Let's build a sandclock
What you need:
What you need:
two bottles
dry sand
tape
a nail
How to do it:
How to do it:
We take two bottles and fill one of them with sand.
Then close one bottle with a tape and pierce a little hole with a nail.
After we take the empty bottle and stick the two bottles together.
Turn the bottle and see how the sand trickles down...
