1. Nitrogen, Sulfur, and the Scientific Method

2. Nitrogen Makes up 78% of atmosphere Necessary for plant growth –Most plants can’t get it from the air

4. 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 NH 3 out of N 2

5. Nitrogen (cont) Also important in auto airbags –Uses sodium azide, NaN 3 –Electrically decompose it to give off N 2 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.

6. Sulfur As a solid, crystal that contains S 8 molecules

8. Sulfur As a solid, crystal that contains S 8 molecules When heated to 113°C, it melts –Physical change

10. Sulfur As a solid, crystal that contains S 8 molecules When heated to 113°C, it melts –Physical change – still S 8 When heated to 159°C, turns brown and becomes viscous –Chemical change – long molecules

12. Sulfur As a solid, crystal that contains S 8 molecules When heated to 113°C, it melts –Physical change – still S 8 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

14. Scientific Method How does a candle burn? Make initial observations

16. 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

17. 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

20. Further support, when you extinguish, can you light vapors again?

21. 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 CO 2 and H 2 O? Test?

22. Why soot? –Incomplete combustion Why? Different colors of flame, Why? –Test?

24. H6 – C2 22, 23, 32 - 35, 52, 57, 59