Activity Introduction

In this lesson, students learn about how sugar causes tooth decay, and then carry out an experiment to independently verify that information.

Students start with the information that while sugar does cause tooth decay, it’s the bacteria in our mouths that turns the sugar into acid, rather than because the sugar is directly acidic. Students then test that information with an experiment to check the pH of sugar in solution. As in the other lessons in this unit, the lesson ends with an opportunity for students to reflect on their learning; this learning in turn will feed into the science communication in the fourth lesson in this unit, Communicating the Science of Tooth Decay.


Learning Intentions

  • Students understand how to use a pH scale to check the acidity and alkalinity of a substance
  • Students understand how sugar relates to tooth decay
  • Students understand how to independently verify a scientific claim, and why that process is important.

Lesson & Curriculum Details

  • Topic: Consumption.
  • This lesson is part of the wider unit of work SugarByHalf – Science – Years 9-10.
  • Time required: 60 mins.
  • Level of teacher scaffolding: Medium – Facilitate class discussions, supervise experiments. 
  • Keywords: acid, base, alkaline, pH, ion, hydrogen, cavities, tooth decay, sugar, experiment, Australian Dental Association, SugarByHalf. 

To view our Australian Curriculum alignment click here.

To view our NZ Curriculum alignment click here.

Cool Australia’s curriculum team continually reviews and refines our resources to be in line with changes to the Australian and New Zealand Curriculums.

Resources Required

  • Bicarbonate soda or equivalent solution with a pH = 7.5
  • Cola
  • Data projector
  • Lactic acid solution or equivalent solution with a pH between 3.0 – 3.5
  • Litmus paper or universal indicator
  • Sugar and Dental Health factsheet
  • Sugar solution
  • Water


These lessons were developed in partnership with SugarByHalf and the Australian Dental Association.



Teacher Worksheet

Teacher Preparation

Learning Intentions: Students understand…

  • … how to use a pH scale to check the acidity and alkalinity of a substance
    … how sugar relates to tooth decay
    … how to independently verify a scientific claim, and why that process is important.

Success criteria: Students can…

  • … use indicators to test the pH of various substances
    … use experimental design to test a hypothesis
    … write a conclusion based on an experimental outcome
    … reflect critically on the practice of teaching and learning.

Teacher content information:

SugarByHalf ( promotes action to reduce sugar-related diseases so that we can live better, stronger and healthier lives.

Their message is simple: to reduce added sugar consumption by half. Eating too much added sugar is a key driver of serious health problems including obesity, type 2 diabetes, heart disease, tooth decay, dementia and mental health conditions. A poor diet also puts children behind their peer

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