KMT
According to the kinetic molecular theory, describe how particle motion differs between solids and gases.
Solids: particles vibrate in fixed positions
Gases: particles move freely and rapidly.
Which two variables primarily determine the phase (solid, liquid, gas) of a pure substance?
Pressure and temperature.
Explain the relationship between the variables in Boyle’s Law.
When pressure increases, volume decreases
When pressure decreases, volume increases
indirect relationship between P and V
Name the three main types of intermolecular forces from weakest to strongest.
London dispersion < dipole–dipole < hydrogen bonding.
Why do aerosol cans warn against puncturing or exposing them to high heat?
Heat raises internal pressure; puncture or heat can cause rapid gas expansion and explosion.
Give two assumptions of the kinetic molecular theory for ideal gases.
(1) Particles are in constant random motion.
(2) Particles occupy negligible volume and are compressible.
(3) Particles have no attractive/repulsive forces.
On a phase diagram, what does the line between solid and liquid represent?
The melting/freezing point between solid and liquid phases.
Write the ideal gas law that relates the four main properties of a gas?
PV = nRT
Which intermolecular force is primarily responsible for the relatively high boiling point of water and why?
Hydrogen bonding between water molecules raises boiling point because strong directional attractions require extra energy to break.
Explain why a pressure cooker cooks food faster, using gas laws or kinetic theory language.
Higher pressure raises boiling point of water, increasing cooking temperature and speeding chemical reactions.
How does temperature affecting molecular speed?
Higher temperature → greater average kinetic energy → higher average molecular speeds.
If you heat a gas in a sealed container, this property increases as particles move faster and collide more with the walls.
pressure
A gas has 2 moles, a temperature of 300 K, and occupies 10 L. What is the pressure?
4.93 atm
Compare the expected boiling points of H2S and H2O, and explain the role of intermolecular forces in the difference.
H2O has hydrogen bonding → much higher boiling point; H2S has weaker dipole and dispersion forces → lower boiling point.
When a sealed basketball is left outside on a cold day, it feels flat because gas particles move slower and exert less force on the container walls. What are the variables and their relationship?
The relationship between temperature and pressure according to kinetic molecular theory.
A sample of gas is at room temperature. Using kinetic theory, explain why the gas exerts pressure on the walls of its container.
Gas particles collide with container walls, transferring momentum; repeated collisions produce pressure.
Explain how increasing pressure can cause a gas to liquefy.
Increasing pressure forces molecules closer, increasing intermolecular interactions and reducing kinetic freedom so gas condenses to liquid.
If a gas has a volume of 10.0 L, pressure of 2.0 atm, and temperature of 400 K, what is the number of moles?
0.61 moles
Explain how molar mass influences the strength of London dispersion forces, using two example molecules.
Larger molar mass increases strength and has stronger dispersion. Example: Br2 (higher molar mass) has stronger dispersion than O2.
When you push down on a syringe and its volume decreases, the pressure increases because gas particles collide more frequently in a smaller space. What are the variables and their relationship?
The inverse relationship between pressure and volume described by Boyle’s Law.
What happens to a sealed bottle when gas particles slow down in the cold?
The bottle collapses because the gas particles move slower and exert less pressure
When the pressure on a gas is constant, increasing its temperature causes this property to expand.
volume
A 5.0 L container holds 0.50 moles of gas at 300 K. What is the pressure inside the container?
3.0 atm
Describe how hydrogen bonding affects the physical properties of ammonia (NH3) compared to methane (CH4), referencing boiling point and solubility.
NH3 forms hydrogen bonds (higher bp, soluble in water); CH4 has only dispersion (low bp, insoluble).
Water beads up on a waxed car because strong attractions between water molecules pull them together rather than spreading out across the surface. What is this type of force?
Intermolecular forces (specifically cohesion due to hydrogen bonding)