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Nitrogen, Sulfur, and theScientific 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
• 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