Kinetic Theory of Matter
Understanding the molecular basis of matter
1 Core Principle
Matter is composed of molecules in constant motion
All matter consists of tiny particles that are always moving, even in solids
Matter Definition
Matter: Anything that occupies space and has mass
Temperature & Motion
Absolute Zero
Temperature: -273°C
SI Unit: Kelvin (K)
The lowest attainable temperature where molecular motion ceases
Diffusion
Definition: The spreading of a substance due to molecular motion
States of Matter
SOLIDS
CHARACTERISTICS
- Low expansion rate
- Not compressible
- Definite shape & volume
- Strong intermolecular forces
MOLECULAR MOTION
Particles vibrate in fixed positions
LIQUIDS
CHARACTERISTICS
- Fixed volume
- Takes container shape
- Not compressible
- Weaker intermolecular forces
MOLECULAR MOTION
Particles slide over each other
GASES
CHARACTERISTICS
- Particles far apart
- Compressible
- No definite shape
- Low density, high expansion
MOLECULAR MOTION
Random motion in all directions
Gas Pressure
Definition
Measure of the average linear momentum of gas molecules
Causes
- Increases with temperature
- Increases with compression
Pressure
Basic Definition
Pressure: Force per unit area
SI Unit: Pascal (Pa)
P = F/A
Pressure in Solids
Factors affecting pressure:
- Force applied
- Area of contact
Pressure in Liquids
P = ρHg
ρ (rho): Density of liquid
H: Height/Depth
g: Acceleration due to gravity
Pascal's Principle
Statement: Pressure applied to an enclosed liquid is transmitted equally throughout the liquid
Key Experiments
1 Gas Pressure & Heat
MATERIALS
Volumetric flask, balloon, heat source
OBSERVATION
Balloon inflates when heated, deflates when cooled
CONCLUSION
Heat increases gas pressure and volume
2 Air Compression
MATERIALS
Bicycle pump or syringe
OBSERVATION
Pump becomes warmer after compression
CONCLUSION
Compression increases temperature due to molecular collisions
3 Diffusion Rate
MATERIALS
Water, potassium permanganate, heat source
OBSERVATION
Color spreads faster in hot water than cold water
CONCLUSION
Higher temperature increases molecular motion and diffusion rate
4 Liquid Pressure
DENSITY TEST
Higher density → Higher pressure (glycerin > water > oil)
DEPTH TEST
Greater depth → Higher pressure
CONCLUSION
Pressure depends on liquid density and depth
Atmospheric Pressure Demonstrations
🥫 Can Crushing
Steam condensation creates vacuum, atmospheric pressure crushes can
🥤 Glass Tumbler
Card stays on inverted water-filled tumbler due to atmospheric pressure
🥤 Drinking Straw
Reduced pressure inside straw allows atmospheric pressure to push liquid up
Real-World Applications
Atmospheric Pressure Effects
Drinking with Straw
Requires atmospheric pressure to push liquid up
Boiling Point
Changes with altitude due to atmospheric pressure variations
Siphon
Transfers liquid using atmospheric pressure
Engineering Applications
Dam Walls
Thicker at bottom to withstand higher water pressure
Water Systems
Use elevation to provide pressure for water flow
Hydraulic Machines
Use Pascal's principle to multiply force
Archimedes' Principle
Statement: An immersed body experiences an upthrust equal to the weight of displaced fluid
Law of Floatation
A floating body displaces its own weight of fluid
Density Applications
Ships & Submarines
Utilize buoyancy principles for floatation
Weather Balloons
Rise due to lower density than surrounding air
Hydrometer
Measures relative density using floatation
Medical Applications
Blood Transfusion
Blood flows into veins due to pressure differences
Relative Density
Definition
Density of an object compared to pure water
Relative Density = Density of Object / Density of Water
Key Points
- If RD < 1: Object floats
- If RD > 1: Object sinks
- If RD = 1: Object suspended
Key Takeaways
Kinetic Theory
All matter consists of molecules in constant motion
States of Matter
Solids, liquids, and gases have different molecular arrangements
Pressure
Force per unit area affects solids, liquids, and gases differently
Applications
Principles apply to engineering, medicine, and daily life
Remember
Temperature affects molecular motion, which influences pressure, diffusion, and state changes. Understanding these relationships helps explain many natural phenomena and technological applications.