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Chemistry Heating Solids Liquids

Materials/Equipment needed:

Bunsen burner

test tubes in stand

Ammonium Chloride

Sodium Hydrogen Carbonate solution

Safety Glasses

Clamp stand

Summary of steps

-place material (see key points) in test tube, standing in stand

-light bunsen

-holding test tube in metal test tube holder, heat carefully in bunsen flame

-when heating is complete, extinguish flame

Demonstration carried out first heating ammonium chloride (example of solid), then again heating solution of sodium hydrogen carbonate (example of liquid)

Ammonium chloride – chosen because it sublimes – something for students to see

Sodium hydrogen carbonate solution – evolves carbon dioxide gas below 100 degrees C.

Thirdly quick demonstration of how to position test tube in clamp stand if this is used.

Equations:

2NaHCO3 -> Na2CO3 + H2O + CO2 (g)

NH4Cl (s) -> NH4Cl (g) ->  NH4Cl (s)

Key points

-put on safety glasses before putting anything into a bunsen flame

-use minimum amount (cost and safety reasons) (reduces chance of spill also)

-this is all the more important if unsure of identity of material being heated

-test tube definitely no more than quarter full.

-bunsen flame blue when material heated, yellow when nothing being heated

-hold test tube with test tube holder (metal), not fingers

-test tube held at angle

-test tube pointed away from any people

-move test tube around gently while heating to spread heat

-hottest part of flame should be on side of test tube quite near bottom of tube

-orange colour around test tube is indication  that tube is hot

DIAGRAM SHOWING HEATING OF LIQUID (TEST TUBE HOLDER NOT SHOWN)

When heating a solid the position is the same.