Year 8 Science. Atoms Elements and compounds. Name: Teacher:

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1 Year 8 Science Atoms Elements and compounds Name: Teacher: 1

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3 Atoms and Elements and Compounds What I need to know. I know there are a small number of elements from which all substances are made I know the names of some elements I know that elements are metals or non metals I know the properties of metals I know the symbols of some elements I know that the elements are arranged in the Periodic Table I know what some elements are used for I have seen some reactions of elements I know that each element is made from just one type of atom I know that compounds are made from different elements joined together I know that elements can be obtained from compounds 3

4 1 Materials Everything in the world is made from different materials. How many different materials do you think are in the world? How many new materials do you think are made every day? All of these different materials are made from substances called ELEMENTS How many different elements are there? We can use these elements to make all of the materials in the world but first let us look at some elements. 4

5 2 Elements There are only about 100 different elements. We can make a list of these, but chemists have found a much better way of writing them down together. This is known as the Periodic Table. Your teacher will give you a copy. One way of separating elements is into METALS and NON METALS. Your teacher will show you the dividing line on the Periodic table. One difference between metals and non metals is that metals conduct electricity, non metals do not ( except graphite ) Testing conductivity Use a simple circuit using a bulb, battery, wires and crocodile clips to see if a substance conducts electricity. Use the pictures below to help you draw a circuit. Place the element in the circuit and see if it conducts electricity. Then complete the table on the following page 5

6 Material being Tested Conductor ( a / r ) Insulator ( a / r ) From the sentence on the previous page we can say all metals and all non-metals. Fill in the following table. Material tested Metal ( a / r ) Non - metal ( a / r ) 6

7 3 Common Elements Although there are over 100 different elements, there are only a few common ones.. and most materials are made from just a few of these joined together as compounds. Look around the laboratory can you see any elements? Ask your teacher if they are elements or compounds ( they will only know if they are chemistry teachers!!) On the table below, write down the names of as many elements as you can describe what they look like and what they are used for. Name Symbol Metal or non metal Appearance ( what it looks like ) Use Now choose 1 metal or non metal. use the internet to write an A4 sheet for display. Find out as much as you can about the element use pictures.. anything to make it interesting. Try to choose a different element to the others in your class!! 7

8 4 What are elements made from? There are only about 100 different elements. You have seen that some are metals, and some are non metals. Some are solids, some are liquids ( only 2!!) and some are gases. Give the names and symbols of 6 elements that are solids 5 elements that are gases 2 elements that are liquid What are elements made from? All elements are made from ATOMS. Each element has a different type of atom to the others. We normally show these in diagrams as small circles like this.. All the atoms in an element are identical this means they are the same. or Remember: An element contains only 1 type of atom. 8

9 5 The Periodic Table Chemists use a special table to show all the elements. This is known as the Periodic Table. A copy of it is shown below: The transition metals Alkali metals Metal/non metal dividing line The Halogens The Inert gases The main features of the periodic table are: 1. Vertical columns are known as GROUPS. Elements below each other are similar to each other. 2. There is a dividing line between METALS and NON METALS 3. Some groups have special names. Your teacher will now show you the elements in the first group the ALKALI METALS 9

6 The Alkali metals The alkali metals are in the first group

teacher will show you some reactions of the alkali metals What

What type of solution is formed when they react with water?

10 6 The Alkali metals The alkali metals are in the first group in the Periodic Table Lithium Li Sodium Na Potassium K Your teacher will show you some reactions of the alkali metals What do they look like? What happens when you put them into water? What type of solution is formed when they react with water? Are they reactive or unreactive? Which one is the most reactive? 10

7 Other groups As well as the Alkali metals, there are other groups with special names. These are: 1. The Noble or Inert gases 2. The Transition metals 3.

11 7 Other groups As well as the Alkali metals, there are other groups with special names. These are: 1. The Noble or Inert gases 2. The Transition metals 3. The Halogens The Inert gases These gases are all found in the air. They do not react with anything ( that is what inert means! ). The most famous one is Neon. This gas glows red when electricity is passed through it and is used in neon signs The transition metals The transition metals contain all the traditional metals. They are generally hard, strong metals.. such as Iron, Copper, Zinc, Gold.. The halogens This group contains Chlorine, bromine and Iodine. These are used as bleaches and antiseptics. 11

12 8 Compounds Although there are only about 100 elements, there are millions of different materials. These are made from different elements joined together.. they are known as COMPOUNDS Making Iron Sulphide 1. Weigh out approximately 4 g of sulphur and 7 g of iron filings 2. Put the iron and sulphur on a filter paper and mix them thoroughly with a spatula. 3. Put the mixture into a test tube but keep some for looking at later. 4. Heat the tube until the mixture starts to glow. Take the test tube out of the flame and leave to cool on the heatproof mat. 5. When the tube is completely cold, put it in a polythene bag. 6. Tap the tube gently with a hammer to break it. 7. Tip the contents onto the heatproof mat and pick out the pieces of iron sulphide with tweezers. 8. Carefully throw the rest of the mixture away 12

13 In the space below sketch how the mixture looks before and after the experiment. Describe the mixture before and after. Before ( mixture ) After ( compound ) How could you get the iron out of the mixture of iron and sulphur? It is very difficult to get the iron out of the compound, iron sulphide!! We can write an equation for this reaction: Iron + Sulphur Iron Sulphide Fe S FeS 13

