(1) Try floating a sewing needle on water. In order for this activity to work, the needle needs to be very clean as even the oilfrom your fingers can be sufficient to affect the surface properties of the needle. (2) Place the bristles of a paint brush intowater. Pull the brush out and notice that for a short while, the bristles will stick together. The surface tension of the watersurrounding the bristles is sufficient to hold the bristles together. As the bristles dry out, the surface tension effect dissipates.(3) Place a loop of thread on the surface of still water in such a way that all of the thread is in contact with the water. Notethe shape of the loop. Now place a drop of detergent into the middle of the loop. What happens to the shape of the loop?Why? (4) Sprinkle pepper onto the surface of water. Add a drop of detergent. What happens? Why? (5) Float two matches parallel to each other and add a drop of detergent between them. What happens? Note: For each new experiment, the waterneeds to be replaced and the bowl washed to free it of any residual detergent.
(1) Try floating a sewing needle on water. In order for this activity to work, the needle needs to be very clean as even the oil
from your fingers can be sufficient to affect the surface properties of the needle.
(2) Place the bristles of a paint brush into
water. Pull the brush out and notice that for a short while, the bristles will stick together. The surface tension of the water
surrounding the bristles is sufficient to hold the bristles together. As the bristles dry out, the surface tension effect dissipates.
(3) Place a loop of thread on the surface of still water in such a way that all of the thread is in contact with the water. Note
the shape of the loop. Now place a drop of detergent into the middle of the loop. What happens to the shape of the loop?
Why?
(4) Sprinkle pepper onto the surface of water. Add a drop of detergent. What happens? Why?
(5) Float two matches parallel to each other and add a drop of detergent between them. What happens? Note: For each new experiment, the water
needs to be replaced and the bowl washed to free it of any residual detergent.
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