Bonding and substance properties

• What are the three states of matter?


  Solids, liquids, and gases
• How does the state of a substance depend on temperature?


  A substance can exist in all three states depending on temperature and pressure
• What are the points at which state changes occur?

  State changes occur at the melting point and boiling point
• What happens during melting and freezing?


  Melting and freezing occur at the melting point
• What occurs during boiling and condensing?


  Boiling and condensing take place at the boiling point
• How do individual atoms differ from bulk matter?


  Individual atoms do not share the same properties as bulk matter
• How can the three states of matter be represented in a simple model?


  • Particles are represented by small solid spheres
  • Each state has different arrangements and movements of particles
• What are the properties of solids, liquids, and gases?

  **Solid:**

  • Regular arrangement of particles
  • Vibrate about a fixed position
  • Very close particles

  
  

  Liquid:

  • Randomly arranged particles
  • Move around each other
  • Close particles

  
  

  Gas:

  • Randomly arranged particles
  • Move quickly in all directions
  • Far apart particles
• What determines the amount of energy needed to change state?

  The strength of the forces between the particles determines the energy needed
• How does the strength of forces between particles affect melting and boiling points?


  The stronger the forces, the higher the melting and boiling points
• What type of change is changing states of matter?


  Changing states is a physical change
• What is melting?

  Melting is when a solid changes into a liquid
• What happens to thermal energy during melting?


  Heat/thermal energy absorbed by the particles is transformed into kinetic energy
• At what temperature does melting occur?


  Melting happens at a specific temperature known as the melting point
• What is the difference between boiling and evaporation?


  Boiling occurs with bubbles forming inside the liquid, while evaporation occurs only at the surface
• At what temperature does boiling occur?


  Boiling happens at a specific temperature known as the boiling point
• What is freezing?


  Freezing is when a liquid changes into a solid
• What is the relationship between melting point and freezing point?


  The melting point and freezing point of a pure substance are the same
• At what temperature does water freeze and melt?


  Water freezes and melts at 0 ºC
• What is evaporation and when does it occur?


  Evaporation occurs over a range of temperatures and can happen below the boiling point
• What factors affect the rate of evaporation?


  The larger the surface area and the warmer the liquid surface, the more quickly a liquid can evaporate
• What is condensation?


  Condensation occurs when a gas changes into a liquid on cooling
• What happens to gas particles during condensation?


  Gas particles lose energy and group together to form a liquid
• What is sublimation?


  Sublimation is when a solid changes directly into a gas
• What is desublimation?


  Desublimation is the reverse reaction of sublimation
• What does particle theory explain?


  • How matter changes state
  • The energy and forces present between particles
  • The relationship between energy and state changes
• How does heating affect particles in a solid?

  Particles absorb thermal energy, converting it into kinetic energy, causing them to vibrate more
• What happens when the boiling point is reached?


  All particles gain enough energy for intermolecular forces to break and the liquid boils
• What are the limitations of particle theory?


  • Considers all particles to be small, solid, and inelastic
  • Does not account for differences between atoms, ions, or molecules
  • Fails to consider intermolecular forces between different particles
• What does a heating/cooling curve represent?


  The horizontal sections represent phase changes during which the temperature doesn’t change
• How can the physical state of a substance be predicted?


  By using melting and boiling point data
• What state is a substance below its melting point?


  The substance will be in the solid state
• What state is a substance between its melting point and boiling point?


  The substance will be in the liquid state
• What state is a substance above its boiling point?


  The substance will be in the gas state
• How to predict the states of substances A, B, C, and D at given temperatures?


  • A at -150 ºC: Gas (boils above -173 ºC)
  • B at 50 ºC: Solid (melts at 1736 ºC)
  • C at 1400 ºC: Liquid (melts at 1105 ºC, boils at 1450 ºC)
  • D at 400 ºC: Solid (melts at 650 ºC)
• What does the reversible arrow (⇌) indicate in state change questions?


  It indicates that the process can go forwards and backwards
• What are state symbols in chemical equations?


  • Indicate the physical state of each substance
  • Written after each formula in brackets
  • Examples: (s) for solid, (l) for liquid, (g) for gas, (aq) for aqueous
• What does the state symbol (aq) represent?


  (aq) means the substance is dissolved in water
• Why should state symbols be included in chemical equations?


  State symbols provide information about the physical state of substances involved
• What is an example of a reaction with state symbols?


  CuCO₃ (s) + 2HCl (aq) ⟶ CuCl₂ (aq) + CO₂ (g) + H₂O (l)