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Questions 1.9e

  1. Laboratory experiments normally use non-luminous flame, and not luminous flame. Explain --------------------
  2. Study the picture of a wire gauze, tripod stand and clay triangle which are normally used with a Bunsen flame when heating a substance.

  3. Wire gauze edukitnetwork.com

    Tripod stand

    Clay triangle



  4. The arrangements for heating are typically as follows.

  5. (a) Heating a beaker or flask
    heating-water-over-bunsen-burner

    (b) Heating a substance in a test tube

    (c) Strong heating of a solid in a crucible youtube.com


    What property of hardened steel wire gauze do you think makes it suitable for use with hot flames as indicated in (a)? ---------------------------------------

  6. Study diagram (b) showing the heating of a test tube in a Bunsen flame.

    1. How would you protect yourself and neighbors when heating a liquid in a test tube (or boiling tube)? -------------------------------------------------------------
    2. Overheating one part of a test tube can cause it to crack, especially when heating a solid. How would you protect the test tube when heating a solid in it? ---
    3. Suggest two reasons why a wire gauze is not used in the set-up in (c). ---------


Answers to Questions 1.9e

  1. Unlike a luminous flame, non-luminous flame is hot and does not produce soot that covers and soils the beaker or test tube.
  2. Non-uniform heating can cause glass to crack.
  3. Hardened steel wire gauze has a high melting point and does not burn in air.
    1. Directing the mouth of the test tube away from yourself and neighbours; moving the test tube gently over the flame, and totally removing it as the liquid content tends to spit out.
    2. Moving the test tube gently over the flame rather than holding it at one position.
    3. A wire gauze conducts away some heat; yet strong heating is required. Unlike glass, crucible does not easily crack when heated non-uniformly.