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.