nitrogen, sulfur, and the scientific method. nitrogen makes up 78% of atmosphere necessary for plant...

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