Dancing snowflakes

Watch the snowflakes dance!

Warn­ing! Only un­der adult su­per­vi­sion

Equip­ment

  • glass with stem;
  • wa­ter;
  • bowl;
  • salt;
  • cling film;
  • snowflake sten­cil.

Step-by-step in­struc­tions

Fill a glass about half­way with wa­ter, then moist­en your fin­ger and run it light­ly along the rim of the glass – it will make a sound! Now set a bowl about lev­el with the glass and stretch some cling film over it. Pour some salt onto the re­sult­ing mem­brane through a sten­cil. Set the glass next to it and run a damp fin­ger light­ly along the rim of the glass once more. You'll see the grains of salt bounc­ing across the film!

Sci­en­tif­ic de­scrip­tion

When you run your fin­ger along the rim of the glass, your fin­ger en­coun­ters re­sis­tance to its move­ment due to fric­tion. How­ev­er, at some point, the wa­ter on your fin­ger forms a cush­ion that re­duces fric­tion, al­low­ing your fin­ger to slide along. Thus, its move­ment is in­ter­mit­tent and caus­es the glass to vi­brate. The walls of the glass trans­mit the vi­bra­tions to the sur­round­ing air, cre­at­ing sound waves. They are also trans­ferred to the mem­brane on the bowl, caus­ing it to vi­brate as well. The vi­bra­tions of the mem­brane ag­i­tate the grains of salt. This al­lows you to see the sound!

Cool ex­per­i­ments await you in the MEL Sci­ence sub­scrip­tion.

Try it