Grade 9 Science: Particle Theory of Matter

Particle Theory of Matter

• All matter is composed of tiny particles.
• These particles are constantly moving.
• Particles attract each other.
• Particles have spaces between them.
• Heating increases particle speed and energy, potentially breaking bonds, leading to phase changes (e.g., ice to water).

Classification of Matter

• Pure Substances: Contain only one type of particle.
  • Elements: Examples include oxygen (O₂) and gold (Au).
  • Compounds: Examples include water (H₂O) and carbon dioxide (CO₂).
• Mixtures: Contain more than one type of particle.
  • Mechanical Mixtures (Heterogeneous): Distinct parts are visible (e.g., trail mix, sand and iron filings).
  • Solutions (Homogeneous): Uniform appearance, particles evenly distributed (e.g., saltwater, vinegar).

Properties of Matter

• Physical Property: Characteristics observed without changing the substance's composition.
  • Qualitative: Describes qualities (e.g., color, texture, state).
  • Quantitative: Describes measurable quantities (e.g., density, melting point, viscosity).
• Chemical Property: Describes the substance's ability to undergo a chemical change, forming new substances (e.g., flammability, reactivity).

Changes in Matter

• Physical Change: No new substance is formed; it alters the physical state, shape, or size (e.g., melting ice, breaking a stick).
• Chemical Change: New substances are created; recognizable signs include:
  • Color change
  • Gas production (bubbles)
  • Precipitate formation (solid in a liquid)
  • Heat or light release/absorption
  • Irreversibility (e.g., rusting, burning wood).

Density

• Definition: Mass per unit volume.
• Formula: Density = Mass ÷ Volume
• Units: g/cm³ or g/mL.
• Example: A sample with 50 g and 25 cm³ has a density of 2 g/cm³.

The Periodic Table

• Key Groups:
  • Metals: Shiny, good conductors, malleable (e.g., aluminum).
  • Non-Metals: Dull, poor conductors, brittle (e.g., sulfur).
  • Metalloids: Properties of both metals and non-metals (e.g., silicon).
• Families (Groups): Elements with similar chemical properties.
  • Alkali Metals (Group 1): Highly reactive, soft, 1 valence electron.
  • Alkaline Earth Metals (Group 2): Reactive, 2 valence electrons.
  • Halogens (Group 17): Very reactive non-metals, form salts.
  • Noble Gases (Group 18): Unreactive, full outer energy levels.
• Trends: Properties change progressively across periods (rows) and exhibit similarities within groups (columns).

Atoms and Subatomic Particles

• Subatomic Particles:
  • Proton: Positive charge, in the nucleus, mass ≈ 1 amu.
  • Neutron: Neutral charge, in the nucleus, mass ≈ 1 amu.
  • Electron: Negative charge, outside the nucleus, negligible mass.
• Atomic Number: Number of protons (and electrons in a neutral atom).
• Atomic Mass: Number of protons + neutrons.
• Example (Carbon): Atomic number 6 (6 protons, 6 electrons); Atomic mass 12 (6 protons + 6 neutrons).

Bohr-Rutherford Diagrams

• Drawing Steps:
  1. Place protons and neutrons in the nucleus.
  2. Distribute electrons in shells (2 in first, 8 in second, etc.)

Molecules and Ions

• Molecule: Two or more atoms bonded together (e.g., H₂O, O₂).
• Ion: Charged particle formed when an atom gains/loses electrons.
  • Cation: Positive ion (loses electrons).
  • Anion: Negative ion (gains electrons).

Static Electricity

• Static Electricity: Buildup of electric charge on a material's surface.
• Electron Movement: Only electrons can move between objects.
• Neutral Objects: Equal numbers of protons and electrons.
• Charging Methods:
  • Friction: Rubbing transfers electrons.
  • Conduction: Direct contact transfers electrons.
  • Induction: Rearranging electrons without contact.

Electric Discharge and Lightning

• Electric Discharge: Rapid electron transfer.
  • Example: Spark from doorknob.
• Lightning: Large discharge in clouds, usually caused by air friction.
• Lightning Rods: Conduct lightning safely to the ground.
• Dangers of Lightning: High voltage and heat.

Conductors and Insulators

• Conductor: Allows easy electron flow (e.g., metals).
• Insulator: Resists electron flow (e.g., rubber, plastic).

Grounding

• Grounding: Connecting a charged object to the earth to neutralize the charge by transferring electrons.

Current Electricity

• Electrical Energy: Energy from electron movement.
• Electric Cells: Convert chemical energy to electrical energy (e.g., batteries).
• Direct Current (DC): Electrons flow one way (batteries).
• Alternating Current (AC): Electrons change direction (wall outlets).

Electrical Circuits

• Circuit Components:
  • Energy source (e.g., battery)
  • Load (e.g., lamp, motor)
  • Conducting wires
  • Switch
• Circuits:
  • Series: One path, all loads share current, failure stops the circuit.
  • Parallel: Multiple paths, loads independent, failure doesn't stop the entire circuit.

Measuring Electricity

• Electric Current (I): Electron flow, measured in amperes (A) by an ammeter.
• Potential Difference (Voltage): Energy difference between circuit points, measured in volts (V) by a voltmeter.
• Resistance (R): Opposition to current, measured in ohms (Ω).
• Ohm’s Law: V = I × R

Astronomy

• Celestial Objects: Objects in space (planets, stars, moons, comets).

• Stars: Luminous objects generating energy via nuclear fusion.

• Planets: Orbit stars, are massive enough to be rounded by gravity, and have cleared their orbits.

• Solar System: Star (e.g., Sun) and all objects orbiting it.

• Galaxy: A massive system of stars, planets, gas, and dust.

• Universe: Everything that exists (galaxies, stars, matter).

• Orbit: Path a celestial object takes around another due to gravity.

• Electromagnetic Radiation: Energy waves like light and radio waves.

• Solar Phenomena:

  • Sunspots: Dark areas on the Sun from magnetic activity.
  • Solar Flares: Sudden bursts of solar energy.
  • Prominences: Large, bright gas loops.
  • Aurora Borealis: Northern Lights from solar particles interacting with Earth's atmosphere.

• Solar System Objects:

  • Astronomical Unit (AU): Average Earth-Sun distance (150 million km).
  • Dwarf Planet: Orbits the Sun but hasn't cleared its orbit (e.g., Pluto).
  • Asteroid: Small, rocky object orbiting the Sun.
  • Meteoroid: Small rock or particle in space.
  • Comet: Ice, rock, and dust with a tail when near the Sun.

• Celestial Motion:

  • Gravity: Attraction between objects with mass.
  • Solstices: Extreme points in Earth's orbit, causing longest or shortest days.
  • Equinoxes: Day and night are equal length.
  • Lunar Cycle/Phases: Moon's changing appearance.
  • Eclipses: Solar (Sun blocked by Moon) and Lunar (Earth blocks Sun from Moon).
  • Tides: Ocean level changes from Moon's and Sun's gravity.

• Earth's Motion:

  • Rotation: Spinning of Earth on its axis (day and night).
  • Revolution: Earth orbiting the Sun (seasons).

• Models of the Solar System:

  • Geocentric: Earth at the center.
  • Heliocentric: Sun at the center.

• Constellations: Groups of stars forming patterns.

Test your understanding of the Particle Theory of Matter and the classification of different types of matter. This quiz covers pure substances, mixtures, and the properties of matter. It's designed for Grade 9 science students looking to reinforce their knowledge on these fundamental concepts.