Page 12 - Chemistry - XI

EXPERIMENT - 2

Objective
To bend a glass tube.

Materials Required
Glass tube, asbestos sheet, burner, and glazed tile

Procedure
1. Heat Glass Tube: Take a glass tube, hold the portion of the tube to be bent in the blue fl ame of burner
and keep rotating in fl ame for uniform heating.
2. Bending the Glass Tube: When the tube appears to soften, apply gentle pressure so that it bends by
its own weight and place it on asbestos sheet. Press it gently to make it coplanar. Adjust the angle

according to the use of the tube.

Hot end
Glazed tile

Heating of Glass Tube Bending of Glass Tube

Fig. 2.1: Heating and Bending of Glass Tube

Precautions
1. Carry out the process slowly to avoid fl attening of the glass tube while bending.

2. Rotate the tube continuously to ensure uniform heating.
3. Select a glass tube of suffi cient length for bending.
4. Keep the limbs of the tube in the same plane.
5. Do not apply too much pressure while bending.

VIVA VOCE

Q1. Why is red hot glass tube bent slowly?
Ans. If it is not bent slowly, the uniformity in shape will not be attained.

Q2. Why should we not put the hot tube on a table?
Ans. It is because table may be cold and sudden cooling may result in breakage of the tube.
It is because table may be cold and sudden cooling may result in breakage of the tube.
Q3. Why do we keep on rotating the glass tube while heating?
Q3. Why do we keep on rotating the glass tube while heating?
Ans. It is done so that the glass tube is uniformly heated from all sides.
Ans. It is done so that the glass tube is uniformly heated from all sides.
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