Chapter 11, Problem 11.39UTC

Interpretation Introduction

To determine:Match the following physical and chemical properties with potassium chloride, KCl, used in salt substitute, or butane, C₄H₁₀ used in lighters:

1. Melts at -138 ^oC
2. Burns vigorously in air
3. Melts at 770^oC
4. Contains ionic bonds
5. Is a gas at room temperature

Answer to Problem 11.39UTC

Solution:

1. Melts at -138 ^oC:Physical property of butane
2. Burns vigorously in air: Chemical property of butane
3. Melts at 770 ^oC: Physical property of KCl
4. Contains ionic bonds: Chemical property of KCl
5. Is a gas at room temperature: Physical property of butane

Explanation of Solution

Physical property is the property that can be observed or measured without changing the element, like color, shape and volume. On the other hand, chemical properties are observed by changing the chemical identity of substance.

1. Melts at -138 ^oC: Melting is change of state from solid to liquid. No chemical identity of the substance is changed.So, it is a physical property. Butane has a melting point -138 ^oC. So, this is a physical property of butane.
2. Burns vigorously in air: Butane is a carbon containing compound, C₄H₁₀.When come in contact with air (O₂), it burns to give CO₂and H₂O. Chemical identity of butane is changed. So, it is a chemical property.
3. Melts at 770 ^oC: Melting is change of state from solid to liquid. At 770 ^oC, KCl melts. So, this is physical property of KCl.
4. Contains ionic bonds: Ionic bonds are formed when a metal forming positive ion and nonmetal forming negative ion interact together. In case of KCl, potassium (K) is metal and Cl is nonmetal. So ionic bond will be form in KCl.Butane has carbon, hydrogen. Both are nonmetal, so ionic bond is not there.
5. Is a gas at room temperature: Gas represents the physical state of a substance.At room temperature, butane is a gas and KCl is solid. So, this represents physical property of butane.

Conclusion

The properties are assigned physical and chemical on basis of their observable properties and where there is any change in the chemical identity of the substance. Melting is a physical property and -138 ^oC and 770 ^oC represent physical property of butane and KCl. Combustion and formation of ionic bonds are chemical properties.