Changes of State & the Particle Model

• What is density defined as?

  The mass per unit volume of a material
• How does the density of low density materials compare to their mass?

  Objects made from low density materials typically have a low mass
• What can be inferred about similarly sized objects made from high density materials?

  They have a high mass
• Which would be lighter: a bag full of feathers or a similar bag full of metal?

  A bag full of feathers
• How does the density of a balloon compare to that of a small bar of lead?

  A balloon is less dense than a small bar of lead
• What is the relationship between density, mass, and volume?

  Density is related to mass and volume by the equation rho = m / v

  
• Why are gases less dense than solids?

  Because the molecules in gases are more spread out
• What happens to the density of a material if it is more dense than water?

  It will sink
• How can the volume of an object be calculated if it is not given directly?

  By using the appropriate equation depending on the object’s shape
• What are the characteristics of solids, liquids, and gases in terms of particle arrangement and movement?

  • Solids:
  • Particles are closely packed
  • Particles vibrate about fixed positions
  • Definite shape and volume
  • Liquids:
  • Particles are closely packed
  • Particles can flow over one another
  • No definite shape, definite volume
  • Gases:
  • Particles are far apart
  • Particles move randomly
  • No definite shape or fixed volume

  
• What is the difference in density between solids and liquids?

  The density of solids and liquids is roughly the same
• Why do gases have significantly lower densities than solids or liquids?

  Because the molecules in a gas are widely separated
• What is the approximate density of water?

  1000 kg/m³
• What is the approximate density of air at sea level and room temperature?

  1. 3 kg/m³
• What is the method for measuring the density of regularly shaped objects?

  1. Measure the mass using a digital balance.
  2. Measure dimensions using a ruler, Vernier calipers, or micrometer.
  3. Calculate the volume based on shape.
  4. Use the formula \( \rho = \frac{m}{V} \) to find density.
• What is the resolution of a digital balance used in density experiments?

  0.01 g
• What is the independent variable in the density experiment of regularly shaped objects?

  The type of shape/volume

  
• What is the dependent variable in the density experiment of regularly shaped objects?

  The mass of the object
• What is the method for measuring the density of irregularly shaped objects?

  1. Measure the mass using a digital balance.
  2. Use a eureka can to measure the volume of displaced water.
  3. Calculate density using \( \rho = \frac{m}{V} \).
• What is the resolution of a micrometer used in density experiments?

  0.001 mm
• What is the resolution of a Vernier caliper used in density experiments?

  0.01 mm
• Why is it important to convert units when measuring density?

  To ensure consistency in calculations
• How would you convert 125 m to cm?

  125 m = 125 × 100 = 12,500 cm
• How would you convert 5 g to kg?

  5 g = 5 ÷ 1000 = 0.005 kg
• What are the key differences between mass, weight, and density?

  • Mass: Amount of matter in a substance, measured in kg
  • Weight: Force acting on an object due to gravity, measured in N
  • Density: Amount of matter in a fixed volume, measured in kg/m³
• How can density be visualized at the atomic level?

  By considering the number of particles in a cubic centimeter
• Why is liquid water denser than steam?

  Because liquid water contains more particles in the same volume than steam
• What happens to the volume of steam compared to liquid water when both have the same mass?

  Less dense steam will take up a greater volume
• What is the significance of recognizing empty space between particles at the atomic level?

  It helps in understanding the concept of density

  
• What is the formula for density?

  rho = m/V

  
• How does the arrangement of particles in solids contribute to their properties?

  Particles are closely packed, giving solids a definite shape and volume
• How does the arrangement of particles in gases contribute to their properties?

  Particles are far apart and move randomly, giving gases no definite shape or fixed volume
• What is the relationship between the distance between molecules in a gas and its density?

  The distance between molecules in a gas is roughly ten times greater than in solids or liquids, resulting in lower density
• Why are gases highly compressible?

  Because there are large gaps between the particles
• What is the formula for calculating the volume of a cube?

  Volume = side³

  
• What is the formula for calculating the volume of a sphere?

  Volume = 4/3 pi r^3

  
• What is the formula for calculating the volume of a cylinder?

  Volume = pi r^2 x l
• What is the purpose of using a eureka can in measuring density?

  To measure the volume of displaced water for irregularly shaped objects

  
• What is the significance of averaging measurements in density experiments?

  To improve accuracy and reliability of the results
• What is the unit of density when mass is measured in kilograms and volume in cubic meters?

  kg/m³