Molecules and Matter

• Equation for density? mass divided by volume
• Describe atoms in a solid(2)? vibrates in fixed positions
• Atoms are packed together in a regular structure
• It is difficult to change the shape of a solid as it is held together by strong forces.
• Describe atoms in a liquid(2)? Atoms are close together and are free to move, allowing them to change shape to fit the container.
• Forces keep atoms in a liquid in contact.
• Liquids are difficult to compress as atoms are close together.
• Describe atoms in a Gas(2)? Atoms are in a constant state of random motion and are separated by large distances.
• The forces in a gas are small.
• Gases have low densities because atoms are far apart.
• Solids have high density because atoms have high mass and are packed close together.
• Internal energy is the energy stored inside a system by particles that make up the system.
• When heating increases, energy stored increases, increasing internal energy.
• Internal energy increases as atoms move faster and kinetic energy rises.
• The consequence of an increase in internal energy is a change of state.
• Melting and boiling are caused by an increase in internal energy.
• Freezing and condensation are caused by a decrease in internal energy.
• A change of state is a physical change that does not produce a new substance and is not irreversible.
• Specific heat capacity is the amount of energy required to raise the temperature of 1kg of a substance by 1 degree Celsius.
• Change in thermal energy equals mass * specific heat capacity * temperature change.
• When particles of a gas hit a wall, they exert force.
• Energy is supplied to increase the internal energy of atoms when a substance evaporates.
• When the volume of a gas is tripled, the pressure is divided by three.
• When the volume of a gas is halved, the pressure doubles.
• The pressure of a gas decreases inside a container at constant temperature when the volume increases.
• Particles do not lose energy when colliding with each other and the container.
• The equation for the change of state is: energy for change of state = mass * specific latent heat.
• The temperature of a gas is related to the average kinetic energy of particles.
• Temperature increase depends on the mass of the substance, the type of material, and the energy supplied to the system.
• Water continues to boil after it reaches 100 degrees because there is no further increase in temperature.
• Specific latent heat is the energy required to change the state of 1kg of a substance without a change in temperature.
• When a substance freezes, the internal energy of atoms reduces and energy is released to the surroundings.
• Gas atoms move in random motion.
• When a substance condenses, the internal energy of atoms reduces and energy is released to the surroundings.
• The equation for constant pressure is: p1 * v1 = p2 * v2.
• Specific latent heat of vaporisation is the energy required to turn 1kg of a liquid into 1kg of a vapour at the same temperature.
• Specific latent heat of fusion is the energy required to turn 1kg of solid into 1kg of a liquid at the same temperature.
• The temperature of a gas increases when the average kinetic energy of molecules increases.
• Energy is supplied to increase the internal energy of the atoms when a substance melts.