Many substances in nature are not pure substances, instead they are mixtures. And lemonad is a mixture - a combination of two or more elements and/or compounds.
The mixture has properties that are similar to the components that make it up. Each component in the mixture retains its individual chemical properties.
Lemonade is comprised of ingredients (such as water, sugar and lemon juice) that have their own chemical formulas.
The sour taste of lemon is caused by the presence of organic acids. The major acid in lemons is citric acid (C₆H₈O₇) which makes up around 5 to 6% of the lemon's juice.
Other acids are also present, although in much lower concentrations than citric acid. Malic acid (C₄H₆O₅) is one of these, present at around 5% of the concentration of citric acid.
Lemons contain high levels of vitamin C, also known as ascorbic acid (C₆H₈O₆). The levels in lemon are around 50mg per 100g.
Simple sugars are called monosaccharides and glucose is one of them with a chemical formula C₆H₁₂O₆. This means that in one molecule of sugar there are six carbon atoms, twelve hydrogen atoms and six oxygen atoms.
Lastly, water as we all know has a chemical formula of H₂O.