IB MYP Sciences: Key concepts in MYP Sciences – Study Guide

This study guide teaches the key concepts of IB MYP Sciences, what each means in science, and how they combine with related concepts and a global context to build a statement of inquiry. It follows the IB MYP Sciences guide (for use from September 2014/January 2015; published May 2014, updated May 2019), and suits MYP years 4 and 5. There is no SL/HL split in the MYP.

MYP has no prescribed content list: schools design their own science units. Key concepts are different: the guide prescribes them, and teachers must use them to plan the curriculum.

Use this page with the key concepts revision notes and the key concepts practice questions. The course hub is at /boards/ib/ib-myp/myp-sciences/ and the printable checklist is at /checklists/ib/ib-myp/myp-sciences/.

What this unit covers

Area	What you should be able to do
The MYP key concepts	Say what a key concept is, and name the three the guide gives for sciences
Change	Describe change as a difference in a system’s state over time; sort changes into qualitative or quantitative, and reversible, irreversible or self-perpetuating
Relationships	Find, describe and test a link between variables; connect form and function; explain why scientists model relationships
Systems	Identify the parts of a system and how they depend on each other; tell open systems from closed ones
Other key concepts	Explain how development, creativity, and time, place and space also matter in science
Building an inquiry	Combine a key concept, related concepts and a global context into a statement of inquiry; write factual, conceptual and debatable questions

What a key concept is

The guide describes a concept as a “big idea” that lasts and reaches beyond one topic or time. Key concepts are the broadest of these. They work across every MYP subject, which is how they link your science lessons to the rest of your timetable.

There are sixteen MYP key concepts in total. Here they are, with the three sciences ones marked.

Key concept	Contributed by sciences?
Change	Yes
Relationships	Yes
Systems	Yes
Aesthetics, communication, communities, connections, creativity, culture, development, form, global interactions, identity, logic, perspective, time, place and space	No (but some still matter in science – see below)

Within sciences, key concepts link biology, chemistry and physics; across subjects, they link science to, say, geography or design. In the guide’s example units, each statement of inquiry is built on one key concept. Your teacher’s unit plan will name the one for your unit.

Change

General meaning. Change is a movement or conversion from one form, state or value to another. To inquire into change, you look at its causes, the process, and its consequences.

In sciences. The guide frames change as the difference in a system’s state when you observe it at different times. That gives you two questions to ask about any change.

1. Is it qualitative or quantitative?

• Qualitative change is a difference in kind: structure, behaviour or level. A tadpole growing legs and losing its tail is qualitative.
• Quantitative change is a difference you measure as a number or a rate. A ball’s speed rising as it falls is quantitative.

2. Is it reversible, irreversible or self-perpetuating?

Type	Biology	Chemistry	Physics
Reversible	Blood glucose rises after a meal, then the body brings it back down	Blue hydrated copper(II) sulfate turns white when heated; adding water turns it blue again	Ice melts and the water can be refrozen
Irreversible	A tadpole becomes a frog	Methane burns to carbon dioxide and water	A spring stretched past its elastic limit stays longer
Self-perpetuating	A bacterial population: each new cell can divide again, so growth feeds more growth	A fire: the heat released ignites more fuel, which releases more heat	A fission chain reaction: neutrons released by one split nucleus split others

Worked example: describing a change fully

Question. A fictional cup of tea cools from 80 °C to 52 °C in 10 minutes. Describe this change using the key concept of change.

Answer. The system is the cup of tea and its surroundings. The change is quantitative: the temperature falls by 28 °C, a mean rate of 2.8 °C per minute. It is reversible, because the tea can be reheated. The cause is energy transfer from the hotter tea to the cooler air. The consequence is that the rate of cooling slows as the temperature difference shrinks.

Note the four parts: system, type, cause, consequence.

Relationships

General meaning. Relationships are connections between properties, objects, people and ideas. A change in a relationship has consequences, small or far-reaching.

In sciences. A relationship is a connection between variables that you find by observation or experiment, and that you can test by experiment. The guide picks out two more ideas.

Form and function. Scientists often look for the link between how something is built and what it does.

• Biology: lungs contain millions of tiny alveoli with walls one cell thick. Many alveoli give a large surface area; thin walls give a short diffusion path. Both speed up gas exchange.
• Chemistry: a car’s catalytic converter coats its catalyst on a honeycomb structure. The honeycomb gives a large surface area, so more exhaust gas meets the catalyst.
• Physics: a high-speed train has a long, pointed nose. The streamlined form reduces air resistance at high speed.

Modelling. When a relationship involves huge scales, too much data or very long times, scientists model it instead of observing it directly. Climate models and models of planetary orbits are examples.

Worked example: finding a relationship in data

Question. In a fictional experiment, magnesium ribbon reacts with hydrochloric acid at three concentrations. The time for the ribbon to disappear is recorded.

Concentration (mol/dm³)	Time (s)
0.5	80
1.0	40
2.0	20

Describe the relationship between concentration and rate.

Answer. Each time the concentration doubles, the time halves, so 1/time (a measure of rate) goes 0.0125, 0.025, 0.050 s⁻¹. Rate is directly proportional to concentration over this range. A scientific reason: more acid particles in the same volume means more frequent collisions with the magnesium.

