Chemistry Test

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Elements

Elements

All matter is made of atoms. There are over a hundred different types of atom, called elements, and each one has a symbol. The atoms of a particular element are identical to each other. Elements are represented by one or two letters. The first letter is always a capital and the second is always lower case.

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Atoms

Atoms

Atoms make up everything in the universe. Atoms consist of electrons surrounding a nucleus that contains protons and neutrons. Neutrons are neutral, but protons and electrons are charged. Protons have a positive charge, while electrons have a negative charge. The number of protons in an atom is called its atomic number. In the periodic table atoms are arranged in atomic number order.

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Compounds

Compounds

Compounds are substances that contain atoms of at least two elements chemically combined. For example: magnesium oxide consists of magnesium atoms and oxygen atoms chemically bonded together.

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Formulae

Formulae

A formula is a way of representing compounds, using a series of letters. To find a formula, you first find the elements in the compound. For example, there is 1 carbon and 2 oxygen in a carbon dioxide molecule. Then, you write both the symbols for the elements in the correct order. For example, CO2.

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Reactions

Reactions

Chemical reactions take place when 2 or more types of molecules join together. For example, by heating copper you make copper oxide.

A physical reaction is where a reaction takes place, but the molecules don't join. For example, boiling water.

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Equations

Equations

Equations are used when showing chemical reactions. For example, the equation for copper oxide is

Cu + O -> CuO

To write an equation you look at the compound name, for example carbon dioxide, and write the symbols for the element:CO. Then, look for prefixes like di and add in the correct number:CO2.

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Particle Diagrams

Particle Diagrams

Particle diagrams are a visual way of showing a certain element or compound. You draw different sized circles depending on how many protons they have. You then write the symbol of the particle in the circle.

(http://bio.libretexts.org/@api/deki/files/2722/oxygen_molecule,_O2.gif?size=bestfit&width=387&height=213&revision=1)

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Metals

Metals

  • Lustrous (shiny)
  • Hard
  • High density (are heavy for their size)
  • High tensile strength (resist being stretched)
  • High melting and boiling points
  • Good conductors of heat and electricity.
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