Chapter 14, Problem 20A

Interpretation Introduction

Interpretation:

The similarities and differences between the arrangement of molecules and forces between molecules in liquid water versus steam and in liquid water versus ice are to be discussed.

Concept introduction:

A liquid water molecule contains an oxygen atom which connected with two hydrogen atoms. Pure water freezes to form a solid at ${\text{0}}^{\text{o}}\text{C}$ and vaporizes completely to form a gas at ${\text{100}}^{\text{o}}\text{C}$ at $\text{1 atm}$ pressure. Heating of water converts liquid water into steam. The temperature of water rises and the motions of the water molecule increase. Cooling of water converts liquid water into ice. The temperature of water and motions of the water molecule decreases. No chemical bond is broken during the heating and cooling of liquid water.

Answer to Problem 20A

Ice water is a solid in which water molecules are held together in a crystalline structure and they are not free to move. As liquid water molecules are free to move but are less tightly held together than ice water molecules. The gaseous water molecules move individually in random motion. All these phases of water molecules are held together by hydrogen bonding.

Explanation of Solution

In a water molecule, the oxygen atom is bonded with two hydrogen atom by a covalent bond. While two water molecules are held together by hydrogen bonding. In liquid water, molecules are free to move and tightly held together by hydrogen bonding. When water temperature increases to ${\text{100}}^{\text{o}}\text{C}$ , liquid water molecules get converted into gaseous molecules and randomness of molecules increases. The arrangement of steam molecules is far apart from each other than the liquid state. In ice, water molecules are held together in crystalline form, as they are not free to move. When water temperature decreases to ${\text{0}}^{\text{o}}\text{C}$ , liquid water molecules get converted into ice and the randomness of molecule decreases. The arrangement of ice molecules is far close to each other than the liquid state. Although, the forces between water molecules are hydrogen bonding, held the water molecules together in a particular phase.

Conclusion

From ice to liquid to gas, the randomness of water molecules increases, and the molecules are together by hydrogen bonding.