States of matter Flashcards
What’s the arrangement of gas particles?
random
How do gas particles move?
fast in all directions
What’s the arrangement of solid particles?
regular pattern
What’s the arrangement of liquid particles?
close together
What’s the movement of solid particles?
They vibrate about fixed positions
How do liquid particles move?
around each other
How much energy do solid particles have?
little/the least
How much energy do gas particles have?
lots/the most
What 3 things happen during a state change?
- Energy is transferred to or from the particles.
- The arrangement of particles changes.
- The movement of particles changes.
What does a substance do at it’s melting point?
- Melt if energy is transferred to the particle
- Freeze if energy is transferred to the surroundings
What does a substance do at its boiling point?
- Boil if energy is transferred to the particle
- Condense if energy is transferred to the surroundings
When does a substance evaporate?
If it changes from a liquid to a gas below its boiling point.
- Particles with high enough energy leave the surface of the liquid
- The remaining particles have less energy
- The liquid cools down unless it is heated
What theory models the states of matter, with particles described as hard spheres?
The particle theory.
The table shows some data about bromine.
Melting point (degrees C): -7 Boiling point (degrees C): 59
a) Predict the state of bromine at 25 degrees C.
b) Describe, in terms of the particle theory, what happens when bromine boils.
a) liquid
b) Forces of attraction between bromine particles are overcome and the particles move far apart.
The particles no longer move around each other, but move quickly in all directions.
Are state changes physical changes or chemical changes?
Physical changes, they can be undone and what they are made of doesn’t change.
Naphthalene is a solid that can change directly from a solid to a gas at room temperature.
Name this change of state, and describe what happens to the particles.
sublimation
Forces of attraction between the particles are overcome as energy is transferred to the particles.
Arrangement changes from regular to random.
Arrangement changes from close together to far apart.
Particles no longer just vibrate about fixed positions, but can move quickly in all directions.
state change from solid to liquid
melting
state change from liquid to solid.
freezing
state change from solid to gas.
sublimation
state change from gas to solid.
deposition
state change from liquid to gas.
evaporating or boiling
state change from gas to liquid.
condensing
Are the forces of attraction between particles strongest in solids or gases?
Solids
What happens during melting?
The particles move out of a fixed position. They move around each other and have a random arrangement. The forces of attraction between them weaken, they vibrate faster and have more energy. The particles move faster.
What happens during evaporating?
The forces of attraction weaken, the particles stay in a random arrangement. The particles move away from each other and move fast in all directions. The move very quickly and have lots of energy. The particles get faster/vibrate faster.
Explain what happens during condensing.
The particles lose energy, the forces of attraction grow stronger. The particles get slower and closer together.
Describe the following for solid, liquid and gas - arrangement of particles, movement of particles, the particles relative energy.
Solid: The particles are in a fixed and regular position. They vibrate slightly. They have little energy.
Liquid: The particles are arranged randomly but are still touching. They move quickly over each other. They have more energy than a solid.
Gas: The particles are far apart and random. They move quickly in all directions until they bounce off something. They have a lot of/the most energy.
Water molecules have forces of attraction between themselves. This is what holds the particles in their solid state.
What must happen to the strength of these attractive forces when changes of state happen, such as melting and evaporating? Explain your answer.
They weaken as the particles gain more energy and are able to move away from each other.
What causes attractive forces to weaken or strengthen during changes of state?
The particles gaining or losing energy.
What does a horizontal line on a temperature/time graph represent?
A state change taking place.
