Grade 8 Chemistry and Earth Science Study Notes

Classification of Matter

  • Metals: Left side of periodic table; shiny, malleable, ductile, good conductors.
  • Nonmetals: Right side of periodic table; dull, brittle, poor conductors.
  • Metalloids: Along the zig-zag line; have properties of both metals and nonmetals (semiconductors).

Chemical Formulas

  • Coefficient (e.g., 2 in 2H₂O): Number of molecules.
  • Subscript: Number of atoms of an element.
  • Chemical Symbol: Represents name of element.
  • Number of Elements: Corresponds to number of capital letters in the formula.

Chemical Equations

  • Reactants: Starting materials, e.g., 6CO₂ + 6H₂O.
  • Products: Resulting materials, e.g., C₆H₁₂O₆ + 6O₂.
  • Law of Conservation of Mass: Mass of reactants = Mass of products.

Changes in Matter

  • Physical Change: Changes form, no new substances (e.g., dissolving sugar).
  • Chemical Change: New substances created (e.g., baking a cake).
  • Evidence of Chemical Change: Temperature/color changes, gas production, precipitate formation.

Forces and Motion

  • Net Force: Same direction - add; opposite - subtract.
  • Balanced Force: No change in motion.
  • Unbalanced Force: Causes change in motion.
  • Calculating Speed: Speed = distance/time; Average speed = total distance/total time.

Energy

  • Potential Energy: Stored energy.
  • Kinetic Energy: Energy of motion.
  • Energy Forms: Mechanical, electrical, thermal, radiant, chemical, sound, nuclear.

Newton's Laws

  1. First Law: Objects at rest/motion stay that way unless acted upon.
  2. Second Law: a = F/m (acceleration depends on net force and mass).
  3. Third Law: For every action, there is an equal and opposite reaction.

Weather and Climate

  • Convection: Warm fluids rise, cold fluids sink; drives atmospheric currents.
  • Tropical Cyclones: Form in warm waters & low pressure; names vary by location.
  • Weather Maps: High pressure = clear skies; Low pressure = precipitation.

Earth Sciences

  • Plate Tectonics: Movement via convection; leads to landforms like mountains (convergent) and rifts (divergent).
  • Oceans: Formed by tectonic activity; essential for climate.

Ecosystems

  • Competition for Resources: Limited resources lead to competition.
  • Energy Transfer: 10% energy passed to next trophic level; includes producers, consumers, and decomposers.
  • Biodiversity: Variety of species increases sustainability.

Adaptations and Evolution

  • Adaptations: Traits suited for survival; influenced by natural and selective breeding.
  • Cell Theory: All living things made of cells; cells arise from pre-existing cells.

Cell Biology

  • Cell Organelles: Nucleus, cell membrane, mitochondria, chloroplasts, vacuoles.
  • Types of Cells: Prokaryotic (no nucleus) and Eukaryotic (with nucleus).
  • Reproductive Types: Sexual (greater diversity) vs. Asexual (less diversity).