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IB Class 6 Science★ IB MYP Year 1 Sciences · Full Unit Coverage · Board: IB MYP

The Scientific Method, Matter and Energy — How Science Works

How do scientists KNOW what they know? The answer is the SCIENTIFIC METHOD — the most powerful TOOL ever invented for understanding the universe. Plus: What is EVERYTHING made of? MATTER. And what makes everything HAPPEN? ENERGY. IB MYP Year 1 Sciences.

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By the end of this chapter you'll be able to…

1State the 7 steps of the scientific method in order
2Define independent, dependent, and controlled variables with examples
3Distinguish hypothesis (testable prediction) from theory (well-tested explanation) from law (mathematical description)
4Describe the Semmelweis case study: observation, hypothesis, experiment, resistance, vindication
5Use the Kinetic Particle Theory to explain the 3 states of matter
6Name the 6 changes of state and whether each absorbs or releases energy
7Name 8 forms of energy and give one example of each
8Trace 3 energy transformations (e.g. burning candle, solar panel, eating food)
9State the 4 SI base units for length, mass, time, and temperature

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Why this chapter matters

This IB MYP Year 1 Sciences unit establishes the scientific thinking skills used throughout MYP and assessed in every lab. The scientific method steps (observe→question→hypothesise→experiment→analyse→conclude→communicate) are the backbone of Criterion B: Inquiring and Designing and Criterion C: Processing and Evaluating. The variable types (independent/dependent/controlled) are tested in EVERY lab report and must be defined precisely. The distinction between hypothesis/theory/law (theory is NOT a guess — it's a well-tested explanation) is a criterion D: Reflecting on the Impacts of Science conceptual anchor. The states of matter (solid/liquid/gas particle arrangement) and the 8 energy forms with transformations are core criterion A content.

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The Scientific Method, Matter and Energy

MYP Unit Framework

Key Concept: SYSTEMS Related Concepts: Evidence. Models. Transformation. Global Context: Scientific and Technical Innovation (How do we understand the natural world?) Statement of Inquiry: Scientists construct MODELS of the natural world based on EVIDENCE — and these models EVOLVE as new evidence emerges, transforming our understanding of MATTER and ENERGY.

Inquiry Questions

Type	Question
Factual	What are the steps of the scientific method? What are the states of matter?
Conceptual	How does a HYPOTHESIS differ from a THEORY? Why do scientific models CHANGE over time?
Debatable	Is there a 'scientific truth' — or are scientific facts just theories that haven't been disproven YET? Should scientists be responsible for HOW their discoveries are USED?

1. The Scientific Method — How We Know What We Know

The Cycle of Inquiry

OBSERVE (notice something interesting or puzzling) → QUESTION (ask 'why?' or 'how?') → HYPOTHESISE (make an educated guess — a testable prediction) → EXPERIMENT (design a fair test. Change ONE variable. Control the rest. Measure. Record.) → ANALYSE (look at the data. Does it support the hypothesis?) → CONCLUDE (what did you learn?) → COMMUNICATE (share your findings so others can test them too).

'And then — ASK A NEW QUESTION. Science NEVER ends. Every answer opens new questions.'

Variables in an Experiment

Variable	What It Is	Example
Independent	What YOU change	Amount of sunlight
Dependent	What you MEASURE	Plant growth (height)
Controlled	What you keep THE SAME	Type of plant. Amount of water. Soil.

Hypothesis vs. Theory vs. Law

Hypothesis: A testable PREDICTION. 'If I give the plant more sunlight, it will grow taller.'
Theory: A WELL-TESTED EXPLANATION supported by a LARGE BODY of evidence. 'The Theory of Evolution by Natural Selection.' 'The Germ Theory of Disease.' 'Theories are the HIGHEST level of scientific understanding — NOT "just a guess."'
Law: A DESCRIPTION of what ALWAYS happens under certain conditions. Often expressed mathematically. 'Newton's Law of Gravitation.' 'The Law of Conservation of Energy.'

