Chapter 14 Flashcards
What are the properties of Gases
- low density
- volume and shape; shape the space available, because particles move independently of one another.
- compressibility; compresses easily
- ability to mix; rapidly mix together
What are some properties of liquids
- high density
- fixed volume,adopt shape of container, because particles are affected by attractive forces.
- all other incompressible
- slowly mix together unless stirred
What are the properties of solids?
- high density
- fixed volume and shape, because particles are affected by attractive forces
- almost incompressible
- do not mix unless finely divided
Why do gases have low density?
The low density of gases relative to that of liquids and solids suggests that the particles in a gas are much more widely spaced.
The mass of any gas in a given VOLUME will be less than the mass of a liquid or solid in the same volume.
Why do gases have high compress-ability
This consistent with the observation that gases are easily compressed. Gases spread to fill the space available. This suggests that the particles of a gas move independently of each other.
The wide spacing and independent movement of particles explains why different gases mix rapidly.
What is volume?
Volume is amount of space that a substance occupies. It can be calculated by multiplying length by width by depth of a regular solid. Otherwise it can be determined by finding the volume of water displaced by the substance.
What is kinetic molecular theory of gases?
It is a model to explain gas behaviour based on the behaviour of the particles of a gas.
It is a theory that aims to explain the behaviour of gases by assuming gases are composed of a large number of particles in a random motion, these particles move in straight lines and have elastic collisions, the gas particles are very small, there is no attraction between the particles, and the average kinetic energy is related to the temperature of the gas.
What assumptions is the Kinetic Molecular theory based on? (7)
- Gases are composed of small particles, either atoms or molecules.
- The total volume occupied by the particles in a gas is negligible compared to the average distance between them. Consequently most of the volume occupied by a gas is empty space.
- Gas particles move rapidly in random, straight line collisions.
- Particles collide with each other and with walls of the container.
- The forces between the particle are extremely weak.
- Kinetic energy, the energy of motion can be transferred from one particle to another, but the total kinetic energy remains constant. Therefore collisions between gas particles are Elastic Collisions- kinetic energy is conserved.
- The average kinetic energy of the particles increases as the temperature of the gas increases.
What are elastic collisions
Collisions between particles where kinetic energy is conserved.
What is kinetic energy?
The energy that a particle or body has due to its motion (KE=1/2mv^2)
What are ideal gases?
Gases that behave according to the kinetic molecular theory are ideal gases.
In particular in an ideal gas the total volume occupied by the particles in a gas is negligible compared to the total volume of the gas, and collisions between gas particles are elastic.
Ideal gas behaviour allows us to predict the behaviour of gases in terms of how they respond to changes in pressure, volume or temperature.
Eg Oxygen, Hydrogen and Carbon Dioxide behave as ideal gases - especially as high and low temperatures, - when the space between the atoms are maximised.
When do gases not act as an a ideal gas?
As gases cool down or are placed under high pressures, the particles come closer together and the increased interactions between the particles causes the gases to show non-ideal behaviour.
Likewise gases that contain molecules with higher relative molecular masses will not behave ideally due to the larger size of the particles in the gas.
What is the relationship between molecular kinetic energy and temperature?
According to the kinetic molecular theory, the average kinetic energy of gas particles in a sample is directly proportional to the temperature of the gas. This means that as the temperature of gas sample increases, the average kinetic energy of the particles in the gas also increases.
- The average kinetic energy of a gas does not depend on the chemical identity of the gas. Eg H molecules of H2 and O molecules of O2 will have the same kinetic energy at the same temperature.
- not all particles within a sample will have the same energy. Some particles will have a lower kinetic energy and some will have higher kinetic energy. The temperature reflects the average kinetic energy of all particles in the sample.
What is the Maxwell-Boltzmann distribution graph
Also known as the kinetic energy distribution diagram is a graph which showcases the distribution of molecular kinetic energies at different temperatures.
What is diffusion?
Diffusion is the process whereby gases in a mixture spread out to uniformly fill the total volume available.
The rate at which diffusion occurs depends on the temperature of the gases, their molar masses and the average velocity of their particles.
*lighter particles like H have a higher speed (rate of velocity)
