Forces, Motion, Chemical Reactions & Genetics

MYP Unit Framework

Key Concept: CHANGE Related Concepts: Interaction. Evidence. Transformation. Global Context: Scientific and Technical Innovation (How do we explain and predict CHANGE in the natural world?) Statement of Inquiry: Scientists explain CHANGE — in motion, in matter, and in living things — by identifying the UNDERLYING CAUSES and developing MODELS that allow us to PREDICT and, sometimes, CONTROL those changes.

Inquiry Questions

Type	Question
Factual	What are Newton's three laws of motion? What happens to atoms during a chemical reaction? How are traits INHERITED?
Conceptual	Why do unbalanced forces cause ACCELERATION (not just motion)? What is CONSERVED in a chemical reaction — and what CHANGES? Why do offspring RESEMBLE their parents — but NOT exactly?
Debatable	Is there such a thing as a 'law of nature' — or are scientific laws just human CONSTRUCTIONS? Should we genetically MODIFY organisms — or is that 'playing God'?

1. Forces and Motion — Newton's Universe

Newton's First Law (Inertia)

An object at REST stays at rest. An object in MOTION stays in uniform motion — UNLESS acted upon by an external UNBALANCED force. 'This is why you lurch FORWARD when a bus stops suddenly. Your body was in motion. It WANTS to stay in motion. The seatbelt provides the EXTERNAL FORCE.'

Newton's Second Law — F = ma

Force = mass × acceleration. Unit: Newton (N). 1 N = force needed to accelerate 1 kg by 1 m/s². 'The SAME force applied to a heavier object produces LESS acceleration. A small car accelerates FASTER than a loaded truck — with the same engine force.'

Newton's Third Law — Action and Reaction

For every action, there is an EQUAL and OPPOSITE reaction. Action and reaction act on DIFFERENT bodies. 'You push DOWN on the Earth when you jump. The Earth pushes YOU up. The forces are EQUAL. But the Earth is SO massive that it barely moves — while YOU fly into the air.'

Balanced vs. Unbalanced Forces

Balanced: NO change in motion (at rest OR constant velocity). Net force = 0.
Unbalanced: ACCELERATION (change in speed OR direction). Net force ≠ 0. 'Objects don't need a force to KEEP moving. They need a force to CHANGE their motion. This was Newton's GREAT insight — and it's deeply COUNTER-INTUITIVE (Aristotle got it wrong for 2,000 years).'

2. Chemical Reactions — Atoms Rearranged

Physical vs. Chemical Change

Physical	Chemical
NO new substance. Usually REVERSIBLE.	NEW substance(s) formed. Usually IRREVERSIBLE.
Change in STATE, SHAPE, or SIZE. Melting ice. Tearing paper.	Rusting iron. Burning wood. Cooking egg.

What Happens in a Chemical Reaction?

Atoms are REARRANGED. Bonds BREAK (energy ABSORBED). New bonds FORM (energy RELEASED).
Mass is CONSERVED — total mass of reactants = total mass of products (Lavoisier's Law). 'Atoms are neither created nor destroyed — only REARRANGED.'

Types of Reactions

Type	Pattern	Example
Combination	A + B → AB	2H₂ + O₂ → 2H₂O
Decomposition	AB → A + B	CaCO₃ → CaO + CO₂
Displacement	A + BC → AC + B	Zn + CuSO₄ → ZnSO₄ + Cu
Combustion	Fuel + O₂ → CO₂ + H₂O (+ energy)	CH₄ + 2O₂ → CO₂ + 2H₂O

Exothermic vs. Endothermic

Exothermic: RELEASES energy (feels HOT). Combustion. Respiration. Neutralisation.
Endothermic: ABSORBS energy (feels COLD). Photosynthesis. Melting.

3. Genetics — The Code of Life

Mendel's Discoveries (1865 — Ignored for 35 Years!)

Gregor Mendel, an Austrian monk, bred PEA PLANTS. He observed: traits don't BLEND (red + white ≠ pink). They're passed on as DISCRETE UNITS (now called GENES). Some traits are DOMINANT. Others RECESSIVE. 'Mendel published in 1865. Almost NO ONE read his work. It was REDISCOVERED in 1900 — and became the foundation of modern genetics.'

Key Terminology

Gene: A section of DNA coding for a trait.
Allele: A variant of a gene. Example: T (tall) or t (short).
Genotype: The genetic makeup (TT, Tt, tt). Phenotype: The physical appearance (Tall, Short).
Homozygous: Two SAME alleles (TT or tt). Heterozygous: Two DIFFERENT alleles (Tt).

Monohybrid Cross (Tt × Tt)

Gametes: T or t. Punnett Square: TT, Tt, tT, tt. Phenotype ratio: 3 Tall : 1 Short. Genotype ratio: 1 TT : 2 Tt : 1 tt.

DNA — The Molecule of Heredity

Deoxyribonucleic Acid. Double HELIX (Watson & Crick, 1953). 'If you uncoiled all the DNA in ONE human cell, it would be ~2 metres long. If you uncoiled ALL the DNA in your body, it would stretch to the Sun and back — DOZENS of times.' Four bases: A (Adenine), T (Thymine), G (Guanine), C (Cytosine). Base pairing: A=T. G≡C.

'The sequence of bases IS the genetic code. A-T-G-C-C-A... It spells out instructions for building PROTEINS — the molecules that make your body WORK. A single "typo" (mutation) in this code can cause a genetic disease.'

Your Summative Assessment

Task: 'The Science Investigation' Choose ONE of: (a) Investigate how MASS affects ACCELERATION with constant force. (b) Investigate a CHEMICAL REACTION — measure mass before and after to verify CONSERVATION. (c) Create a Punnett Square model to predict offspring traits in a real or hypothetical cross. Write a formal lab report.