4 Chemistry

Switch on 1 We use chemicals every day. Some chemicals can

be dangerous. Match the warning symbols w i t h the meanings below.

- - 5 f t d X 1 2 3 4

This chemical is... a an irritant. If it touches your skin, it may cause an

itching or burning feeling. b flammable. It burns very easily. c corrosive. It can badly damage people and things. d toxic. It may kill you if you drink it.

2 All of the items below are chemicals. Which chemicals should have warning symbols? Which symbol(s) should they have? 1 petrol 2 drinking water 3 chlorine, the chemical used in swimming pool

water 4 oxygen used in hospitals 5 strong cleaning chemicals used for kitchen and

bathroom drain cleaning 3 Where might you find these symbols in the place

where you study or work? What about in your home?

Reading Elements and symbols

1 Do you know what the table below is called? Can you say anything about what it shows?

0

Group

1 ;»

hydrogen

Group

III IV V VI VII 2 He helium

2

3

4

5

6

7

beryllium boron carbon

> nitrogen oxygen fluorine neon

2

3

4

5

6

7

Sodum >^ magnesium

The t rans i t i on e l ements aluminium phosphorus

5^ S 16 ^

sulphur

3 . S „

chlorine

2

3

4

5

6

7

potasS'um calcium

> scandium litanium vanadium chromium manganese cobalt nickel copper

l> gallium

germanium l> arsenic

selenium

- B r

bromine krypton

2

3

4

5

6

7

l> rubidium

> strontium

89 Y 39 yurium zirconium niobium

> o molyDdenum technetium ruthenium rhodium palladium

'> silver cadmium indium antimony tellurium iodine xenon

2

3

4

5

6

7

'IP barium " [

:anTh„inium

hafnium

- l a

tantalum

'> tunqsien >̂

osmium

indium platrnum qold

80 ^ mercury thallium lead bismuth poloniLm astatine radon

2

3

4

5

6

7 trancum radium

^ " A C 89'^'^ K

Lanthanldes cenum neodymiiirn prorretMium samarium europium gadolinium terbium

Dy 66 '

dysprosium holm um erbium Ihutiurn ytterbium lutetium

Actinides 90 thorium protaciinium uranium neptunium Plutonium amencium berkeiium

251 (-^

9 8 ^ ^ califormium einsteinium

100 fermium nobehum lawrenoum

A t o m s

All matter - everything in the world - is made up of tiny particles called atoms. Atoms cannot be broken down into smaller parts by chemical processes; the atom is the smallest particle of matter. An element is a chemical substance that is made of only one kind of atom. The chemical sodium is made only of sodium atoms, so it is an element. There are around 9 0 elements in the Earth and the Earth's environment. Nearly 30 other elements have been created in laboratories by scientists. These 'artifrcial' elements last for only a few seconds before breaking down into other elements - which is why they are not found in the natural world. T h e p e r i o d i c t a b l e

The periodic table of the elements gives the name and symbol of every element. It groups elements into families of elements that are similar. If you understand the behaviour of one element in Group 1, for example, you can make a good guess about the nature and characteristics of the other elements in the same group. The red line near the right side of the table separates the metals from the non-metals. The non-metals (except for hydrogen) are to the right of the red line. N a m i n g t h e e l e m e n t s

Some elements are named after people who discovered them, and each element has a symbol -one or two letters. For example the symbol for zinc is Zn, and the symbol for hydrogen is H. The symbol for potassium is K, taken from its Latin name kalium. The symbols and names for elements are grouped together in order of their atomic number. This is the lower number to the left of each symbol in the table. This is the number of s m a l l particles called protons found inside every atom.

2 Read the text. Choose the best answer to each question. 1 Which of these things isn t an example of matter? a a stone b a piece of ice c a thought

2 Which of these things can be broken down into smaller parts through chemical processes?

a water, made from hydrogen and oxygen atoms b a sodium atom c a proton

3 How many elements can be found in nature? a 30 b 90 c 120

4 How does the periodic table group elements? a Elements that are more difficult to make are

together. b Elements that are found together in nature are

together. c Elements w i t h similar qualities are together.

