What it shows
Water is lost through sweat, breath and urine, and has to be replaced by drinking and by the water in food. A diary of how much students drink shows the range between individuals and how heat affects it.
The science
The body loses water as sweat to cool itself, as water vapour in breath, and as urine. On hot days we lose more. Thirst tells the body when it needs more water. The diary records volumes, and a mean helps find the usual range for a class.
Materials
Cost: free. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- Water bottles with measurement marks drawn on the side
- A diary table sheet
- A thermometer for classroom temperature
- Graph paper
- A calculator
- Teacher permission
Safety
For this project: Do not ask anyone to drink more or less than they wish. This project gives no health advice; persistent thirst or dehydration signs need a doctor.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Mark each bottle at 100 ml intervals with a permanent marker.
Ask volunteers to note the volume of water they finish at school each day.
Record the classroom temperature at noon every day.
Make a table of the volume drunk and the temperature each day for each volunteer.
Calculate the class average for each day.
Draw a line graph with the temperature and the average volume on the same day axis.
Look for a pattern between hotter days and larger volumes.
Write a short report with the range, the average and the possible reasons for differences.
What you should see
A graph of the class’s average water intake each day, usually higher on hotter days, and a range that shows people differ.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1How does the body lose water?
Through sweat, breath, urine and faeces.
2Why do we sweat?
Evaporation cools the body.
3Why mark bottles in 100 ml steps?
To measure how much water was drunk accurately.
4Why is a class average not advice for one person?
Each person’s needs depend on age, size and activity.
Take it further
Compare the diary on a sports day with a normal day.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
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