Physci

Physical Science Review

Origin of the Universe

  • Big Bang Theory

    • Universe began from an infinitely hot and dense singularity.

    • Expanded over approximately 13.7 billion years and continues to expand.

  • Nucleosynthesis

    • Creation of new atomic nuclei.

    • Types of Nucleosynthesis:

      • Big Bang Nucleosynthesis

        • Formed light elements like helium and hydrogen.

      • Stellar Nucleosynthesis

        • Occurs in stars, forming heavier elements beyond iron.

Atomic Models

  • Proponents of Atomic Models:

    • John Dalton

      • Atoms are indivisible and combine in fixed ratios.

    • JJ Thomson

      • Proposed the "plum pudding model" where electrons are scattered within a positively charged "pudding."

    • Ernest Rutherford

      • Discovered the nucleus through the gold foil experiment; concluded that atoms have a dense, positively charged nucleus.

    • Niels Bohr

      • Introduced the planetary model where electrons orbit the nucleus in fixed energy levels.

  • Structure of an Atom

    • Protons (positive), electrons (negative), and neutrons (neutral).

    • Atomic number = number of protons = number of electrons in a neutral atom.

    • Neutrons = mass number - atomic number.

Radioactive Decay

  • Types of Radioactive Decay:

    • Alpha Decay

      • Releases an alpha particle (helium nucleus).

    • Beta Decay

      • Negative Beta Decay: Releases a negative beta particle.

      • Positron Emission: Releases a positron.

    • Gamma Decay

      • Releases gamma radiation; does not change the identity of the element but stabilizes it.

Motion

  • Types of Motion:

    • Celestial Motion

      • Urinal Motion: Daily rotation of Earth affects the apparent motion of stars.

      • Annual Motion: Yearly movement of stars due to Earth's revolution around the sun.

      • Precession of Equinoxes: Slow rotation of Earth's axis affecting the position of the North Star over 26,000 years.

Models of the Universe

  • Geocentric Model (Ptolemy)

    • Earth is the center; all celestial bodies revolve around it.

  • Heliocentric Model (Copernicus)

    • Sun is the center; planets, including Earth, revolve around the sun.

  • Geohiliocentric Model (Tycho Brahe)

    • Earth and sun are centers; only the sun and moon revolve around Earth.

Kepler's Laws of Planetary Motion

  1. First Law: Planets orbit in elliptical paths.

  2. Second Law: Equal areas in equal time intervals.

  3. Third Law: The square of the orbital period is proportional to the cube of the average distance from the sun.

Aristotle vs. Galileo on Motion

  • Vertical Motion

    • Aristotle: Heavier objects fall faster.

    • Galileo: All objects fall at the same rate in a vacuum.

  • Horizontal Motion

    • Aristotle: Continuous force is needed to keep an object moving.

    • Galileo: An object in motion stays in motion unless acted upon by an external force.

Motion Graphs

  • Distance-Time Graph

    • Straight slanting line: Constant speed.

    • Horizontal line: Object at rest.

  • Velocity-Time Graph

    • Slanting line: Object is accelerating.

    • Horizontal line: Object moving at constant speed.

Newton's Laws of Motion

  1. First Law (Inertia): An object remains at rest or in uniform motion unless acted upon by an external force.

  2. Second Law (Acceleration): Acceleration is directly proportional to the force and inversely proportional to mass.

  3. Third Law (Action-Reaction): For every action, there is an equal and opposite reaction.

Momentum

  • Formula: Momentum = mass × velocity.

  • Conservation of Momentum: Total momentum before and after a collision remains constant.

  • Types of Collisions:

    • Elastic: Both momentum and kinetic energy are conserved.

    • Inelastic: Only momentum is conserved; objects may stick together.

Properties of Light

  • Reflection: Bouncing back of light from a surface.

  • Refraction: Bending of light when passing through different media.

  • Absorption: Light is absorbed by materials and converted to other forms of energy.

  • Transmission: Passage of light through a material.

Waves

  • Mechanical Waves: Require a medium to propagate.

  • Electromagnetic Waves: Can travel through a vacuum.

  • Types of Mechanical Waves:

    • Longitudinal: Parallel oscillations.

    • Transverse: Perpendicular oscillations.

Chemistry Topics

  • Polar vs. Nonpolar Molecules:

    • Polar: Unequal charge distribution; soluble in water.

    • Nonpolar: Equal charge distribution; not soluble in water.

  • Macromolecules:

    • Carbohydrates: Building blocks are monosaccharides (e.g., glucose).

    • Proteins: Made of amino acids; examples include enzymes and hemoglobin.

    • Lipids: Formed from glycerol and fatty acids; used for stored energy.

    • Nucleic Acids: Store genetic information (DNA and RNA).

  • Factors Affecting Reaction Rates:

    • Temperature: Higher temperature increases kinetic energy and reaction rates.

    • Concentration and Surface Area: Increased concentration and smaller particle size increase reaction rates.

    • Catalysts: Lower activation energy and speed up reactions.

Conclusion

  • Review all topics thoroughly to prepare for the upcoming exam.