Physical and Chemical Properties and Changes







LESSONS



HOMEWORK






Each substance has a unique set of physical and chemical properties that identifies that substance


PHYSICAL PROPERTY

A property that can be observed without changing the nature of the substance

Examples:

    1. Mass - amount of matter in an object

    2. Volume - amount of space an object occupies

    3. Density - mass per unit volume

    4. Boiling Point - temperature at which a liquid's vapor pressure equals atmospheric pressure

    5. Freezing Point - temperature at which a liquid changes into a solid

    6. Shininess - tendency of an object to reflect light without scattering it

    7. Conductivity - tendency to allow the flow of heat or electricity

    8. Ductility - ability to be stretched into wires

    9. Malleability - ability to be shaped


CHEMICAL PROPERTY

A property that can be observed only if the substance undergoes a change into another substance

Examples:

    1. Reactivity with air (oxygen)

    2. Reactivity with a acid, reactivity with a base

    3. Corrosiveness or ability to be corroded

    4. Flammability

    5. Reactivity with another element or compound to produce a different compound



EXTENSIVE VS. INTENSIVE PROPERTIES

EXTENSIVE PROPERTIES
    1. Depends on the amount of the sample

    2. Changes from sample to sample (different)

    3. Not usually useful for identifying substances

    4. Examples: volume, mass, weight, length

INTENSIVE PROPERTIES
  1. Independent of the amount of the sample

  2. Same for every sample; useful for identifying substances

  3. Examples: color, density, boiling point

     



PHYSICAL CHANGES

    1. Only physical properties change in a physical change - a change in size, the state or the shape of matter

    2. No new substances are formed - no change in the type of element, compound, atom, or molecule

    3. After the physical change, you have the same substance you began with - no chemical change has occurred

    4. Reversible by ordinary physical means

    5. Examples: change of state (gas, liquid, solid), grinding, making solutions, dissolving a solid in a liquid


CHEMICAL CHANGE

    1. New substances with new properties are formed; chemical and physical properties change

    2. These changes are not easily reversed

    3. Evidences of Chemical Change:


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Copyright © 2003 - Created by Lorraine Bratcher and Modified by Robert F. Williams, Ph.D.
Adjuct Faculty, Chemistry/Earth Sciences/Astronomy Department
San Antonio College, San Antonio, Texas

Last updated May 30, 2003