topic 1 – the particle nature of matter · web views2/3 chemistry elements, compounds and...

S2/3 Elective Chemistry

S2/3 ChemistryElements, Compounds

and Mixtures

Study Booklet

Elements and the Periodic Table

Activity 1

GOGGLES MUST BE WORN

S2/3 Elective Chemistry

Heat a piece of bread until only a black solid remains.

Much of the bread is lost during the burning but a black solid is left. The black solid is carbon. It is an example of a simple chemical called an element.

An element is the simplest type of chemical substance. An element is made up of only one type of atom (the simplest particle of matter). The atoms of one element are different from the atoms of any other element.

There are just over 100 elements and they are listed in a chart called the Periodic Table.

The elements are arranged in the table depending on what they are like and how they behave. e.g. the elements which are metals are found on the left hand side of the periodic table; the elements which are non-metals e.g. gases such as oxygen, are found on the right hand side of the table.

Symbols are used for the elements. Examples of these symbols include :-

Oxygen O Hydrogen H Chlorine ClCopper Cu Iron Fe Sodium NaGold Au Carbon C Aluminium AlLead Pb Sulfur S Tin Sn

All symbols of the elements have 1 or 2 letters. The first letter must always be written as a capital letter. The second letter (where there is a second letter) must be written as a lower case letter.

What is an element? What element is formed when bread is heated until only a black solid

remains? What is each element made up of? How many elements are known? What name is given to the chart which lists all the elements? What decides the position of an element on this chart? Where are the metals and non-metals found on the table? How many letters are in the symbols of elements and how must they be

written? Write down the names of the 10 different elements and symbol which

represents the element.

S2 Elective Chemistry


Collect a copy of the Periodic Table to include in your notes.

Mark on your copy of the Periodic Table the zig-zag line which separates the metals from the non-metals.

Copy the following table which gives information on some solid metal and non-metal elements into your notes.

METAL and NON-METAL ELEMENTS

Element Is it a good

conductor of

heat?

Is it a good

conductor of

electricity?

Does it break easily?

Melting Point (C)

Boiling Point (C)

Metal or non-

metal?

Aluminium

Yes Yes No 660 2467 Metal

Carbon(graphite)

Yes Yes Non-metal

Copper Yes No 1083 MetalIron Yes Yes No 2750Lead Yes No 328 1740Phosphorus

No No Yes Non-metal

Sulfur No Yes 113 445Tin Yes Yes No MetalZinc Yes No 420 907

Activity 2

Design an experiment to test the electrical conductivity of the substances where it is not shown in the table. After having your plan approved by your class teacher, carry out your experiment.

Use the information in the following passage and any sources of information provided by your teacher to find out more about the properties of these metal and non-metal elements and use it to complete any remaining gaps in the table.


Metals are hard, shiny solids which are good conductors of heat and electricity. They are strong, do not break easily and with the exception of mercury are all solids at room temperature.

Non-metals are poor conductors of heat and electricity, with the exception of carbon (graphite) which is a good conductor of both heat and electricity. Only a few of the non-metal elements are solids are room temperature; most are liquids or gases.

Are metals good conductors of heat and electricity? Are non-metals good conductors of heat and electricity? Which type of element, metal or non-metal breaks most easily? Describe the general pattern in the melting and boiling points of

metal and non-metal elements?

**Practice Problem Exercise No 1**

1. Are the majority of elements in the Periodic Table, metals or non-metals?

2. We have sorted the elements into metals and non-metals, but they can also be classified in other ways e.g. solid, liquid or gas; natural or man-made.

a. Are the majority of the elements natural or man-made? b. Where are the man-made elements found in the Periodic

Table?c. Give the names of 2 elements which are normally solids, 2

which are normally liquids and 2 which are normally gases.3. Find out names of at least 6 elements whose name and symbol both

begin with the letter C.


Chemical reactions

Did you know your life is full of chemical reactions?Here are just a few examples of chemical reactions which occur in our day-to-day lives:

burning coal or wood in a fireburning petrol in a car enginedigesting your foodgrowing plantsthe rusting of the body of a car

Give examples of chemical reactions from our day-to-day lives

When chemical reactions take place a number of changes might occur, which could indicate that a chemical reaction has taken place. These changes include :

colour changesgases being given offenergy being taken in or given outa solid being formedchanges in smell

Some chemical reactions are given special names. e.g. a precipitation reaction involves the formation of a precipitate. A precipitate is a solid which forms in a liquid when a chemical reaction takes place.

