Matter: Chemical Properties

Becoming Something New -chemical properties describe a substance based on its ability to change into a new substance with different properties -Examples: Wood burns (makes ash and smoke; 2 new substances with different properties) -ability to burn is called flammability and is a chemical property

Something New Continued -other examples: reactivity with -oxygen -acid -water -reactivity: something happens when one substance comes into contact with another substance -chemical properties can be observed by the senses, but usually only during or after a reaction

Steel rusts Paper burns An egg can be cooked -all examples of chemical properties -chemical properties and physical properties are characteristic properties -always the same for a particular substance An egg can be cooked

Physical and Chemical Changes -a physical change affects one or more physical properties of a substance -Example: ripping a piece of paper no matter how many times you rip it, it's still paper -more examples: melting, freezing, dissolving, bending, cutting, crushing -a physical change can be undone because the identity of the substance remains the same -Example: a stick of butter will melt if left out, but will return to its solid state if put in the refrigerator

-a chemical change occurs when one or more substances are changed into new substances with different properties -Example: baking a cake -each ingredient has its own properties -when mixed together and baked something new and different forms -heat interacts with ingredients to cause a chemical change -many chemical changes require heat

More Examples -soured milk, hot gas from the combustion of fuel, oxidation of metals, fizzing of alka-seltzer -most chemical changes cannot be undone because it is not possible to separate the ingredients using physical means (you can't un-bake a cake!) -some chemical changes can be reversed under the proper conditions and using other chemical changes

Look for Clues Watch the BrainPop Try the quiz -chemical changes can be recognized by the clues they give *color change *fizzing (release of gas bubbles) *produce heat, light, sound or odor *a precipitate forms Watch the BrainPop Try the quiz