How meals are cooked faster in a pressure cooker ?

                                         A pressure cooker is like a pot but with a more elaborated lid that seals the pot completely. Heat water inside the pot, it boils and the steam cannot escape.So it remains inside and the pressure is increases. Under pressure cooking temperature raise much higher than under normal condition. So the food is cooked much faster.

How Soap Clean ?

                           Substance which can be dissolved in water and others that cannot. For example water and oil. water and oil do not mix together. So we try to clean oil stain from a cloth or hand water is not enough. So we need a soap.
                           Soap is formed by a molecules of hydrophilic and hydrophobic. So that soap molecules act like a diplomat, and improving the relation ship between water and oil.

How?
                    When soap is added to the water

• The hydrophilic heads of molecules stay into the water.
• The long hydrophobic chain join the oil.

                      Then they formed circular groups named micelles, with the oil material absorbed inside and trapped. An emulsion of oil in water is then formed after that the oil particles becomes suspended and dispersed into the water. Soap cleans by acting as an emulsifier. It allows oil and water to mix. So that oily grime can be removed during rinsing.

Thrust :

                  All aero planes with engines and all rockets depend on thrust. Thrust makes them move forward. They push large amount of air or other gases in one direction. This makes the aircraft fly in the other direction. Now you can see how thrust work in these experiments with balloons.

Things need :

o   Long balloon

o   Heavy paper

o   Tape

o   Felt-tipped pens

Uncontrolled flight :

   v  Use felt-tipped pen to decorate the balloon as an aero plane if you like. It is easier to draw on the   balloon if you blow it up first. Do not tie it shut. Tie it round a matchstick or a pencil.

   v  Cut wings from the heavy paper. Tape them to the Centre top of the plane.

   v  Remove the matchstick or pencil. Blow the balloon up as full as you can. Let it go. Thrust will make it fly around the room in a series of loops and turns until it runs out of air. 

Make the lemon peel dive :

Things need :

    §  Piece of balloon

    §  Lemon peel

    §  Broad mouthed bottle or rubber band

    §  Water

Instruction :

v  Fill the bottle with water till the brim.

v  Put a peel or lemon in the shape of a boat in water.

v  Stretch the piece of balloon on the mouth of the bottle and with the rubber band seal it in place on the mouth of the jar. The balloon should be slightly stretched. It should not sag.

v  Using you finger gently press down on the lid (balloon cover ) and the lemon peel will dive to the bottom of the jar.

v  Release you finger the lemon peel will return to the top of the jar.

Why ?

              The pressure exerted by hand squashes air bubbles in the lemon peel allowing the water. This makes the lemon peel heavy and sink. When the finger is released the air in the lemon peel expands and returns to the top.

Bring the balls together :

Things need :

   §  Ping pong balls

   §  Table

   §  Straw

Instruction :

            ·         Place the ping pong balls a short distance a part on a table.

            ·         Use the straw to blow air between them. The ball move towards each other.

Why ?

                   Air presses on all things. This is called air pressure. When you blow between the ping pong balls, you blow away the air that is between them. This means that air is no longer presses against one side of each ball. But air still presses against the other sides of the balls, and that air pressure pushes the ball together.

Make the paper rise :

Things need :

v  A piece of paper

Instruction :

•    Hold a piece of paper by the corners of edge.
•    Bring it up to your mouth. The paper will droop towards the floor.
•    Blow gently across the top surface of the paper. Does the paper still droop.
•    Take a deep breath and blow harder.
•    The paper rise. Before you blow, the air on both the sides of the paper is still.

§                                                    The pressure is same on both the sides. When you blow over the upper surface, the pressure on the side is reduced. But the pressure underneath is the same as before. The higher pressure underneath forces the paper up. Blowing harder reduces the pressure on the upper surface even more.  This makes the paper rise even higher.

Why water won’t run through the bottle ?

Things need :

            ·         Glass jar with narrow neck

            ·         Funnel

            ·          plasticine

            ·         Screwer

            ·         Water

Instruction :

                 Position a funnel in the neck of the jar.

                 Seal it tightly with plasticine.

                 Fill the funnel with water.

The water cannot flow into the jar. Now  make a hole in the plasticine , the water flow into the jar because the pressure is same inside and outside of the jar.

( i.e ) why you need to make a holes before you can pour liquid from a tin.