Physical vs Chemical Changes and Properties

Properties – what are they?

Property The arrangement of atoms determines the properties of the substance Shape Color Texture Odor Luster Transparency Density Size Volume Mass Melting Point Boiling Point Mass Melting Point Boiling Point Freezing Point Hardness Resistance Flamable Conductivity Magnetism Insulator Will every substance have all these properties? Is the lack of a property a property?

Physical Properties

Observations made about a substance that doesn’t change the substance itself You can stretch a rubber band, bend a piece of wire, or break a piece of gum. Because you are still left with the same substance when you are done, it is a physical property.

Physical Properties Appearance: How would you describe a tennis ball? (shape, color, state of matter) How would you describe a soft drink? (color, state of matter, taste) You could also measure its volume and temperature—these are all physical properties

Physical Properties Behavior: Some physical properties describe the behavior of a substance For instance, objects containing iron (I.e. safety pins) are attracted by a magnet Think about a soft drink. If you were to knock it over, it would spread onto the table and floor—the ability to flow is a physical property of liquids

Physical Changes

Physical Change physical changeA physical change is a change in which a substance changes its physical properties without changing its chemical identity. These changes might involve energy changes, but the kind of substance— the identity of the element or compound—does not change!

Physical Change Heat Curve

Physical Change

Physical Changes KEYWORDS: –Freezing –Melting –Boiling –Condensing –Vaporizing –Evaporating –Change in size or shape –Dissolving

Chemical Properties

The chemical characteristics of a substance that tend to change the chemical identity. A chemical property of Fe (Iron) is rusting. Limestone and acid gives off gas in the form of bubbles –good indication that there is a chemical change occurring.

Chemical Changes

Chemical Change The change of a substance into other substances through a reorganization of atoms. Chemical reactions involve chemical changes.

Chemical Changes KEYWORD: –New substance formed? –Burning –Change in color –Gas given off (bubbles) –Precipitate (solid that falls out of solution) –Change in odor –Rusting

Chemical Reactions

Bonds between atoms are formed or broken causing substances to combine and recombine as different molecules. Represented by chemical equations Metabolism – all of the chemical rxns that occur within an organism

Chemical Reactions 2H 2 + O 2 2 H 2 O ReactantsProducts YIELDS Atoms are neither created nor destroyed in a chemical reaction, just rearranged! The Chemical Equation must be balanced!!

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