Case Study — Semmelweis and Handwashing (1847)

Dr. Ignaz Semmelweis noticed: women in one maternity ward were DYING at MUCH higher rates than in another ward. The difference? One ward was staffed by DOCTORS (who came directly from autopsies). The other by MIDWIVES. Hypothesis: the doctors were carrying 'cadaverous particles' on their hands. Experiment: mandatory HANDWASHING with chlorinated lime. Result: death rates PLUMMETED. 'Semmelweis was RIDICULED by the medical establishment. Germ theory did not yet exist — doctors couldn't believe invisible "particles" were killing their patients. He died in an asylum. Years later, Pasteur and Koch proved him RIGHT. His story illustrates: NEW evidence often faces RESISTANCE — but the evidence EVENTUALLY wins.'

2. Matter — What Everything Is Made Of

The Kinetic Particle Theory

ALL matter is made of TINY PARTICLES (atoms/molecules). These particles are in CONSTANT, RANDOM MOTION. They have SPACES between them. They ATTRACT each other. 'The states of matter are just DIFFERENT ARRANGEMENTS of the SAME particles.'

States of Matter

State	Arrangement	Motion	Energy
Solid	Tightly packed. Fixed positions.	VIBRATE in place.	LOWEST
Liquid	Loosely packed.	SLIDE past each other.	Moderate
Gas	Very loose. Far apart.	MOVE FREELY and FAST.	HIGHEST

Changes of State — Energy Transfers

Melting (solid → liquid: heat ABSORBED). Freezing (liquid → solid: heat RELEASED). Evaporation (liquid → gas: heat ABSORBED). Condensation (gas → liquid: heat RELEASED). Sublimation (solid → gas directly: heat ABSORBED — e.g., dry ice). 'Matter doesn't "disappear." It CHANGES FORM. Mass is CONSERVED.'

3. Energy — What Makes Everything Happen

What Is Energy?

'The CAPACITY to DO WORK. Energy is NEVER created or destroyed — only TRANSFORMED from one form to another (Law of Conservation of Energy).'

Forms of Energy

Form	Description	Example
Kinetic	Energy of MOTION	Moving car. Flowing river. Wind.
Potential (Gravitational)	Energy of POSITION	Water at top of a dam. Raised hammer.
Thermal (Heat)	Energy of moving particles	Hot coffee. Sun's heat.
Chemical	Energy stored in BONDS	Food. Batteries. Fossil fuels.
Electrical	Energy of moving CHARGES	Lightning. Current in wires.
Light (Radiant)	Energy of EM waves	Sunlight. Light bulb.
Sound	Energy of VIBRATIONS	Guitar string. Vocal cords.
Nuclear	Energy stored in the NUCLEUS	Sun (fusion). Nuclear power plant (fission).

Energy Transformations

Burning candle: Chemical → Heat + Light
Solar panel: Light → Electrical
Electric fan: Electrical → Kinetic (movement) + Sound + Heat
Eating food: Chemical (food) → Kinetic (muscles) + Thermal (body heat)

4. Scientific Measurement — The SI System

Quantity	Unit	Symbol
Length	metre	m
Mass	kilogram	kg
Time	second	s
Temperature	kelvin	K

Prefixes

kilo (1000). centi (1/100). milli (1/1000). micro (1/1,000,000).

Your Summative Assessment

Task: 'The Bouncing Ball Investigation' Design and conduct an experiment to investigate: 'How does the HEIGHT from which a ball is dropped affect the HEIGHT of its bounce?' Write a full scientific report.

ATL Skills

Skill	Development
Critical Thinking	Designing experiments. Analysing data. Distinguishing correlation from causation.
Information Literacy	Collecting and recording data systematically.
Communication	Writing a scientific lab report.

Key formulas & results

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Scientific Method, Matter, Energy, and Measurement

