3B Group 9

Chemistry Reading Competition

• Introduction of the book• Article 1 : Why doesn't the 3 Second

Glue adhere to the tube? • Article 2 : What are the differences

among green tea, red tea and

oolong tea?

Content

Introduction of BookTitle: 蘇老師生活化學快問妙答

(Dr. Joe & What You Didn't Know: 177

Fascinating Questions & Answers about

the Chemistry of Everyday Life)

Author: 蘇瓦茲 Schwarcz, Joe

• Dr. Joe used simply scientific theory to explain many everyday problems ignored by us ↪ easy to understand ↪ cause our curiosities

• The problems involved many regionse.g. daily activities, health care, history, food

scienceBut all of them can be explained by

science

Why did we find it interesting

Let’s us show you two interesting articles in the book!!!

Why doesn't the

3 Second Glue adhere to the

tube?

What is 3 Second Glue• Generic Name:

Cyanoacrylate• is used for

gluing of various materialsBut why it

doesn’t adhere to the tube?

• Main component of 3 Second Glue:

Ethyl 2-cyanopropenoate (ECA)

(氰基丙烯酸酯 )• a colourless liquid with low

viscosity

Firstly, let’s me tell you why 3 Second Glue can glue materials together!!!

ECA directly contacts with the air when pressed out of the tube

reacts with the hydroxide ions (OH– 氫氣根離子 ) in the water vapour in the air

long, strong chains are formed

join the bonded surfaces together

oxygen atom

hydrogen atom

CH2(CN)CO2Et + CH2O ➩ CH2=C(CN)CO2Et + H2O

Polymerization( 聚合作用 ) occurs!!!

• The tube is made of plastic• separate the Ethyl 2-

cyanopropenoate from the hydroxide ions outside

• no polymerization occurs ↪ 3 Second Glue does not

adhere to the tube

We notice that...• Chemistry seems to be abstract

to many students• But this article shows that

Chemistry is related to our life• We have never noticed the

reason why 3 Second Glue doesn't adhere to the tube

↪we should be more sensitive to our

surroundings

What are the differences among them?

Green Tea Black (Red) tea Oolong tea

Tea is the most widely consumed drink in the world But we don’t know much about it…… (we think that all the teas are the same)

WHY DO WE CHOOSE THIS ARTICLE ?

They are similar to one another, aren’t they?

All real teas come from leaves of Camellia Sinensis

But different processing methods produce different types of tea

Green Teathe result of curing the

tender camellia leaf various methods and

degrees of heat can be use

Green rooibos

GREEN TEAoxidation process is omittedsundried foliages develop a

yellow-tan colour contains a substantially higher

amount of phenolic phytochemicals and other antioxidants

Red tea

• is made by cutting to oxidize the foliages before sun drying

Red tea

The oxidation process turns the cut plant parts into reddish-orange colour

Red rooibos

Oolong tea

• fully oxidised before drying by a careful withering process

Oolong tea

• the raw leaves are sun-wilted and then bruised

• exposes their juices to the air

• leaves oxidise ➩ turn brown

Now we know the differences among green tea, red tea and oolong tea !

Tea is classified based on the techniques with which it is produced and processed

Also we find that tea benefits our health ! Tea leaves contain more than 700 chemicals e.g. Green tea is rich in catechin polyphenols, particularly in epigallocatechin gallate (EGCG)• EGCG is a powerful anti-oxidant inhibiting the growth of cancer cells killing cancer cells without harming healthy tissue lowering LDL cholesterol levels inhibiting the abnormal formation of blood clots

Group ListNg Wai Kwan (24)

Tse Oi Chu (31)

Tsui Yu Ping (32)

Yai Ying Wai (38)

End