Particle Model of Matter and Changes of State

Particle Model of Matter

• Substances are made of tiny particles.
• Particles in a pure substance are identical.
• Particles have spaces between them.
• Particles are always moving.
• Particles in a substance attract each other.
• Solids have a structured, tightly packed arrangement; particles cannot move past each other.
• Liquids have an unstructured arrangement; particles can flow past each other. They take the shape of their container.
• Gases have an unstructured arrangement; particles spread out and move quickly. They fill the entire container.

Changes of State

• Cooling loses energy; heating gains energy, causing changes of state.
• Melting: solid to liquid
• Vaporization: liquid to gas
• Evaporation: particles at the surface have enough energy to vaporize.
• Boiling: all particles have enough energy to vaporize.
• Condensation: gas to liquid
• Freezing: liquid to solid
• Sublimation: solid to gas
• Deposition: gas to solid
• Freezing point of water: 0°C at sea level
• Boiling point of water: 100°C at sea level

Cohesive Force

• Cohesive force is the attraction between particles.
• Cohesive force is stronger in liquids than in gases.

Viscosity

• Viscosity is a fluid's resistance to flow.
• It depends on intermolecular bonds and molecule shape.
• Viscosity varies with temperature.
• Liquids: Increased heat = Decreased viscosity Decreased heat = Increased viscosity
• Gases: Increased heat = Increased viscosity Decreased heat = Decreased viscosity

Flow Rate

• Flow rate is how quickly a liquid moves.
• Calculated as volume/speed (e.g., L/min, mL/sec).

Solubility

• Solubility is a solute's ability to dissolve in a solvent.
• Water is a universal solvent, dissolving many solutes.
• Solute: substance dissolving
• Solvent: liquid the solute dissolves in
• Solution: solute dissolved in solvent
• Soluble: can dissolve in the solvent
• Insoluble: cannot dissolve in the solvent
• Solubility: amount of solute dissolved in a given amount of solvent (e.g., g/100 mL).

Saturation

• Saturation is how much solute is dissolved in a solution.
• Unsaturated: more solute can dissolve.
• Saturated: no more solute can dissolve.
• Supersaturated: more solute than usual is dissolved.

Variables Affecting Dissolve Rate

• Agitation: increased particle collisions, faster dissolving.
• Particle size: smaller particles dissolve faster.
• Temperature: higher temperature speeds up particle movement and dissolving.
• Pressure: affects collision frequency of particles.

Density

• Density is mass per unit volume (g/cm³ or g/mL).
• Density of solids is higher than liquids, which is higher than gases
• Solids - particles tightly packed, unable to move past each other.
• Liquids - more loosely packed than solids, can flow to take the shape of their container
• Gases - particles widely spaced, can be compressed easily

Measuring Volume

• Volume can be measured by water displacement Method

1. Place object in a beaker with enough water to cover the object.
2. Measure the water level in the beaker.
3. Submerge the object.
4. Measure the new water level.
5. Subtract the original water level from the final water level. The result is the volume of the object..

Buoyancy

• Buoyancy is a fluid's ability to support an object.
• Objects with lower density than the fluid float. Objects with higher density than the fluid sink.
• Average density: total mass of object divided by its total volume

Explore the fundamental concepts of the particle model of matter and the various changes of state. This quiz covers the behavior of solids, liquids, and gases, as well as processes like melting and evaporation. Test your understanding of how temperature affects energy and state changes in different substances.