Solids, Liquids, and Gases - AP Chemistry

1. What is the main difference between crystalline and amorphous solids?

   Crystalline solids have ordered structures; amorphous do not. Structural organization distinguishes these two solid types.

2. What is the Kinetic Molecular Theory?

   Theory explaining the behavior of gases in terms of particle motion. Model treating gases as point particles in constant random motion.

3. State the unit of the gas constant $R$ in the ideal gas law.

   L·atm/(mol·K). Units derived from $PV = nRT$ rearranged to solve for $R$.

4. What determines the boiling point of a liquid?

   Intermolecular forces and atmospheric pressure. Stronger intermolecular forces require higher temperature to overcome.

5. What is the formula for the ideal gas law?

   $PV = nRT$. Fundamental equation relating pressure, volume, moles, and temperature for ideal gases.

6. What is the definition of a volatile substance?

   A substance that readily vaporizes at low temperature. High vapor pressure leads to easy evaporation.

7. What is the primary component of air?

   Nitrogen. Comprises approximately 78% of Earth's atmospheric composition.

8. Find the density of a gas with molar mass 44 g/mol at 2 atm and 273 K.

   3.92 g/L. Using $d = \frac{PM}{RT}$ with given values yields this density.

9. What is Henry's law?

   The solubility of a gas is proportional to its partial pressure. Gas solubility increases linearly with increasing partial pressure.

10. What is the unit of pressure in the SI system?

    Pascal (Pa). Base SI unit equivalent to $N/m^2$ or $kg/(m \cdot s^2)$.

11. What is the Kinetic Molecular Theory?

    Theory explaining the behavior of gases in terms of particle motion. Model treating gases as point particles in constant random motion.

12. What is an ideal gas?

    A hypothetical gas that perfectly fits the ideal gas law. Theoretical model with no intermolecular forces or molecular volume.

13. Define 'freezing point depression'.

    Decrease in freezing point due to solute addition. Colligative property that lowers the temperature at which freezing occurs.

14. What is Avogadro's law?

    $\frac{V_1}{n_1} = \frac{V_2}{n_2}$ (constant $P$ and $T$). States that volume is directly proportional to amount of gas.

15. Define the term 'molarity'.

    Molarity is moles of solute per liter of solution. Standard concentration unit expressed as $mol/L$ or $M$.

16. What is Boyle's law?

    $P_1V_1 = P_2V_2$ (constant $T$ and $n$). Describes inverse relationship between pressure and volume at constant temperature.

17. Define 'surface tension'.

    Surface tension is the energy required to increase surface area of a liquid. Results from unequal intermolecular forces at liquid-gas interface.

18. What is the Kinetic Molecular Theory?

    Theory explaining the behavior of gases in terms of particle motion. Model treating gases as point particles in constant random motion.

19. What is the formula for calculating partial pressure?

    $P_i = X_i \times P_{\text{total}}$. Partial pressure equals mole fraction times total pressure.

20. What is the normal boiling point of a liquid?

    The boiling point at 1 atm pressure. Standard reference temperature for comparing boiling points.

21. What is Charles's law?

    $\frac{V_1}{T_1} = \frac{V_2}{T_2}$ (constant $P$ and $n$). Shows direct proportionality between volume and absolute temperature.

22. What is the critical point of a substance?

    The temperature and pressure above which a gas cannot be liquefied. Beyond this point, distinct liquid and gas phases cannot exist.

23. What is the cohesive force in liquids?

    The force of attraction between molecules in a liquid. Intermolecular attractions that hold liquid molecules together.

24. What is the relationship between temperature and vapor pressure?

    Vapor pressure increases with temperature. Higher temperature provides more kinetic energy for molecules to escape liquid phase.

25. Define 'sublimation'.

    The transition of a substance directly from solid to gas. Phase change that occurs when vapor pressure exceeds atmospheric pressure.

26. What is the boiling point of water at 1 atm in Celsius?

    100°C. Standard boiling point of pure water at standard atmospheric pressure.

27. What is the standard atmospheric pressure in atm?

    1 atm. Standard reference pressure at sea level.

28. Define 'enthalpy of fusion'.

    The change in enthalpy when 1 mole of solid melts to liquid. Energy needed to break intermolecular forces during melting process.

29. What is the term for the transition from solid to gas?

    Sublimation. Direct phase transition bypassing the liquid phase entirely.

30. Calculate the number of moles in 22.4 L of gas at STP.

    1 mole. At STP, 22.4 L equals one molar volume of any ideal gas.

31. Define the term 'vapor pressure'.

    The pressure exerted by a vapor in equilibrium with its liquid. Represents dynamic equilibrium between evaporation and condensation.

32. What is Raoult's law?

    Vapor pressure of solution is proportional to mole fraction of solvent. Describes how solutes reduce vapor pressure of solutions.

33. What is Dalton's law of partial pressures?

    Total pressure is the sum of partial pressures of gases. Each gas contributes independently to total system pressure.

34. What is the main difference between crystalline and amorphous solids?

    Crystalline solids have ordered structures; amorphous do not. Structural organization distinguishes these two solid types.

35. What is the critical temperature of a substance?

    The temperature above which a gas cannot be liquefied. Above this temperature, no amount of pressure can create liquid phase.

36. Identify the phase change from liquid to gas.

    Vaporization. Phase transition requiring energy input to overcome intermolecular forces.

37. What is the enthalpy of vaporization?

    The heat required to vaporize 1 mole of liquid. Energy required to convert liquid molecules to gas phase.

38. What is Gay-Lussac's law?

    $\frac{P_1}{T_1} = \frac{P_2}{T_2}$ (constant $V$ and $n$). Describes direct relationship between pressure and absolute temperature.

39. What is the boiling point elevation?

    Increase in boiling point due to solute addition. Colligative property dependent on solute particle concentration.

40. Define the term 'viscosity'.

    Viscosity is a measure of a fluid's resistance to flow. Property that determines how easily a fluid flows or moves.

41. What is the triple point of a substance?

    The condition where all three phases coexist in equilibrium. Unique temperature and pressure where solid, liquid, and gas phases coexist.

42. What is the main difference between crystalline and amorphous solids?

    Crystalline solids have ordered structures; amorphous do not. Structural organization distinguishes these two solid types.

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