LAB: Properties of Ionic and Covalent Compounds

Summary

In this science experiment, a conductivity tester and a Bunsen burner are used to explore the electrical conductivity and melting points of various substances. The experiment demonstrates how certain materials, such as potassium iodide and hydrochloric acid, conduct electricity, while others like glucose and paraffin do not. Additionally, the substances are heated to observe their melting points, revealing the varying temperatures at which they change state. The experiment emphasizes safety precautions, particularly when handling high temperatures and potentially hazardous chemicals, providing an insightful look into fundamental chemistry concepts.

Takeaways

• 😀 The conductivity tester uses a light bulb connected to an AC outlet with two leads inside plastic cylinders to test conductivity.
• 😀 The brightness of the light bulb depends on whether the circuit is complete, indicating the presence of a conductive material.
• 😀 Pure distilled water does not conduct electricity and does not light up the bulb.
• 😀 Substances like KI (Potassium Iodide), KCl (Potassium Chloride), KNO3 (Potassium Nitrate), and HCl (Hydrochloric Acid) conduct electricity and light up the bulb.
• 😀 Glucose, Paradichlorobenzene, Benzoic Acid, Paraffin, and Acetic Acid do not conduct electricity, so the bulb does not light up.
• 😀 The Bunsen burner is used to heat substances and observe their melting points, with the flame’s hottest part being the inner blue cone.
• 😀 Potassium Iodide (KI) melts quickly when exposed to the Bunsen burner flame.
• 😀 Potassium Chloride (KCl) has a high melting point and does not melt under the flame after 80 seconds of heating.
• 😀 Substances like Glucose, KNO3, Paradichlorobenzene, Benzoic Acid, and Paraffin melt relatively quickly when heated with the Bunsen burner.
• 😀 Acetic Acid and Hydrochloric Acid are already in liquid and gaseous forms at room temperature, so no melting is required.
• 😀 Care must be taken when working with the Bunsen burner as the flame is very hot and can be dangerous.

Q & A

What is the purpose of the conductivity tester in the experiment?

The conductivity tester is used to determine how well various substances conduct electricity. The tester consists of a light bulb connected to an AC outlet, and the light bulb illuminates when the circuit is complete.

How does the conductivity tester work?

The tester works by completing the circuit with two leads. When these leads are connected by a conductive substance, the circuit is completed, and the light bulb lights up. If the substance is non-conductive, the bulb does not light.

What happens to the light bulb when the circuit is unplugged?

When the circuit is unplugged, the light bulb goes out because the circuit is incomplete and no electricity flows through it.

What substances are tested for conductivity in the experiment?

The substances tested for conductivity include pure distilled water, potassium iodide (KI), potassium chloride (KCl), glucose, potassium nitrate (KNO₃), para-dichlorobenzene, acetic acid, benzoic acid, paraffin wax, and hydrochloric acid (HCl).

Why are the leads cleaned between each substance test?

The leads are cleaned between tests to prevent contamination between substances, which could interfere with the results and accuracy of the conductivity measurements.

How is the Bunsen burner used in the experiment?

The Bunsen burner is used to heat the substances in a crucible to determine their melting points. The flame is adjusted to achieve a hotter temperature by controlling the oxygen supply, which creates an inner blue cone that is used to heat the substances.

What is the significance of the inner blue cone of the Bunsen burner?

The inner blue cone of the Bunsen burner is the hottest part of the flame. It is used to melt the substances in the experiment because it provides the highest temperature necessary to observe melting.

What happened to potassium chloride (KCl) during the melting point test?

Potassium chloride (KCl) did not melt during the test. After 80 seconds of heating, it was assumed that KCl's melting point was higher than the temperature of the flame, so it was no longer heated.

Why doesn't acetic acid need to be melted in the experiment?

Acetic acid does not need to be melted because it is already a liquid at room temperature, so no heating or melting is necessary.

What is the safety precaution mentioned in the experiment?

The safety precaution mentioned is that the inner cone of the Bunsen burner is extremely hot and can cause burns. It is essential to handle the burner carefully, avoid direct contact with the flame, and conduct the experiment with proper safety measures.