Activity 6.5 NCERT class 10 science chapter 6 Life processes
Brief procedure: Activity 6.5 asks us to pass the air produced by yeast on sugar solution or fruit juice into lime water.
Explanation: Yeast is a unicellular bacteria. It lives on organic food like sugar, flour etc. Yeast breaks down food material and releases carbon dioxide through the process called Fermentation. When this air pass through the bent tube It makes lime water milky.
Ca(OH)2(aq) + CO2(g) ——–> CaCO3(s)
(Lime) (Insoluble milky Precipitate)
This experiment shows that yeast lives on fruit juices, sugar and produces carbon dioxide.
You must have seen people who use yeast powder in making a base for pizza or bread. They first put yeast in a warm sugar solution. Warm temperature and sugar are favourable conditions to the yeast cells. Yeast cells multiply and produce carbon dioxide which raises the dough and makes it spongy. To know more you can read an article ‘Science of bread‘ by exploratorium.edu.