Aim: What are the States of Matter

Nature of Gases Gases: ◦No definite shape or volume ◦Particles are very far apart and move all over ◦Total disorder- particles move in all directions

Gas Pressure Gas particles exert pressure when they collide with walls of the container they are in.

Atmospheric pressure  Atmospheric pressure results from the collisions of atoms and molecules in air with objects.  SI unit for pressure is the pascal (Pa).  Other units are atmosphere (atm) and millimeters of mercury (mm Hg).  1 atm = 760 mm Hg = kPa

Atmospheric pressure Atmospheric pressure is greater at sea level.

Kinetic Energy and Temperature What is energy? ◦The capacity to do work or produce heat What is Kinetic Energy (K.E.)? ◦The energy an object has because of its motion.

Kinetic Energy and Temperature Temperature is a measurement of the average kinetic energy of atoms or molecules.

Kelvin Temperature Scale 1. K = o C 2. o C = K K = absolute zero Standard temperature = 0 o C = 273 K

Nature of Liquids Liquids have: ◦Definite volume and take the shape of the container ◦Particles are still close together and move while touching each other ◦No regular pattern or arrangement of particles.

Evaporation Evaporation is when liquid changes into gas.

Vapor Pressure Vapor Pressure- Some liquid is changed into vapor (gas) and vapor exerts a pressure on the sides of the container.

Vapor Pressure As the temperature of a gas increases, vapor pressure increases. Molecules have more K.E. and some can overcome the force holding the liquid molecules together and escape to form a gas. More gas molecules  higher vapor pressure.

Vapor Pressure When you heat a liquid, the particles in the liquid absorb the heat which increases the kinetic energy. The increase in the kinetic energy allows more particle to enter the gas phase. The particles escape the liquid and collide with the walls of the container which increases the pressure on the container from the gas particles.

Boiling Point The boiling point is the temperature at which the particles change from liquid to gas. Boiling occurs when the vapor pressure equals the external pressure.

Boiling Point The higher the external pressure on the liquid the higher the boiling point. The normal boiling point is at kPa (1 atm).

Table H Vapor Pressure of Four Liquids

Nature of Solids Solids have: ◦Definite shape and volume ◦Particles are close together in fixed positions, vibrate but do not move. ◦Crystalline structure

Crystal Structure Crystals have particles arranged in a regular geometric pattern

Allotropes Allotropes are two or more molecular forms of the same elements in the same physical state. Allotropes have different properties because their structures are different.

Examples of Allotropes  Two allotropes of oxygen (dioxygen, O 2, and ozone, O 3 ), can both exist in the solid, liquid and gaseous states.  Coal and diamonds are allotropes of carbon

Changes of State Gas  liquid = condensation Liquid  gas = evaporation Solid  liquid = melting Liquid  solid = freezing Gas  solid = deposition Solid  gas = sublimation

Summary 1. Describe the behavior of particles in the solid, liquid, and gas phase. 2. Sketch how the particles would look like in each phase.