Difference Wiki

Acidic vs. Alkaline: What's the Difference?

Edited by Aimie Carlson || By Harlon Moss || Published on December 15, 2023
Acidic substances have a pH less than 7, often taste sour, and turn litmus paper red; alkaline substances, with a pH above 7, taste bitter and turn litmus paper blue.

Key Differences

Acidic substances have a pH value below 7, indicating a higher concentration of hydrogen ions. This makes them corrosive and reactive, especially with metals. Alkaline substances, also known as bases, have a pH value above 7, indicating lower concentrations of hydrogen ions and a higher concentration of hydroxide ions.
In terms of taste, acidic substances often have a sour flavor, characteristic of foods like lemons and vinegar. Alkaline substances, on the other hand, tend to have a bitter taste, which is noticeable in foods like baking soda and certain leafy greens.
From a chemical reaction standpoint, acidic substances readily donate hydrogen ions in reactions, a hallmark of their chemical behavior. Alkaline substances, in contrast, are known for accepting hydrogen ions and often producing hydroxide ions in reactions.
In environmental contexts, acidic substances can contribute to phenomena like acid rain, which impacts soil and aquatic ecosystems. Alkaline substances, while less often discussed in environmental impacts, can also affect ecosystems, particularly by altering soil pH and affecting plant growth.
Commonly, acidic solutions turn blue litmus paper red, a classic test in chemistry. Conversely, alkaline solutions turn red litmus paper blue, which is a simple yet effective way to differentiate between the two.

Comparison Chart

PH Value

Below 7
Above 7



Chemical Behavior

Donate hydrogen ions
Accept hydrogen ions, produce hydroxide ions

Environmental Impact

Contributes to acid rain
Alters soil pH, affects plant growth

Litmus Test

Turns blue litmus paper red
Turns red litmus paper blue

Acidic and Alkaline Definitions


Acidic substances often have a sour taste.
Lemons are acidic, contributing to their sour flavor.


Alkaline substances usually have a bitter taste.
Baking soda is alkaline and has a distinct bitter flavor.


Acidic environments can accelerate metal corrosion.
Battery acid is acidic and can corrode metal quickly.


Alkaline describes a substance with a pH above 7.
Soap is alkaline and effective in cleaning greasy stains.


Acidic rain, caused by pollution, harms ecosystems.
Acidic rain damages forests and aquatic habitats.


Alkaline soils can affect plant nutrient availability.
Alkaline soil requires special plants that can tolerate high pH.


Acidic refers to a substance with a pH less than 7.
Vinegar is acidic and used in various culinary applications.


In chemistry, alkaline solutions accept hydrogen ions.
Alkaline solutions are used to neutralize acidic spills.


In chemistry, acidic solutions donate hydrogen ions.
Acidic compounds are crucial in many chemical reactions.


Alkaline substances are often used in cleaning agents.
Many household cleaners are alkaline to dissolve dirt and grease.




Of, relating to, or containing an alkali.


Tending to form an acid.


Having a pH greater than 7.


(chemistry) Having a pH less than 7, or being sour, or having the strength to neutralize alkalis, or turning a litmus paper red.


Having a relatively low concentration of hydrogen ions.


(mineralogy) Containing a high percentage of silica; opposed to basic.


Of or relating to a common disposable battery made of zinc and manganese dioxide.


Of or relating to acid; having the character of an acid.
An acidic solution


Of, or relating to an alkali, one of a class of caustic bases.


Containing a high percentage of silica; - opposed to basic.


(chemistry) Having a pH greater than 7.


Of or relating to acid; having the character of an acid, as an acidic solution.


An alkaline battery.


Having characteristics of both an acid and a base and capable of reacting as either


Of or pertaining to an alkali or to alkalies; having the properties of an alkali.


Tasting sour like acid


Relating to or containing an alkali; having a pH greater than 7;
Alkaline soils derived from chalk or limestone


Are acidic substances dangerous?

Some acidic substances can be corrosive and harmful, requiring careful handling.

Are alkaline substances safe?

Alkaline substances can be caustic and harmful, especially at high pH levels.

What does acidic mean?

Acidic refers to substances with a pH less than 7, often sour and corrosive.

Can acidic foods affect health?

Consuming too many acidic foods may affect digestive health and tooth enamel.

What are common acidic household items?

Vinegar, lemon juice, and battery acid are common acidic items.

What does alkaline mean?

Alkaline describes substances with a pH above 7, typically bitter and basic.

How do you measure acidity?

Acidity is measured using pH scales, litmus paper, or pH meters.

Are alkaline diets beneficial?

Alkaline diets are claimed to benefit health, but scientific evidence is mixed.

What are common alkaline household items?

Baking soda, soap, and ammonia are common alkaline items.

Are acidic substances good for cleaning?

Acidic substances can remove mineral deposits and stains effectively.

Do acidic substances react with bases?

Yes, acidic substances react with bases to form salt and water.

Do alkaline substances react with acids?

Yes, alkaline substances react with acids in neutralization reactions.

How is alkalinity measured?

Alkalinity is measured using pH scales, indicators, or titration methods.

What is an acidic solution's effect on metals?

Acidic solutions can corrode metals, causing rust and deterioration.

Are alkaline substances effective in laundry detergents?

Yes, alkaline substances in detergents help remove grease and stains.

Can alkaline substances neutralize acids?

Yes, alkaline substances can neutralize acids, often used in antacids.

How does alkalinity impact water quality?

High alkalinity in water can affect taste and plumbing over time.

What is the effect of alkaline solutions on organic matter?

Alkaline solutions can break down organic matter, used in cleaning.

Can acidity affect plant growth?

High acidity in soil can harm plant growth and nutrient absorption.

Can acidic substances neutralize alkaline substances?

Yes, acidic substances can neutralize alkaline substances in a neutralization reaction.
About Author
Written by
Harlon Moss
Harlon is a seasoned quality moderator and accomplished content writer for Difference Wiki. An alumnus of the prestigious University of California, he earned his degree in Computer Science. Leveraging his academic background, Harlon brings a meticulous and informed perspective to his work, ensuring content accuracy and excellence.
Edited by
Aimie Carlson
Aimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.

Trending Comparisons

Popular Comparisons

New Comparisons