Chapter 3 Solids, Liquids & Gases

Chapter 3 Solids, Liquids & Gases BIG IDEA Substances can exist in all states matter. The state of matter is related the energy within the substance. ESSENTIAL INFORMATION The (3) main states of matter & their properties The phase change processes & energy flow Charles’ Law, Boyle’s Law & Ideal Gas Law

Solids A solid has a definite shape and a definite volume. The particles in a solid are closely locked in position and can only vibrate. 2 types of solids exist Crystalline solids: are solids that are made up of crystals. Examples are salt, sugar, and snow. Amorphous solids: these contain particles that are not arranged in a regular pattern. Amorphous solids do not melt, instead they become softer. Examples are plastics, rubber, and glass.

Liquids A liquid has a definite volume but no definite shape of its own. Compared to particles in a solid, the particles in a liquid are more loosely connected and can collide with and move past one another. A liquid is an example of a fluid, meaning a substance that flows. Gases are also considered fluids.

Liquids Continued Two characteristic properties of liquids are surface tension & viscosity. Surface tension is the result of an inward pull among the molecules of a liquid that brings the molecules on the surface closer together. Viscosity is a liquids resistance to flowing. Liquids with high viscosity flow slowly (cold maple syrup, honey). Liquids with low viscosity flow quickly (water, olive oil).

Liquids Cont. Surface tension Viscosity

Gases A gas can change shape & volume very easily – it has no fixed shape or volume. In gases, the atoms and molecules are free to move independently, colliding frequently. The distance between particles in a gas is much larger than the distance between particles in a solid or a liquid. Gases are also considered fluids.

You should be able to draw a symbolic picture of the particle view of each state of matter. Essential components in the picture are the distance between particles and the type of motion the particles exhibit.

Solid  Liquid The change in state from a solid to a liquid is called melting. Thermal energy is required for this process to occur. In most pure substances, melting occurs at a characteristic temperature called the melting point. When a substance melts, the particles in the solid vibrate so fast that they break free from their fixed positions. Freezing is when a change from a liquid to a solid occurs. Thermal energy is removed from the substance. When a substance freezes, the particles in the liquid move so slowly that they begin to take on fixed positions.

Liquid  Gas Vaporization – Boiling & Evaporation The change from a liquid to a gas is called vaporization. It takes place when the particles in a liquid gain enough energy to move independently forming a gas. Vaporization that takes place only on the surface of a liquid is called evaporation. Boiling is the action of a liquid changing to a gas all throughout the substance, below its surface as well as at the surface. The boiling point of a substance depends on the pressure of the air above it. The lower the pressure, the less energy needed for the particles of the liquid to escape into air.

Gas  Liquid Condensation Condensation is the change in state from a gas to a liquid. During condensation, the particles in a gas lose thermal energy to form a liquid.

Solid  Gas Sublimation Sublimation occurs when the surface particles of a solid gain enough energy that they form a gas. During sublimation, particles of a solid do not pass through the liquid state as they form a gas. CO2 dry ice in solid state.

Gas  Solid Deposition (sublimation) Deposition is the process of gas particles directly forming solids, usually in the form of crystals. During deposition, particles of a solid do not pass through the liquid state as they form a solid. Frost

Graph Skills What processes are happening at (B) and (D)? What letters correspond to the 3 states of matter?

Measuring Gases When working with a gas, it is helpful to know its volume, temperature, and pressure. Volume is the amount of space that matter fills, measures in cm3, mL, L and other units. Temperature is a measure of the average energy of motion of the particles of matter. The pressure of the gas is the force of its outward push divided by the total area of the container. Pascal is the unit that force is measured in.

Temperature & Volume Charles’s Law Relationship between temperature & volume At constant pressure; When the temperature of a gas is increased, its volume increases. When the temperature of a gas is decreased, its volume decreases. The graph of Charles’s Law shows that the volume of a gas is directly proportional to its Kelvin temperature under constant pressure. (linear)

Pressure and Volume Boyle’s Law Relationship between pressure and volume At constant temperature; When the pressure of a gas increases, the volume of the gas decreases. When the pressure of a gas is decreased then the volume increases. The graph of Boyle’s law shows that gas pressure is inversely proportional to the volume at constant temperature. (exponential)

LINEAR EXPONENTIAL

Pressure and Temperature Ideal Gas Law Relationship between temperature & pressure At constant volume; When the temperature is increased, the pressure of the gas increases. When the temperature is decreased, the pressure of the gas decreases. Pressure and temperature are directly related.