1. Kindergarten No 240
Warsaw, Poland
Density, surface tension,
properties of liquids

2. Floating, sinking paper clip
Make sure you’re in a place where it’s ok if water spills, prepare some paper
towels.
You will need:
A soup plate, a paperclip, liquid soap or dishwashing soap, tap water

3. Procedure
Fill up the soup plate with
water. Hold your paperclip
flat against the edge of the
cup and carefully slide it
Conclusion
toward the middle of the cup. The surface tension of water is
The paperclip should be strong enough to even support
floating on top of the water. a paperclip. When you put the
Put a drop of liquid soap into soap into the water, it disrupts
the order of the water
the water. Your paperclip will
molecules. The surface
sink. tension isn’t strong enough to
support the weight of the
paperclip, so the paperclip falls
into the water just as quickly
as if you had dropped it into
the soup plate.

4. Why the boat is made of steel float
on water when a bar of steel sinks?
You will need:
A soup
plate, plasticine (a type
of modeling clay) , tap
water

5. Procedure: Conclusion:
Fill the soup plate with cold tap The clay ball sinks in the water. The same
water. Separate two walnut-size amount of clay, when formed into the shape of
a boat, floats on the surface of the water.
pieces of clay. The pieces should
Different phisical phenomena, including
be of equal size. Roll one of the density, buoyancy, and surface tension, explain
clay pieces into a ball. Carefully the floating and sinking of objects. The average
place the clay ball on the surface of density of a boat -- the combination of the
the water in the bowl. Remove the steel and the air -- is very light compared to the
clay ball from the water and set it average density of water. So very little of the
aside. Take the second piece of boat actually has to submerge into the water
clay and form it into a boat. Gently before it has displaced the weight of the boat.
In other words the boat floats because it takes
place the clay boat on the surface
up more space than the clay ball of equal
of the water. weight; thus, it has a lower density. Buoyancy
is this upward water pressure pushing on the
bottom of the boat that is causing the boat to
float. Objects with a density lesser than water
will float. The weight of the water displaced by
an object is equal to the buoyant force exerted
by the water on the object. The larger-size clay
boat displaces more water, making it more
buoyant than the smaller clay ball of equal
weight.

6. A festival of color
You will need:
A soup plate, whole milk, food dyes, dishwashing soap, cotton swabs.
Procedure
Pour milk in the soup plate. Add a few drops of food colorings of your choice.
Now submerge a cotton swab in dishwashing soap. Touch the soapy end of the
cotton swab in the middle of the dyes in milk and hold it there for 10 to 15
seconds.

7. Conclusion
Milk contains fat. Dishwashing soap
repels fat molecules (the same is
happening when we wash the dishes).
Fat is "pushed aside". Along with fat
molecules food coloring dyes also move.

8. How to make oil ran away?
You will need
A soup plate, water, cotton swabs, dishwashing soap, cooking oil.
Procedure
Pour water into a plate. Add a few drops of cooking oil. Submerge a cotton
swab into dishwashing soap and touch a surface of the water near the
cooking oil. At first oil will rush to the outer edges of the plate. After some
time it will stop moving.

9. Conclusion
When you add detergent to water the surface tension of the water is lowered.
Detergent (also water, oil and everything else) is build from small particles
called molecules . Detergent is attracted to both water and oil helping them all
join together. In other words dish soap like water and oil. Imagine a molecule of
detergent as a piece of string. One end like water, other end like fat. The end of
the detergent molecule which attaches to fat tries to avoid being around water
molecules (water fearing). By attempting to move away from the water
molecules, the part of molecule which "like" fat ends is pushed up to the
surface. The result is a break in the surface tension of the water. It is very handy
when we wash the dishes with dish soap.