Atoms, elements and compounds

• Which of these substances is carbon dioxide (CO2)?

  C

  
• How many types of atom are contained in an element?

  1
• Which of these substances contains a compound made up of exactly 2 different types of atom?

  B

  
• Which of the samples shown contains a mixture?

  D

  
• Aluminium is used for aircraft bodies primarily because it is reactive.
• Two elements are found together in a substance. They are not chemically combined. Is this substance an element, a mixture or a compound?

  Mixture
• Look at the table. What word completes label 1?

  Element

  
• Which 2 substances show pure elements?

  A and C

  
• Which of these substances is pure nitrogen (N2)?

  B

  
• An element is a pure substance that cannot be broken down into any other substances. An element is made from just one type of atom.
• A liquid element is when the particles are close together and arranged in a random way.
• A gas element is when the particles are far apart and arranged in a random way.
• Some non-metal elements are made from atoms which are bonded into clusters called molecules.
• A molecule is made up of two or more atoms. These can be the same type or different.
• A compound is a pure substance that is made from more than one element. In a compound, elements are chemically bonded together, which makes it very difficult to separate them.
• A mixture is formed when to or more elements or compounds are present without being chemically bonded together.
• In a mixture, the two ingredients can be separated using physical processes, without chemical reactions, this is because they are not chemically bonded together.