Physical and Chemical Changes

Physical Change A change that affects one or more physical properties of a substance Chemical identity remains unchanged Appearance, shape, or size may be altered Example: wool

Physical Change Change in state of matter is a physical change Ex. Boiling, freezing, melting, subliming, deposition, condensation

Chemical Change A chemical change occurs when one or more substances change into entirely new substances with different properties. Example: cake

Chemical Change vs Properties Burning is a change, flammability is a property Chemical properties describe which chemical changes can or cannot occur Chemical changes are the process by which substances actually change into new substances

Identity Change? Particles and chemical bonds get rearranged Often times this rearrangement involves some sort of temperature change Higher temperature means higher kinetic energy This allows particles to move around faster and rearrange more easily Back to the cake example

How Can You Tell? Production of a gas Production of an odor Bubbling, fizzing, foaming Production of an odor Rotting eggs, sour milk, lightning changing the smell of the air Formation of a Precipitate A precipitate is a solid formed from a reaction of 2 liquids Example: potassium iodide and lead nitrate react to form lead iodide Change in color Change in Energy Often times seen as light or felt as heat

Change Observation Type of Change Metal Rusting Ice Cream Melting Painting a Door Baking cookies Barbequing Chicken

Law of Conservation of Mass The law of conservation of mass states that in ordinary chemical and physical changes, mass is not created or destroyed but is only transformed into other substances Discovered by Antoine Lavoiser