- Slides: 12
Chemical and Physical Changes
Physical Property �A property that can be observed without changing the composition of a substance �Viscosity �Conductivity �Malleability �Hardness �Melting and Boiling Points �Density
Chemical Property �A change that can only be observed when the substances in a sample of matter are changing into different substances �Flammability �Reactivity
Physical Change �A physical change is when the properties of the material change, but the substances in the material stay the same. �Change in state � Solid melting to a liquid � Liquid evaporating to a gas � Gas condensing to a liquid � Liquid freezing into a solid � Usually occur with a change in temperature �Can also be when a substance dissolves in a liquid, but does not change its chemical make-up. � When sugar dissolves in water, the sugar is still sugar, just surrounded by water particles. �Can also be a change in shape. �These changes can usually be easily undone.
Filtration �A physical change �Separating one substance from another. �Uses the difference in the size of the substance
Distillation �Separates substances based on differences in the physical properties of two of more substances.
Chemical Change �A change that occurs when a substance reacts and forms one or more new substances. �A substance changes chemically. �New products are formed �A nail rust in the outdoors � Food is burned on a stove top � Acid is mixed with a base to neutralize the two. �Usually cannot be easily undone. �Identified by changes in color, formation of gas or precipitate.
Physical v. Chemical Changes �Physical changes are: ___________ �Examples: � 1. � 2. � 3. �Chemical Changes are: _________ �Examples: � 1. � 2. � 3.
Whiteboarding �Salt is mixed with water � Physical �Coal is burned � Chemical �A Sweet Tart is crush into powder � Physical �A copper roof turns green � Chemical �Alka-Seltzer is mixed with water. � Chemical �Bread grows mold � Chemical �A bicycle chain breaks � Physical �A bicycle chain rust � Chemical
States of Matter �Solid �Definite volume, definite shape �Liquid �Definite volume, indefinite shape �Gas �Indefinite volume, indefinite shape
Systems �Open System �System may exchange mass and molecules with the surroundings �Closed System �System is cut-off from surroundings, no mass or molecules can enter or exit.
Conservation of Mass �Not matter what happens in a chemical or physical change in a closed system, the amount of mass that exist before the change must be exactly the same after the change has happened. � 15 grams of water is evaporated, how much water vapor is produced?