2. Hydrogen Explosions Balloons filled with hydrogen gas explode with a loud boom when lit.

3. Purpose  To observe a violent but contained explosion of an extremely reactive gas

4. Demonstration  The flame held up to the balloon provided the necessary energy of activation  The hydrogen in the balloon reacted with oxygen in the atmosphere  The hydrogen was oxidized to water  The oxygen was reduced to water 2H 2 + O 2 2H 2 O+ heat

5. Concepts 1.Combination Reactions 2.Explosions 3.Gases 3.Hydrogen Gas

6. 1.Combination Reactions  Combination reactions are of the general form A + BAB  Combination reactions are redox reactions  one reactant is oxidized  the other reactant is reduced

7. 2.Explosions  Exothermic chemical reactions which proceed with a rapid expansion of gas volume and, most often, sound  May involve solid, liquid, or gaseous reactants  In this demonstration the reactants are gases

8. 3.Gases  A gas is a substance which  has particles separate from each other  has particles flying freely  has low density compared to solids and liquids  fills its container completely  The balloon in this experiment is filled with hydrogen gas

9. 4.Hydrogen Gas  Hydrogen gas is a combination of two hydrogen atoms: H-H  Since two identical atoms are together we say that hydrogen gas is “diatomic” where the prefix “di” means “two”  Hydrogen gas is dangerously explosively  Hydrogen gas is less dense than air and therefore hydrogen balloons float

10. Conclusions  This combination reactions proceeded with explosive violence  Hydrogen and oxygen were the reactants in the reaction  Drops of the water product were felt at a distance

11. Comments  The flame not only ignites the hydrogen it causes the balloon to burst  Bursting the balloon allows the hydrogen gas to mix with the other necessary reactant, oxygen  The oxygen constitutes 20.9% of the atmosphere and exists as diatomic oxygen