Respiration + gas exchange
-Activity 11.3 (book page 143)
(Lime water & hydrogen carbonate indicator→ to detect carbon dioxide)
A1; Why it is important to boil the water?
It is important to boil the water because doing so will take away any dissolved air.
A2; Why must the sugar solution be cooled before adding yeast?
The sugar solution must be cooled before adding the yeast because if the yeast is added before it is cooled (when water is hot) it will die without releasing carbon dioxide for the experiment.
A3; What is the liquid paraffin for?
The liquid paraffin is used to separate the yeast from the air (oxygen).
A4; What happened to the limewater or hydrogen carbonate indicator solution in each of your pieces of apparatus? What does this show?
The limewater turned cloudy in apparatus A . We can observe that the yeast respired CO2 and that the limewater absorbed it. However, in the other apparatus the yeast did not respired CO2, and therefore the lime water was clear and couldn´t absorb the carbon dioxide.
A5; I would expect to find ethanol (alcohol), as the process of anaerobic respiration in yeast results in the production of alcohol.
-Activity 11.8 (book page 149)