acids and bases

gain or lose electrons to form a full outer shell of electrons to form an ion

positively-charged ions which have donated electrons

are negativley-charged ions which have received electrons

formed when a cation (+) bonds to an anion (-) via an ionic bond. the process to form the ions from their neutral atoms must involve a transfer of electron(s).

Acids release hydrogen ions (H⁺) when dissolved in water, forming an acidic solution.

When a substance is aqueous (aq), it means it’s dissolved in water, not turned into a liquid. For example, sugar becomes aqueous when mixed with water — it’s sugar in water, not melted sugar.

Chemical name and formula Common name Uses Hydrochloric acid (HCl), Stomach acid, Helps digest food in the stomach Acetic acid (CH₃COOH), Vinegar, Used in food and cooking Ascorbic acid (C₆H₈O₆), Vitamin C, Found in fruits and vegetables

Acids are common in many foods we eat. Citrus fruits like oranges and lemons contain citric acid and ascorbic acid (vitamin C). Yoghurt contains lactic acid, and vinegar contains acetic acid.

Acids are corrosive, meaning they can damage or destroy materials on contact. The effect depends on their strength — strong acids can cause severe burns, while weaker acids, like those in soft drinks, can slowly cause tooth decay.

Acids and bases are chemical opposites. When they are combined, they neutralise each other, forming a balanced solution.

Acids can be classified as strong or weak. A strong acid produces a high concentration of H⁺ ions when dissolved in water. For example, hydrogen chloride (HCl) is a strong acid because it almost completely ionises into H⁺ and Cl⁻ ions, allowing it to react easily. The stronger the acid, the more corrosive it is.

Weak acids have a lower concentration of H⁺ ions when dissolved in water. For example, vinegar (HC₂H₃O₂) is a weak acid because most of its molecules do not ionise and stay intact, producing fewer H⁺ ions. Weak acids are less corrosive than strong acids, but they can still cause damage.

An acid’s strength depends on how well it ionises in water. An acid’s concentration depends on how much water is in the solution — more water means it’s diluted, less water means it’s concentrated. A strong acid can still be diluted, and a weak acid can be concentrated — these are separate properties.

Bases release anions that accept H⁺ ions (such as hydroxide, OH⁻) when dissolved in water. A base in aqueous form is called an alkaline solution. While acids release H⁺ ions, bases release ions that accept H⁺. When they react, they neutralise each other and form water

Chemical name and formula Common name Uses Sodium hydroxide (NaOH), Caustic soda, Used to make soap Ammonium hydroxide (NH₄OH), Ammonia water, Cleaning product; used to make fertilisers Sodium hydrogen carbonate (NaHCO₃), Baking soda, Makes cakes rise and fluffy Sodium carbonate (Na₂CO₃), Washing soda, Used in glass making and as a cleaning product Calcium hydroxide (Ca(OH)₂), Slaked lime Reduces soil acidity; used to test for carbon dioxide

If you’ve ever accidentally tasted soap or baking soda, you’ll know that it has an unpleasant bitter taste to them.

The same way that strong acids are corrosive, strong bases are caustic. They are both identical in the sense they cause damage, but the damage is considered caustic if the reaction is from a base.

The next time you use baking soda, dissolve some in water and rub your fingers between the solution. It should feel soapy and slippery!

Acids and bases are chemically opposite one another. When combined, they neutralise each other

Bases react with oils to make soap through a process called saponification. This creates tiny, slippery particles called micelles that trap and remove oils from surfaces — like when you wash grease off dishes or use micellar water to clean your face.

A strong base releases more H⁺-accepting ions, while a weak base releases fewer. A base becomes diluted when more water is added, and its corrosiveness depends on how well it ionises in water.

• used to measure the ratio of H+ and OH- ions in a solution • ranges from 0-14, neutral solution at pH 7 • solutions under pH 7 are acidic; solutions over pH 7 are basic • further away the pH is from 7, stronger it is

• chemicals that change colour when the pH changes • indicators are used to estimate the pH of solutions

• litmus paper • universal indicator