chem 30 term two test
matter definition
* Anything that has mass and occupies space. Mass is the amount of matter in an object.
physical states of matter
* Solid: Has a definite shape and volume, with tightly packed particles that vibrate in place and strong intermolecular forces (IMFs).
* Liquid: Has a definite volume but no definite shape, particles move freely, are moderately attracted to each other, and take the shape of the container.
* Gas: Has no definite shape or volume, particles are far apart with weak or no attraction, and is highly compressible.
* Plasma: ionized gas
types of solids
1. Crystalline Solids
* Particles have a regular repeating pattern (e.g., ionic compounds like salt).
2. Amorphous Solids
* Particles are arranged randomly (e.g., plastic, glass).
liquids- properties and behavior
* Slightly compressible, particles have translational motion, and liquids can flow.
gases- properties and behavior
2. Gases
* Highly compressible, particles move by diffusion (high to low concentration) and effusion (high to low pressure through an opening). Gases, like liquids, are fluids, meaning they can flow.
definition of pressure
* Result of gas particles colliding with container walls; calculated as force per unit area.
pressure units
* Common units: atmosphere (atm), millimeters of mercury (mmHg or torr), and pascal (Pa), with SI unit being pascal (Pa) or kilopascal (kPa).
measuring atmospheric pressure
Measured with a barometer; mercury is used due to its high density, which allows a measurable column at sea level (760 mmHg or 1 atm)
pure substance
* Has a fixed composition and properties, cannot be separated by physical processes.
* Element: Pure substance with one type of atom.
* Compound: Two or more elements chemically combined, with unique properties.
mixture
2. Mixture
* Variable composition and properties, can be separated by physical processes.
physical properties
* Characteristics that don’t change the substance’s composition (e.g., density, color, melting point).
chemical properties
* Characteristics describing how a substance reacts with other substances, changing composition (e.g., flammability, reactivity).
physical change
* Change that doesn’t alter the substance's composition and is often reversible (e.g., melting, dissolving).
chemical change
* Change that forms new substances and alters composition; generally not reversible (e.g., burning, rusting).
definition of heat
* Thermal energy transferred due to a temperature difference between two bodies.
temperature
* Measures average kinetic energy of particles in a substance (K.E. = ½ mv²).
heat transfer
* Flows from high to low temperature and can occur by:
* Conduction: Heat transfer through direct contact.
* Convection: Heat transfer by motion of fluids.
* Radiation: Heat transfer without a medium (e.g., sunlight).
KMT of gases key info
* Gases consist of tiny, fast-moving particles with little attraction.
* The distance between particles is large, so the actual volume of particles is minimal.
* Particles move in straight lines, with elastic collisions causing pressure.
* Average kinetic energy of particles is directly proportional to temperature.
kinetic energy distrubution curve
* Shows the number of particles at various speeds in a sample at a certain temperature; higher temperatures increase the average speed and kinetic energy of particles.
change of state
* Occurs when matter absorbs or releases energy without changing temperature (e.g., melting, boiling).
energy absorbtion and release
* Absorbing energy: Solid → Liquid (melting), Liquid → Gas (evaporation).
* Releasing energy: Gas → Liquid (condensation), Liquid → Solid (freezing).
temperature plateaus
* During phase changes, energy overcomes IMFs rather than raising temperature, resulting in a constant temperature until the phase change completes.
definition of vapor pressure
* Pressure of a vapor in equilibrium with its liquid or solid in a closed container.
* Higher temperature increases vapor pressure, allowing more particles to escape into the vapor phase.
influence of imfs on vapor pressure
* Stronger IMFs in a liquid lower vapor pressure as fewer molecules can escape.
boiling vs evaporation
1. Boiling Point
* Temperature at which vapor pressure of a liquid equals atmospheric pressure, allowing bubbles to form and rise within the liquid.
2. Evaporation
* Surface-only process of liquid turning into gas at temperatures below boiling point.
phase diagrams purpose
1. Purpose
* Graphical representation of a substance's phases under varying temperatures and pressures.
phase diagrams key points
* Triple Point: Where all three phases coexist in equilibrium.
* Critical Point: Beyond which a substance becomes a supercritical fluid, with no distinction between liquid and gas.
phase diagrams boundaries
* Fusion (Melting) Curve: Transition between solid and liquid.
* Vaporization Curve: Transition between liquid and gas.
* Sublimation Curve: Transition between solid and gas.
moving on a phase diagram
* Moving vertically (upward) increases density, while moving horizontally (rightward) increases kinetic energy.