5 What does the red line in the table separate? a flammable from non-flammable b metals from non-metals c man-made from natural

6 Where does the symbol K for potassium come from? a the Latin word for the chemical b the name of a scientist c the atomic number of the element

7 How many protons does helium have? a 2 b 3 c 4

3 Use the periodic table to answer the questions. 1 What's the symbol for rubidium? 2 What group is oxygen in? 3 Which element is more similar to l ithium: sodium

or beryllium? 4 Is boron a metal or a non-metal? 5 What is the atomic number of iron?

Listening Compounds

1 Read the short text and look at the table. Can you fill in any of the missing information? When atoms of different elements join together, they make a compound. The compound is described by a formula that shows how many atoms of each element are in the compound. This table shows three compounds.

Name of compound Elements in it How the atoms are joined Formula of compound

water hydrogen and .

- dioxide carbon and GO© ethanol carbon,. ' and oxygen

2 Listen and check your answers.

3 (ft) Listen to the explanation about how compounds are named. Complete the notes.

J

J

J

J

J

J

• sodium, chlorldt J- (+ -iele)

Name these compounds. 1 HCl hydrogen chloride

2 NaCl 3 FeO 4 CaH2 5 HF 6 AIN

vu)\^-vM,tal with the Lower + tht other M\n,-/Mtai (+ -li^g)

Pronunciation ch

How is ch pronounced in each of these words? Tick (/) the correct sound.

J Note: whem, there's.. com-poui^d, it's, a l w a y s VMVMA f irst . For «;)cnkM,-pLe,

dydrogeiA- ^ « hujdrogei^ iodide

\Mtal + J com.-p>ow.iA-ds dov^'t exLst

/k/ /t j/ 1 characteristic • • 2 charge • • 3 chart • • 4 check • • 5 chemical • • 6 chloride • •

2 Q Listen and check your answers.

Reading states of matter

1 Name one thing that is near you that is... • a liquid • a solid • a gas

2 Look at the pictures. Complete the text w i t h words from the labels.

3 Answer the questions. 1 What do you use ice for? 2 What do you use liquid water for? 3 What do you use boiling water for?

Vocabulary 1 Read the information and answer the questions.

- thermometer shows 0 "C

ice cubes melting

When you put ' in a warm place, it slowly changes to liquid water. This is called ^ Until the ice melts, the thermometer shows ^ °C.

- water vapour

Some of the. " changes to water. when it's heated. This is called evaporation.

- thermometer shows 100°C

- water vapour (invisible)

- steam (visible)

- boiling water

heat

When bubbles appear in the water, it is. The thermometer shows ' °C and the water turns to which is visible. It also turns into vapour, which isn't visible.

1 The temperature at which a substance melts is called the m e l t i n g point . What is the melting point of ice?

2 The temperature at which a substance boils is called the b o i l i n g p o i n t . What is the boiling point of water?

3 A s o l i d has a fixed shape and volume (the amount of space that something fills), and doesn't flow. What is the solid form of water?

4 A gas does not have a fixed volume or shape. It spreads out to f i l l its container. By volume, a gas is hghter than a solid or a liquid. Which is heavier: a one-litre container of gas, or a one-litre container of liquid water?

5 A liquid flows easily. It has a fixed v o l u m e , but its shape changes. It takes the shape of the container you pour it into. Which has greater volume, liquid water or steam?

2 Complete the text below w i t h words in bold from above. At room temperature (about 27 °C), iron is a

If you heat it to 1540 °C - the ^ of iron - it becomes a liquid. If you

continue to heat it , bubbles w i l l form in the liquid iron when it reaches its ^ which is 2900 °C. If the iron continues to be heated, it w i l l evaporate and turn into a It w i l l no longer have a fixed shape, and its ^ w i l l increase i f the vapour is allowed to expand.

Absolute zero Scient is ts believe tha t the coldest possible tempera tu re is

—273.15 °C. At th is point, they say all of the part ic les of

mat ter wou ld stop moving. They have come very close to

cool ing th ings to th is temperature , but have never reached it.

