Chemical and Physical Changes

Chemical & Physical Changes

            It is important to understand the difference between chemical and physical changes. The two types are based on studying chemical reactions and states of matter. 

·         Chemical Changes

               Chemical changes take place on the molecular level. A chemical change produces a new substance. Examples of chemical changes include combustion (burning), cooking an egg, rusting of an iron pan, and mixing hydrochloric acid and sodium hydroxide to make salt and water.

·         Examples of Chemical Changes

1)      burning wood

2)      dissolving salt in water

3)      mixing acid and base

4)      digesting food

·         Physical Changes

              Physical changes are concerned with energy and states of matter. A physical change does not produce a new substance. Changes in state or phase (melting, freezing, vaporization, condensation, sublimation) are physical changes. Examples of physical changes include crushing a can, melting an ice cube, and breaking a bottle.

·         Examples of Physical Changes

1)      crumpling a sheet of paper

2)      melting an ice cube

3)      casting silver in a mold

4)      breaking a bottle

·         How to Tell Chemical & Physical Changes Apart

              A chemical change makes a substance that wasn't there before. There may be clues that a chemical reaction took place, such as light, heat, color change, gas production, odor, or sound. The starting and ending materials of a physical change are the same, even though they may look different.

WHMIS

Workplace Hazordous Materials Information System or WHMIS helps to keep workers and students safe by informing them of possible safety and health hazards.

There are 6 classes hazordous materials including:
Class A Compressed Gasses
-gasses under pressure
-may explode under pressure or heat

Class B Flammable And Combustible Materials
-these are potential fire hazards that can light at low temperatures
-may burst into flame in air or release a flammable gas on contact with water
 -Division 1: Flammable gases

 -Division 2: Flammable liquids (with flashpoints of less that 37C)

 -Division 3: Combustible liquids (with flashpoints of greater than 37C)

 -Division 4: Flammable Solids

 -Division 5: Flammable Aerosols

 -Division 6: Flammable reactive materials

Class C Oxidizing Materials
-these are a fire or explosion risk near combustible materials
-may burn skin or eyes on contact
-may or may not burn on its own but release oxygen to feed a fire

Class D Poisonous And Infectious Materials
-these materials are potentially fatal and should not be inhaled, swallowed, or absorded through the skin
-proper protective gear should be worn at all times when working with these materials

 -Division 1: Materials Causing Immediate And Serious Toxic Effects
  -these materials are immediately dangerous to life and health, and can kill you quickly

 -Division 2: Materials Causing Other Toxic Effects
  -these materials are poisonous but are not immediately dangerous to health, they may cause death or permanent damage over a long time of exposure
 
 -Division 3:Biohazardous Infectious Material
  -these are any organisms, like bacteria and viruses, and the toxins that they may produce that cause disease

Class E Corrosive Material
 -caustic or acid materials that can eat through skin or metals
 -these also include corrosive gases

Class F Dangerously Reactive Materials
 -products which undergo dangerous reactions when introduced to water, heat, pressure, or shock

Each class has a label and border that can tell you how dangerous a material is, octagon being the most dangerous and triangles just needing caution
Always make sure you understand the experiment and have permission before starting an experiment