Worked example: a relationship between size and surface

Question. Model three cells as cubes of side 1 cm, 2 cm and 4 cm. Find each surface area to volume (SA:V) ratio and state the relationship.

Answer.

side 1 cm: SA = 6 cm²,  V = 1 cm³,  SA:V = 6 : 1
side 2 cm: SA = 24 cm², V = 8 cm³,  SA:V = 3 : 1
side 4 cm: SA = 96 cm², V = 64 cm³, SA:V = 1.5 : 1

As side length doubles, SA:V halves. Bigger organisms have less surface per unit of volume, which is why large animals need exchange surfaces such as alveoli. The cube is a model, but the relationship holds.

Systems

General meaning. A system is a set of interacting or interdependent parts. Systems give structure and order to natural, human and built environments. They can be static or dynamic, simple or complex.

In sciences. A system’s parts work because they depend on, or complement, each other. Remove one part and the whole behaves differently.

• Biology: the circulatory system. The heart pumps, vessels carry, blood transports.
• Chemistry: a reaction mixture in a flask. Reactants, products, solvent, container and surroundings all interact.
• Physics: an electric circuit. The cell, wires, switch and lamp only work together; break the circuit anywhere and the current stops everywhere.

Open and closed systems. In the guide’s sense, a closed system is one where resources are not removed or replaced. An open system has its resources renewed regularly.

• A sealed bottle garden is close to a closed system for matter: water and carbon are recycled inside. Light energy still enters through the glass.
• A pond is open: water, nutrients and organisms enter and leave.
• Steel wool burned on a balance in open air gains mass, because oxygen from outside the system combines with the iron. Burn it in a sealed container and the total mass stays the same.

The guide notes that models often use closed systems to simplify or limit variables. A “frictionless” pendulum in a physics model is an example: no energy leaves it.

Later you will meet stricter meanings: in physics and chemistry, a closed system exchanges energy but not matter, and an isolated system exchanges neither.

Other key concepts that matter in sciences

The guide says other key concepts can be important too, and names three.

• Development. Scientific knowledge grows through change. Mendeleev left gaps in his periodic table and predicted the properties of undiscovered elements; when gallium and germanium were found, they fitted his predictions.
• Time, place and space. Science shapes how we define and measure these. The SI second is defined using the radiation from a transition between two energy levels in caesium-133 atoms. Astronomers measure distance in light-years.
• Creativity. Scientists need imagination to extend what is known. Designing an experiment to measure something you cannot see directly, such as estimating the size of a molecule from the area an oil drop spreads to, is a creative act.

From key concept to statement of inquiry

Key concepts never work alone. In an MYP unit they combine with two other parts.

1. A key concept – for example, systems.
2. Related concepts – narrower, discipline-based ideas. The guide lists twelve for each science. Nine appear in all three lists: consequences, energy, evidence, form, function, interaction, models, movement and patterns. Biology adds balance, environment and transformation; chemistry adds balance, conditions and transfer; physics adds development, environment and transformation. Teachers may choose others.
3. One global context – the reason the inquiry matters. The six are identities and relationships; orientation in space and time; personal and cultural expression; scientific and technical innovation; globalization and sustainability; fairness and development. The guide says many science inquiries fall naturally into scientific and technical innovation, but over time you should meet all six.

A statement of inquiry puts the concepts into the global context in one sentence. A useful check (a Marlbridge planning aid, not IB wording): is it true beyond the unit’s single topic?

Worked example: building a statement of inquiry

Unit topic: acid rain and limestone buildings (chemistry). Key concept: change. Related concepts: conditions, consequences. Global context: globalization and sustainability.

• Weak: “Acid rain damages limestone.” This is a fact about one topic. It has no concept and no global context.
• Better: “The conditions humans create in the environment can cause changes whose consequences reach far beyond their source.”

It uses change, conditions and consequences, points at sustainability, and would also fit a unit on ocean acidification. That transferability is what makes it strong.

Inquiry questions

The statement of inquiry generates three kinds of question.

Type	What it does	Example for the acid rain unit
Factual	Remembers facts and topics	What gas forms when acid reacts with calcium carbonate?
Conceptual	Analyses big ideas	How do changes in conditions alter the rate of a chemical change?
Debatable	Evaluates perspectives and develops theories	Should countries that cause acid rain pay for damage in neighbouring countries?

A quick test of our own: a textbook settles a factual question; a conceptual answer explains a pattern that applies elsewhere; a debatable one can be argued either way with evidence.

Common errors

• Naming a key concept without saying what it means in science. “Change is when something changes” earns little; “a difference in the system’s state at two times” earns more.
• Calling every change “irreversible”. Melting, dissolving and many reactions such as dehydrating copper(II) sulfate can be reversed.
• Treating a correlation as a tested relationship. In science, a relationship should be testable by experiment.
• Writing a statement of inquiry that is just a topic fact. It needs concepts and a global context, and should transfer.

Where next

Revise from the key concepts revision notes, then try the practice questions. For concepts in real units, see the cycles study guide and the evolution and interactions guide; for assessment, see criteria in practice.

Official syllabus

This page is aligned to the IB MYP Sciences guide (for use from September 2014/January 2015; published May 2014, updated May 2019), International Baccalaureate Organization. Your teacher will share the task-specific clarifications for any assessed work.