What is the physical change of matter

Basic concept structure of matter

Questions about the properties, the composition, the changes and the origin of matter are fundamental questions in physics and chemistry. The macroscopic view of matter leads to the characterization and classification of substances and their properties, while the submicroscopic view uses models to describe the structure of matter, depending on the context to be represented. The investigation of material phenomena (states and processes) and their interpretation with the help of models at the submicroscopic level are fundamental concerns of teaching in chemistry and physics. The basic concept of matter summarizes the essential phenomena, experimental findings, logical considerations and models that have led the natural sciences to present-day ideas about the structure of matter and the interactions between the small particles that make up matter.

Students first encounter matter in objects from their daily area of ‚Äč‚Äčexperience (physics calls them bodies) and the substances they are made of and which determine their properties. They learn to differentiate, characterize and classify bodies and substances according to their appearance, properties and possible uses. Body have z. B. Surface, mass and volume. Bodies and substances can be gaseous, liquid or solid. Substances have characteristic physical properties such as B. density, melting and boiling temperature and specific conductivity and chemical properties. They react to heating or cooling by changing their density and, if necessary, can also change their physical state and thus their appearance. Some substances are inherently magnetic or magnetizable.

Substances can be present as pure substances or as a mixture of substances. A mixture is created by physical processes (mixing), whereby the properties of the pure substances (element substances, compounds) are retained. A mixture can be broken down into its components (pure substances) using physical separation processes.

Chemical reactions create chemical compounds from elemental substances (substances from one type of atom). Their properties cannot be derived from the properties of the element substances. Chemical reactions do more than just rearrange the particles involved. Chemical compounds can only be broken down into elemental substances through chemical reactions.

In addition to a description of material phenomena, students should get to know simple models for the structure of matter at a very early stage. Many properties and changes in substances that can be observed macroscopically can be explained by the structure of substances from atoms, which can be bound to one another to different degrees. But even some elementary electrical phenomena such as electrostatic charges suggest that the atoms in turn must consist of positive and negative components. A simple core-shell model thus creates a differentiated picture of the "small particles" and explains the corresponding observations.

Atomic nuclei are made up of electrically positively charged protons and electrically neutral neutrons. Chemical elements differ in the number of their protons. Ions differ from atoms in having an excess or a lack of electrons. Radioactive isotopes can later be characterized by elements with different numbers of neutrons, which make the atomic nucleus unstable. While the nucleus makes up almost the entire mass of an atom, the spatial expansion is determined by the shell of electrons.

On the basis of this knowledge, students in chemistry lessons get to know the principles of the periodic table. They are increasingly using it for predicting the properties and reaction behavior of element substances. You will learn that the properties of a substance are not only influenced by the types of atoms and the ratio of the number of atoms. In addition to the atomic composition, the type and manner of linkage, interaction and cohesion between the particles, i.e. H. the structure of a substance, decisive for its properties. This even applies to substances that only consist of a single type of atom (e.g. diamond and graphite).

Solid bodies play a special role in physics. With the help of the shell model, it is possible to distinguish between types of bonds in these bodies and thus conductors, semiconductors and insulators.

In physics lessons there is an in-depth treatment of radioactivity and nuclear energy. The relatively simple particle models of secondary level I are further differentiated in physics lessons in upper secondary school with the help of quantum physics ideas.

These materials are part of the curriculum navigator offer of the Quality and Support Agency - State Institute for Schools (QUA-LiS NRW)