MYP FRAMEWORK: Key Concept = SYSTEMS. Related Concepts = Evidence, Models, Transformation. Global Context = Scientific and Technical Innovation. Statement of Inquiry = 'Scientists construct MODELS of the natural world based on EVIDENCE — and these models EVOLVE as new evidence emerges.' SCIENTIFIC METHOD (7 steps): OBSERVE → QUESTION → HYPOTHESISE → EXPERIMENT → ANALYSE → CONCLUDE → COMMUNICATE. Then: ask a new question (science never ends). VARIABLES: INDEPENDENT VARIABLE: what YOU change (one variable only). DEPENDENT VARIABLE: what you MEASURE. CONTROLLED VARIABLES: everything kept the SAME to ensure a FAIR TEST. Example: Testing 'Does height of drop affect bounce height?' Independent = drop height. Dependent = bounce height. Controlled = ball type, surface, air pressure. HYPOTHESIS vs THEORY vs LAW: HYPOTHESIS: testable PREDICTION. 'IF I give more sunlight, THEN the plant will grow taller.' Must be FALSIFIABLE. THEORY: WELL-TESTED EXPLANATION supported by large body of evidence. NOT 'just a guess.' Examples: Evolution by Natural Selection, Germ Theory of Disease, Big Bang Theory, Cell Theory. LAW: DESCRIPTION of what ALWAYS happens under specific conditions, often mathematical. Newton's Laws, Law of Conservation of Energy, Boyle's Law. SEMMELWEIS CASE STUDY: Observation: women dying more in doctor-attended ward than midwife ward. Hypothesis: doctors carry 'cadaverous particles' from autopsies. Experiment: mandatory handwashing with chlorinated lime. Result: death rate PLUMMETED. Response: RIDICULED by establishment (germ theory didn't exist yet). Vindication: Pasteur and Koch later proved germ theory → Semmelweis vindicated. Lesson: new evidence faces RESISTANCE, but eventually prevails. KINETIC PARTICLE THEORY: All matter = tiny PARTICLES in CONSTANT RANDOM MOTION. Particles attract each other. Spaces between particles. STATES OF MATTER: SOLID: tightly packed, fixed positions, VIBRATE in place, lowest energy. LIQUID: loosely packed, SLIDE past each other, moderate energy. GAS: far apart, move FREELY and FAST, highest energy. CHANGES OF STATE: Melting (solid→liquid, heat ABSORBED). Freezing (liquid→solid, heat RELEASED). Evaporation (liquid→gas, heat ABSORBED). Condensation (gas→liquid, heat RELEASED). Sublimation (solid→gas directly, heat ABSORBED, e.g. dry ice/CO₂). Deposition (gas→solid directly, heat RELEASED). MASS IS CONSERVED through state changes — matter doesn't disappear, it changes form. FORMS OF ENERGY (8): Kinetic (motion). Potential/Gravitational (position). Thermal/Heat (particle movement). Chemical (stored in bonds). Electrical (moving charges). Light/Radiant (EM waves). Sound (vibrations). Nuclear (nucleus). LAW OF CONSERVATION OF ENERGY: Energy cannot be created or destroyed — only TRANSFORMED from one form to another. ENERGY TRANSFORMATIONS: Burning candle: Chemical → Heat + Light. Solar panel: Light → Electrical. Electric fan: Electrical → Kinetic + Sound + Heat (useful + wasted energy). Eating food: Chemical → Kinetic (muscles) + Thermal (body heat). SI BASE UNITS: Length = metre (m). Mass = kilogram (kg). Time = second (s). Temperature = kelvin (K). PREFIXES: kilo (×1000), centi (÷100), milli (÷1000), micro (÷1,000,000).

IB MYP ASSESSMENT CONNECTIONS: (1) Criterion B (Inquiring and Designing): Every lab must state: research question, hypothesis, independent/dependent/controlled variables, method, list of materials. The scientific method is the STRUCTURE of criterion B. (2) Criterion C (Processing and Evaluating): Data analysis, conclusion tied back to hypothesis, evaluation of the method (limitations + improvements). (3) Criterion D (Reflecting): Semmelweis case = classic example of 'How does science progress?' and 'What is the relationship between scientists and society?' (4) HYPOTHESIS FORMAT in IB labs: 'If [independent variable], then [dependent variable], because [scientific reasoning].' Example: 'If the drop height increases, then the bounce height will increase, because a ball dropped from higher has more gravitational potential energy which converts to kinetic energy, giving a harder bounce.' (5) THEORY IS NOT A GUESS: This is one of the most important scientific literacy points. In everyday language 'just a theory' means a weak idea. In SCIENCE, a theory is the STRONGEST type of explanation — it has been tested many times by many scientists and has survived every test.

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Common mistakes & fixes

These are the exact errors that cost students marks in board exams. Read them once, save yourself the trouble.

