Question

Olivia noticed that the \(\mathrm{pH}\) of her garden soil decreased after it rained. Did her garden soil become more acidic or less acidic?

Short answer

The garden soil became more acidic.

Step-by-step solution

Understand the pH scale

Start with settling in mind that pH is a scale used to specify how acidic or basic a water-based solution is. Acidic solutions have a lower pH, while basic solutions have a higher pH. pH levels range from 0 to 14, with 7 being neutral.

Relate the pH change to acidity

Equipped with the knowledge of the pH scale, the change in the garden soil can be interpreted. If the pH decreased, it means the acidity of the soil increased. Thus, her garden soil became more acidic.

Key concepts

Understanding Acidity and Alkalinity

Acidity and alkalinity are two fundamental concepts when discussing the pH scale. The pH scale is a measure that determines how acidic or basic (alkaline) a substance is. It ranges from 0 to 14, with values less than 7 indicating acidity and values greater than 7 indicating alkalinity. A pH of 7 is considered neutral, which is the pH of pure water.

Every unit change in the pH scale corresponds to a tenfold change in acidity or alkalinity. For instance, a substance with a pH of 6 is ten times more acidic than one with a pH of 7. Understanding this scale is crucial as it affects a multitude of chemical reactions, biological processes, and environmental conditions. Acidity is often linked with more hydrogen ions present in a solution, while alkalinity is associated with fewer hydrogen ions. This concept applies to various scenarios, including soil composition, the human body, and industrial processes.

The Importance of pH in Soil

Soil pH is a vital factor that affects the health of plants, determining their growth, nutrient absorption, and resistance to pests. Soil can vary in pH, largely due to the influence of climate, mineral content, and organic material. If the pH level of soil is too acidic or too alkaline, certain nutrients become less available to plants.

The ideal pH for most plants is between 6 and 7.5, although some plants prefer soil that is more acidic or more alkaline. For farmers and gardeners like Olivia, monitoring soil pH is essential to ensure it contains the optimal balance for plant health. Correcting soil pH can involve adding materials like lime to raise the pH or sulfur to lower it. Regular testing and adjusting of soil pH can lead to a lush, productive garden.

Characteristics of Acidic Solutions

Acidic solutions are those that have a pH level below 7. In a garden setting, acidic rainwater can cause the pH of soil to decrease, as seen in Olivia's garden. Acidic solutions have a high concentration of hydrogen ions relative to hydroxide ions.

These solutions usually taste sour, like the flavor of citrus fruits, which contain citric acid. Vinegar, with acetic acid, is another common acidic substance. In the environment, acidic solutions can result from industrial emissions that produce acid rain, affecting soil and aquatic ecosystems. In addition to having distinct tastes, acidic solutions often react vigorously with metals, leading to corrosion, and can change the color of certain chemical indicators, which is something often verified in chemistry classes.