Kinetic Theory

States of Matter: Kinetic Theory Kinetic Theory is an explanation of how the particles in matter behave All matter is composed of small particles These particles are in constant random motion These particles are colliding with each other and the walls of their containter

Thermal Energy Thermal enegy is the total energy of a material’s particles, including kinetic and potential. Kinetic energy is energy of motion If a substance’s temperature is lowered, particles will have less thermal energy and vibrate slower. The average kinetic energy of an object is it’s temperature

Solid State In the solid state, particles are closely packed together. The particles still vibrate. Solids have a definite shape and volume Most solids have a specific geometric arrangement of particles This arrangement gives some chemical and physical properties to the substance.

Liquid State Particles in a liquid state move more freely than in a solid. They have enough kinetic energy to move out of the ordered arrangement of a solid The melting point is the temperature at which a solid begins to liquefy. The amount of energy neccesary to transform a solid to a liquid is it’s heat of fusion. The melting point of ice 0°C

Liquid State Liquids have partially overcome their attraction to other particles, allowing them to slide past each other. Because of this, liquids have no definite shape but still have a definite volume.

Gas State Gas particles have enough kinetic energy to overcome the attractions between them. Gases do not have a fixed shape or volume Gases will expand to fill their container through diffusion Diffusion is the spreading of particles through a given volume until they are uniformly distributed

Gas State A liquid can turn into a gas through vaporization Vaporization is when particles of a liquid have enough kinetic energy to escape the attractive forces of the liquid. The heat of vaporization is the amount of energy required for a liquid at it’s boiling point to become a gas The boiling point of a liquid is the temperature at which the vapor pressure in a liquid is equal to the external pressure a acting on a liquid.

Gas State Evaporation is vaporization that occurs at the surface of a liquid due to having more than the average kinetic energy. Evaporation can occur at temperatures lower than the boiling point.

Plasma – the fourth state of matter Plasma is made up of highly charged positive and negative atoms It is the most common state of matter in the universe. Plasma can be found in lightning bolts, neon signs, and stars.

Heating Curve A heating curve shows the temperature change in a substance as energy is added In the horizontal sections, energy is being used to overcome the attractive forces between molecules

Thermal Exapansion Thermal expansion is the increase in size of something as it’s temperature increases.

How does thermal expansion help us? Thermal expansion causes the liquid in a thermometer to expand and the air in a hot-air balloon to become less dense

Water Water is an exception to the usual rules of thermal expansion As water freezes, it expands It has highly positive and negative regions. As the particles become closer together, they repel each other creating empty spaces in the ice.

Solid or Liquid? Amorphous solids soften gradually and turn to liquid over a temperature range and do not have a definite point at which they change from solid to liquid. Examples are glass and plastics Liquid crystals do not lose their ordered arrangement during the change from solid to liquid.