class 6-8

Optical illusions are visuals that tend to be deceptive to the eye and brain.

The phenomenon of floatation is based on the density of the object and the fluid in which it is placed. If the density of the object is less than the density of the fluid, it will float. Conversely, if the density of the object is greater than the density of the fluid, it will sink 

Water expands in volume as its temperature rises. The extra volume caused by thermal expansion must go somewhere. If not, the heated water creates an increase in pressure.

The burning candle heats the air inside the container and this hot air expands quickly. When the flame goes out, the air cools down and creates a weak vacuum or lower pressure inside the glass. On the other hand, the air outside the glass remains the same. This creates a difference in air pressure which results in the water rising inside the glass.

Two identical balloons are inflated to different diameters and connected by means of a tube. A valve controls the flow of air through the tube. When the valve is opened, air will flow from the balloon at higher pressure to the balloon at lower pressure. The lower pressure balloon will expand. The smaller balloon has the higher pressure. So, when the valve is opened, the smaller balloon pushes air into the larger balloon. It becomes smaller, and the larger balloon becomes larger. The airflow ceases when the two balloons have equal pressur

This amazing experiment works on surface tension. Surface tension is a thin sheet or skin formed by water. Surface tension tightly holds the water molecules together. Thus, if the surface tension of the water remains undisturbed, it will be able to support the paper clip. Thus, the paper clip is not actually floating, it is simply being held on the water surface due to surface tension. Several insects such as grasshoppers and water spider use this “sheet” to walk across water.

The surface tension of water molecules actually allows water molecules to bond together enough to help keep the water from leaking out of the holes in the bottle. With the help of the surface tension, and the difference of air pressure outside of the bottle and inside the bottle is why the water does not leak out of the bottle.

1. Drop the Clip :  A paper clip on the surface of water will float but if you add a drop of soap in water it sinks because the soap breaks the surface tension of water.
2. Soap Powered Paper Boat: A paper water boat can be made to move in water using soap drops as it will break the surface tension and water molecules force the boat to move.
3. Do Not Open: When we make holes in a plastic bottle full of water, the water does not drip out as surface tension holds the water but if we open the cap of the bottle, air pressure from top makes the water drip.
4. Poke Me Not: In a plastic bag full of water, many pencils can be put through without making the water drip because of the same phenomenon.
5. Milk Rainbow: When we add some food colour drops in milk and add soap, the milk molecules move around making the colour spread and giving rainbow like effect.
6. Poke the Pepper: When we add a drop of soap in a water bowl filled with pepper, the pepper moves around because the surface tension of the water breaks.
7. Terry Triangle: The same happens when we make a shape using some toothpicks in water, on adding soap, the toothpicks move around.
 

 According to Newton’s third law of motion, the walls of the balloon will exert an equal and opposite reaction force on the air molecules inside the balloon. This reaction force causes the balloon to expand and become inflated.