Unit 5: States of Matter & Gas Laws

Unit 5:
States of Matter & Gas Laws

Chemistry - Semester A

Mrs. Randolph

Multiple Select

What are the 3 states of matter ?

• solid

• volume

• liquid

• shape

• gas

Lesson 1:
Crystalline &
Amorphous Solids

Kinetic Molecular Theory

●Explains the physical states of matter, based on the combined movements and
interactions of the particles within a substance

●Summarized by the following 7 postulates

1.All matter is made up of tiny particles called atoms, ions, or molecules

2.

These particles are in constant motion, which is rapid and random

3.

Particles in motion possess KE, which increases as particles gain energy
(greatest in gases, less in liquids, and least in solids)

4.

Particle motion is least in solids, greater in liquids, and greatest in gases

5.

Energy is transferred between particles when they collide, but the collisions
are elastic (no net loss of energy)

6.

Particles of a gas have little or no interaction; particles of a liquid have greater
interactions; particles of a solid have the greatest interactions

7. The temperature of a substance is determined by the average KE of the
particles within that substance.

Note: It's called the Kinetic MOLECULAR theory because at the time
scientist thought all substances were composed of molecules, but we now
know that its atoms, ions, or molecules)

Multiple Choice

Which of the following is an assumption of the kinetic-molecular theory of gases?

• Collisions between gas particles are inelastic.

• Gases consist of closely spaced particles.

• Gas particles move around in an orderly manner.

• The temperature of a gas depends on the average kinetic energy of the gas particles.

Multiple Choice

The energy of movement is ___.

• potential energy

• kinetic energy

• mechanical energy

Multiple Choice

Matter that has its own shape and definite volume.

• solid

• liquid

• gas

• plasma

SOLIDS

●Physical Properties of Solids:
○Definite shape & volume

○Definite melting point

○High density

○Incompressibility

○Low rate of diffusion

●Not all solids are “hard,” but solids will keep their shape unless force is applied

●When you “pour” a rock from one container to another, the shape doesn’t change

●The temperature at which the solid melts is the same always

●Solids have high mass compared to their volume, so most will not float

●Incompressibility: they cannot be forced into a smaller space

●Diffusion is the mixing of the particles of one substance with another substance particles
when they are placed in same area. If you place two rocks next to each other, they will
not morph into one

SOLIDS

●Solid particles are in constant motion, but you do not see the movement
because its very limited to back-and-forth vibrations

●Since these particles are in constant motion, they possess both KE and PE

●As particles move they collide with each other and energy is transferred from
one particle to another, but no energy is lost

○When larger items collide, some energy is lost (usually in the form of heat)

●When particles collide, energy is transferred from one to the other, but they are
elastic – meaning that the total KE of two particles before a collision is equal to
the total KE of the two particles after the collision

●Because no energy was lost during the collision, particles remain in constant
motion

This is a good thing because if heat was lost every time a particle collides, then all
matter would end up at absolute zero (-273°C)

SOLIDS

●Solid particles have the greatest interaction because the particles in a solid are
held together by intermolecular forces (dipole-dipole, London dispersion
forces, H-bonding, or metallic bonding)

●These intermolecular forces are the reasons solids have the properties they do

●The motion of the particles are proportional to the temperature of the solid –
meaning if the solid increases in temperature, the particles move faster and
further apart // vise versa

●IF the temperature reaches a specific temperature (melting point) the particles
overcome the intermolecular forces and the solid turns to a liquid (it melts)

Multiple Choice

Has definite shape and definite volume

• mass

• liquid

• gas

• solid

CRYSTALLINE SOLIDS

● A solid may have one of two forms – crystalline or

amorphous – based on the arrangement of its molecules

● A crystalline solid is a substance whose molecules are

arranged in orderly, geometric, repeating patterns called
CRYSTALS

● There are 4 types of crystalline solids:

○

1. Ionic crystals

○

2. Covalent network crystals

○

3. Metallic crystals

○

4. Covalent molecular crystals

CRYSTALLINE STRUCTURE

● Crystalline solids may also be classified according to their

crystalline structure since crystals form exact geometric
patterns

● Sometimes it’s easy just by examining, but sometimes its

difficult to determine because it may consists of one crystal
or many crystals fused together or its worn down so it
distorts its shape

● X-ray crystallography - x-rays diffract in a specific pattern to

reveal the 3D arrangement of particles within the crystal

Crystal Systems

●Determined by:

○The shape of the crystal

○Symmetry of the crystal

○The arrangement of the particles within the crystal

●Simple, body-centered, face-centered, and
base-centered refer to the arrangement of
particles within a crystal system

●An unit cell is the smallest portion of a crystal
lattice that still retains the crystalline structures

Amorphous Solids

●One whose particles are arranged in a random manner

●It has a shape, but it does not a specific shape

●Examples: rubber, plastic, glass

Allotropic

●An element that can exhibit more than one structural form in the same state -
solid, liquid, or gas is allotropic

●Examples: sulfur, carbon

Multiple Choice

particles are not arranged in a regular pattern such as plastics

• crystalline solids

• amorphous solids

• plasma

• surface tension

Multiple Choice

• CRYSTALLINE

• AMORPHOUS

Multiple Choice

• CRYSTALLINE

• AMORPHOUS

Multiple Choice

• CRYSTALLINE

• AMORPHOUS