Bell work: 12/2/13 Would you classify eating turkey as a chemical change or physical change? Why?

Physical & Chemical Changes Changing Matter Physical & Chemical Changes

Matter has properties Two basic types of properties that we can associate with matter. Physical properties Chemical properties

Physical Properties Anything that can be observed without changing the identity of the substance. (Tends to be measurable.) melting point density boiling point thermal conductivity electrical conductivity ductility color malleability

Physical Changes Do NOT CHANGE THE TYPE OF MATTER Nothing new or different is formed Could be a change in: Mass Volume Density Change in state Color Shape Size

Examples of Physical Changes Boiling Freezing Dissolving Breaking Making a mixture 2 or more types of matter (substances) mixed together Not in specific amounts Can be separated physically

Chemical Properties The way a substance may change or react to form other substances heat of combustion Reactivity to other chemicals reactivity with water PH Oxidation Flammability Chemical properties of matter describes its "potential" to undergo some chemical change or reaction by virtue of its composition. What elements, electrons, and bonding are present to give the potential for chemical change. It is quite difficult to define a chemical property without using the word "change". Eventually you should be able to look at the formula of a compound and state some chemical property. At this time this is very difficult to do and you are not expected to be able to do it. For example hydrogen has the potential to ignite and explode given the right conditions. This is a chemical property. Metals in general have they chemical property of reacting with an acid. Zinc reacts with hydrochloric acid to produce hydrogen gas. This is a chemical property.

Picture from www.chem4kids.com Chemical Changes The composition of the substance changes. The substances present at the beginning of the change are not present at the end; new substances are formed. The change cannot be “undone.” Picture from www.chem4kids.com

Chemical Changes Evidence of a chemical change Formation of gas Formation of precipitate Change in color Change in energy Alka-Seltzer: (Baking soda or sodium bicarbonate) NaHCO3 + Citric acid ---> CO2 + H2O + Sodium Citrate

Chemical Changes Atoms are re-arranged, NOT created or destroyed

Law of Conservation of Mass Mass is conserved  amount of atoms cannot change Nothing is created or destroyed