Effervescence means bubbling and fizzing when a gas is given off.

Any of the above changes might occur when a chemical reaction takes place, however, the most important aspect of any chemical reaction is that at least one new substance is always formed.

What changes might occur which would indicate that a chemical reaction has taken place?

What is a precipitate? What is effervescence? What always happens in a chemical reaction?


Activity 3

Experiment 1 - Reaction of cobalt chloride solution and sodium carbonate solution


1. Put a small volume of cobalt chloride solution into a test-tube. A depth of about one centimetre would be adequate.

2. Add about the same volume of sodium carbonate solution.3. Look closely for any changes which might take place.

Write a short report on your experiment.Include: A title A description of what you did A list of any changes you observed

What is the special name given to this type of reaction?

Activity 4

Experiment 2 - Heating copper carbonate


1. Put a spatulaful of copper carbonate into a dry test-tube.2. Make sure that you point the open end of the test-tube in a safe

direction. It should not point at yourself or anyone else.

3. Heat it over a blue bunsen flame.4. Look closely for any changes which might take place.



Activity 5

Experiment 3 - Reaction of powdered chalk with hydrochloric acid


1. Put a spatulaful of powdered chalk into a test-tube.2. Add a small volume of hydrochloric acid.3. Look closely for any changes which might take place.


What is the special name given to this type of reaction?


Compounds

Everything in the world is built from elements. Different elements join together to make new substances called compounds.

A compound has different properties from its elements.

What are compounds? What is the difference between a compound and the elements which

make it up?

Activity 6

Your teacher will make the compound copper chloride by joining together the elements copper and chlorine in a chemical reaction. Watch carefully what happens.

Draw a diagram of the apparatus used for this reaction? Describe what happened. Was there any sign that energy was given out in the reaction?

A word equation can be written to describe the change of substances in a chemical reaction. For the above reaction the word equation would be :-

Copper+ Chlorine Copper chloride

The ‘+’ sign in the word equation means ‘and’The ‘’ sign in the word equation means ‘changed into’

The above word equation therefore says :-copper and chlorine changed into copper chloride

Write a word equation for the reaction between copper and chlorine What do the ‘+’ and ‘’ signs mean in the word equation?

Activity 7

GOGGLES MUST BE WORNCollect a piece of magnesium ribbon. Hold the piece of magnesium ribbon with tongs and burn it in a blue bunsen flame.

Describe what you did.


How did you know that a new substance had formed? What sign was there that energy had been given out?


Burning involves a substance joining with the element oxygen.Therefore, the word equation for this reaction is :-

Magnesium + Oxygen Magnesium oxide(silver (invisible gas) (white powder)coloured metal)

Write a word equation for the reaction between magnesium and oxygen

Which of these substances are elements and which are compounds?

Elements are the simplest substances. Chemical changes cannot produce anything simpler. When the atoms of different elements join together during a chemical reaction they form a new type of substance called a compound.

The atoms of the different elements must be joined to form a compound. If 2 or more elements are simply mixed together but not chemically joined, then a compound has not been formed.

A compound is a substance made up of two or more different elements joined together.

What is a compound? What is the difference between a compound and a mixture of different

elements?

The name of a compound can tell you the names of the elements in it.

If the name of a compound ends in -ide, the compound contains the 2 elements obvious from the name.

e.g. lithium chloride contains lithium and chlorinemagnesium oxide contains magnesium and oxygencalcium carbide contains calcium and carbon

There are 2 exceptions to this rule. These exceptions involve compounds whose names end in hydroxide or cyanide.

“anything” hydroxide contains “anything”, hydrogen and oxygen“anything” cyanide contains “anything”, carbon and

nitrogen

e.g. potassium hydroxide contains potassium, hydrogen and oxygen

sodium cyanide contains sodium, carbon and nitrogen


If the name of a compound end in -ite or -ate, the compound contains the 2 elements obvious from the name AND oxygen.

e.g. copper sulphate contains copper, sulfur and oxygenzinc nitrate contains zinc, nitrogen and oxygensodium sulphite contains sodium, sulfur and oxygen

What is the meaning of -ide at the end of the name of a compound? What are the two exceptions to the -ide rule? What elements are contained in each of these two exceptions? What is the meaning of -ate or -ite at the end of the name of a

compound?

