Building blocks of matter Atom – smallest unit of an element that maintains the properties of that element. Element - a pure substance made of only one kind of atom. Compound - a substance made from the atoms of two or more elements that are chemically bonded. Molecule – smallest unit of an element or compound that retains all the properties of that element or compound

Properties and Changes in Matter Extensive properties – depend on the amount of matter that is present. For example, mass, volume and the amount of energy in a substance. Intensive properties – do not depend on the amount of matter present. For example melting point, boiling point, density and the ability to conduct heat and electricity.

Physical properties and physical changes A physical property is a characteristic that can be observed or measured without changing the identity of the substance. Examples include melting point and boiling point, density, magnetism. A physical change is a change in a substance that does not involve a change in identity of that substance. For example, melting, cutting.

Chemical properties and chemical changes A chemical property relates to a substance’s ability to undergo changes that transform it into different substances. For example, coal can burn in air, iron can rust. A chemical change or reaction is a change in which one or more substances are converted into a different substance. Examples are burning and rusting.

Energy and Changes in Matter When physical and chemical changes occur, energy is almost always involved. The energy can take several different forms such as heat or light. When ice absorbs heat energy it melts – a physical change. When paper burns it becomes carbon dioxide and water – a chemical change. Energy can be absorbed or released in a reaction, but it is never lost or gained. This is the Law of Conservation of Energy.

raw egg becomes cooked egg                                                                                     cake mix becomes cake                                        paper becomes ash steel becomes rust

Classification of Matter A pure substance is an element or compound. The composition is the same throughout. A mixture contains more than one substance. It can vary in composition and properties from sample to sample.

Mixtures A mixture is a blend of two or more kinds of matter each of which retains its own identity and properties. A homogeneous mixture is a mixture of uniform composition. It is also called a solution.

A heterogeneous mixture is a non-uniform mixture. If you wait long enough and stir, this one will eventually become homogeneous.