Problem 65 - Chemistry Matter and Change

Question

Write word equations for the following skeleton equations. a. \(\mathrm{Cu}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{g}) \rightarrow \mathrm{CuO}(\mathrm{s})\) b. \(\mathrm{K}(\mathrm{s})+\mathrm{H}_{2} \mathrm{O}(1) \rightarrow \mathrm{KOH}(\mathrm{aq})+\mathrm{H}_{2}(\mathrm{g})\) c. \(\mathrm{CaCl}_{2}(\mathrm{aq})+\mathrm{Na}_{2} \mathrm{SO}_{4}(\mathrm{aq}) \rightarrow \mathrm{CaSO}_{4}(\mathrm{s})+\mathrm{NaCl}(\mathrm{aq})\)

Step-by-Step Solution

Answer

a. Copper (s) + Oxygen (g) → Copper oxide (s) b. Potassium (s) + Water (l) → Potassium hydroxide (aq) + Hydrogen (g) c. Calcium chloride (aq) + Sodium sulfate (aq) → Calcium sulfate (s) + Sodium chloride (aq)

Step 1: Identify the elements and compounds in skeleton equations

For each skeleton equation, list the chemical elements and compounds. Also, note the states (solid, liquid, gas, or aqueous) of these elements and compounds. a. Elements and compounds in the first skeleton equation: - Copper (Cu) - solid (s) - Oxygen (O₂) - gas (g) - Copper oxide (CuO) - solid (s) b. Elements and compounds in the second skeleton equation: - Potassium (K) - solid (s) - Water (H₂O) - liquid (l) - Potassium hydroxide (KOH) - aqueous (aq) - Hydrogen (H₂) - gas (g) c. Elements and compounds in the third skeleton equation: - Calcium chloride (CaCl₂) - aqueous (aq) - Sodium sulfate (Na₂SO₄) - aqueous (aq) - Calcium sulfate (CaSO₄) - solid (s) - Sodium chloride (NaCl) - aqueous (aq)

Step 2: Write the word equations

Convert the skeleton equations into word equations by replacing the chemical symbols with the names of the elements and compounds and their respective states. a. Copper (s) + Oxygen (g) → Copper oxide (s) b. Potassium (s) + Water (l) → Potassium hydroxide (aq) + Hydrogen (g) c. Calcium chloride (aq) + Sodium sulfate (aq) → Calcium sulfate (s) + Sodium chloride (aq) These word equations represent the same chemical reactions as the original skeleton equations, but using the common names of the reactants and products.

Key Concepts

Skeleton Equations

Skeleton equations are the basic outlines of chemical reactions. They serve as a shorthand method to represent the substances involved and the changes that occur. Unlike word equations, skeleton equations use chemical formulas instead of words to describe the reactants and products of a reaction. This format succinctly shows the transformation of specific chemical substances without detailing the amounts involved. Each component in the equation is identified by its chemical formula, which can be more efficient for chemists to read.

• Skeleton equations don't provide information about the proportions of each substance involved, hence they aren't balanced
• These equations include the states of matter for each element or compound, such as solid (s), liquid (l), gas (g), or aqueous (aq).

Although skeleton equations may seem cryptic at first, understanding them is a foundational step in learning to balance chemical reactions.

Word Equations

Word equations translate the skeleton equations into a more descriptive form using the names of the reactants and products. This process involves converting the chemical symbols and formulas into words, which can be especially helpful for those new to chemistry. By focusing on the compound names, students can better grasp what substances are actually reacting.
For example, the equation \(\mathrm{Cu}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{g}) \rightarrow \mathrm{CuO}(\mathrm{s})\) translates to the word equation: Copper (s) + Oxygen (g) → Copper oxide (s).
Word equations remain crucial in chemical education because they:

• Help students visualize the components and products of a reaction.
• Are instrumental in accurately communicating chemical phenomena between scientists and learners.

Although not as concise as skeleton equations, word equations foster a deeper understanding.

Chemical Reactions

Chemical reactions are processes that involve the transformation of one set of chemical substances to another. At the core of any chemical reaction are the basic concepts of reactants and products. Reactants are the starting substances, which undergo changes, while products are the substances formed as a result of the reaction.
Key characteristics of chemical reactions include:

• Transformation - new substances are formed with properties different from those of the reactants.
• Energy changes - reactions may release (exothermic) or absorb (endothermic) energy.
• Conservation of mass - matter is neither created nor destroyed, which is central to balancing chemical equations.

Understanding chemical reactions is crucial because they form the basis of countless natural and industrial processes, from digestion in our bodies to the manufacturing of pharmaceuticals.

States of Matter

In chemical equations, identifying the states of matter of the reactants and products is crucial as it affects how substances interact. The state of matter refers to the distinct forms that different phases of matter take on, including:

• Solid (s) - Definite shape and volume; particles are closely packed.
• Liquid (l) - Definite volume but no definite shape; particles are close together but can move past each other.
• Gas (g) - No definite shape or volume; particles are far apart and move freely.
• Aqueous (aq) - A substance dissolved in water that behaves as a special state.

Understanding these states helps predict the behavior of reactants during a chemical reaction. For example, gaseous reactants may react faster compared to solid ones due to the higher energy and mobility of the gas particles.
The states of matter are indicated in both skeleton and word equations to provide a complete and informative picture of a chemical reaction.