Physical and Chemical Changes - 7.2 Understanding Physical Change [ARCHIVE] Flashcards
What is the particle model?
A simplified representation of solids, liquids and gases explaining of their properties
What are the assumptions of the particle model?
Particles are…
- Hard/incompressible
- Indivisible
- Attracted to each other
- Constantly moving.
Why are solids incompressible and hold their shape?
Because the particles are tightly bound together by strong attraction and vibrate in fixed positions.
How do particles in liquids behave compared to solids?
Liquid particles are packed closely but move freely, allowing liquids to flow and take the shape of their container.
Why are gases compressible? (Pressure)
Gas particles have large spaces between them and move freely in straight lines until they collide.
How does the particle model explain expansion in solids?
As temperature increases, particles vibrate more, pushing them further apart, causing expansion.
What happens to solids when they contract?
When cooled, particles vibrate less and pack more tightly, causing contraction.
How does temperature affect the particles in a liquid?
Higher temperatures increase particle vibrations and movement, causing liquids to expand.
Why do gases expand when heated?
Gas particles move faster and hit the container more frequently, causing the container to expand if flexible.
What is melting in terms of the particle model?
When a solid is heated, particle vibrations increase until they break free from their fixed positions, becoming a liquid.
How does freezing occur?
As a liquid cools, particles lose energy and the attraction between them fixes them into solid positions.
What is a mixture?
A combination of two or more pure substances that keep their own properties.
What happens to solute particles when a solution is formed?
Solvent particles surround and carry away the solute particles, making them spread throughout the solvent.
What is evaporation?
When liquid particles gain enough energy to break free from the surface and form a gas.
At what point does boiling occur?
When liquid particles move so fast that they fly apart and form bubbles within the liquid.
How does diffusion occur in gases?
Gas particles move in straight lines until they collide with others, eventually spreading evenly.
What is condensation?
When gas particles cool, slow down, and stick together to form liquid droplets.
What is diffusion?
Where particles of two gases/liquids mix evenly without stirring.
Why does increasing temperature speed up diffusion?
Particles move faster at higher temperatures (spreading quicker).
Why is diffusion slower in liquids compared to gases?
Because liquid particles are packed more closely together than gas particles.
What is the effect of a gust of wind on diffusion?
It speeds up diffusion by pushing air particles across the room.
How does temperature affect gas pressure in a flexible container?
Higher temperatures cause particles to hit the sides more frequently, increasing pressure and expanding the container.
What happens to gas particles when cooled?
They slow down, hit the container less often, and cause the container to contract if flexible.
How are solid particles arranged?
In a fixed, tightly packed structure, only vibrating in place.
How are liquid particles arranged?
Close together but free to move past one another, allowing the liquid to flow.
How are gas particles arranged?
Far apart with little to no attraction, moving freely in straight lines until they collide.
What is the main cause of expansion in solids?
Increased vibration of particles with temperature.
What role does attraction play in the state of matter?
It binds particles in solids, is weaker in liquids, and nearly absent in gases.
How does mixing occur at the particle level?
Particles of substances mix evenly by spreading through each other, as seen in solutions and alloys.
Why do liquids evaporate faster at higher temperatures?
Because particles gain more energy, allowing more particles to escape from the liquid’s surface.
