Key Takeaways
- Three states of matter: solid (fixed shape/volume), liquid (fixed volume), gas (fills container)
- Physical change = no new substance; Chemical change = new substance formed
- Energy forms: kinetic, potential, thermal, light, sound, electrical
- Newton's 1st Law: Objects resist change in motion (inertia)
- Six simple machines: lever, wheel/axle, pulley, inclined plane, wedge, screw
Last updated: January 2026
4.3 Physical Science
Physical Science covers about 34% of the Science subtest, including matter, energy, forces, and motion.
States of Matter
| State | Particle Movement | Shape | Volume |
|---|---|---|---|
| Solid | Vibrate in place | Fixed | Fixed |
| Liquid | Slide past each other | Takes container shape | Fixed |
| Gas | Move freely, spread out | Takes container shape | Fills container |
Changes of State:
- Melting: Solid → Liquid (add heat)
- Freezing: Liquid → Solid (remove heat)
- Evaporation: Liquid → Gas (add heat)
- Condensation: Gas → Liquid (remove heat)
- Sublimation: Solid → Gas (dry ice)
Physical vs. Chemical Changes
| Physical Change | Chemical Change |
|---|---|
| No new substance formed | New substance formed |
| Usually reversible | Usually irreversible |
| Examples: cutting, melting, dissolving | Examples: burning, rusting, cooking |
Properties of Matter
Physical properties: Can be observed without changing the substance
- Color, shape, size, texture
- Mass, volume, density
- Melting point, boiling point
Chemical properties: How matter reacts with other substances
- Flammability
- Reactivity with acids
Density = Mass ÷ Volume
Energy
Forms of energy:
| Form | Description |
|---|---|
| Kinetic | Energy of motion |
| Potential | Stored energy (position, chemical, elastic) |
| Thermal (Heat) | Energy from particle motion |
| Light | Electromagnetic energy |
| Sound | Energy from vibrations |
| Electrical | Energy from moving electrons |
Energy can change forms but cannot be created or destroyed (Law of Conservation of Energy)
Forces and Motion
Force: A push or pull on an object
Newton's Laws of Motion:
- Inertia: Object at rest stays at rest; object in motion stays in motion (unless acted on by a force)
- F = ma: Force = mass × acceleration
- Action-Reaction: Every action has an equal and opposite reaction
Types of forces:
- Gravity: Pull between objects with mass
- Friction: Resistance between surfaces
- Magnetism: Push/pull between magnets
Simple Machines
| Machine | Function | Example |
|---|---|---|
| Lever | Lifts loads | Seesaw, hammer |
| Wheel and Axle | Reduces friction | Doorknob, steering wheel |
| Pulley | Changes direction of force | Flagpole, blinds |
| Inclined Plane | Reduces effort needed | Ramp |
| Wedge | Splits objects | Axe, knife |
| Screw | Holds objects together | Jar lid |
Test Your Knowledge
Which of the following is a chemical change?
A
B
C
D
Test Your Knowledge
According to Newton's First Law, what happens to an object at rest?
A
B
C
D
Test Your Knowledge
A ramp is an example of which simple machine?
A
B
C
D
Test Your Knowledge
What is the formula for density?
A
B
C
D
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