Chapter 16: Solids, Liquids, and Gases Section 1: Kinetic Theory Click on Picture for link

Kinetic Theory Kinetic Theory: the explanation of how particles in matter behave. Based on 3 assumptions: All matter is composed of small particles. These particles are in constant, random motion The particles are colliding with each other and the walls of their container http://comp.uark.edu/~jgeabana/mol_dyn/

Thermal Energy Thermal Energy: the total energy of a material’s particles Even ice has thermal energy! The tiny water molecules may be packed together, but they are still moving in place (vibrations) Average Kinetic Energy: the temperature of a substance When temperature is lower, particles move more slowly When temperature is higher, particles move more quickly All particle motion stops at absolute zero (0K) or -273°C http://preparatorychemistry.com/Bishop_KMT_frames.htm

4 States of Matter: Solid, Liquid, Gas and Plasma Particles are packed closely together Most have a specific geometric arrangement (organized) Have a definite shape and volume Melting Point: the temperature at which a solid begins to become a liquid

Liquids Liquid: Particles move past each other, but don’t move far apart—liquids flow Liquids take the shape of their container, but still have enough attractive force to keep them together Have no definite shape; have a definite volume Heat of Fusion: the amount of energy required to change a substance from a solid to a liquid

Gases Gas: Particles move quickly and randomly More collisions than a liquid Have no definite shape nor volume Heat of Vaporization: the amount of energy required to change a substance from a liquid to a gas http://preparatorychemistry.com/KMT_flash.htm

Gases Boiling point: the temperature at which a liquid’s vapor pressure is equal to the pressure of the atmosphere. Particles in a liquid gain enough energy that they escape from each other and become a gas. Depends on atmospheric pressure Water boils faster at higher elevations Gases fill their container due to the loss of attractive forces

Gases Diffusion: the spreading of particles throughout a given volume until they are uniformly distributed. Example: air freshener—eventually spreads throughout the room (the container) Particles in a liquid gain enough energy that they escape from each other and become a gas. Depends on atmospheric pressure Water boils faster at higher elevations Gases fill their container due to the loss of attractive forces

Plasma Plasma: a gas that has positively and negatively charged particles. When gases reach extremely high temperatures, like in the sun Or have high voltage electricity sent through them, like a plasma television Large collision forces cause the particles to come apart.

Heating curve of a liquid http://resources.yesican-science.ca/lpdd/g07/lp/nelson/graph.gif

Expansion of Matter Particles move faster and separate as the temperature rises Thermal expansion: the increase in the size of a substance when the temperature is increased Occurs in most solids, liquids and gases Liquid example: a thermometer Gas example: hot air balloon

Water: It’s Different What happens when you place a can of soda pop in the freezer? Water expands when it freezes! Why? Highly positive at one end, highly negative at the other Charges line up from one particle to another like magnets; causes empty space between particles Empty space also decreases the density of water ice. Does ice float or sink?

Water in all 3 Phases http://www.bio.miami.edu/~cmallery/150/chemistry/sf2x10b.jpg

Solid or Liquid? Amorphous solids: “without form” Liquid crystals Do not have an exact phase change temperature, unlike regular solids Glass and plastic are examples Particles are jumbled and twisted, unlike regular solids Liquid crystals Flow during the melting phase, but do not lose their ordered arrangement completely Respond to temperature changes and electric fields, making them useful in displays for clocks & watches, calculators, & video