General Science — Physics, Chemistry, and Biology Fundamentals

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General science on the Qimiyah Exam covers foundational concepts in physics, chemistry, and biology. Focus on the laws of motion, thermodynamics, atomic structure, chemical bonding, cell biology, and human body systems. The emphasis is on conceptual understanding rather than heavy calculations.

High-Yield Facts for Qimiyah:

• Newton’s Laws of Motion: (1) Inertia — objects at rest stay at rest unless acted upon; (2) F=ma (force = mass × acceleration); (3) Action–reaction — every force has an equal and opposite reaction
• Atomic structure: Nucleus (protons + neutrons) surrounded by electrons in shells/orbitals; proton number = atomic number = element identity
• Periodic table: Elements arranged by atomic number; groups (columns) have similar chemical properties; periods (rows) show trends
• Cell theory: All living organisms are composed of cells; cells come from pre-existing cells; the cell is the basic unit of life
• DNA: Double helix; genetic information stored as base pairs (A-T, G-C); found in the nucleus of eukaryotes
• ⚡ Exam tip: The mitochondria is the “powerhouse of the cell” — produces ATP through cellular respiration (glycolysis → Krebs cycle → electron transport chain)

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General Science — Qimiyah Exam (Saudi) Study Guide

Physics Fundamentals

Motion and Forces

Speed vs Velocity vs Acceleration:

• Speed: Distance traveled per unit time (scalar — no direction)
• Velocity: Speed in a given direction (vector)
• Acceleration: Change in velocity per unit time (m/s²)

Newton’s Three Laws of Motion:

1st Law (Inertia): An object remains at rest (or in uniform motion) unless a net external force acts on it. Tendency to resist changes in motion.

• Example: Seat belts in cars — your body continues moving forward when the car stops suddenly

2nd Law: F = ma (Force = mass × acceleration)

• Force measured in Newtons (N); 1 N = 1 kg·m/s²
• Example: A 10 kg object accelerating at 2 m/s² experiences a force of 20 N

3rd Law: For every action, there is an equal and opposite reaction.

• Example: Rocket propulsion — gas is expelled downward (action); rocket moves upward (reaction)

Energy

Forms of Energy:

• Kinetic energy (motion): KE = ½mv²
• Potential energy (position/gravity): PE = mgh (mass × gravity × height)
• Thermal energy: Heat from molecular motion
• Chemical energy: Stored in chemical bonds
• Electrical energy: From moving electric charges
• Light energy: Electromagnetic radiation

Conservation of Energy: Energy cannot be created or destroyed — only converted from one form to another. Total energy in a closed system remains constant.

Work: W = F × d × cos(θ) — force applied over a distance in the direction of the force

• Unit: Joule (J) = 1 N·m

Power: Rate of doing work — P = W/t

• Unit: Watt (W) = 1 J/s

Heat and Thermodynamics

Temperature vs Heat:

• Temperature: Measure of average kinetic energy of particles
• Heat: Transfer of thermal energy between objects

Three methods of heat transfer:

1. Conduction: Through solids (metal is a good conductor; wood, plastic are insulators)
2. Convection: Through fluids (liquids and gases) — hot fluid rises, cool fluid sinks
3. Radiation: Through electromagnetic waves — does not require a medium (e.g., Sun’s heat reaching Earth)

Laws of Thermodynamics:

• 1st Law: Energy is conserved — ΔU = Q – W (change in internal energy = heat added – work done)
• 2nd Law: Heat flows naturally from hot to cold objects; no process is 100% efficient — entropy (disorder) always increases in an isolated system

Waves and Sound

Wave properties:

• Wavelength (λ): Distance between successive crests
• Frequency (f): Number of waves per second (Hz)
• Speed (v): v = f × λ
• Amplitude: Height of the wave — related to energy and loudness/intensity

Sound:

• Requires a medium to travel (cannot travel through vacuum)
• Speed in air: ~343 m/s at room temperature
• Pitch determined by frequency — higher frequency = higher pitch
• Loudness determined by amplitude
• Infrasound: <20 Hz; Ultrasound: >20,000 Hz

Light:

