MatterSection 3 Physical Changes 〉 A physical change affects one or more properties of a substance without changing the identity of the substance. physical change: a change of matter from one form to another without a change in chemical properties

MatterSection 3 Physical Changes, continued Physical changes do not change a substance’s identity. –Examples of physical changes: cutting, crushing, reshaping, changing state Dissolving is a physical change.

MatterSection 3 Chemical Changes 〉 A chemical change happens when one or more substances are changed into entirely new substances that have different properties. chemical change: a change that occurs when one or more substances change into entirely new substances with different properties

MatterSection 3 Chemical Changes

MatterSection 3 Chemical Changes, continued Chemical changes happen everywhere. –Examples of chemical changes: burning, rusting, digesting, decomposing Chemical changes form new substances. Chemical changes can be detected. –Signs include: change of color, change of smell, fizzing, production of heat, production of sound, production of light Chemical changes cannot be reversed by physical changes.

MatterSection 3 Breaking Down Mixtures and Compounds 〉 Mixtures can be separated by physical changes, but compounds must be broken down by chemical changes.

MatterSection 3 Breaking Down Mixtures and Compounds, continued Mixtures can be physically separated. Examples of separating a mixture: –Separating saltwater into its parts by heating it: When the water evaporates, the salt remains. –Using a distillation device to heat a mixture whose components have different boiling points: The component that boils and evaporates first separates from the mixture. –Using a centrifuge: The mixture spins rapidly until the components separate.

MatterSection 3 Breaking Down Mixtures and Compounds, continued Some compounds can be broken down through chemical changes. Examples of separating a compound: –When mercury(II) oxide is heated, it breaks down into the elements mercury and oxygen. –When a current is passed through melted table salt, the elements sodium and chlorine are produced. –When you open a bottle of soda, carbonic acid in the soda breaks down into carbon dioxide and water.

MatterSection 3 Start of Class Review Chapter 2 All matter can be classified as either an element, a compound, or a mixture. Compounds contain 2 or more elements. Physical properties can be observed without changing the substance A physical change effects the substance without changing its identity Mixtures can be separated by physical changes, compounds require a chemical change to broken down

MatterSection 3 End of Class Review Chapter 2 Each element is made of one kind of atom Elements and compounds are pure substances A chemical property describes how substance changes into a new substance A chemical change happens when one substance changes into a entirely new substance