Theory:

Pascal's law:
Pascal's law states that pressure applied at any point in a liquid at rest enclosed in a closed system, will be equally distributed through all regions of the liquid in the closed system.
You can understand this with an experiment involving two syringes connected to each other with a rubber tube.
Fill one of the syringes with liquid and connect them with the rubber tube. Apply pressure to the syringe with liquid by pressing it upwards, the piston in the other syringe will move downwards slightly and the liquid will start filling inside the other syringe.
syringe.png
It is understood that,that pressure applied at any point in a liquid enclosed in a closed system, will be equally distributed through all regions of the liquid in the closed system.
  
Most important applications of pascal's law:
  
Hydraulic lifts where the pascal's law is used to lift the entire car to a certain height by applying pressure on the other side of the piston.
 
A device that operates on the principle of  pascal's law (the pressure in the liquid is distributed evenly in all directions) is a hydraulic press (jack). It consists of two connected cylinders: one narrow, the other wide. The cylinders are filled with oil. When the piston is pushed into the narrowest cylinder, the pressure in the largest cylinder is as many times as the area of ​​the working piston is greater than the area of ​​the piston in the larger cylinder . That is if the area of working piston (S1) is 4 times greater than the area of piston in the larger cylinder (S2), the pressure in the larger cylinder will be quadrapled. Thus, for example, a person can lift the car with one hand jack .
 
per.jpg
Surface tension
Raindrops are spherical in shape. But rainwater in the streams and lakes is different. We know that liquids and fluids are shapeless.

Then how raindrops are spherical in shape?
It is because of surface tension. When the water molecules fall from the sky due to gravity they experience a contraction (tension) in their extent of the surface making it spherical in shape.
Surface tension can be defined as the amount of force acting per unit length on any liquid. It's unit is
Nm1.
An experiment where surface tension is involved:
 
Activity:
 
Try it at your home:
 
Take a plate and pour water in it. Now take pepper and sprinkle pepper all over the water poured. If you dip your finger alone pepper will stick onto your hand. Apply some soap in your finger and touch the water now, you can see the pepper will spread to the sides of the plate. This is because the water molecules want to keep its surface tension so they pull themselves away from the soap carrying the pepper along with it.
 
pepper.png
 
Some more applications of surface tension:
  • The capillary action of xylem tissues inside a plant.
  • Water strider insect walking on the surface of the water.