Heating Substances and Containers in the Lab

Heating Containers

  • When using heating containers adhere to the following rules:

    • Beakers and evaporating dishes can be placed directly on a gauze mat for heating.

    • Never look directly into a container while it is being heated.

    • Wait until the equipment has cooled properly before handling it.

Equipment for Heating Substances

  • Common equipment used:

    • Beaker

    • Gauze mat

    • Bunsen burner

    • Tripod

    • Heatproof mat

    • Evaporating dish

Experiment 1.3: Heating a Substance in a Test Tube

  • Aim: To practice heating a liquid in a test tube safely.

  • Materials:

    • 100 mL beaker

    • Bunsen burner and heatproof mat

    • Matches

    • Safety glasses

    • Test tube

    • Test-tube rack

    • Test-tube holder

    • Food coloring

Safety Precautions

  • Before using a Bunsen burner:

    • Ensure safety glasses are worn.

    • Ensure the Bunsen burner is on a heatproof mat.

    • Tie back long hair.

Method

  1. Fill a test tube with approximately 2 cm depth of water from a beaker.

  2. Add a drop of food coloring to the test tube to improve visibility.

  3. Light the Bunsen burner correctly.

  4. Heat the test tube gently in the blue flame.

  5. Ensure the open end of the test tube points away from other students and yourself.

  6. Move the base of the test tube gently in and out of the flame to prevent splashing.

  7. Keep the test-tube holder away from the flame.

  8. Stop heating once the liquid starts boiling.

  9. Place the test tube in a test-tube rack to cool before cleaning.

  10. Note the changes observed inside the test tube as the colored water is heated.

Observations

  • A test tube was filled to a depth of about 2 cm of water.

  • The test tube was heated gently in the blue flame.

Discussion Questions

  1. Why should the test-tube holder be positioned at the top of the test tube?

  2. Why is the blue flame used for heating?

  3. Describe any safety precautions to take when heating substances in a test tube that you did not have to take when heating a substance in a beaker.

  1. The test-tube holder should be positioned at the top of the test tube to ensure that the user can safely hold the test tube while heating it without getting too close to the flame or the hot liquid inside.

  2. The blue flame is used for heating because it indicates a hotter and more efficient flame compared to a yellow or orange flame. The blue flame provides a consistent heat source, which is essential for controlled heating when conducting experiments.

  3. When heating substances in a test tube, specific safety precautions that differ from heating substances in a beaker include:

    • Ensuring that the open end of the test tube points away from yourself and others to prevent any splashes from causing injury.

    • Using a test-tube holder to avoid direct contact with the hot glass of the test tube, unlike a beaker that can be handled with heat-resistant gloves or beaker tongs.

    • Moving the test tube gently in and out of the flame to prevent splashing, which is less of a concern when using a beaker.

Conclusion

  • Properly filling a test tube with a specific volume of liquid (approximately 2 cm depth of water).

  • Adding a drop of food coloring to enhance visibility of changes during heating.

  • Correctly lighting a Bunsen burner and ensuring it is placed on a heatproof mat for safety.

  • Safely holding and heating the test tube in the blue flame, ensuring the open end points away from oneself and others.

  • Gently moving the test tube to prevent splashing while heating.

  • Recognizing when to stop heating the liquid (when it starts boiling).

  • Safely placing the heated test tube in a rack to cool before handling and cleani