CBSE Class 11 chemistry · basic laboratory techniques · Basic laboratory techniques
Source: CBSE Class 11 chemistry practical syllabus · use your school laboratory manual (NCERT Lab Manual where your school uses it).
Drawing a glass jet (Class 11 chemistry practical)
You soften a short length of soda-glass tube and draw it out to a fine jet while the glass is hot.
Jet bore and overall length follow your laboratory manual.
Published practice page. Concentrations, masses, and numerical answers come from your school laboratory manual and your own readings — not invented here. Not yet reviewed by a named chemistry reviewer. Version 1.0.0, updated 2026-10-03.
Safety — read before you start
Safety warning. Practise here. Perform the real experiment only in your school lab, with your teacher present.
- Open flame.
- Hot glass.
- Capillary cuts if snapped.
Wear: Lab coat, Splash goggles, Gloves, as your teacher directs.
Follow your teacher’s disposal instructions. Do not pour leftovers down a household drain.
Loads only after you tap. Use the lab hands to pick up and use equipment (pointer hidden in the scene). Falls back to a flat diagram if WebGL is unavailable.
Aim
To draw a soda-glass tube into a fine jet suitable for a wash bottle or similar apparatus, following your laboratory manual.
Methods and quantities can differ between schools. Follow your teacher's instructions.
Apparatus and chemicals
| Item | Note |
|---|---|
| Soda-glass tube | Often a piece you cut yourself in the same practical series. |
| Bunsen burner | For heating the zone to be drawn. |
| Glazed tile | Cool the finished jet. |
| Cork or rubber bung (later) | To test fit — only when your teacher says. |
| Soda-lime glass tube (soda-lime glass) | Drawn when soft; do not pull cold glass. |
Theory and reaction
Open
When a band of glass is soft, pulling the ends apart thins the wall and narrows the bore — forming a jet.
Even heating before drawing keeps the jet axial. A cold or one-sided soft zone gives a bent or blocked jet.
The jet must be open. Closing the tip requires re-heating and gentle blowing only if your teacher demonstrates that step.
No chemical equation. Physical drawing of softened glass.
Picture guide
Procedure
- Hold the tube horizontally with both hands. Heat a central band several centimetres long, not a point.
- Rotate steadily so the wall softens evenly around the circumference.
- When the band is soft, remove from the hottest flame if directed, and draw the ends apart smoothly along the tube axis.
- Stop pulling when the capillary section reaches the fineness your manual describes.
- Cool on a tile. Check that the jet bore is open (light pass or gentle air test only as your teacher allows).Safety: Never blow hard into hot glass unless your teacher has taught that technique.
Observation table
Enter the readings from your school lab in the practical file below. This page does not fill them in for you.
Calculation
No calculation.
Result
Note whether the jet is straight, open, and fine enough for the apparatus your teacher assigns.
Precautions
- Heat a band, rotate, then draw — do not yank cold glass.
- Pull along the axis; twisting while drawing kinks the capillary.
- Hot glass burns; cool before testing in a bung.
Viva questions
Answer one question at a time. The full answers stay closed until you open them.
Question 1 of 4
Drawing a glass jet means…
Pick an answer first.
Show all questions and answers
Drawing a glass jet means…
Answer: Pulling softened glass to form a narrow capillary. Reason: Soft glass is lengthened and thinned by pulling.
Why rotate while heating before you draw?
Answer: So the tube softens evenly and the jet stays straight. Reason: Uniform softening keeps the bore central.
A wash-bottle jet should ideally be…
Answer: Open with a fine bore for a steady spray. Reason: Fine capillary gives controlled delivery of liquid.
If the jet tip is sealed after drawing, the usual school fix is…
Answer: Re-soften gently and open the tip as your teacher shows. Reason: Controlled re-heating can reopen a sealed tip when taught.
Common mistakes
- Drawing before the glass is evenly soft → uneven wall or closed tip.
- Over-pulling until the capillary snaps.
- Heating only one side → bent jet.
Frequently asked questions
- Can I do this at home?
- No. Use this page to practise the order of steps and viva. Do the real experiment only in your school laboratory, with your teacher present.
Your practical file
Name, school, and roll number are optional and are not sent anywhere.
The practical file opens on this device.
Review
Not yet reviewed by a named chemistry reviewer. Published for practice only — follow your teacher and laboratory manual for quantities and safety.
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