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

2. EVIDENCE of a CHEMICAL REACTION (aka a CHEMICAL CHANGE)

3. The decomposition of hydrogen peroxide H2O2 !!
2 H2O2  2 H2O + O2

4. EVIDENCE of a CHEMICAL REACTION (aka a CHEMICAL CHANGE)
a GAS is produced

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

6. These chemical reactions RELEASE heat!
Sodium (Na) in water:
2 Na + 2 H2O  2 NaOH + H2 + BOOM

7. These chemical reactions RELEASE heat!
Sodium (Na) in water:
2 Na + 2 H2O  2 NaOH + H2 + BOOM
Potassium (K) in water:
2K + 2H2O  2KOH + H2 + BOOM

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

9. These reactions ABSORB heat!
Barium hydroxide (Ba(OH)2) mixed with ammonium chloride (NH4Cl)…
HEAT + Ba(OH)2 + 8 H2O + 2 NH4Cl → 2 NH H2O + BaCl2

10. These reactions ABSORB heat!
Barium hydroxide (Ba(OH)2) mixed with ammonium chloride (NH4Cl)…
HEAT + Ba(OH)2 + 8 H2O + 2 NH4Cl → 2 NH H2O + BaCl2
COLD PACK!

11. 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

12. 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

13. Sulfuric acid and sugar shows all 4 signs of a chemical change…BUT ESPECIALLY COLOR CHANGE!…

14. 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

15. A color change is an OBVIOUS sign of chemical reaction & change.
Color change indicates a new substances has been formed…
first 1:14 of
But what is a PRECIPITATE?

16. 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 liquid reactants turn into new solid products

17. nylon rope demo