Science summative 1

Definition of Atmosphere
- The atmosphere is a layer of gases surrounding Earth.
- It protects life by absorbing harmful solar radiation and maintaining temperature.
Composition of the Atmosphere
  - Main gases:
    - Nitrogen: 78%
    - Oxygen: 21%
    - Carbon dioxide (CO₂): 0.3%
    - Other gases: 0.97% (including argon, hydrogen, etc.)
Layers of the Atmosphere
  - Troposphere:
    - Closest layer to Earth.
    - Weather occurs here.
  - Stratosphere:
    - Contains the ozone layer.
    - Absorbs UV radiation.
  - Mesosphere:
    - Closest layer where meteors burn up.
  - Thermosphere:
    - Hottest layer.
    - Auroras can be seen here.
  - Exosphere:
    - Outermost layer.
    - Merges with outer space.
Climate Change
  - Definition: Long-term change in global temperature and weather patterns.
  - Causes of Climate Change:
    - Natural Causes:
      - Volcanic eruptions releasing gases.
    - Natural changes in the atmosphere.
    - Examples include volcanic activity, solar output changes.
    - Human Causes:
      - Burning fossil fuels.
      - Deforestation.
      - Agricultural practices.
  - Mitigation:
    - The process of preventing climate change from occurring.

Greenhouse Gases
  - Major greenhouse gases include:
    - Methane (CH₄)
    - Carbon dioxide (CO₂)
    - Water vapor (H₂O)
Air Pollution
  - Sources can be natural or human-induced.
  - Consequences for health: lung cancer, heart disease, and mortality due to air pollution.
  - Types of air pollution include smog, which reduces visibility and affects breathing.
Causes of Air Pollution
  - Natural Causes:
    - Dust storms, volcanic eruptions, wildfires.
  - Human Causes:
    - Emissions from vehicles.
    - Industrial activities.
    - Waste disposal practices (e.g., plastic waste).
Types of Smog
  - Photochemical Smog:
    - Formed by the reaction of sunlight with pollutants.
  - Industrial Smog:
    - Results from burning coal and heavy industrial emissions.
Chemical Reactions
- Chemical indicators can show if a substance is an acid or a base.

Indicators
- No color indicates an acid.
- Presence of color indicates a base.
Periodic Table Elements
  - Top 20 elements:
    - Hydrogen (H), Helium (He), Lithium (Li), Beryllium (Be), Boron (B),
    - Carbon (C), Nitrogen (N), Oxygen (O), Fluorine (F), Neon (Ne),
    - Sodium (Na), Magnesium (Mg), Aluminum (Al), Silicon (Si),
    - Phosphorus (P), Sulfur (S), Chlorine (Cl), Argon (Ar),
    - Potassium (K), Calcium (Ca).
Definitions
  - Atom: The smallest particle of an element.
  - Element: A pure substance made of only one type of atom.
  - Molecule: A group of two or more atoms chemically bonded together. It can have the same or different atoms.
  - Compound: A substance formed from two or more different elements chemically bonded in a fixed ratio.
  - Ion: An atom or group of atoms with an electric charge due to loss or gain of electrons.
Chemical Symbols
  - Symbols for phases:
    - (s) - solid
    - (l) - liquid
    - (g) - gas
    - (aq) - aqueous (dissolved in water)
Basic Chemical Reactions
  - Metals + Oxygen → Metal Oxides.
  - Metals + Water → Metal Hydroxides + Hydrogen Gas.
  - Acids + Bases → Salt + Water.
  - Metals + Acids → Salt + Hydrogen Gas.

Displacement Reaction
- Involves a more reactive metal displacing a less reactive metal in compounds.
Reactivity Series
  - Order of reactivity:
    1. Potassium
    2. Sodium
    3. Calcium
    4. Magnesium
    5. Aluminum
    6. Zinc
    7. Iron
    8. Tin
    9. Lead
    10. Copper
    11. Silver
    12. Gold
    13. Platinum
  - Mnemonic to remember: "Please Stop Calling Me A Nice Zebra Instead Try Learning Copper Saves Gold."