Do raisins float or sink?
It was our Science focus and the required items were FRESH RAISINS, GLASS, CARBONATED -CLEAR SODA.
The glass was filled half way with soda and then the kids dropped raisins into the glass…. They had to observe the experiment over a few minutes…..as the raisins quickly sank to the bottom after a few minutes the raisins started to float back up to the top of the glass and then quickly drop again to the bottom. Kids learned that bubbles form inside the raisin and the CO2-carbon dioxide makes the rain float to the top of the glass once the raisin gets to the top bubbles POP and causes the raisin to loose the ability to float.
I also took in very old raisins and tried the experiment out of 5 cups of experiments only one raisin floated to the top only once so my recommendation as lesson reads fresh raisins work best.
Carbon dioxide gas dissolved in soft drinks gives them their fizz. You can use the carbon dioxide fizz from a soft drink to make raisins dance.
For this experiment you will need:
- a
can of colorless soda (e.g., 7-Up or Sprite)
- a
tall, clear glass or plastic cup
- several raisins (fresh raisins work the best)
Pour the can of
soda into the tall glass. Notice the bubbles coming up from the bottom of the
glass. The bubbles are carbon dioxide gas released from the liquid.
Drop 6 or 7 raisins
into the glass. Watch the raisins for a few seconds. Describe what is happening
to the raisins. Do they sink or float? Keep watching; what happens in the next
several minutes?
Raisins are
denser than the liquid in the soda, so initially they sink to the bottom of the
glass. The carbonated soft drink releases carbon dioxide bubbles. When these
bubbles stick to the rough surface of a raisin, the raisin is lifted because of
the increase in buoyancy. When the raisin reaches the surface, the bubbles pop,
and the carbon dioxide gas escapes into the air. This causes the raisin to lose
buoyancy and sink. This rising and sinking of the raisins continues until most
of the carbon dioxide has escaped, and the soda goes flat. Furthermore, with
time the raisin gets soggy and becomes too heavy to rise to the surface.
You might want
to try other objects to see if they exhibit this behavior. Any object whose
density is just slightly greater than water’s and has a rough surface to which
the gas bubbles can attach should be able to dance in the carbonated water.
Some of the more common dancing substances are mothballs and pieces of uncooked
pasta. Try putting other objects in the carbonated water. Can you find other
substances that dance?
Carbonated
beverages are prepared by putting the beverage into a can under high pressure
of carbon dioxide gas. This high pressure causes the carbon dioxide gas to
dissolve in the liquid. When you open a can of soda, the noise you hear is
produced by the carbon dioxide gas as it rushes out of the can. When the can is
opened, the decreased pressure allows some of the carbon dioxide gas dissolved
in the liquid to escape. This is what makes the bubbles in a soft drink.
