[4.1] Kinetic Molecular Theory

• Since the late ___th century, certain observations such as ice melting when removed from the freezer, dry ice disappearing, or the cold sensation after getting out of a pool, have been explained by the kinetic molecular theory.

  19
• The KMT was originally a set of ___ pertaining to the behavior of gases.

  postulates
• It is called the KMT of matter when pertaining to all ___, and the KMT of gases only when pertaining to gases.

  matter
• It is made of particles (atoms/ions/molecules) that have energy and are in constant motion.

  matter
• The energy varies depending on the ___ of the substance.

  temperature
• What particles move less and have the least amount of energy?

  solid
• Which particles move fast and have the greatest amount of energy?

  gas
• The temperature of a substance is a measure of the average ___ ___ of its particles.

  kinetic energy
• A change in ___ may occur when the particles' energy is changed.

  phase
• The empty spaces between the particles of solids are ___ than those of gases.

  smaller
• ___ forces exist between particles.

  Attractive
• Particles in solids have small spaces between them; thus the attractive forces between them are ___.

  strong
• Particles in gases have larger spaces between them; thus, the attractive forces between them are ___.

  weaker
• It explains how matter can change into different phases, such as from solid into liquid and into gas.

  KMT of matter
• Water exists in solid, liquid, or gas. The particles of water in its solid (ice) form have very little energy, and the spaces between them are so small such that motion becomes limited.
• Due to greater attractive forces, the water molecules are held closely together.
• If ice is heated, it will melt because the energy of the water molecules increaes.
• The water molecules move farther apart, forming enough space that allows the water molecules to slide over one another and flow.
• The available empty spaces in liquid water allow the molecules to move freely.
• If liquid water is heated further, it will evaporate and become water vapor.
• As mentioned, gas molecules, have more energy than liquid molecules, which allows them to move farther away from one another.
• Because the spaces between gas molecules are larger compared to those of liquids and solids, the attractive forces between them are very week.
• The movement of particles amounts for various observations involving matter.
• ___ is the spreading of particles of matter in all directions to any empty space available to them.

  Diffusion
• It involves the movement of particles from a region of high concentration toward a region of low concentration.

  Diffusion
• Diffusion occurs only if the kinetic energy of the particles overcomes the ___ ___ between them.

  attractive forces
• The KMT of matter states that particles of matter are in ___ motion.

  constant
• The particles of dense gases such as CO-2 are heavier and therefore move more ___ than those of lighter gases such as helium in ballons.

  slowly
• Carbon dioxide, a denser gas, diffuses more ___ than helium, a lighter gas.

  slowly
• Even though the sugar crystals seem to disappear when stirred in water, the sweet taste proves that sugar molecules are still present in the solution
• Based on the KMT of matter, the sugar molecules occupy available spaces and spread out between the water molecules.
• Solids tend to expand when heated.
• Diffusion is slower in liquids than in gases because the attractive forces between liquid particles are stronger than those of gas particles.
• The stronger attraction between particles leaves little space and kinetic energy for the particles to move about and diffuse.
• When a teabag is soaked in a cup of hot water, both the flavor and the color of the tea spread throughout the water.
• During diffusion, the tea particles gradually spread throughout the water uniformly.
• Diffusion in solid particles is not as observable as those in liquids and gases.
• Solid particles are packed tightly together, leaving smaller spaces for the particles to move about.
• Diffusion does occur between solids, albeit slowly.
• When a balloon is placed near a lighted candle, the high temperature of the flame causes the gas particles to move faster, which, in turn, increases the pressure inside the balloon. When the pressure exceeds the pressure "limit" of the balloon, the balloon bursts.