Problem 19 - Chemistry: The Central Science

Question

In the process of attempting to characterize a substance, a chemist makes the following observations: The substance is a silvery white, lustrous metal. It melts at \(649^{\circ} \mathrm{C}\) and boils at \(1105^{\circ} \mathrm{C}\). Its density at \(20^{\circ} \mathrm{C}\) is \(1.738 \mathrm{~g} / \mathrm{cm}^{3}\). The substance burns in air, producing an intense white light. It reacts with chlorine to give a brittle white solid. The substance can be pounded into thin sheets or drawn into wires. It is a good conductor of electricity. Which of these characteristics are physical properties, and which are chemical properties?

Step-by-Step Solution

Answer

The physical properties of the substance include: being a silvery white, lustrous metal; a melting point at \(649^{\circ} \mathrm{C}\) and boiling point at \(1105^{\circ} \mathrm{C}\); a density at \(20^{\circ} \mathrm{C}\) of \(1.738 \mathrm{~g} / \mathrm{cm}^{3}\); the ability to be pounded into thin sheets or drawn into wires; and being a good conductor of electricity. The chemical properties of the substance include: burning in air, producing an intense white light; and reacting with chlorine to form a brittle white solid.

Step 1: Define Physical and Chemical Properties

To identify physical and chemical properties in the given observations, it's essential to understand the distinction between these two types of properties. Physical properties are characteristics that can be observed or measured without changing the substance's chemical composition. Examples of physical properties include color, density, and boiling point. Chemical properties, on the other hand, describe a substance's ability to undergo a chemical change or reaction and result in the formation of new substances. Examples of chemical properties include flammability and reactivity with other substances.

Step 2: Identify Physical Properties

Review the observations mentioned by the chemist and classify them as physical properties, based on whether they can be observed or measured without any change in the substance's chemical composition. 1. The substance is a silvery white, lustrous metal. 2. It melts at \(649^{\circ} \mathrm{C}\) and boils at \(1105^{\circ} \mathrm{C}\). 3. Its density at \(20^{\circ} \mathrm{C}\) is \(1.738 \mathrm{~g} / \mathrm{cm}^{3}\). 4. The substance can be pounded into thin sheets or drawn into wires. 5. It is a good conductor of electricity. All the above observations are examples of physical properties, as they can be observed or measured without changing the substance's chemical composition.

Step 3: Identify Chemical Properties

Now, review the observations made by the chemist and classify them as chemical properties, based on whether they describe the substance's ability to undergo a chemical change or reaction and form new substances. 6. The substance burns in air, producing an intense white light. 7. It reacts with chlorine to give a brittle white solid. These two observations are examples of chemical properties, as they describe the substance's ability to undergo chemical reactions and form new substances.

Step 4: Present the Results

Based on the analysis, the observations can be classified into physical and chemical properties as follows: Physical Properties: 1. Silvery white, lustrous metal 2. Melting point at \(649^{\circ} \mathrm{C}\) and boiling point at \(1105^{\circ} \mathrm{C}\) 3. Density at \(20^{\circ} \mathrm{C}\) is \(1.738 \mathrm{~g} / \mathrm{cm}^{3}\) 4. Substance can be pounded into thin sheets or drawn into wires 5. It is a good conductor of electricity Chemical Properties: 6. Burns in air, producing an intense white light 7. Reacts with chlorine to form a brittle white solid