Understanding The Atom

Source: http://www.youtube.com/watch?v=T6UujimddEc

The atom is the fundamental building block of matter. An atom consists of three main parts: protons, neutrons, and electrons. Protons have a positive electrical charge. Neutrons have no electrical charge. Electrons have a negative electrical charge. Protons and neutrons are found together in what is called the nucleus of the atom. Electrons circle around nucleus. Chemical reactions involve interactions between the electrons of one atom and the electrons of another atom. Atoms which have different amounts of electrons and protons have a positive or negative electrical charge and are called ions. When atoms bond together, they can make larger building blocks of matter called molecules. Here are some useful facts about atoms:

• Atoms cannot be divided using chemicals. They do consist of parts, which include protons, neutrons, and electrons, but an atom is a basic chemical building block of matter.
• Each electron has a negative electrical charge.
• Each proton has a positive electrical charge. The charge of a proton and an electron are equal in magnitude, yet opposite in sign. Electrons and protons are electrically attracted to each other.
• Each neutron is electrically neutral. In other words, neutrons do not have a charge and are not electrically attracted to either electrons or protons.
• Protons and neutrons are about the same size as each other and are much larger than electrons.
• The nucleus of an atom contains protons and neutrons. The nucleus carries a positive electrical charge.
• Electrons move around outside the nucleus.
• Almost all of the mass of an atom is in its nucleus; almost all of the volume of an atom is occupied by electrons.
• The number of protons (also known as its atomic number) determines the element. Varying the number of neutrons results in isotopes. Varying the number of electrons results in ions. Isotopes and ions of an atom with a constant number of protons are all variations of a single element.
• The particles within an atom are bound together by powerful forces. In general, electrons are easier to add or remove from an atom than a proton or neutron. Chemical reactions largely involve atoms or groups of atoms and the interactions between their electrons.

Calculating Average Velocity or Speed

This video taken from Khan Academy presents an illustrated explanation to calculate average velocity or speed. The Khan Academy is a not-for-profit organisation that aims to improve the approach to presenting a concept primarily through the use of videos. These videos as well as other materials and resources are freely available for your use. Among others, their video library also covers areas such as K-12 math, biology, chemistry, physics, finance and history. Each video is presented in digestible chunks of 10 minutes and is designed to be viewed via the computer. In addition, the Khan Academy also provides statistics on what you have learned and the videos you spend most time viewing.

In the Table below critique the three visuals on biology, chemistry and physics by inserting a (+) or a (-) against each one of the six recommendations of UNESCO on teaching good science. A (+) indicates that video has met the expectations of the recommendation and a (-) indicates that it has not.