WATCH OUT

✗ Calling a scientific theory 'just a guess' or confusing the independent and dependent variables

✓ TWO CORRECTIONS: (1) THEORY IN SCIENCE: In everyday English, 'theory' can mean a vague guess. In SCIENCE, a THEORY is the HIGHEST level of scientific explanation — it means an explanation supported by a LARGE BODY of evidence from many experiments over many years. Example: The Theory of Evolution by Natural Selection has been supported by fossils, genetics, comparative anatomy, and direct observation — and has never been disproven. Saying 'evolution is just a theory' misunderstands how science works. HIERARCHY: Hypothesis (early, testable prediction) → Theory (well-tested explanation) → some become so universal they are called Laws (mathematical descriptions of what always happens). (2) VARIABLES: INDEPENDENT = what YOU decide to CHANGE in the experiment (the cause). DEPENDENT = what CHANGES AS A RESULT (the effect you measure). Simple test: 'The dependent variable DEPENDS ON the independent variable.' Example: 'How does temperature affect the speed of sugar dissolving?' INDEPENDENT = temperature (you choose and change it). DEPENDENT = time for sugar to dissolve (you measure it, it depends on the temperature). CONTROLLED = same type of sugar, same amount, same stirring. Memory aid: INDEPENDENT = I set it. DEPENDENT = it DEPENDS on what I set.

Practice problems

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Q1EASY· variables-energy-transformations

A student investigates: 'How does the amount of sugar added to water affect the boiling point?' Identify (a) the independent variable, (b) the dependent variable, (c) three controlled variables. Then trace the complete energy transformation chain for a hydroelectric power plant, starting from the Sun.

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VARIABLE IDENTIFICATION: Research question: 'How does amount of sugar added affect boiling point?' (a) INDEPENDENT VARIABLE: Amount of sugar added (in grams). This is what the student CHANGES — they decide to test different amounts (e.g. 0g, 10g, 20g, 30g, 40g). (b) DEPENDENT VARIABLE: Boiling point of the water (in °C). This is what the student MEASURES — it depends on how much sugar was added. (c) THREE CONTROLLED VARIABLES (keep the same to ensure a FAIR TEST): Same volume/amount of water each time (e.g. always 200 mL). Same type of sugar (e.g. always white granulated sugar). Same heating apparatus and heat level. (Could also include: same container/beaker size, same thermometer, same atmospheric pressure.) HYPOTHESIS (bonus): 'If more sugar is added to water, then the boiling point will increase, because dissolved solutes raise the boiling point of a solvent (boiling point elevation).' ENERGY TRANSFORMATION CHAIN — HYDROELECTRIC POWER PLANT: (1) SUN: Nuclear energy (fusion in the Sun's core) → LIGHT and HEAT energy (radiant energy reaching Earth). (2) WATER EVAPORATION: Solar/thermal energy heats ocean and lake water → evaporation → water vapour rises (kinetic energy of gas particles). (3) RAIN AND RIVER: Water vapour condenses → falls as rain → collects in rivers. Water held behind a DAM has GRAVITATIONAL POTENTIAL ENERGY (it is high up, stored energy of position). (4) TURBINE: Water is released from the dam, falling rapidly. Gravitational potential energy → KINETIC energy (moving water). Moving water spins the TURBINE. (5) GENERATOR: Turbine spins the generator. Kinetic energy → ELECTRICAL energy. (6) TRANSMISSION AND USE: Electrical energy travels through power lines → homes and factories → LIGHT (in bulbs), HEAT (in heaters), KINETIC (in motors/fans). Complete chain: Nuclear (Sun) → Radiant (sunlight) → Thermal (evaporation) → Gravitational Potential (stored water) → Kinetic (falling water) → Electrical (generator) → [Light/Heat/Kinetic in homes].

5-minute revision

The whole chapter, distilled. Read this the night before the exam.

