GLOW STICK reaction! C14H10O4 + H2O2 __C6H6O + C2O4

How many molecules of C6H6O do we make here? C14H10O4 + H2O2 __C6H6O + C2O4

Behold the GLOW STICK reaction! C14H10O4 + H2O2 2 C6H6O + C2O4

A BIG color change is an OBVIOUS sign of chemical reaction & change. Color change indicates a new substances has been formed… first 1:14 of http://www.youtube.com/watch?v=ti_E2ZKZpC4 then 7:25-8:10

SIGNS of a CHEMICAL REACTION (aka a CHEMICAL CHANGE) a GAS is created as a product a TEMPERATURE change temp heat EXITS reaction—EXOTHERMIC temp heat ENTERS reaction-ENDOthermic a DRAMATIC COLOR change WHAT’S THE LAST SIGN?????

corroded batteries and pennies…

SIGNS of a CHEMICAL REACTION (aka a CHEMICAL CHANGE) a GAS is created as a product a TEMPERATURE change temp heat EXITS reaction—EXOTHERMIC temp heat ENTERS reaction-ENDOthermic a DRAMATIC COLOR change a PRECIPITATE forms

But what is a PRECIPITATE? http://www.youtube.com/watch?v=Q7fjH2G0y7w

Batteries are chemical reactions inside a metal shell or plastic box Batteries are chemical reactions inside a metal shell or plastic box. When these reactions occur, often we get a precipitate.

SIGNS of a CHEMICAL REACTION (aka a CHEMICAL CHANGE) a GAS is created as a product a TEMPERATURE change temp heat EXITS reaction—EXOTHERMIC temp heat ENTERS reaction-ENDOthermic a DRAMATIC COLOR change a PRECIPITATE forms WHEN REACTANTS TURN INTO NEW SOLID PRODUCTS

nylon rope demo

END onto blue lab