Humboldt State University ® Department of Chemistry

Richard A. Paselk

	Science 331
Fall 2004	Lecture/Activity	Office: SA560a
Notes: 6 October		Phone: x 5719 Home: 822-1116
		e-mail: rap1

Rates of Chemical Reaction

Rate vs. Temperature:

• Cooking at sea level vs. at altitude, vs. pressure cooker.
• Oxidation of paper (browning) vs. burning.
• Alka Seltzer in book.
  • Graphs vs. tables; line plots vs. bar graphs; trends and kids.

Why do reactions take place faster at higher temperature?

• Particles moving around faster, so run into each other more frequently.
• Run into each other harde, so easier to overcome repulsion of outer electrron 'envelope'.

Rate vs. Concentration:

• Bleach.
• examples?

Why do concentrated chemicals react faster? Again, more molecules, more likely a collision will occur. Or, for some chemicals (and radioactivity), there are more particles to break down.

Heat, Temperature & Chemical Change

We talked about temperature and rate.

• What is temperature.
  • how is temperature measured?
  • Absolute zero
• What is heat
  • how is heat measured?
  • Heat, temperture and phase change.

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© R A Paselk

Last modified 5 October 2004