Lab session 5

In this lab session, we explored various changes, namely CHEMICAL and PHYSICAL changes in elements through heating.

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)