Try Practice Problem Exercise No 2


Write down the names of the elements contained in each of the following compounds.

1. sodium oxide 8. magnesium carbonate2. silver chloride 9. potassium sulphite3. iron carbide 10

.sodium hydride

4. potassium sulphide 11.

iron hydroxide

5. copper cyanide 12.

lead oxide

6. calcium hydroxide 13.

sodium cyanide

7. aluminium sulphate 14.

silver nitrate

Suggest names for compounds containing

15.

copper and oxygen only

16.

copper, sulfur and oxygen

17.

iron and chlorine only

18.

sodium, hydrogen and oxygen

19.

potassium and hydrogen only


20.

lead, carbon and oxygen


Word Equations

Scientists usually tell us what happens in a chemical reaction by writing a chemical equation. Equations tell us which substances are present at the start of the reaction i.e. the reactants, and which substances are formed by the time the reaction has finished i.e. the products.

Equations do not give any information on the energy changes which take place during the reaction or any information about the rate of the reaction.

The simplest type of chemical equation is called a word equation. A word equation puts the names of the reactants on the left hand side and the names of the products on the right. The names of the different reactants are separated by a + sign This sign simply means "and". The different products are also separated from each other by + signs.The names of the reactants are separated from the names of the products by an arrow. The arrow means "changes into".

A word equation does not give any details about the states of the substances involved, colours etc. It only gives the names of the reactants and products.

If in an experiment powdered zinc is reacted with hydrochloric acid to form zinc chloride solution and hydrogen gas the word equation would be:

zinc + hydrochloric acid zinc chloride + hydrogen

What is the purpose of a chemical equation? Where are the names of the reactants written in a word equation? Where are the names of the products written in a word equation? What is the purpose of plus signs ( + ) and an arrow ( ) in a word

equation? What information is NOT given in a word equation? Describe any chemical reaction and write a word equation for your

reaction.

Try Practice Problem Exercise No 3



Write word equations for the following chemical reactions.

1. Sodium reacts with oxygen and changes to sodium oxide.2. Iron and chlorine react to give iron chloride.3. Sodium hydroxide and copper sulphate and change into sodium

sulphate and copper hydroxide.4. Hydrogen gas and oxygen gas react explosively to produce steam.5. Magnesium bubbles and fizzes when it reacts with sulfuric acid, giving

off hydrogen gas and forming magnesium sulphate.6. When green copper carbonate powder is heated very strongly, it breaks

down into black copper oxide and carbon dioxide gas.


Mixtures

When a compound is formed, different elements have joined together in a chemical reaction. However, not everything that contains atoms of different elements is a compound.

If substances are simply mixed together without joining in a chemical reaction they still have the same properties and can be fairly easily separated. This is called a mixture.

A mixture of the elements iron and sulfur can be easily separated with a magnet. Activity 8

SEPARATING IRON FILINGS FROM SULFUR POWDER (Teacher Demonstration)GOGGLES MUST BE WORN

Your teacher will demonstrate the separation of iron filings from sulfur powder using a magnet.

Mixtures can be made up of different elements only, different compounds only or of both elements and compounds. Air is a mixture of gases – some are elements e.g. nitrogen, oxygen, argon, but some are compounds e.g. carbon dioxide.

What is a mixture? Write a short report describing how mixture of the elements iron and

sulfur can be easily separated. Mixtures can be made up of ............... Copy and complete this

sentence in three different ways. What type of mixture is air?


1. What must be true of atoms in a compound that is not true of the atoms in a mixture of elements?

2. How could you separate a mixture of :-a. chalk mixed with waterb. salt dissolved in waterc. powdered iron, salt and sand


Breaking up a compound

Although mixtures are usually easier to separate, it is possible to break up a compound and get back the elements which make it up. In an earlier experiment your teacher demonstrated the reaction between copper and chlorine to make the compound copper chloride. We will now try to break up a solution of blue copper chloride to obtain copper and chlorine.

Activity 9

GOGGLES MUST BE WORNSet up the equipment as in the diagram.Watch what happens at each electrode.After a few minutes your teacher may allow you to replace the carbon electrode joined to the negative terminal of the battery with a ‘silver’ coin.

Write a report on your experiment. Include a title, a description of what you did, a diagram of the

equipment used and a clear statement of what happened at each electrode in the experiment.

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