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• What is matter made of?

  Particles
• What is a particle?


  A tiny bit of matter
• What do chemists usually mean when they talk about particles?

  Atoms, ions, and molecules
• What does the particle model explain about substances?

  • Properties of a substance depend on its state
  • Solids and liquids cannot be compressed due to lack of space for particles to move
  • Solids have a fixed shape and cannot flow
• Why can't you compress a solid or liquid?

  Because there is no space for the particles to move into
• What happens to particles in a solid state?

  They vibrate around fixed positions and cannot move from place to place
• What is a chemical change?


  A change that produces one or more new substances
• What are examples of chemical changes that are difficult to reverse?

  • Cooking eggs
  • Baking cakes
  • An acid reacting with an alkali
• What is a physical change?

  A change that happens when a substance changes state or shape, or breaks into pieces without forming new substances
• What are examples of physical changes that can be reversed?


  • Freezing juice to make an ice lolly
  • Mixing sand with water
  • Dissolving sugar in water
• What are the limitations of the particle model?

  • Does not account for intermolecular forces between particles
  • Does not consider the size of particles
  • Ignores air space between particles
• What happens to particles during physical changes?

  Particles stay the same, but their arrangement and movement change
• What happens to particles during chemical changes?

  Particles break up and then join together in different ways
• What is the chemical reaction for methane and oxygen?


  $\text{methane} +$$\text{oxygen} \rightarrow \text{carbon dioxide} +$$\text{water}$
• What are elements made of?

  Only one type of atom
• What are compounds made of?

  Two or more different types of atoms bonded together
• What are molecules?


  Two or more atoms bonded together
• What are the three subatomic particles found inside an atom?

  Protons, neutrons, and electrons
• Where are protons and neutrons located in an atom?

  Inside the nucleus
• What is the charge of protons and neutrons?

  Protons are positively charged, and neutrons are neutral
• Where are electrons located in an atom?

  Orbiting the positively charged nucleus in shells
• Why are atoms neutral?

  Because they have the same amount of positive and negative charges that cancel out
• What keeps electrons in their orbit around the nucleus?

  Electrostatic attraction between positive protons and negative electrons
• What is the mass of an atom concentrated in?

  The nucleus
• What happens to an atom if it loses electrons?

  It becomes positively charged
• What happens to an atom if it gains electrons?

  It becomes negatively charged
• What are isotopes?


  Atoms with the same number of protons and electrons, but different numbers of neutrons
• What does the atomic number tell you?

  The number of protons and electrons and what the element is
• What does the mass number represent?

  The number of protons plus the number of neutrons
• How do you calculate the number of neutrons in an atom?


  $\text{Number of neutrons} =$$\text{mass number} - \text{atomic number}$
• What is the mass of an atom in grams?

  $10^{-23} \text{ g}$
• What is the atomic radius?

  $10^{-10} \text{ m}$
• What is the radius of the nucleus?

  $2.5 \times 10^{-11} \text{ m}$
• What is the smallest particle of an element that still has its chemical properties?

  An atom
• What is a molecule made from?

  Two or more atoms joined together
• What are chemical bonds?


  Attractive forces that join atoms in a molecule
• What is an oxygen molecule made from?

  Two oxygen atoms
• What is a carbon dioxide molecule made from?

  A carbon atom and two oxygen atoms
• What were John Dalton's main ideas about atoms?


  • All matter is made of tiny particles called atoms
  • Atoms cannot be broken down into anything simpler
  • Atoms of a given element are identical to each other
  • Atoms of different elements are different
  • During chemical reactions, atoms rearrange to form different substances
• What improvements did Niels Bohr make to the atomic model?

  • Showed that electrons occupy shells or energy levels around the nucleus
  • Each shell has a fixed energy
  • Supported by many experiments