Chemistry of Baking Soda and Yeast

The short video from  American Chemical Society was so interesting. It shows the chemistry of bread baking.

Yeasts are actually living microorganisms. Once in contact with warm water, the yeast added feeds on the sugars in flour and produces carbon dioxide. The release of carbon dioxide makes bread rise.

Baking soda works more quickly than yeast.  Baking soda consists of sodium bicarbonate, calcium acid phosphate & corn starch. Bread dough rises faster as chemical reaction occurs and produces carbon dioxide.

Litmus Paper

Self Inflate Ballon through Reaction involving Acids

The self inflate ballon attracts small kids' attention during K2M 2011

How?

1. Add 1 table spoon of baking powder to a ballon with a funnel.
2. Fill a bottle with halfull of vinegar.
3. Attach the ballon with the baking powder to the bottle.
4. Quickly por baking powder from ballon the bottle.

Why?

When the baking powder(sodium bicarbonate) is mixed with vinegar(ethanoic acid), the reaction produce carbon dioxide, water and salt.  The production of carbon dioxide gas inflate the ballon

Dilution method formula

Many students always get confused when using the dilution method formula especially when susbstituting value for V₁.

For the above situation, we shall substitute the value as follows.

M₁V₁ = M₂V_{2
2V1 = 0.2(100)
V1= 10 cm³}

From the calculation, we know that

1. 10 cm³ of is pipetted from 2.0 mol dm^-3 sodium hydroxide solutoin and transferred into a volumetric flask.
2. 90 cm³ of distilled water is added into the volumetric flask. The volumetric flask is shaken well.
3. 100 cm³ of 0.2 mol dm^-3 sodium hydroxide solution is ready.

Red Cabbage Juice as An Acid Base Indicator

Have you ever tried this red cabbage(Brassica oleracea var. capitata f. rubra) before? It's often used for salads. Some of friends do not dare to tried even a small piece of it because of its colour.

The cabbage is red/purple, due to the presence of a colour pigment called anthocyanin. Its colour depends at the pH value of the soil. 

More acidic soil, the leaves grow more reddish.

More alkaline soil, more greenish yellow cabbage is produced.

Due to this special characteristic, red cabbage juice can be used as a home made acid base indicator. For more details, please visit http://www.funsci.com/fun3_en/acids/acids.htm.

Try to look around your garden too. May be you can colloect some flower petals and test whether there is any colour when difference acidic/alkaline substances are added. Who knows you might discover your own natural indicator too! Please don't forget to share with me your new finding too!!!

Rate of Reaction between Zinc and Hydrochloric Acid

This video shows the reaction between zinc and hydrochloric acid.  Hydrogen gas is released in both conic flasks.

Points to ponder:

1. Any possible reasons that contribute the different size of ballons in both experiments?
2. How to measure the of rate of reaction?

Relationship Between Concentration of Acid and pH Value

Chemistry SPM 2009 Paper 3 Q3 from sweemoi khor

This question appeared in Negeri Sembilan Trial paper. Those students from this state are very lucky.

Some students said they didn't carry out this experiment in their chemistry laboratory. Thus they have no idea how the experiment plan should be.

To my dear current form 4 students, Let's discuss this question together.

Moles

 

Concept of moles is an important concepts in chemistry. Students learn the basic concepts in Chapter 3 Chemical Formulae and Equation during form 4. Later, they relate the moles concepts with molarity of a solution in Chapter 7 Acids and Bases and Chapter 8 Salts.

 

During form 5, students are expected to apply the concept well in various numerical problems in Chapter 1 Rate of Reaction, Chapter 4 Thermochemistry.

Some common wrong concepts that I have come across:

• students thought that the moles is the same with molarity.
• they thought that volume refer for both solution and gas.

Plese my dear students, please study the relationship above thoroughly. Whenever come across any question related to this concepts, understand the questions and substitute the value given in the equation correctly.

Strength Of Acid And Alkali

Strength Of Acid And Alkali

View more documents from sweemoi khor.

Preparing a Standard Solution

Preparing a Standard Solution

View more documents from sweemoi khor.

To determine the end point in the titration of hydrochloric acid and sodium hydroxide solution using acid-base indicator

PEKA 2

Titration is an important method to determine the concentration of a solution.
Through Acid-base titration, concentration of acidic or alkaline solution can be determined.

Format of the Report
(Refer practical book page 103)

1. Aim
2. Materials
3. Apparatus
4. Diagram
5. Procedure
6. Result
7. Observation
8. Discussion
9. Conclusion

Please get ready before come to the lab. You might find video in this blog that show the correct method to carry out acid-base titration. 

Schedule for PEKA is as follows :
4E : 15/9/09(Tuesday)

4D : 18/9/09(Friday)*
*Subjected to changes, might be earlier.

Acid Base Indicator

Acid Base Titration

Preparation of Ammonium Fertiliser

Ammonium fertiliser is a type of salt. It can be prepared through a reaction of ammonium hydroxide solution and acid.

 

ammonium hydroxide + acid --> ammonium fertiliser  + water

 

For example, to prepare ammonium sulphate, reactants required are ammonium hdyroxide solution and sulphuric acid.

 

Method used to prepare ammonium sulphate in the laboratory is using titration method.

1. 25 cm³ of ammonium hydroxide 1 mol dm^-3 is pipetted into a conical flask and few drops of phenolphthalein is added.
2. A buret is filled with aulphuric acid. Initial burette reading, V₁ is recorded.
3. Sulphuric acid is added into drops by drops into the ammonium hydroxide solution and the content of the conical flask is swirled.
4. Continue adding sulphuric acid until the colour of phenolphthalein turn to colourless from pink.
5. Final burette readind, V₂ is recorded.
6. Steps 1 - 5 is repeated by adding (V₂- V₁) cm³ of sulphuric acid from the burette into 25 cm³ of ammonium hydroxide solution in the conical flask(with adding phenolphthalein) and the conical flask is swirled.
7. The content of the conical flask is then poured into an evaporating dish and heated until the volume become one third from the initial volume.
8. The content is cooled into room temperature and filtered. The crystal (ammonium salt) is dried by using filter paper.

Diagram to show the set-up of apparatus.