Question

Match the following physical and chemical properties with potassium chloride, KCl, used in salt substitutes, or butane, \(\mathrm{C}_{4} \mathrm{H}_{10}\), used in lighters: a. melts at \(-138^{\circ} \mathrm{C}\) b. burns vigorously in air c. melts at \(770^{\circ} \mathrm{C}\) d. contains ionic bonds e. is a gas at room temperature

Short answer

Properties of KCl: c, d. Properties of butane: a, b, e.

Step-by-step solution

Identify properties related to potassium chloride (KCl)

Potassium chloride (KCl) has ionic bonds because it is a salt. Typically, substances with ionic bonds have high melting points. Therefore, it is realistic to assign the property 'melts at 770°C' to KCl.

Identify properties related to butane (\text{C}_{4}\text{H}_{10})

Butane is an organic compound and is highly flammable. It also has a low melting point and is a gas at room temperature. Therefore, it is realistic to assign the properties 'burns vigorously in air' and 'is a gas at room temperature' to butane.

Match remaining properties

Given that KCl was identified with 'melts at 770°C' and has ionic bonds, the remaining property of 'melts at -138°C' matches butane.

Key concepts

Physical Properties

Physical properties describe characteristics of substances that can be observed or measured without altering the chemical composition. These properties include melting point, boiling point, density, and state of matter at room temperature.

For example:

• Melting Point: The temperature at which a substance changes from a solid to a liquid. Potassium chloride (KCl) has a high melting point of 770°C, while butane has a much lower melting point of -138°C.
• State of Matter: Whether a substance is solid, liquid, or gas at room temperature. KCl is a solid at room temperature, while butane is a gas.

Understanding physical properties helps in identifying substances and predicting their behaviors in different scenarios.

Potassium Chloride

Potassium chloride (KCl) is an ionic compound often used in salt substitutes and fertilizers.

• Ionic Bonds: KCl consists of potassium (K) and chloride (Cl) ions held together by strong ionic bonds. This type of bond occurs between metals and non-metals and is characterized by the transfer of electrons from one atom to another, resulting in high melting and boiling points.
• Melting Point: Because of these strong ionic bonds, KCl has a high melting point of 770°C, making it stable under a wide range of temperatures. This is a characteristic physical property of salts.
• Uses: KCl is commonly used to replace sodium chloride (table salt) in diets to reduce sodium intake. It's also important in agriculture and medicine.

Understanding KCl's properties helps in various applications, from food seasoning to industrial processes.

Butane

Butane (C₄H₁₀) is a hydrocarbon commonly found in lighters and as a fuel.

• Flammability: Butane is highly flammable, making it useful as a fuel. It burns vigorously in air, which is a chemical reaction producing carbon dioxide and water.
• Physical State: At room temperature, butane is a gas. This is because its molecules are held together by relatively weak van der Waals forces, unlike the strong ionic bonds in potassium chloride.
• Low Melting Point: Butane melts at -138°C, which is significantly lower than the melting point of KCl. This is a notable physical property that affects how butane is stored and handled.

Knowing the properties of butane is essential for its safe and effective use in everyday applications, from portable lighters to camping stoves.