, bases and saltsAcids and of acids and relative strengths of acids and an of of preparing soluble of preparing insoluble about for different saltsCrystal of water of of salts in questions●● Acids and the substances shown in Figure contain an one sort or another. Acids are certainly all . What properties do these substances have you think that they are acids or contain acids?Figure Some common alkaline What do all these foods have in common?The word acid means ‘sour’ and all acids possess . They are also:.●●.●●soluble in are very different from acids. They are ‘opposite’ of acidsThey will remove the sharp taste from an acid●● They have a soapy feel●●Some common alkaline substances are shown would be too dangerous to taste a liquid to find out was acidic. Chemists use substances called change colour when they are added to alkalis. Many indicators are dyes which have from natural sources, for example litmusMethyl orange, a common indicator used (see p. 129) is pink in an acid solution to show a yellow colour in an alkaline solutionSome other indicators are shown in Table , the colours they turn in acids and alkalisTable Indicators and their colours in acid and alkaline solutionIndicatorColour in in litmusRedBlueMethyl orangePinkYellowMethyl redRedYellowPhenolphthaleinColourlessPinkRed 1176/5/14 1:10 , bases and saltsThese indicators tell chemists whether a acid or alkaline (Figure ). To obtain an how acidic or alkaline a substance is, we indicator known as a universal indicatorThis indicator is a mixture of many other indicatorsThe colour shown by this indicator can be a pH scale. The pH scale was developed by chemist called Søren Sørenson. The runs from below 0 to 14. A substance with a less than 7 is an acid. One with a pH of greater is alkaline. One with a pH of 7 is said to be nor alkaline, that is neutral. Water is the example of a neutral substance. Figure the universal indicator colour range along substances with their particular pH way in which the pH of a substance can is by using a pH meter (Figure ). electrode is placed into the solution and a is given on the digital A digital pH of acids and have been many attempts to define between acids and bases. The first took place in 1777, when the Lavoisier (Figure ) suggested that substances that contained Indicators tell you if a substance is acid or juice,..()6milk78bloodwater,. 11 12 13 cleaner,.dilute , ammoniaa The pH Universal indicator in solution, showing the colour rangeFigure Antoine Lavoisier (1714–1794) at work in his 1186/5/14 1:10 and alkalisIt was not long after this that the ‘hydro-halic’ acids.(HCl, HBr, and so on) were discovered and no oxygen present in them. This produced theory in 1810 when the English Humphry Davy (1778–1829) suggest