•SCIENTIFIC METHOD (7 STEPS): Observe → Question → Hypothesise → Experiment → Analyse → Conclude → Communicate. Never linear in practice — scientists go back and forth as new evidence emerges.
•VARIABLES: INDEPENDENT = what you CHANGE (cause, only one per experiment). DEPENDENT = what you MEASURE (effect, depends on independent). CONTROLLED = what you keep the SAME to ensure a FAIR TEST.
•HYPOTHESIS FORMAT (IB requires this): 'If [independent variable changes], then [dependent variable will respond], because [scientific reasoning].' Must be FALSIFIABLE — possible to prove wrong.
•HYPOTHESIS vs THEORY vs LAW: Hypothesis = testable prediction (early). Theory = WELL-TESTED EXPLANATION (NOT a guess; supported by many experiments). Law = mathematical description of what always happens (e.g., Conservation of Energy).
•SEMMELWEIS CASE STUDY (1840s): Observed women dying in doctor wards more than midwife wards. Hypothesised contamination from autopsies. Tested with chlorinated hand-washing. Death rate plummeted. RIDICULED by establishment. Later VINDICATED by Pasteur's germ theory. Lesson: scientific resistance to new ideas is real but eventually overcome.
•KINETIC PARTICLE THEORY: All matter = particles in constant random motion. SOLID = tightly packed, vibrate in place. LIQUID = loosely packed, slide past each other. GAS = far apart, move freely. Energy increases solid → liquid → gas.
•SIX CHANGES OF STATE: Melting (S→L, absorb), Freezing (L→S, release), Evaporation (L→G, absorb), Condensation (G→L, release), Sublimation (S→G direct — dry ice, absorb), Deposition (G→S direct — frost, release).
•8 FORMS OF ENERGY: Kinetic (motion), Potential/Gravitational (position), Thermal (heat), Chemical (bonds), Electrical (charges), Light/Radiant (EM waves), Sound (vibrations), Nuclear (nucleus).
•LAW OF CONSERVATION OF ENERGY: Energy cannot be created or destroyed — only TRANSFORMED. The total energy of a closed system is constant. Energy 'lost' to heat or sound is still energy, just less useful.
•SI BASE UNITS (4 essential): metre (m) for length, kilogram (kg) for mass, second (s) for time, kelvin (K) for temperature. Prefixes: kilo (×1000), centi (÷100), milli (÷1000).

IB marks blueprint

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Where this shows up in the real world

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Exam strategy

Battle-tested tips from teachers and toppers for this chapter.

Scientific method questions: list all 7 steps IN ORDER. Don't skip 'communicate' — that step is what allows science to advance collectively. Use the word 'iterative' to show you understand science isn't linear.
Variables: ALWAYS identify all 3 types (independent, dependent, controlled). For IB labs, this is a Criterion B requirement and earns specific marks.
Hypothesis: ALWAYS use IF-THEN-BECAUSE format. The 'because' part (scientific reasoning) is where most students lose marks — don't skip it.
Particle diagrams: draw clearly different spacing for solid/liquid/gas. Add arrows showing motion. Label energy levels.
Energy transformation chains: trace from ORIGINAL SOURCE (usually the Sun) through each intermediate form to the FINAL OUTPUT. Use arrows. Identify wasted energy (usually as heat or sound).

Going beyond the textbook

For olympiad aspirants and curious learners — topics that build on this chapter.

Research the philosopher of science Karl Popper and his concept of FALSIFIABILITY (1934) — Popper argued that for a statement to be scientific, it must be possible to PROVE IT WRONG. Unfalsifiable claims (like 'invisible undetectable fairies exist') are not science. This criterion separates science from pseudoscience and explains why religious or philosophical claims, however meaningful, are not 'scientific.'
Investigate Thomas Kuhn's 'The Structure of Scientific Revolutions' (1962) — Kuhn argued that science doesn't progress smoothly but through 'PARADIGM SHIFTS' — periods where the old framework is abandoned and a new one adopted (e.g., Newtonian → Einsteinian physics; geocentric → heliocentric astronomy). The Semmelweis case is a mini paradigm shift in medicine.
Explore the THIRD LAW OF THERMODYNAMICS and the concept of ABSOLUTE ZERO (0 K = −273.15°C) — the temperature at which all particle motion theoretically stops. Scientists have approached but never reached absolute zero in laboratory experiments (the current record is a few billionths of a degree above 0 K). Investigate why absolute zero is unreachable in principle.
Research PHASE DIAGRAMS — graphs showing the state of matter (solid/liquid/gas) at different combinations of temperature and pressure. The 'TRIPLE POINT' is where all three states coexist (for water: 0.01°C at 611 Pa). Above the 'critical point,' liquid and gas become indistinguishable (supercritical fluid). Investigate how supercritical CO₂ is used for decaffeinating coffee.

