Essential Science Concepts: Atoms, Tissues, and Physics
1. Journey Inside the Atom
What is an atom?
The smallest basic unit of matter that makes up every element and chemical substance.
What are subatomic particles?
Particles smaller than an atom that form its internal structure. The three main particles are:
- Electrons
- Protons
- Neutrons
Define an electron
A negatively charged subatomic particle found outside the nucleus. Its relative charge is -1, and its mass is negligible (1/1836 of a proton).
Define a proton
A positively charged subatomic particle located inside the nucleus of an atom.
Define a neutron
A subatomic particle with no net electrical charge (neutral) located in the nucleus, having a mass nearly equal to that of a proton.
Atomic and Mass Numbers
- Atomic Number (Z): The total number of protons in the nucleus.
- Mass Number (A): The sum of protons and neutrons in the nucleus.
Isotopes and Isobars
- Isotopes: Atoms of the same element with the same atomic number but different mass numbers (e.g., Hydrogen: Protium, Deuterium, Tritium).
- Isobars: Atoms of different elements with different atomic numbers but the same mass number (e.g., Calcium-40 and Argon-40).
Valency
The combining capacity of an atom, determined by the number of valence electrons in its outermost shell.
2. Tissues in Action
What is a tissue?
A group of similar cells specialized to perform a specific common function together.
Plant Tissues
- Meristematic: Actively dividing tissues responsible for growth (Apical, Lateral, and Intercalary).
- Permanent: Tissues that have lost the ability to divide and have taken up a permanent shape and function.
- Parenchyma: Living cells with thin walls, responsible for food storage.
- Collenchyma: Living tissue with thickened corners providing flexibility.
- Sclerenchyma: Dead tissue with lignified walls providing rigidity.
Animal Tissues
- Epithelial: Protective covering and lining of organs.
- Connective: Includes blood, bone, cartilage, and adipose tissue.
- Muscular: Responsible for movement (Skeletal, Smooth, and Cardiac).
- Nervous: Specialized for transmitting electrical signals; the functional unit is the neuron.
3. Forces and Laws of Motion
What is a force?
A push or pull that can change an object’s state of motion. SI unit: Newton (N).
Balanced vs. Unbalanced Forces
- Balanced: Forces are equal and opposite; net force is zero.
- Unbalanced: Net force is not zero, causing acceleration.
Newton’s Laws
- Inertia: The tendency to resist changes in motion.
- First Law: Objects remain at rest or in uniform motion unless acted upon by an external force.
- Second Law: The rate of change of momentum is proportional to the applied force (F = ma).
- Third Law: To every action, there is an equal and opposite reaction.
Momentum and Friction
- Momentum (p): The product of mass and velocity (p = mv).
- Friction: The opposing contact force between sliding surfaces.
- Conservation of Momentum: Total momentum remains constant in an isolated system.
4. Simple Machines
What is a simple machine?
A device that changes the direction or magnitude of a force to make work easier.
Types of Simple Machines
- Lever: A rigid bar turning around a fulcrum (Load, Effort, Fulcrum).
- Inclined Plane: A tilted surface used to raise heavy objects.
- Pulley: A wheel with a grooved rim used to lift loads.
- Wedge: A triangular tool used for splitting or cutting.
- Screw: An inclined plane wrapped around a cylinder.
- Wheel and Axle: A larger wheel attached to a smaller axle.
Efficiency and Advantage
- Mechanical Advantage (MA): Ratio of Load to Effort.
- Efficiency: Ratio of useful work output to total work input.
5. Work and Energy
Work and Power
- Work (W): Done when force causes displacement (W = F × s).
- Power (P): The rate of doing work (P = W/t). SI unit: Watt (W).
Energy Forms
- Kinetic Energy (KE): Energy of motion (KE = 1/2mv²).
- Potential Energy (PE): Stored energy due to position.
- Mechanical Energy: The sum of KE and PE.
- Conservation of Energy: Energy cannot be created or destroyed, only transformed.
Electrical Energy
The commercial unit is the kilowatt-hour (kWh), where 1 kWh = 3.6 × 10⁶ Joules.