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To challenge students to look below the surface.

by Oliver Harrison

Suitable for Key Stage 3


To challenge students to look below the surface.

Preparation and materials

  • You need three bottles of water – one pure water, one with salt and one with sugar (the salt and sugar dissolve better if the water is warmed, but allow it to cool before using in the assembly). Try to make the one with salt and the one with sugar as clear as possible, so that all three bottles look the same. However, they should also have a strong enough taste to be instantly recognizable for what they are!
  • Three (or multiples of three) drinking glasses (optional: drinking straws).
  • For information about salt, see
  • For information about sugar, see
  • A sachet of ‘Dioralyte’, or equivalent.
  • Information about oral rehydration therapy is available on
  • (Optional) A reader for the Bible reading: Matthew 5.13.


  1. Ask for volunteers to choose a bottle of water, and then taste it and report on its flavour and properties.

    Ask the students if there was any way that they could have told which was the pure bottled water apart from tasting it.
  2. Ask the students for other examples of instances when you cannot tell what is really ‘in the bottle’ and you might make the wrong assumptions.
  3. Ask the students if they know the role of water, sugar and salt in keeping us healthy or unhealthy.
  4. Ask if any of the students have ever drunk a liquid that tasted both salt and sugar?

    Show the sachet of Dioralyte and explain that it contains a powder consisting of sugars and salts. (Explain that water is the most important substance for health in the human body. Talk about the dangers of dehydration, which can be caused by vomiting and diarrhoea. In the 1950s it was discovered that a mixture of sugar and salt added to water could prevent death in anyone suffering from severe dehydration. Oral rehydration therapy, as this amazingly cheap and easy to administer treatment is called, saves the lives of millions of children a year in the developing world. In 1978, in an article in the medical journal Lancet, it was described as ‘potentially the most important medical advance of [the twentieth] century’.)
  5. End with Jesus’ saying about salt (Matthew 5.13):

    ‘You are the salt of the earth; but if salt has lost its taste, how can its saltiness be restored? It is no longer good for anything, but is thrown out and trampled underfoot.’

    Salt (but not too much salt) is vital for health. We all know that a little salt goes a long way and makes a big difference. Salt is also a preservative. Jesus was referring to rock salt, which was mined from close to the Dead Sea. This salt could lose its saltiness and was then useless.

Time for reflection

(Light a candle and pause)

Are you health-giving in your community today?

Think about how you could be pure water, bringing refreshment to thirsty people around you.

What will you be today?


‘Colours of day’ (Come and Praise, 55)

Publication date: April 2012   (Vol.14 No.4)    Published by SPCK, London, UK.
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