User Manual

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Doing the experiment

1. Join the two pieces of card

together by gently pushing the tabs

in the large piece into the slots in the

smaller piece. Pull the sides together

to make a three-sided shape and ﬁx with

sticky tape if necessary.

2. Stand the silver box on the ground in hot

sunshine so that the Sun’s rays shine into the corner.

Place a small piece of transparent plastics sheet in the

bottom (to prevent the condensed water drops damaging the cardboard). Put the black plastic

cup in the corner, on the plastic sheet.

3. Fill the cup with water

4. Examine the indicator. Pull the ﬁshing line through the holes until one washer is next to

the end cap at the opposite end of the tube to the wax. This end will be the bottom end of

the indicator.

5. Put the indicator into the water, making sure that the wax is at the top of the tube. Hang

the spare ﬁshing line over the edge of the cup.

6. Cover the whole cup with the transparent glass. The water will now start to be warmed by

the Sun’s heat. (You could put a weight (e.g. a stone) on top of the inverted glass so that its

rim is pressed ﬁrmly onto the plastic. This will prevent heat leaking away.)

7. Every half hour lift out the indicator and check the state of the wax. When the wax has

melted and run to the bottom of the tube, the water is hot enough

and has been pasteurized. You should be able to pasteurize the

cup of water in around two hours on a sunny day. You might

also see condensation inside the glass. The plastic

sheet will prevent the condensed water from

damaging the silver reﬂector cardboard.

Note: to use the WAPI again, simply slide

the transparent tube to the other end

of the ﬁshing line.

Warning: The solar-heated water could reach a temperature of 60 degrees Celsius (149 degrees

Fahrenheit) or more. Handle the heated water with care. Adult supervision is required.

In this experiment you purify water by a process called solar pasteurization. When water is

heated to 65 degrees Celsius (149 degrees Fahrenheit), dangerous micro-organisms in the

water are killed. Heat from the Sun is used to heat the water to pasteurize it. The experiment

involves the use of a simple device called a water pasteurization indicator (WAPI) to determine

if the water has been heated to the required temperature.

You will need: black plastic cup, silver card, the parts for making a Water Pasteurization

Indicator (WAPI), i.e. metal washers, ﬁshing line, transparent tube, transparent caps

and wax.

Also needed from home (but not included in kit): a tall glass that will cover the whole of the

black plastic cup. A small piece of transparent plastic sheet (e.g. kitchen food wrap).

Assembling the water pasteurization indicator (WAPI)

You need to assemble the WAPI before the experiment:

1. Push the wax into one end of the transparent tube.

2. Push the transparent caps into the tube.

3. Tie a washer to one end of the ﬁshing line.

4. Feed the other end of the line through the hole in one transparent cap and then through

the other transparent cap.

5. Pull some spare line through and tie a washer to the end.

E. EXPERIMENT 3 - SOLAR PASTURIZATION

2 2

Soft

Wax

65°C

8 9

Condensation

Transparent

plastics sheet

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