Unit 6 Matter as Particle

Topic

The magic coke

Curriculum Link

5.3 The water cycle: evaporation
6.2 Illustrations for the support of the claims of the particle theory: particle spacing
6.5 Density

Estimated Lesson Time

80 minutes

Introduction

In this activity, students are expected to explain the phenomena of sinking and floating with reference to what they have learnt about density and evaporation of solution. In other words, this activity serves as a consolidation exercise for students to apply their scientific knowledge in a new context.

Different schools would adopt different teaching sequences for the Junior Science Curriculum. For those schools which teach Unit 5 first and then Unit 6, teachers can use Worksheet 1 when they teach the concept of density. For those schools which teach Unit 6 first and then Unit 5, teachers can use Worksheet 2 when they teach the concepts of boiling and evaporation.

Key Question

Why do the cokes react differently?

Learning Objectives

In this activity, the students should be able to

  1. apply the concept of density to explain the sinking and floating of cokes (SP 1);
  2. explain the density of cokes with reference to the sugar content;
  3. design an alternative approach to compare the sugar content of two cokes (SP 3 & SP 4);
  4. represent the particle arranged of a complex system which consists of solid, liquid and gas.

Teaching Plan for Worksheet 1

Task (Time) Brief Description Materials Objectives

Engagement &
Explanation
(20 min)
  • Teacher prepares two plastic bottles of cokes (A: diet coke; B: regular coke) with equal volume (500ml) but don't let the students to know the difference of two bottles. Then, teacher drops these two bottles into a tank of water and engage students to explain the phenomenon (refer to Q1 and Q2).
  • The two bottles are wiped dry by a towel and their masses are measured by electron balance (Q3). Teacher guides students to
    • compare their masses
    • describe the meaning of volume and mass
    • explain sinking and floating with reference to the volume and mass
 (1) & (2)

Exploration
(20 min)
  • Students explore how addition of sugar affects the sinking and floating of bottle.
  • Teacher measures certain amount of sugar in front of the class (The amount of sugar added depends on the volume and brand of coke used in the demonstration. The added amount should make the bottle sink) (Q4).
    • Ask students to predict the new mass with reason if the measured sugar is added into bottle A.
    • Add large amount of sugar into the bottle.
    • Ask students to make observation on the position of bottle A and refine the explanation based on 2(c).
    • Asks students to explain any change in the coke volume as to remind students about the conservation of mass.
  • Teacher concludes that sinking and floating of cokes are related to its density which is influenced by the sugar content.
 (1) & (2)

Engagement & Explanation
(20 min)
  • Students explore an alternative to compare the sugar content of the two cokes (by evaporation) in addition to the above method (Q5).
  • Students design and conduct the experiment (Q6-Q8).
  • Students try to draw the particle arrangement in a complex system which consists of solid, liquid and gas (Q10).
  • Teacher evaluates students' application of evaporation for comparing the sugar content.
(3) & (4)

*Apparatus and materials required:

Teaching Plan for Worksheet 2

Task (Time) Brief Description Materials Objectives

Engagement &
Explanation
(20 min)
  • Students explore how evaporation can be used to compare the sugar content of the two cokes. They need to design and conduct the experiment (Q1-Q5). Teacher evaluates if students can apply the concepts of evaporation.
  • Students try to draw the particle arrangement in a complex system which consists of solid, liquid and gas (Q6). Teacher evaluate whether students can distinguish the different states of matter.
 (3) & (4)

Exploration
(20 min)
  • Teacher evaluates if students can apply the concepts of density to compare the sugar content (Q7).
  • Teacher prepares two plastic bottles of cokes (A: diet coke and B: regular coke) with equal volume (500ml) but don't let the students to know the difference of two bottles. Then, teacher drops these two bottles into a tank of water. Students explain the phenomenon (refer to Q8).
  • The two bottles are wiped dry by a towel and their masses are measured by electron balance (Q9). Teacher guides students to:
    • compare their masses
    • describe the meaning of volume and mass
    • explain sinking and floating with reference to the volume and mass
 (1) & (2)

Engagement & Explanation
(20 min)
  • Students explore how the sugar affects the sinking and floating of bottle.
  • Teacher measures certain amount of sugar in front of the class (The amount of sugar added depends on the volume and brand of coke used in the demonstration. The added amount should make the bottle sink) (Q 10).
    • Ask students to predict the new mass with reason if the measured sugar is added into bottle A.
    • Add large amount of sugar into the bottle.
    • Ask students to make observation on the position of bottle A and refine the explanation based on 9(c).
    • Asks students to explain any change in the coke volume as to remind students about the conservation of mass.
  • Teacher concludes that sinking and floating of cokes are related to its density which is influenced by the sugar content.
 (1) & (2)

*Apparatus and materials required: