Lesson No: 1 Unit Title: Simple Chemical Reactions
 Lesson 2 Lesson 3 Lesson 4Lesson 5 

 

Unit No: 7Fa

Lesson Title: Getting a Reaction

NC Ref:3-5

Objectives:

MX —colour changes, evolution of gases and heat changes are criteria for deciding whether a reaction has occurred; chemical reactions result in the formation of new substances; chemical reaction, physical change.

SK —chemical reactions generally irreversible; physical changes usually reversible; chemical reactions can be useful or harmful; e.g.s of chemical reactions; some chemical reactions happen as soon as two chemicals are mixed, others need an energy input to start them off; reversible, irreversible, permanent.

CK — how to classify a range of different reactions as useful or harmful

 

Lesson outline:

Starter: Pupils either discuss meanings of reversible and irreversible

Heat lard and fry an egg. discuss that lard is a reversible (physical change) (melts then freezes) and the egg is irreversible. (chemical change)

 

Discussion of ideas — link in to chemical I physical changes.  DEMO — Lead nitrate solution + potassium iodide —+ yellow ppt.  Zinc in dilute hydrochloric acid —‘ fizzing of hydrogen (get someone to touch the reaction vessel to confirm heat given off)

 

Summary of ideas into books (page 66 Exploring Science 7) — by

 

dictation or by answering purple box questions 3 & 4.

 

PRACTICAL:

 

Introduce investigation into whether reactions have happened and if the

 

 change is reversible or irreversible, physical or chemical. Reasons for

 

 decisions are as important as the decision.

                      

E.g.s, chemical change = colour, heat, gases made, permanent.                                                                                  

                      

I. lemon juice i- bicarbonate of soda (chemical reaction, irrev)

 

2. baking power + water (chemical, irrev)

 

3. plaster and water (Ensure not too much water).

 

4. zinc oxide heated (physical, reverses on cooling)

 

5. iron wool + copper sulphate solution (chemical, irrev) water -

 

6- anyhydrous copper sulphate (can be regarded as chemical change in

 

 this lesson — but can be reversed by heating).

 

There is a worksheet,  7Fa/1but annhydrous copper sulphate is unavailable

 

and extra experiments are available.

 

 

PRACTICAL WORK — record results

 

Clear up

 

 

 Timing:

5 mins

 

10 mins

 

10 mins

 

25 mins

 

 

 

10 mins

 

 

 

 

Resources:

Potassium iodide, lead nitrate, zinc, hydrochloric acid.

Worksheets 7Fa/l for less able, 7Fa/2 for those competent in recording results

Homework:

Reinforcement of ideas using worksheets 7Fa3 and 7Fa4 (different levels of difficulty)

Classifying reactions as useful or harmful - worksheet 7FaJ5

 

Risk Assessment:

Lead nitrate toxic, copper sulphate is harmful, plaster substitutes can get hot

 

 

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