• Speed of light: c = 3 × 10⁸ m/s in vacuum
• Electromagnetic spectrum: Radio → Microwave → Infrared → Visible → UV → X-ray → Gamma
• Visible light: ROYGBIV (Red, Orange, Yellow, Green, Blue, Indigo, Violet) — red has longest wavelength, violet shortest
• Light can be reflected, refracted (bent through a lens/prism), or absorbed

Chemistry Fundamentals

Atomic Structure

Subatomic particles:

Particle	Symbol	Charge	Mass
Proton	p⁺	+1	1 amu
Neutron	n⁰	0	1 amu
Electron	e⁻	–1	~0 amu (1/1836)

• Atomic number (Z): Number of protons — defines the element
• Mass number (A): Protons + neutrons
• Isotope: Same element (same Z), different number of neutrons (different A)
• Electron configuration: Arrangement of electrons in shells (energy levels) — e.g., Carbon (6): 2, 4

Electron shells and the Periodic Table:

• Shell 1: Maximum 2 electrons; Shell 2: Maximum 8; Shell 3: Maximum 18 (but stability rule applies for first 20 elements)
• Octet rule: Atoms tend to gain, lose, or share electrons to achieve 8 electrons in their outer shell

The Periodic Table

Groups (columns, 1–18): Elements in the same group have the same number of valence electrons → similar chemical properties

• Group 1: Alkali metals — highly reactive (especially with water)
• Group 2: Alkaline earth metals
• Groups 3–12: Transition metals
• Group 17: Halogens — highly reactive non-metals
• Group 18: Noble gases — inert (full outer shell)

Periods (rows, 1–7): Elements in the same period have the same number of electron shells

Chemical Bonding

Ionic bonds: Transfer of electrons from metal to non-metal → oppositely charged ions attract

• Example: NaCl (sodium chloride) — Na⁺ + Cl⁻
• Properties: High melting point, soluble in water, conduct electricity when dissolved

Covalent bonds: Sharing of electrons between non-metals

• Single bond: one shared pair (e.g., H₂, Cl₂)
• Double bond: two shared pairs (e.g., O₂, CO₂)
• Triple bond: three shared pairs (e.g., N₂)
• Properties: Usually gases, liquids, or low-melting-point solids; do not conduct electricity

Metallic bonds: Metal atoms share delocalized electrons in a “sea of electrons” — explains conductivity and malleability

Chemical Reactions

Types of reactions:

1. Combination/Synthesis: A + B → AB (e.g., 2H₂ + O₂ → 2H₂O)
2. Decomposition: AB → A + B (e.g., 2H₂O → 2H₂ + O₂)
3. Single replacement: A + BC → AC + B (e.g., Zn + 2HCl → ZnCl₂ + H₂)
4. Double replacement: AB + CD → AD + CB (e.g., AgNO₃ + NaCl → AgCl + NaNO₃)
5. Combustion: Organic compound + O₂ → CO₂ + H₂O (e.g., CH₄ + 2O₂ → CO₂ + 2H₂O)

Balancing chemical equations:

• Atoms cannot be created or destroyed — total atoms of each element must be equal on both sides
• Adjust coefficients (numbers in front of formulas), NOT subscripts

Biology Fundamentals

Cell Biology

Cell Theory (three principles):

1. All living organisms are composed of one or more cells
2. The cell is the basic unit of structure and function in living organisms
3. All cells arise from pre-existing cells (Rudolf Virchow, 1855)

Prokaryotic vs Eukaryotic Cells:

Feature	Prokaryote	Eukaryote
Examples	Bacteria, archaea	Plants, animals, fungi, protists
Nucleus	No (nucleoid region)	Yes — true membrane-bound nucleus
DNA	Circular chromosome	Linear chromosomes in nucleus
Membrane-bound organelles	Very few or none	Mitochondria, ER, Golgi, etc.
Size	~1–10 μm	~10–100 μm
Cell wall	Yes (peptidoglycan in bacteria)	Plants (cellulose); fungi (chitin); animals: no

Key organelles and their functions:

