Kinetic Theory of Matter

Kinetic Theory of Matter

used to explain physical changes

Solids

-have fixed volume that cannot be compressed

-are rigid with a definite shape

rigid because of the atoms/ions/molecules that make it up

liquids

-flowing matter with a definite volume but an indefinite shape

Gases

• flowing, compressible matter that has no definite volume or shape

Kinetic Theory of Matter

• Robert Brown - Scottich botanist (1827)

• Brownian motion - constant, random motion of tiny chunks of matter

• kinetic theory of matter - all matter is made up of tiny particles and those particles are in constant motion

Gases

• Collisions of particles in a gas are called elastic collisions because no kinetic energy is lost

• Ideal gas - a gas with particles that are in constant random motion but have no attraction for each other

• All undergo elastic collisions

Pressure

• the force acting on a unit area of a surface

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Liquids

• interparticle forces - forces between the particles that make up a substance

Solids

• The particles occupy fixed positions in a well-defined 3D arrangement

• crystal lattices extend throughout solids

• Crystal lattice - the 3D arrangement repeated throughout a solid.

Other forms of matter

• liquid crystal - a material that loses its rigid organization in only one or two dimensions when it melts. 

• Amorphous material - a substance with a haphazard, disjointed, and incomplete crystal lattice. (wax, cotton candy, candles)

• Plasma - an ionized gas (stars)

Open Ended

Analyze and compare the structure and shape of liquids and gases in terms of particle spacing and particle motion.

Open Ended

How do the particles of an ideal gas behave?

Kinetic Energy & Changes of State

• kinetic energy - energy of motion

Relationship between kinetic energy & temperature

•  As a gas is heated, the average kinetic energy of its particles increases.   

• As a gas is cooled, the average kinetic energy and speed of its particles decreases.

Kevlin Scale

• kelvin scale - measures the amount of kinetic energy within any given material

• absolute zero - minimum motion of a substances particles ( 0 K )

• degree symbol is not used with temperatures expressed in Kelvin.

How does heat affect particle motion?

• how is the temperature of the particles related to their kinetic energy?

Open Ended

What do you think will happen to the food coloring after we add it to each bowl?

What is your hypothesis?

Temperature Conversions

• absolute zero = 0 K

• 0 K =

   $-273.15\ ^{\circ}C$  

•  $T_k\ =\ \left(T_c\ +\ 273\right)\ K$  

•  $T_c\ =\ \left(T_k\ -\ 273\right)^{\circ}C$  

Multiple Choice

 $What\ is\ 25^{\circ}C\ in\ Kelvin?$  

• 298 K

• 273 K
  
  

• 280 K

• 250 K

Multiple Choice

What is 310 K in Celsius?

•  $37^{\circ}C$  

•  $30^{\circ}C$  

•  $310^{\circ}C$  

Mass and Speed of Particles

• It takes more work and more kinetic energy to move heavier objects

Diffusion

• The motions of particles of a gas cause them to spread out to fill the container uniformly.

• Diffusion = the process by which particles of matter fill a space because of random motion.

Changing States

• evaporation - process by which particles of a liquid form a gas by escaping from the surface

• 3 things that affect rate of evaporation: surface area, temperature, humidity

• volatile liquids - evaporate quickly

sublimation

• process by which particles of a solid escape from its surface and form a gas

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condensation

• Water vapor in air condenses into its liquid state

• Reverse of evaporation

vapor pressure & boiling

• vapor pressure - pressure of a substance in equilibrium with its liquid

• boiling point - the temperature of the substance when its vapor pressure equals the pressure exerted on the surface of the liquid.

melting point

• the temperature of the solid when its crystal lattice begins to disintegrate

• If more heat is applied it’ll become a liquid

freezing point

• the temperature of a liquid when it begins to form a crystal lattice and becomes a solid

• Heat of fusion - the energy released as 1kg of a substance solidifies at its freezing point 

• The melting point and freezing point of a substance are the same temperature, provided the pressure is the same

Open Ended

Two persons, one burned by water at 100 degrees Celsius and the other by a similar amount of steam at 100 degrees Celsius over a similar area of skin, are taken to the emergency room of a hospital. Which person has the more severe burn? Why?

Open Ended

Why do you blow on a spot of water on fabric to make the spot disappear faster?

Open Ended

Explain why a car's radiator is likely to boil over on a trip through mountains, even though the air is colder.

Open Ended

Explain why you can detect the aroma of fried bacon more quickly than you can the aroma of cold bacon.