AP Chemistry Powerpoints, Slides of Chemistry

Download AP Chemistry Powerpoints and more Slides Chemistry in PDF only on Docsity!

Chapter 10

States of Matter

10.1 The Kinetic-Molecular

Theory of Matter

Kinetic-Molecular Theory of Gases

• Particles of matter are ALWAYS in motion;

constant, rapid motion. (kinetic energy!)

• Particles are very small and relatively far

apart.

• Collisions of particles with container walls

cause pressure exerted by gas.

• Volume of individual particles is ≈ zero.
• Particles exert no attractive or repulsive

forces on each other.

Ideal Gas

• An imaginary gas that perfectly fits all the

assumptions of the kinetic-molecular theory

• A gas with its particles in constant random

motion without attraction for each other is

called an Ideal Gas. These particles undergo

elastic collisions.

• Nearly all real gases behave as ideal gases

EXCEPT at very low temperatures or high

pressures.

Real Gases

• A gas that does not behave completely according to the assumptions of the kinetic-molecular theory.
• Real gases occupy space and exert attractive forces on one another

Likely to behave nearly ideally:

Likely not to behave ideally:

Gases at high temperature & low pressure

Gases at low temperature & high pressure

Small non-polar gas molecules Large polar gas molecules

Kinetic-Molecular Theory of the Nature of Gases

• Diffusion

Spontaneous mixing of particles of two substances caused by their random motion

• Rate of diffusion is dependent upon: - speed of particles - diameter of particles - attractive forces between the particles

• Effusion

Process by which particles under pressure pass through a tiny opening

• Rate of effusion is dependent upon: - speed of particles (small molecules have greater speed than large molecules at the same temperature, so they effuse more rapidly)

Kinetic-Molecular Theory of the Nature of Gases

Some Properties of a Liquid

❖ Surface Tension:

The resistance to an increase in its surface area (polar molecules, liquid metals). A force that tends to pull adjacent parts of a liquid's surface together, thereby decreasing surface area to the smallest possible size. Cohesion is when alike molecules are attracted to one another.

Some Properties of a Liquid

❖ Capillary Action: Spontaneous rising of a liquid in a narrow tube. ❖ Meniscus: Curved surface of liquid in a container. May be concave or convex. ❖ Concave when the liquid is more attracted to the container than itself, adhesion. (water) ❖ Convex when the liquid is more attracted to itself than the container. (mercury)

Some Properties of Liquids

Volatility

• Liquids that have weak forces of

attraction and evaporate easily

Nonvolatile Liquids

• Liquids that have strong forces of

attraction and do not evaporate easily

Properties of Fluids

Relative High Density

• 10% less dense than solids (average)
• Water is an exception
• 1000x more dense than gases

Relative Incompressibility

• The volume of liquids doesn't change appreciably when pressure is applied

Ability to Diffuse

• Liquids diffuse and mix with other liquids
• Rate of diffusion increases with temperature

Kinetic Molecular Theory

• Particles are fixed in position, but vibrating

and bouncing in place.

• More organized structures in general.
• Intermolecular forces are relevant as

particles are closely packed.

• Definite shape and volume
• High density (except water), considered

incompressible.

• Diffusion can occur in metals over time

Amorphous Solids

❖ Also known as supercooled liquids: considerable disorder in their structures.

• Greek for "without shape"
• Formation of amorphous solids: - Rapid cooling of molten materials can prevent the formation of crystals
• Examples: plastics, glass

*** They do not have definite melting points**

Representation of Components in a Crystalline Solid

Lattice: A 3-dimensional system of points designating the centers of components (atoms, ions, or molecules) that make up the substance.

Types of Crystalline Solids

Ionic Solid: contains ions at the points of the lattice that describe the structure of the solid (NaCl).