Module 2

• Kinetic Molecular Theory (KMT) is a model used to explain the behavior of states of matter from a microscopic point of view
• KMT helps explain why matter exists in different phases (solid, liquid, and gas) and how matter can change from one phase to the next
• Properties of Liquids:

  • Liquids are fluids that can flow and assume the shape of the container
  • Liquid molecules are close together with very little space allowing them to move past one another freely
  • Liquids are difficult to compress compared to gases
  • Liquids are denser than gases under normal conditions
  • Liquids have a definite volume due to attractive forces holding the molecules together
• Properties of Solids:

  • Solids are rigid and resistant to change
  • Particles in solids are tightly arranged and organized, making them highly dense and incompressible
  • Solids have a definite shape, volume, and melting point
  • Solids have a low rate of diffusion and don't mix easily with other substances
  • Types of solids include crystalline solids and amorphous solids
  • Crystalline solids have particles arranged in a crystal lattice and change sharply when heated
  • Crystalline solids are classified as metallic, ionic, and covalent
• Effect of temperature on coronavirus survival:

  • Low temperatures can increase the rate of spread of diseases caused by the coronavirus
  • Countries with lower air temperatures have shown a steeper increase in new COVID-19 cases per day compared to countries with higher temperatures
  • The activity of the virus is affected by temperature
• Intermolecular forces affect the physical properties of liquids and solids:

  • Surface tension, viscosity, vapor pressure, and molar heat of vaporization are influenced by intermolecular forces
• Ionic crystals are compounds made of metals and nonmetals
• Ionic crystals are good conductors of heat in a solid state like NaCl
• Covalent network crystals have extremely high melting points like quartz and diamond
• Quartz will show a well-defined arrangement of atoms
• Covalent molecular crystals contain two or more nonmetals like CH4, NH3, and H2O
• Amorphous solids lack a well-defined arrangement of basic units found in crystals
• Surface tension is the amount of energy required to stretch the surface of a liquid by a unit area
• Liquid molecules with high intermolecular forces have high surface tension
• Capillary action is the attraction between liquid and solid materials
• Cohesion is the intermolecular attraction between the same molecules
• Adhesion is the intermolecular attraction between unlike molecules
• Viscosity is the resistance to flow in a liquid
• Glycerol has the highest intermolecular forces and viscosity
• Decane is more viscous than hexane
• Acetone has more molecules turning into a gaseous state at STP condition
• Vapor pressure is created by weak interactions between molecules
• Molar heat of vaporization is the energy required to vaporize 1 mole of a liquid
• Boiling point is the temperature at which a liquid converts into a gas
• As boiling point increases, the energy required to vaporize also increases
• Molecules with strong intermolecular forces have low vapor pressure
• Molecules with weak intermolecular forces have high vapor pressure
• Siblings adjust to their differences like how solids and liquids of the same materials have different properties