Chapter 1: Exploration: Entering the World of Secondary Science

The natural world is complex, so science uses simplified models that focus on what matters for a question. A moving car can be a single point, atoms can be spheres and bonds, and the Earth can be a smooth layered sphere.

Building a model means making assumptions and deliberately ignoring some details. For a falling object, air resistance can be ignored to understand the effect of gravity. Such choices are deliberate, not mistakes.

Science uses a shared language of terms, symbols and units so that scientists everywhere can communicate clearly. For example, mass is m, velocity is v, force is F and electric current is I. Each quantity has a defined unit.

The kilogram is used everywhere because measurements are based on agreed international standards, not local objects. Standard SI units make results comparable and avoid conversion errors, as the airplane fuel error showed.

• Law: describes a regular pattern observed in nature, often in words or mathematical relationships. Example: Newton's laws of motion.
• Theory: explains why patterns occur, based on evidence gathered over time. Example: the atomic theory explains how molecules are formed.
• Principle: a broad idea that helps make sense of a situation. Example: conservation of energy when climbing stairs.

A theory is not a guess. It is an explanation based on careful testing, and it can change when new evidence appears.

Well-established laws, theories and models let us predict what will happen under new conditions, often before an experiment is done.

When predictions match observations, confidence grows. When they do not, scientists re-examine their assumptions, models or measurements. Failed predictions drive further exploration. Good scientific questions are measurable: "What is the humidity today?" is more useful than "Will it rain?"

An equation is a compact statement about how quantities are related. Describing motion with distance, time and velocity lets us answer where an object will be later.

Learning to use mathematics in science means understanding the situation first, identifying the quantities, and then using the relationships. It does not mean memorising equations.

An approximate estimate often tells us whether a result is reasonable or impossible, even when an exact value is not needed. This builds intuition and helps detect errors.

Science is shaped by curiosity, creativity, collaboration and careful questioning. It develops over time through many people, cultures and generations, and it grows as people share results and learn from mistakes. No scientific theory is final.

Model: simplified representation of a system. Assumption: a simplification made on purpose. Estimate: a reasonable approximate value. SI unit: the standard international unit, such as the kilogram for mass.