Discrepant Events

Discrepant events are occurrences which defy our understanding of the world by presenting unexpected outcomes. These phenomena are often used in science demonstrations to grab the attention of an audience and engage visual learners, particularly young children. Always encourage students to discuss what will happen before the experiment takes place. Allow them to convince themselves they know what will happen before surprising them with a discrepant event.

Here are some of the discrepant events which I have showed in the class.

1.Disappearing Penny:-
Procedure:- In this experiment first we take penny and then we put it in a glass and then we pour water into the glass.
Concept:- The trick behind the Disappearing Money experiment is the refraction of light. When we poured water into the glass, it was as though the penny had disappeared, but it was really just some bending light rays. After traveling through the water and the side of the glass, none of the rays were able to reach our eyes. Refraction occurs because of the molecules in the substance such as water, the refraction is greater because the molecules are closer together. So when the light rays are traveling from the money through the water, they are refracted and cannot make it to our eyes.

2.Water walking on string:-
Procedure:-

1.    Cut a 2' long segment of the string
2.    Fill one cup about halfway with water
3.    Soak the string in the water for 10 seconds or until it is soaked through
4.    Put one end of the string into the cup with water and hold the other end above the empty cup
5.    Hold the cup with water up, using your pointer finger to keep the string at the bottom of the rim as you turn it towards the empty cup
6.    Pour the water slowly along the string… watch as it clings to the string and drips off the end into the empty cup.
Concept:- Water has some special properties, making it a very unique substance. It has both strong “cohesive” and “adhesive” properties. What this means is that water can stick to itself (cohesion) and other things (adhesion). This goes down to the molecular level in how a water molecule looks: it has two hydrogen atoms and one oxygen atom. These atoms end up having positive and negative charges, which cause them to stick to one another. And  it makes a stream of water as it flows down the string in this experiment!
At first, we soak the string in the water, and the water adheres to it. Even though water may drip out of it, it is still soaked in there. That is adhesion. When you pour water along it, you notice the water clings to other water molecules attached to the string, and you see it form a little stream underneath the string. That is cohesion.

3)  Piercing potato:-
Procedure:-
The challenge is quite simple: Stab the straw through the potato without bending or breaking the straw.
As you hold the potato, keep your fingers on the front and your thumb on the back and not on the top and bottom.cap the top end with your thumb.
Concept:- The real secret is inside the straw—it’s air. Placing your thumb over the end of the straw traps the air inside. When you trap the air inside the straw, the air molecules compress and give the straw strength, which in turn keeps the sides from bending as you jam the straw through the potato. The trapped, compressed air makes the straw strong enough to cut through the skin, pass through the potato, and exit out the other side. Without your thumb covering the hole, the air is simply pushed out of the straw and the straw crumples and breaks as it hits the hard potato surface.

4)  Running pepper:-
Procedure:-
1.    Fill the bowl or pie tin with about an inch of water.
2.    Sprinkle pepper evenly across the surface. Try not to sneeze! The pepper flakes should float, not sink, upon the surface of the water.
3.    Squeeze a tiny bubble of dish soap onto a clean counter.
4.    Touch the tip of the toothpick to the bubble of dish soap. You'll want just a tiny amount of soap on the end of the toothpick.
Concept:- Pepper is hydrophobic, meaning that water is not attracted to it. Because of that, the pepper can't dissolve in the water.Water molecules like to stick together. They line up in a certain way that gives the top of the water surface tension. Because pepper flakes are so light, and hydrophobic, the surface tension keeps them floating on top.Soap is able to break down the surface tension of water—that’s part of what makes soap a good cleaner. As the soap moves into the water, and the surface tension changes, the pepper no longer floats on top. But the water molecules still want to keep the surface tension going, so they pull back away from the soap, and carry the pepper along with them.

5)  Glass resonance:-
Procedure:- Take one glass. Put little water into it. Dip your two fingers into the water. And then rub your fingers around the rim of a glass. And then keep on increasing the level of water.
Concept:- As your finger travels around the glass it sticks and slides at different points. Each stop and start causes the glass to vibrate. These vibrations are at the natural frequency of the glass which is a complex function of its mass and shape. This is why adding the water lowers the pitch.