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Nitrogen, Sulfur, and the Scientific Method. Nitrogen. Makes up 78% of atmosphere Necessary for plant growth Most plants can’t get it from the air. Nitrogen. Makes up 78% of atmosphere Necessary for plant growth Most plants can’t get it from the air
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Nitrogen • Makes up 78% of atmosphere • Necessary for plant growth • Most plants can’t get it from the air
Nitrogen • Makes up 78% of atmosphere • Necessary for plant growth • Most plants can’t get it from the air • Have doubled food production in the last 35 years worldwide • Couldn’t have succeeded with natural fertilizers only • Haber-Bosch process was essential • Found a catalyst to make NH3 out of N2
Nitrogen (cont) • Also important in auto airbags • Uses sodium azide, NaN3 • Electrically decompose it to give off N2 gas in a few hundredths of a second • Synthetic vs. organic fertilizers? • Synthetic use oil or gas that we are running out of • Organic are renewable, but not enough to feed the world.
Sulfur • As a solid, crystal that contains S8 molecules
Sulfur • As a solid, crystal that contains S8 molecules • When heated to 113°C, it melts • Physical change
Sulfur • As a solid, crystal that contains S8 molecules • When heated to 113°C, it melts • Physical change – still S8 • When heated to 159°C, turns brown and becomes viscous • Chemical change – long molecules
Sulfur • As a solid, crystal that contains S8 molecules • When heated to 113°C, it melts • Physical change – still S8 • When heated to 159°C, turns brown and becomes viscous • Chemical change – long molecules • Heating further produces less viscous red liquid • Chemical change – molecules broken into smaller ones
Scientific Method • How does a candle burn? • Make initial observations
Initial Observations • Generates both heat and light • Candle gradually disappears • No other liquid or solid material is produced • Flame is above the top of the wax and encloses the wick • Flame is not uniform throughout • Center is darker than outer portion • Can’t burn solid or liquid wax
Initial Hypothesis • Vapor of the wax is burning. • How can we test? • Put a tube in the flame and draw off what is closest to the wick
Further support, when you extinguish, can you light vapors again?
Candle disappears over time • Doesn’t follow the law of conservation of mass? • Products are gases? • Tests? • Where does the oxygen come from to make CO2 and H2O? • Test?
Why soot? • Incomplete combustion Why? • Different colors of flame, Why? • Test?
H6 – C2 • 22, 23, 32 - 35, 52, 57, 59