GCSE Science₈₄₆₅

The complex and diverse phenomena of the natural and man-made world can be described in terms of a small number of key ideas in biology, chemistry and physics, listed below.

These key ideas are of universal application, and we have embedded them throughout the subject content. They underpin many aspects of the science assessment and will therefore be assessed across all papers.

Key ideas in biology:

• life processes depend on molecules whose structure is related to their function
• the fundamental units of living organisms are cells, which may be part of highly adapted structures including tissues, organs and organ systems, enabling living processes to be performed effectively
• living organisms may form populations of single species, communities of many species and ecosystems, interacting with each other, with the environment and with humans in many different ways
• living organisms are interdependent and show adaptations to their environment
• life on Earth is dependent on photosynthesis in which green plants and algae trap light from the Sun to fix carbon dioxide and combine it with hydrogen from water to make organic compounds and oxygen
• organic compounds are used as fuels in cellular respiration to allow the other chemical reactions necessary for life
• the chemicals in ecosystems are continually cycling through the natural world
• the characteristics of a living organism are influenced by its genome and its interaction with the environment
• evolution occurs by a process of natural selection and accounts both for biodiversity and how organisms are all related to varying degrees.

Key ideas in chemistry:

• matter is composed of tiny particles called atoms and there are about 100 different naturally occurring types of atoms called elements
• elements show periodic relationships in their chemical and physical properties
• these periodic properties can be explained in terms of the atomic structure of the elements
• atoms bond by either transferring electrons from one atom to another or by sharing electrons
• the shapes of molecules (groups of atoms bonded together) and the way giant structures are arranged is of great importance in terms of the way they behave
• there are barriers to reaction so reactions occur at different rates
• chemical reactions take place in only three different ways: proton transfer; electron transfer; electron sharing
• energy is conserved in chemical reactions so can therefore be neither created or destroyed.

Key ideas in physics:

• the use of models, as in the particle model of matter or the wave models of light and of sound
• the concept of cause and effect in explaining such links as those between force and acceleration, or between changes in atomic nuclei and radioactive emissions
• the phenomena of ‘action at a distance’ and the related concept of the field as the key to analysing electrical, magnetic and gravitational effects
• that differences, for example between pressures or temperatures or electrical potentials, are the drivers of change
• that proportionality, for example between weight and mass of an object or between force and extension in a spring, is an important aspect of many models in science
• that physical laws and models are expressed in mathematical form.