# Practical exercise 3: MAKE A CANDLE CLOCK

## Tools

• thick candle,

• small metal balls (diameter up to 0.5 cm),

• PET bottle,

• thin nail,

• matches, photo bowl, marker, stopwatch,

• watch or mobile phone.

## Process

1. Make a candle clock. Mark a regular scale with a marker on a vertical candle.

2. Light the candle and measure the speed of the candle burning according to the scale: first measure the times after which the individual divisions of the scale burn.

3. Record the measured values in a table (see below).

 Measurement number Time Burnt length

4. Draw a graph of the dependence of the burning length of the candle on time. Draw a line connecting the marked points in the graph. Determine from this line the burnt length of the candle per unit time.

5. Mark another scale on the next (same) candle (or on several other identical candles) according to the results of the previous measurement. Push small metal balls into the individual marks. When the candle clock burns, gradually, as the material of the candle melts, the balls will fall off, for example, onto a porcelain base, and thus they will mark the individual time intervals.