What is the difference between Chemical Change and Physical Change?
Chemical Change:
-There is a change in energy (Energy is absorbed of given off)
-A new substance is formed (Chemical properties are changed)
-The process is irreversible (The element(s) used cannot be separated)
E.g. forming of compounds
Physical Change
-There is no change in energy (No energy is absorbed or given off)
-No new substance is formed (Chemical properties stay the same)
-The process is reversible (The element (s) used can be separated by physical means)
E.g. Melting, boiling, sublimation, etc.
Activity: Heating and Cooling Solids
Materials used
-Sodium Chloride (White solid; crystal form)
-Copper (II) Carbonate (Green solid; powder form)
-Magnesium (Silvery metallic strip, solid form)
Procedures
For Sodium Chloride and Copper (II) Carbonate:
-Gently heat a spatula of the solid in a dry test tube
-If there is no observable change, heat strongly by placing the bottom of the test tube at the hottest part of the flame
For Magnesium:
-Hold the strip of magnesium ribbon using a pair of metal tongs and heat it directly using a Bunsen flame
-DO NOT stare directly at the flame.
Copper (II) Carbonate:
Before heating: Green solid in powder form
During heating: White fumes coming out and black solid formed.
After cooling: No visible change.
Type of change: Chemical change.
Before: After:
Word equation: Copper (II) Carbonate -------------------------------> Copper (II) oxide + Carbon dioxide
(Thermal decomposition)
Sodium Chloride:
(Didn't manage to get any pics. :/)
Before: white solid in crystal form.
During heating: Melted into a clear liquid (molten Sodium Chloride)
After cooling: Solidified to form back a white solid.
Type of Change: Physical Change.
Magnesium:
(Didn't manage to get the pics of the reaction cause we were too busy freaking out. :p But it was super cool. :))
Before heating: Silvery metallic strip
During heating: It burned with a bright light (REALLY bright)
After cooling: White powdery solid (Ash)
Type of Change: Chemical change.
Before:
After:
Word equation: Magnesium + oxygen ------------------> Magnesium Oxide
(Combustion)
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