Have you ever had a bad hair day? Did you happen to notice if the air was drier or wetter weather on those days? Usually folks have bad hair days when the air is drier, which is when static charge can build up more easily. Some folks notice every time they touch a doorknob, slide down a plastic slide, or scuff along the carpet in socks that they get zapped. Since there’s less water vapor in the air on drier days, there’s more of a chance for static charge to build up. The water molecule dissipates the static charge, and the more wet the air is (humid), the less static build up there is. Static electricity experiments are really hard to do on humid days, especially if it’s raining outside!
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Can you rub a balloon and stick it to the wall? Why does that work? The wall isn’t positively charged, is it?

No… the wall is not charged at all. It’s electrically neutral. However, when you bring a negatively charged balloon near it, two important things happen: the negative charge on the balloon repels the negative charges in the wall, pushing them further away. At the same time, the positive charges in the wall are attracted to the balloon and move toward it. The result is that the balloon sticks to the wall, and you have just moved charges around in the wall without even realizing it. Polarization means that you separate the charges in an object. The wall became polarized when you brought the balloon close to it.

Like charges repel and opposites attract.This happens in neutrally charged objects, like the yardstick in the electrostatic motor that you’ve done previously on this page. If the object is a conductor, like a metal, the charges move quickly from one side of the object to the other quite freely along the surface.

However if the object is an insulator, the electrons simply redistribute themselves within the atom, since the charges can’t move along the surface as they would with a conductor. The electrons live in an electron cloud that surrounds the nucleus of the atom, which normally is uniform and symmetrical. When an electrical charge is applied to insulators, that cloud will distort and become non-symmetrical as the electrons move in response.  In this way, insulators can be polarized.

Water is a polar molecule. In a molecule, the atoms stay together to form the molecule through bonds that are formed between the negative and positive charges on the individual atoms. For water, the oxygen  and hydrogen have a polar bond because the protons in one are attracted to the electrons in the other. The electrons are shared and their electron clouds overlap.

For water however, the electrons within the clouds are not equally shared which makes the electron cloud distorted, making one side of the water molecule more negatively electrically charged than the other. This makes water a polar molecule because the electron cloud is shifted more toward the oxygen than the hydrogen atoms.

When you bring a charged balloon near a thin trickle of water streaming from the faucet, the stream is deflected and sprayed by the presence of the balloon because the water molecules are polar and align to the balloon.

Just a quick tip: don’t mix up the concepts of polarizing and charging.  Charging is when there’s an imbalance of electric charge, like rubbing the balloon on your head. The balloon now has an excess number of electrons, so it’s negatively charged. Objects that are polarized have their charges separated either on the surface or within the atom itself. The overall charge of a polarized object is balanced (electrically neutral), even if the negative charges are at one end and positive charges are on the other.

Scientific Concepts for Atoms:

• All matter is made of atoms.
• An atom is the smallest part of stable matter.
• Atoms rarely hang out alone. They join together in groups from two to millions of atoms.
• Atoms are made of three basic particles. Neutrons, protons, and electrons.
• Neutrons and protons are together in the middle of the atom and make up the nucleus of the atom. Electrons move around the nucleus. They don’t “orbit” the nucleus. Next lesson we will talk more about how they move. It’s one of the wacky things about electrons.
• Atoms differ from one another by how many protons, neutrons, and electrons they have in them.
• Elements are specific kinds of atoms. Every atom is a type of element.
• There are over 112 elements. Ninety of which are found naturally. Twelve different elements are the major ingredients of over 90% of all matter. Five different elements are the major ingredients of all living things.
• Carbon, Hydrogen, Oxygen, Nitrogen, and Calcium are the five main elements that make up all living matter.
• Most atoms come from stars and have been around since the beginning of time.
• Atoms get used, and reused again and again as things change over time.

Scientific Concepts for Electrons:

• Electrons don’t orbit nuclei. They pop in and pop out of existence.
• Electrons do tend to stay at a certain distance from a nucleus. This area that the electron tends to stay in is called a shell.
• The electrons move so fast around the shell that the shell forms a balloon like ball around the nucleus.
• An atom can have as many as seven shells.
• The number of electrons an atom has determines how many shells it has.
• A shell can only hold so many electrons. The number of electrons a shell can hold can be determined by the formula 2n2 where n is the number of the shell.
• Atoms are “satisfied” if they have a full outer shell or if they have a multiple of eight electrons in their outer shell.
• If an atom is not “satisfied” it will gladly share electrons with other atoms forming molecules.

Click here to go to next lesson on Charging Methods.

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