ACIDS AND BASES LESSON OBJECTIVES Compare acids and bases by describing key characteristics ACIDS • Acids: a solution that contains hydrogen ions (H+) • An acid is strong then it has lots of hydrogen ions (H+) • An acid is week if it does not have many hydrogen ions (H+) ACID CHARACTERISTICS • Characteristics of acids include: • Taste sour • Conduct electricity • Corrosive (break down certain substances) • Some react with metals to produce hydrogen gas • Turns litmus paper red • pH value lower than 7 BASES • Bases: a solution that contains hydroxide ions (OH-) • Also called alkalis • A strong base has lots of hydroxide ions (OH-) • A weak base doesn’t have many hydroxide ions (OH-) BASE CHARACTERISTICS • Characteristics of base include: • Looks slippery/soapy • Bitter taste • Conduct electricity • Do not react with metals • Turns litmus paper blue • pH above 7 PH SCALE • A scale that measures how acidic or basic a substance is . • The pH scale ranges from 0 to 14 • “p” stands for potential • “H” stands for hydrogen • Works by detecting the potential of a substance to attract hydrogen • Bases have a pH more than 7 neutral more acid • Acids have a pH less than 7 more basic highly basic • Anything with a pH of 7 is neutral highly acidic LITMUS PAPER AND UNIVERSAL INDICATOR UNIVERSAL INDICATOR • pH indictor • Universal indictor is a brown solution • Universal indicator is then placed into another solution and the colour will change depending on pH level PH • The concentration of hydrogen ions (H+) in a solution is measured using the pH scale. • In an acidic solution, there are more hydrogen ions (H+) than hydroxide (OH–) ions. In contrast, an alkaline solution has more hydroxide ions than hydrogen ions. • Pure water is neither an acid nor a base. It’s neutral, having equal numbers of hydrogen and hydroxide ions. It has a pH of 7. more basic highly basic neutral more acid highly acidic UNIVERSAL INDICATOR Universal indicator has been added to solutions. The solutions have changed colours. Use the pH scale to determine the pH of the solutions. LITMUS PAPER • pH indicator • Indicates the acidity or alkalinity of a substance • Universal litmus paper will not show specifically the pH level Testing Acidity Testing Alkalinity Red Litmus Paper No change Turns blue Blue Litmus Paper Turns red No change NEUTRALISATION • Acids and Bases will react together to neutralise each other • The reaction produces water and a salt (not always table salt) • Acid + base --> salt + water ACTIVITY • Complete the worksheet analysing acids and bases (you will need access to a laptop)
