lab

closed air holes

Bright Yellow / Orange

Open Air Holes (Non-Luminous)

open air holes

Pale Blue / Nearly Invisible

Closed Air Holes (Luminous)

closed air holes

Incomplete combustion (limited O_2)

Open Air Holes (Non-Luminous)

open air holes

Complete combustion (sufficient O_2)

Closed Air Holes (Luminous)

closed air holes

Black Soot (Carbon deposit)

Open Air Holes (Non-Luminous)

open air holes

No deposit (Clean surface)

Closed Air Holes (Luminous)

closed air holes

Quiet, soft wave

Open Air Holes (Non-Luminous)

open air holes

Roaring / Rustling sound

Closed Air Holes (Luminous)

closed air holes

Cooler

Open Air Holes (Non-Luminous)

open air holes

Much hotter

Sprinkling Powdered Charcoal

• Causes bright sparks/glowing particles in the flame as solid carbon particles ignite instantly.

• Matchstick Resting Above Barrel:

• Does not ignite immediately because the inner cone consists of cool, unburnt gas entering from the jet.

• Glass Tubing in Inner Cone:

• Gas from the unburnt inner cone flows up through the glass tube and can be ignited at the other end.

• Vertical Scorched Cardboard:

• Shows a charred ring shape or hollow middle pattern, demonstrating that the hottest area is the outer boundary (outer envelope/tip of the inner cone) and the inner core is relatively cool.

1. Where is the hottest part of a non-luminous flame?

Just above the tip of the inner blue cone

1. What chemical element makes up the deposit on a porcelain dish?

Elemental Carbon (C) or Soot.

1. What happens if too much air is let into the burner?

The flame will rustle, roar, or strike back ("snap out").

Weighing Techniques & Rules

Never place chemicals directly on the balance pan. Always use a paper box, watch glass, or container.

Weighing Techniques & Rules

• Allow hot objects to cool to room temperature before weighing.

• Why? Hot objects create convection currents of air that cause the balance pan to buoy upward, giving an inaccurate (lighter) reading. Hot objects can also damage the delicate balance mechanism.

Weighing Techniques & Rules

• Zero/Tare Adjustment: If the balance pointer does not rest at zero when empty, request instructor assistance; do not force adjustments.

• Clean up spilled chemicals immediately and return riders to zero after use.

Glass stoppers

Used for acidic solutions. Hold the flat-topped stopper by laying it flat-side down on the table, or hold a winged stopper between fingers (pointer and middle) while pouring.

• Plastic/Rubber stoppers:

• Used for alkaline/basic solutions (bases can cause glass stoppers to "freeze" or stick to the bottle neck).

• Flat-capped/Screw-capped bottles:

• Place cap upside down on the bench to prevent surface contamination.

• Pouring Technique:

• Using a Glass Rod: Hold a glass rod against the rim/lip of the beaker when pouring.

• Why? Adhesion and surface tension guide the liquid down the rod, preventing it from trickling down the outside wall of the pouring vessel.

• Pouring Technique:

• Protecting Labels: Always pour liquids from the side opposite the label so drips do not erase or ruin the bottle label.

• NEVER return excess/unused chemicals back into the original reagent bottle

• Place excess reagents into a separate labelled container marked "excess reagent" to avoid contaminating the main stock.

Pipetting Liquids

• Use a rubber aspirator (pipette bulb) to draw liquid into the pipette—never mouth pipette.

Heating Chemicals Safely

• Fill Level: Half-fill or less.

• Holding Angle: Hold at an angle of about 45° using a test tube holder.

• Movement: Move the tube back and forth across the flame.

Heating Chemicals Safely TARGET AREA

• Apply heat to the upper portion of the liquid (below the liquid level), NOT the dry glass above or the extreme bottom.

• Why upper liquid? Prevents sudden steam expansion (bumping) at the bottom that shoots hot liquid out.

• Why not empty glass above? Extreme temperature changes can crack the glass when liquid touches it.

Heating Beakers/Flasks

• Place the vessel 1-2 INCHES above the burner on an iron ring with a wire gauze.

• Purpose of Wire Gauze: Evenly distributes heat to prevent localized hotspot cracking.

• Always align the vessel over the hottest zone of the Bunsen flame (just above the tip of the inner blue cone).

Precipitate

An insoluble solid formed from the reaction of two liquid solutions

Supernatant Liquid

• Clear liquid resting above a settled precipitate.