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Questions students ask

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In EVERYDAY ENGLISH, 'theory' often means a hunch or guess ('my theory is that he stole the cookies'). In SCIENCE, the word has a much stronger meaning. A SCIENTIFIC THEORY is a WELL-SUBSTANTIATED EXPLANATION of some aspect of the natural world, based on a vast body of evidence from many independent experiments. Examples: the Theory of Evolution, Germ Theory of Disease, Big Bang Theory, Atomic Theory, Cell Theory. These are NOT guesses — they are the strongest explanations science offers. The HIERARCHY in science: HYPOTHESIS (a testable prediction, early-stage) → THEORY (well-tested explanation, supported by extensive evidence). Theories don't become 'facts' — they remain theories because in science, even the best explanations are always open to revision if new evidence emerges. When someone says 'evolution is just a theory,' they're misunderstanding how the word is used in science.

IB requires the IF-THEN-BECAUSE format: 'IF [independent variable changes], THEN [predicted effect on dependent variable], BECAUSE [scientific reasoning].' EXAMPLE: 'IF the temperature of the water increases, THEN the sugar will dissolve faster, BECAUSE higher temperatures mean particles move faster and collide more frequently with the sugar, breaking it apart more quickly.' Notice the three parts: (1) Names the independent variable and what changes. (2) Predicts a specific, measurable outcome on the dependent variable. (3) Gives a scientific REASON based on prior knowledge. The hypothesis must be FALSIFIABLE — possible to disprove. 'My experiment will produce interesting results' is NOT falsifiable and therefore NOT a hypothesis. The IF-THEN-BECAUSE format is required across all IB MYP science labs.

This is one of the most important EXCEPTIONS in chemistry — and life on Earth depends on it. In MOST substances, the solid form is DENSER than the liquid because particles are packed more closely together in solids. So most solid metals, plastics, etc. sink in their liquid form. WATER IS DIFFERENT because of HYDROGEN BONDING. In liquid water, hydrogen bonds form and break constantly — particles can pack relatively closely. When water FREEZES, the hydrogen bonds lock into a RIGID OPEN HEXAGONAL LATTICE — like a cage with empty space. This open structure means ice has MORE EMPTY SPACE than liquid water, so ICE IS LESS DENSE than water. Less dense things float on denser things, so ICE FLOATS. WHY THIS MATTERS for life: lakes and ponds freeze from the TOP DOWN. The ice layer INSULATES the water below, keeping it liquid in winter — allowing fish and aquatic life to survive. If water behaved 'normally,' lakes would freeze solid every winter, killing aquatic ecosystems.

These two terms are often confused but mean very different things. TEMPERATURE measures the AVERAGE KINETIC ENERGY of particles in a substance — how fast they are moving on average. Measured in degrees Celsius (°C) or kelvin (K). A cup of tea at 80°C has higher average particle motion than a bucket of water at 20°C. HEAT is the TOTAL THERMAL ENERGY that flows between objects of different temperatures. Measured in joules (J). Heat depends on BOTH temperature AND amount of substance. A bath of water at 30°C contains MORE HEAT than a cup of tea at 80°C — even though the tea is HOTTER (higher temperature), the bath has FAR MORE particles, so the total thermal energy is greater. ANALOGY: temperature is like the 'speed' of cars; heat is like the 'total energy' of all cars combined. One fast car (high temperature, low total energy) vs many slow cars (low temperature, high total energy). Heat always flows FROM higher temperature TO lower temperature, never the reverse (Second Law of Thermodynamics).

The LAW OF CONSERVATION OF ENERGY says: in any closed system, the total amount of energy stays CONSTANT — energy only changes FORM, never quantity. This single principle organises all of physics and chemistry. APPLICATIONS: (1) Every machine's efficiency = useful energy out / total energy in. The 'wasted' energy goes to heat, sound, etc., but is still energy. (2) Engineers cannot design perpetual motion machines — they would violate conservation. (3) Food → muscle motion → heat (your body radiates heat because you transform food energy). (4) Solar panels: light energy → electrical energy (the panel doesn't 'create' electricity; it transforms light). (5) In nuclear reactions, mass converts to energy (E=mc²) — Einstein's discovery EXTENDED conservation to include mass+energy as one conserved quantity. Without this law, science would be chaotic — we could never predict outcomes. Conservation of energy is one of the most experimentally validated laws in physics.