Particulate Nature of Matter & Brownian Motion

• Matter is made up of tiny particles that are in constant, random motion.

Particulate Nature of Matter

• What John witnessed in the beam of light is known as Brownian motion.
• The particulate nature of matter can explain instances like Brownian Motion

Brownian Motion Discovery

• Named after Robert Brown who studied plants.
• Brown observed pollen grains suspended in water moving on its own.
• Brown later observed similar motion with dust particles.
• Albert Einstein later discovered the motion Brown described was from collisions between water particles and pollen grains.

Particulate Nature of Matter Explained

• Water particles are always moving randomly but are invisible to the naked eye.
• The water particles hit the pollen grain making it visibly move randomly under a light microscope.
• Matter is made up of small, discrete particles.
• Identical particles make up one pure substance.
• All matter particles move constantly and randomly.

States of Matter

• There are 3 states of matter: solid, liquid and gas
• Each state has different properties.
• Particulate nature of matter in 3 states helps us to understand the different properties.
• The air blown into a bubble will take the shape of the bubble

Particulate Model of a Solid

• Particles are held together by very strong forces of attraction.
• Unable to move freely, particles vibrate at a fixed point.
• Particles packed very closely together in a fixed, regular pattern.
• Solids have a definite shape and volume.
• Solids have higher density than liquids and gases.
• Solids cannot be compressed.

Particulate Model of a Liquid

• Held together by strong forces of attraction which allows particles to slide past each other
• Particles are packed closely together but do not have a fixed, regular pattern.
• Liquids have no definite shape but have a fixed volume.
• Liquids normally have a lower density than solids.
• Liquids cannot be compressed.

Particulate Model of a Gas

• Particles are help together by weak forces of attraction, allowing free movement over long distances.
• Particles are far apart from one another with no fixed pattern.
• Gases have no definite shape or volume.
• Gases have the lowest density.
• Gases can be compressed.

Expansion and Contraction

• Changes in movement and arrangement of particles result in expansion or contraction when matter gains or loses heat.
• When heated, particles gain energy and vibrate more vigorously and move apart causing expansion.
• When cooled, particles lose energy and vibrate less, the particle volume decreases causing contraction.
• Increased volume during expansion is due to greater distance between particles.
• Particle size does not change whether heated or cooled.
• The particulate nature of matter explains expansion and contraction while mass remains the same.
• During expansion and contraction, the distance between the metal lock particles changes, but not their size or number, conserving mass.

Changes of State

• Changes in the state of matter are melting, boiling, freezing and condensation.

Melting

• When a solid is heated, the particles gain energy and vibrates vigorously
• Particles with enough energy will overcomes forces of attraction.
• The particles break free from one another and move randomly.
• If solid ice is heated to 0°C, it melts to become liquid water.
• Melting occurs when the melting point is reached.
• Solid changes to liquid state.

Freezing

• When a liquid is cooled, the particles lose energy and move slower.
• When the particles lose enough energy, they cannot overcome the forces of attraction between particles.
• Particles then move closer and less randomly.
• When liquid water is cooled to 0°C, it freezes to become ice.
• Particles return to fixed positions and change to its solid state.

Boiling

• When a liquid is heated, the particles gain energy and vibrate more vigorously.
• Particles with enough energy overcome forces of attraction.
• Particles break free from one another and move randomly.
• When liquid water is heated to 100°C, it boils to become steam (gas).
• Boiling occurs when the boiling point is reached.
• Liquid changes to its gaseous state.

Condensation

• When a gas is cooled, the particles lose energy and move much slower and closer to one another, moving less randomly.
• As the particles get closer, the forces of attraction become stronger.
• When steam is cooled to 100°C, it condenses to become liquid water.
• The particles attract one another and move closer together, changing a gas to a liquid state.

Evaporation vs. Boiling

• Evaporation involves a change in state from liquid to gas.

• Evaporation and boiling are not the same.

• Evaporation is a slow process, boiling is fast.

• Evaporation has slow particle movement, boiling has fast particle movement.

• Parts of liquid exposed to air takes place in evaporation but this takes place throughout the whole matter in boiling.

• Evaporation occurs with non-specific temperatures, where boiling occurs only with specific temperatures above a materials boiling point.

• There is also bubble formation during the boiling process

• During heat gain or heat loss, the particles in matter gain or lose energy.

• This causes changes in the movement and arrangement of particles in matter possibly leading to a change in state.