To prepare & show the production of alcohol by yeast

Question 1

First step for preparation of alcohol involves preparing what and how so?

Answer 1

Prepare a glucose solution by dissolving glucose in water.

Question 2

Boil the solution in what and for how long? (Step 2 of preparation of alcohol)

Answer 2

In conical flask for 5 mins

Question 3

Why do you boil the solution for 5 mins in a clonical flask?

Answer 3

Eliminates gases from the solution, forming anaerobic conditions

Question 4

After boiling, leave it cool and add what? (Step 3)

Answer 4

Dried yeast

Question 5

Why let solution cool before adding dried yeast?

Answer 5

Allow the yeast to survive

Question 6

Step 4: after adding dried yeast what do you do?

Answer 6

Cover liquid in flask with an aerobic lock

Question 7

Why do you cover liquid in the flask with aerobic airlock?

Answer 7

Prevents oxygen from re-entering the solution

Question 8

What’s the purpose of the airlock?

Answer 8

Prevent micro-organisms entering and to allow carbon dioxide to pass out.

Question 9

What could you add to inside the airlock?

Answer 9

Water

Question 10

After adding aerobic airlock, what do you with the apparatus?

Answer 10

Placed in water bath at 30C

Question 11

What temperature water bath do you add the apparatus to and why?

Answer 11

30 degrees C, allows enzymes to work at their best

Question 12

After a few days, how do you know fermentation is complete?

Answer 12

Bubbles of carbon dioxide will be seen in the limewater, once bubbles stop forming then fermentation is complete

Question 13

What do you for your control? What will happen?

Answer 13

Same apparatus and steps but without adding yeast cells, no bubbles will form, water will stay clear

Question 14

What’s the first step for showing production of ethanol?

Answer 14

Filter solution

Question 15

Why do you filter the solution when showing production of ethanol?

Answer 15

Remove yeast cells

Question 16

After filtering solution what do you do?

Answer 16

Place some of the filtrate into a test tube

Question 17

After putting some filtrate into test tube - what do you add to it, how much and what colour is it?

Answer 17

Add an equal amount of potassium iodine solution, which is colourless

Question 18

After adding potassium iodine what do you add and what colour will the solution become?

Answer 18

Add sodium hypochlorite solution. Solution turns brown-orange then yellow

Question 19

After adding everything to the test tube what do you do with it?

Answer 19

Water bath at 50-60 degrees C for 4 or 5 minutes

Question 20

After leaving the test tube cool what appears indicating that ethanol is present?

Answer 20

Yellow

Question 21

What will the control test tube show?

Answer 21

No yellow

Question 22

How do we know fermentation is complete?

Answer 22

Bubbles stop

Question 23

The name for testing for alcohol is called?

Answer 23

Iodoform test

Question 24

Iodoform is a test for what?

Answer 24

Testing for alchohol