Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
The kinetic particle theory states that all matter is made up of tiny particles that are in constant, random motion.
In a solid, particles are packed closely together in a fixed, regular arrangement (lattice). They vibrate about fixed positions and have strong forces of attraction between them.
In a liquid, particles are close together but arranged randomly. They can move and slide over each other, which allows liquids to flow and take the shape of their container.
In a gas, particles are far apart and move rapidly in random directions. There are negligible forces of attraction between them, allowing gases to be compressed and to fill any available volume.
Changes of state occur when energy is added or removed. For example, melting occurs when a solid is heated and its particles gain enough kinetic energy to overcome the forces holding them in place.
Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration, such as the spread of (ammonia) gas in a room.
Thermal expansion occurs when a substance is heated; the particles move more vigorously, pushing each other further apart and increasing the overall volume.
Gas pressure is caused by the collisions of gas particles with the walls of their container. The pressure increases if the temperature rises, as the particles move faster and hit the walls with more force.
📐Formulae
💡Examples
Problem 1:
Explain why a gas like can be compressed into a smaller volume, while a solid cannot.
Solution:
Gases have large spaces between their particles, whereas solid particles are closely packed.
Explanation:
In the gas state, particles are far apart with empty space between them. Applying pressure forces these particles closer together. In a solid, the particles are already touching with no space to move closer, making them incompressible.
Problem 2:
Calculate the density of a block of metal that has a mass of and a volume of .
Solution:
Explanation:
Using the formula , we divide the mass by the volume to find how much mass is contained in each unit of volume.
Problem 3:
Describe what happens to the particles of when ice is heated to form liquid water.
Solution:
The particles gain kinetic energy and vibrate more violently until they break free from their fixed positions.
Explanation:
Heating provides thermal energy which is converted into kinetic energy. At the melting point, the vibrations become strong enough to overcome the attractive forces of the solid lattice, allowing the particles to slide over one another.