What happens if…… simple chemistry expanded September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 1

First year general chemistry examination papers Recall of algorithms>90% Knowledge and Comprehension>70% (Bennett 2007) September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 2

1. year general & inorganic chemistry 4 hours examination papers 1.Formula  names 2.Balance chemical equations 3.pH, concentrations 4.Solubility (+complex formation) 5.Electrode potential, net reactions…. 6.Quantitative analyses to empirical formula 7.What happens if X + Y(xs) (don’t balance) Danish university, large classes (7.5 ECTS) September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 3

A chemical reaction scheme Balancing (recall of algorithms) Cr 2 O Cl - Cr 3+ + Cl 2 (g) stoichiometry or Predicting (recall of principles) Be 2+ aq + nOH - ? possible reaction September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 4 acid

Balancing 1.Oxidation states of individual elements – recall rules 2.Oxidation state changes? – typically only two elements 3.Oxidation state change balance 4.Sum of charges 5.Charge balance – typically add H + or OH - 6.How many atoms on each side 7.Atom balance – typically water September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 5

Predicting 1 A+B→ ? 1.Recall types of reaction – acid-base reaction – redox-reaction – precipitation reaction – complex formation 2.Identify property of components – acidic or basic – oxidising or reducing – solubility – ligand or central ion September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 6

Predicting 2 A+B→ ? Predict possible type(s) of reaction – acid-base reaction – redox-reaction – precipitation reaction – complex formation State formula of products September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 7

Predicting 3 A+B→ ? In each of the following cases: which reaction type(s) 1.Reagent A in excess relative to reagent B 2.Reagent A and reagent B equivalent 3.Reagent B in excess relative to reagent A September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 8

Predicting 4 A+B  ? To what extent do reactions occur? – Balance relevant reaction scheme – Convert amounts (in g) to amounts (in mol) – Look up relevant equilibrium constants – Calculate final concentrations Speed of reaction (qualitatively) – Slow or fast – Chain reaction September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 9

Water Nitric acid Ammonia Hydrochloric acid Sodium hydroxide Some ordinary chemicals (names only!) Copper (-wire) Gold (-foil) Aluminium (-foil) Iodine Sodium hydrogen sulphite Silver nitrate Calcium carbonate September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 10 What happens if you mix this and that ?

Qualitatively Translate names into formula Type of reaction : identify reagent type – properties of components Extent of reaction – equilibrium Speed of reaction – reactivity (kinetics) September, 1st BremenEurovariety in Chemistry Teaching11

Quantitatively Amounts given (in g or % solution): calculate initial amounts in mol balance relevant equations look up relevant equilibrium data calculate final amounts of products concentration of components in solution September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 12

Nitric acid and Ammonia Different things may happen under different conditions Interactive programme (not fancy, nor corny, actually old-fashioned) September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 13

The question September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 14

Click on left bottle September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 15

Mouse over concentration September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 16

Click on concentration September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 17

Click on Yes (to the left) September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 18

Unfolding the question September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 19

Click on acid-base reaction September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 20

Click on Help (4) September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 21

Click Help (9) in Answer September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 22

Back to reaction types September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 23

Redox reaction of NH 4 NO 3 September, 1st BremenEurovariety in Chemistry Teaching24

Toulouse 21 Sept t fertilizer (NH 4 NO 3 ) September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 25 imagine what happened with 2300 t ammonium nitrate in Texas City harbour area m

Fertiliser - Explosive Anfo – cheap commercial explosive Terrorist’s favourite bomb? September, 1st BremenEurovariety in Chemistry Teaching26

Nitric acid and Ammonia Different things may happen under different conditions 1 hour unfolding in class or 1 hour working with the programme in pairs September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 27

Results Open-ended questions of this type are too hard in the first place Instruction helps : – Activation of previous knowledge and skills – Demonstration of why recall of algorithm training is useful – Demonstration of predictive power of (sub-) microscopic models thinking Appreciation of approach – Helpful approach to attack problem – A new way of thinking and learning September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 28

Problem solving sessions to get problems solved or to learn something by solving problems September, 1st BremenEurovariety in Chemistry TeachingJens Josephsen 29