Science exam grade 9

1. Food Web

• Producers: Organisms that make their own food via photosynthesis (e.g. grass, algae).

• Carnivore: Eats only animals (e.g. hawk, fox, snake).

• Herbivores: Eat producers (e.g. rabbit, grasshopper).

• Competition: Two species vying for the same resource—e.g., rabbit and grasshopper both eating grass.

• Sample food chain: Grass → Grasshopper → Frog → Snake → Hawk

• Energy pyramid (starting with 24 000 kJ in producers):

  • Producer (1st): 24 000 kJ

  • Primary consumer (2nd): 2 400 kJ

  • Secondary (3rd): 240 kJ

  • Tertiary (4th): 24 kJ

• Trophic level: The feeding step in a food chain—shows energy flow.

2. Earth Science Spheres

• Lithosphere: Earth’s rocky shell (crust + upper mantle)

• Biosphere: All living things + their environments

• Hydrosphere: All water (liquid, ice, vapor)

• Atmosphere: Gaseous envelope around Earth

3. Predator-Prey (Hare & Lynx)

• Relationship: Predator-prey (lynx depends on hare)

• Timing: Lynx population rises after hare population increases

• Hare population factors: Food availability, predation, disease, shelter, weather

4 & 5. Biotic vs Abiotic

• Biotic: Living things or products (e.g. bacteria, deer, apple tree, decaying wood)

• Abiotic: Non-living environmental factors (e.g. wind, temperature, water depth, air)

6. Ecosystem

A community of life (biotic) interacting with physical environment (abiotic).

7. Photosynthesis & Respiration

• Photosynthesis
  Word: CO₂ + H₂O → C₆H₁₂O₆ + O₂
  Chemical: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

• Respiration
  Word: C₆H₁₂O₆ + O₂ → CO₂ + H₂O + energy
  Chemical: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy

8. Carrying Capacity

The max number of individuals an environment can sustainably support.

9. Population Graph

Typical S-curve population graph:

• A = Lag phase

• B = Log/exponential growth

• C = Carrying capacity plateau

• D = Overshoot

• E = Die-off/crash

• F = Stabilization below capacity

10. Water Cycle

Label these processes:

• Evaporation → Condensation → Precipitation → Runoff → Infiltration & Transpiration

11. Nitrogen Cycle

• Fixation: N₂ → NH₄⁺ (by bacteria/lightning)

• Nitrification: NH₄⁺ → NO₂⁻ → NO₃⁻ (bacteria)

• Assimilation: Plants absorb nitrates

• Ammonification: Decomposition → NH₄⁺

• Denitrification: NO₃⁻ → N₂ gas (bacteria)

12. Carbon Cycle

Label: Photosynthesis, respiration, decomposition, fossil fuel combustion, ocean absorption.

• Extra carbon sources: Burning fossil fuels, deforestation, cement production

• Carbon sink: Natural stores of CO₂ (e.g. forests, oceans, soil)

13. Biotic Limiting Factors

14. Eutrophication

• Caused by nutrient (N/P) runoff—leads to algal blooms.

• Process: Oligotrophic (low nutrients) → nutrient-rich runoff → eutrophic (high nutrients, low oxygen)

15. Succession

• Primary: Begins on lifeless land (lava, rock); soil builds up (e.g. lichens start)

• Secondary: Follows disturbance with existing soil (e.g. after wildfire); faster recovery

16. H.I.P.P.O.

• Habitat loss

• Invasive species

• Pollution

• Population (humans)

• Overharvesting

17. Habitat Destruction Types

1. Deforestation

2. Urban development

3. Wetland drainage

18. Pollution Types

• Air: Smog from factory emissions

• Water: Oil spill contaminates aquatic ecosystems

19. Population Threat

High human population levels → habitat loss, resource overuse → harm to biodiversity

20. Overexploitation

Harvesting species faster than they can reproduce (e.g. overfishing)

21. Invasive Species

Non-native species that spread and harm ecosystems (e.g. zebra mussels stifle native species)

22. Integrated Pest Management

Combines biological, cultural, mechanical, and chemical methods to manage pests sustainably

23. Alternative Farming Methods

1. Organic farming

2. Crop rotation

3. Agroforestry

🔬 CHEMISTRY

1. Particle Theory

Matter is made of tiny particles that are always moving, with spaces in between.

2. States of Matter

3. Physical vs Chemical Properties

*Fragrant smell may hint at a chemical but observing it is physical.

4. Physical vs Chemical Change

• Physical: Change in form (e.g. ice melting)

• Chemical: Substance transforms into new substances (e.g. wood burning)

5. Clues of Chemical Change

1. Color change

2. Gas emission (bubbles)

3. Temperature change

4. Precipitate formation

5. Odor change

6. Solutions vs Mechanical Mixtures

• Solution: Homogeneous mix (e.g. saltwater)

• Mechanical mixture: Heterogeneous (e.g. sand in water)

7. Pure Substances Types

• Elements (one type of atom, e.g. gold)

• Compounds (two+ elements chemically combined, e.g. water)

8. PEN Table

For each, fill atomic info based on the periodic table:

• Hydrogen (H): Z=1, mass=1, p=1, e=1, n=0

• Neon (Ne): Z=10, mass=20, p=10, e=10, n=10
  ...etc.

