Changes of State
The process of changing from a solid to a liquid.
Melting
A state of matter with a definite shape and volume
Solid
The transfer of thermal energy from warmer objects to cooler objects.
Heat
The temperature at which a solid changes into a liquid.
Melting point
The transfer of energy through direct particle contact.
Conduction
The process when a liquid changes to a gas.
Evaporation
A state of matter with a definite volume but no definite shape
Liquid
The total kinetic and potential energy of the particles in an object.
Thermal energy
The temperature at which a liquid becomes a solid.
Freezing point
The transfer of energy by the movement of liquids or gases
Convection
The process of changing from a gas to a liquid
Condensation
The state of matter with no definite shape or volume
Gas
What happens to particle motion when thermal energy is added?
Particles move faster.
The temperature at which a liquid changes to a gas.
What is the boiling point?
The transfer of energy through electromagnetic waves
Convection
The temperature at which a liquid becomes a solid
Freezing Point
Which state of matter is the most dense?
Solid
How are thermal energy, heat, and temperature different?
Thermal energy = total kinetic and potential energy of particles
Temperature = average kinetic energy of particles
Heat = transfer of thermal energy from warmer objects to cooler objects
What must decrease for liquid water to freeze?
Thermal energy
Warm fluids rise and cool fluids sink, creating this cycle.
Convection currents
Why is melting considered a physical change and not a chemical change?
Because it changes the state of matter, not the substance.
What happens to particle motion when thermal energy is removed?
Particle motion slows down, lowering temperature and possibly changing state.
Why doesn’t the total amount of energy in a system ever disappear?
Because of the Law of Conservation of Energy, which states energy cannot be created or destroyed
Explain what happens to particle motion as a substance goes from solid → liquid → gas.
Particles vibrate in place as a solid, slide past one another as a liquid, and move freely/spread apart as a gas, increasing motion with added energy.
A pot of water is heating on a stove. Identify where conduction, convection, and radiation are each taking place in this situation.
Conduction happens when heat transfers from the stove burner to the pot, convection occurs as warm water rises and cooler water sinks inside the pot, and radiation happens as heat leaves the stove and pot as infrared waves.