The lowest tempera tu re ever recorded in nature on Earth w a s

— 8 9 . 2 °C on 21 July 1983 in Antarct ica.

Speaking Talking about temperatures

1 Listen. Circle the temperature you hear, a -119 °C -190 °C b 15 °C 50 °C c 3500 °C 3550 °C d -13 °C -30 °C e 4832 °C 4328 °C

2 Practise talking about temperatures. Work in pairs, A and B. Each of you has part of a table showing the melting and boiling points of different substances. Exchange information w i t h your partner by asking and answering questions. Complete the table. S t u d e n t A Go to p.l62 S t u d e n t B

Substance Melting point/°C Boiling point/°C

oxygen -219

-15 78

sodium 890

sulphur 119

d iamond 4832

U s e f u l l a n g u a g e

What's the boiling/melting point of... What substance has a boiling/melting point of...

Problem-solving A hypothesis is an idea or explanation of something that is based on a few known facts but that has not yet been proved to be true or correct.

1 Put the below stages of a scientific experiment in the correct order. The first one has been completed for you.

come up with a hypothesis analyse the results carry out the experiment

1 ask yourself a question compare results w i t h your hypothesis plan an experiment to test the hypothesis

2 Read the text on p.29 and check your answers to 1 above.

3 Discuss these questions. 1 Which of these is a question? A hypothesis? An

experiment design? A conclusion? a Water w i t h more salt w i l l have a lower freezing

point than water with less salt. b We can put different measured amounts of salt

into water, then check freezing points. Then we can measure the freezing points of salt water w i t h unknown amounts of salt to figure out how much salt they contain.

c We determined how much salt a quantity of salt water contained by measuring its freezing point.

d How can we find out how much salt there is in a quantity of salt water?

2 An experiment report describes equipment, materials and procedures so that other may duplicate your experiment. Why is it important for an experiment to be repeatable?

3 Imagine you have three substances. You know the freezing point and boiling point of each, but you don't know which substance is which. Come up w i t h a question, a hypothesis, an experiment design and a conclusion for that situation.

Checklist

Reporting an experiment E v e r y experimerit begins w i t h a question, for example How does sunlight help plants grow? You - the researcher - then come up w i t h a hypothesis and design an experiment that w i l l test it . When reporting an experiment you should communicate, as clearly and concisely as possible, the rationale (reason) for the experiment, what was done, what the results were and what the results mean. By reading your report someone else should be able to repeat it and get similar results. To achieve this, y o u r report should be as short and simple as possible. H e a d i n g

Give the experiment name and provide the date it was performed. Include your name and the names of any lab partners. A b s t r a c t

Write a short description of the object or purpose of the experiment and a statement of your main results. T h e o r y

Start wit h the reason for the experiment and provide the essential ideas behind the experiment. Include only the most important formulae (explaining the meaning of any symbols used). E x p e r i m e n t

Describe the equipment, materials and procedures used. Report your actions so others may be able to duplicate the experiment from your description. You should demonstrate that you know and understand what you did. Consider using simple illustrations or drawings. These are often the clearest way to explain a process or result. D a t a A n a l y s i s

Provide one example of each calculation made. You may do any other calculations separately but include only the final results. Clearly state the results you obtained and present all information in an organized way. Tables, charts and graphs are great methods of visual communication. Where appropriate you should compare experimental data to theoretical predictions and calculations. C o n c l u s i o n

In two or three paragraphs, summarize your conclusion from the results of your experiment. Compare them to your hypothesis. Be clear about quantities and values. Evaluate any deviations from your expected errors and provide possible reasons for unusual findings. Discuss and comment on the results and conclusions drawn.

Assess your progress in this unit. Tick (/) the statements which are true.

I can use the periodic table of the e lements

I can understand basic chemical

compounds

I can describe states of matter

I can report on an exper iment

My reading and listening are good

enough to understand most of each text

in this unit

Key words Nouns atom

boiling point

chemical

compound

e lement

formula

freezing point

matter

melt ing point -

proton

substance

vapour

volume

Verbs evaporate

expand

Note here anyth ing about how English is used

that is new to you.