• Nucleus: Contains DNA; controls cell activities; site of ribosome assembly (nucleolus)
• Mitochondria: “Powerhouse of the cell” — produces ATP via cellular respiration (aerobic)
• Ribosomes: Site of protein synthesis (translation of mRNA)
• Endoplasmic reticulum (ER): Rough ER (ribosomes attached) — protein modification and transport; Smooth ER — lipid synthesis, detoxification
• Golgi apparatus: Modifies, packages, and ships proteins to their destinations
• Cell membrane: Phospholipid bilayer; controls what enters/exits the cell; cell signaling
• Chloroplasts: Site of photosynthesis in plant cells (contains chlorophyll)
• Lysosomes: Contain digestive enzymes; break down old organelles and foreign material

Cellular Respiration

Process (in mitochondria):

1. Glycolysis (in cytoplasm): Glucose → 2 pyruvate + 2 ATP (anaerobic)
2. Krebs Cycle / Citric Acid Cycle (in mitochondrial matrix): Pyruvate → CO₂ + 2 ATP + NADH + FADH₂
3. Electron Transport Chain (inner mitochondrial membrane): NADH + FADH₂ → ~34 ATP + H₂O (requires O₂ = aerobic)

Total yield: ~38 ATP per glucose (2 from glycolysis + 2 from Krebs + ~34 from ETC)

Photosynthesis (in chloroplasts):

• CO₂ + H₂O + light → glucose + O₂
• Light reactions (thylakoid membrane): Light energy captured; water split → O₂ released; ATP and NADPH produced
• Calvin cycle (stroma): CO₂ fixed into glucose using ATP and NADPH

Genetics — DNA and Inheritance

DNA Structure:

• Double helix (James Watson and Francis Crick, 1953, based on Rosalind Franklin’s X-ray data)
• Backbone: Deoxyribose sugar + phosphate
• Base pairs: Adenine (A) pairs with Thymine (T) [2 hydrogen bonds]; Guanine (G) pairs with Cytosine (C) [3 hydrogen bonds]
• Complementary base pairing: If one strand is 5’-ATGC-3’, the other is 3’-TACG-5’

DNA Replication:

• Semi-conservative: Each new DNA molecule has one original strand and one new strand
• Enzyme: DNA polymerase (adds new nucleotides in 5’→3’ direction)

RNA:

• Single-stranded; ribose sugar (not deoxyribose); uracil (U) replaces thymine (T)
• mRNA: Carries genetic code from DNA to ribosome
• tRNA: Brings amino acids to the ribosome during translation
• rRNA: Component of ribosomes

Mendel’s Laws of Inheritance:

1. Law of Dominance: In a heterozygote, one allele (dominant) masks the other (recessive)
2. Law of Segregation: During gamete formation, paired alleles separate; each gamete gets one allele from each pair
3. Law of Independent Assortment: Alleles for different traits segregate independently during gamete formation (applies to genes on different chromosomes)

Genetic crosses:

• Punnett square: Grid used to predict offspring genotypes and phenotypes
• Monohybrid cross: Single trait; typical ratio for F₂ generation of a monohybrid cross = 3:1 (dominant:recessive phenotype)
• Dihybrid cross: Two traits; F₂ generation ratio = 9:3:3:1

Human Body Systems (Brief Overview)

System	Key Organs	Function
Circulatory	Heart, arteries, veins, blood	Transport O₂, nutrients, hormones, waste
Respiratory	Lungs, trachea, bronchi	Gas exchange: O₂ in, CO₂ out
Digestive	Stomach, intestines, liver, pancreas	Break down food; absorb nutrients
Nervous	Brain, spinal cord, nerves	Control and coordination; respond to stimuli
Musculoskeletal	Bones, muscles, tendons	Support, movement, protection
Immune	White blood cells, lymph nodes, spleen	Defend against pathogens
Endocrine	Glands (pituitary, thyroid, adrenal, pancreas)	Hormones regulate body functions
Excretory	Kidneys, bladder, ureters	Remove waste (urine); maintain water/salt balance

⚡ Exam tip: Know the difference between prokaryotes and eukaryotes. Bacteria (E. coli, Staphylococcus) are prokaryotes — no nucleus, no membrane-bound organelles. All plants, animals, fungi, and protists are eukaryotes. This distinction is fundamental and frequently tested.

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