pH Scale

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pH Scale Noun

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[pee-eych skeyl]

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pH Scale

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A logarithmic scale from 0 to 14 that measures the acidity or basicity of a substance based on hydrogen ion concentration.

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Example: This diagram shows the pH scale from 0 to 14, with colors indicating if a substance is acidic (0-6), neutral (7), or alkaline (8-14).

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Acid Noun

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[as-id]

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Acid

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A compound that releases hydrogen ions (H+) in a solution, resulting in a pH value of less than 7.

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Example: This image displays the pH scale, showing that substances with a pH less than 7, like tomato juice and gastric juices, are considered acidic.

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Base Noun

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[beys]

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Base

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A compound that produces hydroxide ions (OH-) in a solution, resulting in a pH value greater than 7.

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Example: This diagram shows that when a base like sodium hydroxide (NaOH) is added to water, it splits into ions, releasing hydroxide ions (OH-).

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Hydrogen Ion (H+) Noun

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[hahy-druh-jen ahy-on]

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Hydrogen Ion (H+)

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A positively charged ion, also known as a proton, whose concentration in a solution determines the solution's overall acidity.

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Example: This diagram shows a hydrogen ion (H+), also called a proton, combining with a water molecule to form a hydronium ion, which determines a solution's acidity.

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Hydroxide Ion (OH-) Noun

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[hahy-drok-sahyd ahy-on]

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Hydroxide Ion (OH-)

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A negatively charged ion produced by bases, which increases the alkalinity or basicity of an aqueous solution.

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Example: This diagram shows a hydroxide ion (OH-), which is made of one oxygen atom and one hydrogen atom bonded together, carrying a negative charge.

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Alkaline Adjective

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[al-kuh-lahyn]

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Alkaline

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A term used to describe a substance or solution that is basic, having a pH value greater than 7.

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Example: This pH scale shows that substances are alkaline (or basic) when they have a pH value greater than 7, ranging up to 14.

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Neutral Solution Noun

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[noo-truhl suh-loo-shuhn]

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Neutral Solution

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A solution with a pH of exactly 7, where the concentrations of hydrogen ions and hydroxide ions are perfectly equal.

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Example: This diagram of the pH scale shows that a substance with a pH value of exactly 7 is considered neutral, positioned between acidic and alkaline.

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Homeostasis Noun

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[hoh-mee-oh-stey-sis]

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Homeostasis

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The process by which living organisms maintain a stable internal environment, such as a constant and balanced pH level.

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Example: This flowchart shows how the body responds to a stimulus (rising temperature) through sensors, a control center, and an effector to maintain a stable internal state.

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Buffer Noun

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[buhf-er]

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Buffer

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A substance that resists sharp, sudden changes in pH by reacting with and neutralizing added strong acids or bases.

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Example: When acid (H⁺ ions) is added to a buffer solution, the buffer absorbs the acid to resist a change in pH, keeping the solution stable.

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pH Indicator Noun

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[pee-eych in-di-key-ter]

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pH Indicator

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A chemical compound that visually changes color in response to pH changes, used to determine if a solution is acidic or basic.

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Example: This chart shows how a universal pH indicator changes color across the pH scale, from red in strong acids (low pH) to purple in strong bases (high pH).