9. Bohr-Rutherford Diagrams

Use atomic number and mass number to place protons/neutrons in nucleus and electrons in energy levels.

10. Metals vs Non-Metals

• Metals: Shiny, conduct heat/ electricity, malleable (e.g. iron, gold, aluminum)

• Non-metals: Dull, poor conductors, brittle (e.g. sulfur, oxygen, chlorine)

11. Metalloids

Found along the staircase (B, Si, Ge, As, Sb, Te, Po)

12. Periodic Table Labelling

Mark the staircase line, sectors, example period (row), group (column), and families (alkali metals, halogens, noble gases, alkaline earths)

13. Atom Counts in Molecules

• H₂O = 3 atoms

• C₁₂H₂₂O₁₁ = 35 atoms

• C₉H₈O₄ = 21 atoms

14. Element vs Compound vs Atom vs Molecule

15. Atomic Models

• Dalton: Solid sphere

• Thomson: 'Plum pudding' with electrons

• Rutherford: Tiny, dense nucleus + orbiting electrons

• Bohr: Electrons in fixed energy orbits

⚡ ELECTRICITY

1. Triboelectric Predictions

• Rubber + silk → rubber becomes negative, silk positive

• Aluminum comb will become negative, hair positive

• Glass becomes positive, cotton negative

2. Charged rod near water

Water stream bends toward the charged rod (polar molecule aligns)

3. Ebonite rods

They repel (both carry negative charge)

4. P.Balloon near another P.Balloon

They repel (like charges repel)

5. Balloon Charge Possibilities

Could be positive or negative; depends on rubbing material

6. Charge vs Neutral

• Neutral: p = e

• Positive: fewer electrons

• Negative: extra electrons

7. Law of Charges

Like charges repel, unlike attract

8. Insulator vs Conductor

• Insulator: Electrons don’t flow easily (plastic, wood)

• Conductor: Electrons flow freely (copper, metals)

9. Circuit Problems

Likely issues: break in the loop, reversed components, wrong connections

10. Primary vs Secondary Cell

• Primary: non-rechargeable (e.g. alkaline)

• Secondary: rechargeable (e.g. Li-ion)

11. Circuit Diagrams

• Use correct symbols for batteries, lamps, ammeter, voltmeter, switches

  • Series: One path

  • Parallel: Multiple paths—volt across one lamp measured by voltmeter

12. Reading Meters

Ammeter measures current (A), voltmeter measures potential difference (V)

13–15. Ohm’s Law Calculations

• 13: V = I×R = 4 A × 30 Ω = 120 V

• 14: R = V/I = 120 V ÷ 3 A = 40 Ω

• 15: R = 9 V ÷ 2 A = 4.5 Ω

16. Resistance Factors

• Length and thickness of wire, material, temperature

17. Efficiency

• η = output ÷ input = 55 J / 200 J = 27.5%

18. Laptop Cost

• Energy used per day = 0.095 kW × 12 h = 1.14 kWh

• Year = 1.14 × 365 ≈ 416 kWh

• Cost = 416 × $0.065 = $27

19. Safety Devices

• Fuse, circuit breaker, GFCI, grounding—prevent overloads and shocks

🌌 SPACE

1. Sun’s Structure

• Core: Site of nuclear fusion (hydrogen → helium)

• Layers: Radiative zone, convective zone, photosphere, chromosphere, corona

• Features: Solar flares, prominences

2. Planets Summary

3. Galaxy

We are in the Milky Way galaxy.

4. Asteroids vs Comets

• Asteroid: Rocky, in asteroid belt

• Comet: Icy, develops a tail when near Sun

5. Meteoroid → Meteor → Meteorite

• In space rock = meteoroid

• In atmosphere streak = meteor

• Hits ground = meteorite

6. Equinox vs Solstice

• Equinox: Day = night (around March 21, Sept 21)

• Solstice: Longest or shortest daylight (around June 21, Dec 21)

7. Aurora Borealis

Electrons from Sun interact with Earth’s atmosphere near poles, causing light emissions

8. Dwarf Planet

Definition: Orbit Sun, but hasn’t cleared orbit. Example: Pluto

9. Nebula, Supernova, Black Hole

• Nebula: Stellar nursery / gas cloud

• Supernova: Massive star explosion

• Black hole: Collapsed core with intense gravity

10. Hertzsprung–Russell Diagram

• Axes: Temperature (high → low), Luminosity (low → high)

  • Vega: Upper-main sequence

  • Betelgeuse: Red giant region

  • Sirius B: White dwarf region

  • Red giants: Upper right

  • White dwarfs: Lower left

  • Blue supergiants: Upper left

  • Sun: Main sequence mid-position

✅ Study Strategies

1. Break content into daily blocks (e.g. 2 sections per day)

2. Use flashcards for key terms & definitions

3. Draw and label diagrams (e.g. cycles, circuits)

4. Practice sample problems (e.g. Ohm’s Law, atomic diagrams)

5. Quiz yourself or use quizzes online