14 9 Making Aluminium Iodide Your teacher will make aluminium iodide from aluminium and iodine. It must be done in the fume cupboard as Iodine is very dangerous Answer the following questions What colour was the aluminium powder? What colour was the iodine? What colour was the mixture? What colour was the compound? The reaction can be shown by the following equation and diagrams + Aluminium Iodine Aluminium iodide Al + I 2 AlI 3 14

15 10 Equations When chemists want to show what happens in a reaction, they normally give a chemical equation. This uses words or symbols to show what has happened. Word equations You have already seen some of these Iron + Sulphur Aluminium + Iodine Iron Sulphide Aluminium Iodide Naming of compounds. The name of a compound tells us which elements are in it. If the name ends in IDE then there are only 2 elements in it. e.g. Lead Iodide contains only lead and iodine. Iron Chloride contains only Iron and Chlorine. If the compound name ends in ATE then it contains 2 elements AND oxygen. e.g. Copper sulphate contains copper, sulphur and oxygen. Lead Nitrate contains Lead, Nitrogen and oxygen Symbolic equations Instead of using words for equations, we can use symbols instead. This doesn t only tell us what reacts, and what is formed, but also how many atoms of each are involved. This is a lot more difficult!! e.g Fe + S FeS this tells us that 1 atom of Iron reacts with 1 atom of Sulphur to form 1 molecule of Iron Sulphide. 15

16 11 Try these! Formula Name Elements present FeS Iron Sulphide Iron, Sulphur AlI 3 PbO Lead, oxygen AgNO 3 CuBr 2 FeO ZnSO 4 CaCO 3 NaNO 3 NaI PbSO 4 How many atoms are there in the following compounds? NaCl 2 CuSO 4 6 H 2 SO 4 NaOH Al 2 O 3 AlBr 3 H 2 O HNO 3 Write word equations for the following: Cu + Br 2 CuBr 2 4Fe + 3O 2 2Fe 2 O 3 16

12 Splitting up compounds If you look at Iron Sulphide, and Aluminium Iodide you made earlier, you will see that they do not look like the original elements.

17 12 Splitting up compounds If you look at Iron Sulphide, and Aluminium Iodide you made earlier, you will see that they do not look like the original elements. You will also see that they cannot be easily turned back into the elements. Splitting compounds into their elements is not easy!! Getting the elements from Copper chloride. Copper chloride, CuCl 2 contains copper and chlorine joined together. They can be separated, but it is not easy. Set up this circuit and see what happens. Set the voltage a 6v D.C. Do not let the electrodes touch each other!! Results What is formed at the positive ( + ) electrode ( anode )? What is formed at the negative ( - ) electrode ( cathode )? Compounds can be split into their elements but it is not easy!! 17

18 13 Mixtures You have seen that it a substance contains only one kind of atom it is an element. If it contains 2 or more different elements joined together it is a compound but what if we just mix things together?? If we could see the atoms using a microscope, they would look like this Elements look like this: or this: Compounds look like this: or this: So a mixture would look like this!! 18

19 14 Particles You have seen that everything is made from small particles known as atoms. If a substance contains only one type of at it is an element. Different atoms joined together make compound. How are the atoms arranged in solids, liquids and gases? We use the following diagrams to show how the particles are arranged in solids, liquids and gases. Heat Heat Solid Liquid Gas In a solid, the particles are fixed by bonds and only vibrate. They have very little energy In a liquid, the particles move freely and have no fixed shape. They have quite a lot of energy In a gas, the particles move very fast. They have a large amount of energy. The greater energy that, liquids and gases have is provided when we heat them up. Melting a solid breaks all the bonds, boiling a liquid lets the molecules escape from the liquid 19

20 15 Wordbank Element Compound Atom Molecule Metal Non Metal Mixture Formula Alloy Website 20

21 Homework sheet 1 Name 1. Ahmed did an experiment to see if different things conduct electricity. The circuit is shown below. Label each part of the circuit. 2. A table of his results is shown below. Fill in the spaces Object Key Does it conduct electricity? Yes Metal or non metal? Rubber No Pencil sharpener Metal Staple gun Yes Pencil Non metal 21

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23 Homework sheet 2 Name 1. Choose 5 different elements. They should be different from the ones you did in class!!! ( Page 7 in the booklet ) Fill in the spaces on the table below. Name Symbol Metal or non metal? What does it look like? What is it used for? 2. Approximately how many elements are there? 3. What do we call substances made from more than one different element joined together? 23

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25 Homework sheet 3 Name 1. Below is a diagram of the Periodic table You will find it useful to look at pages 9 and 11 in you booklet. Draw in the line which separtes the metals from the non metals Colour the alkali metals in Blue Colour the halogens in Red Colour the Inert gases in Yellow Colour the Transition metals in Green Which metal has been known about for the longest time? 25

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27 Homework sheet 4 Name All substances are made from atoms. Elements contain only one type of atom Compounds contain 2 or more different atoms joined together Mixtures are elements and compounds mixed together. Look at the diagrams below. Are they elements, mixtures or compounds? This diagram shows particles in a I think this because This diagram shows particles in a I think this because This diagram shows particles in a I think this because 27

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Electrodes are normally made out of inert (unreactive) materials. Graphite and platinum are common electrode materials.

Electrodes are normally made out of inert (unreactive) materials. Graphite and platinum are common electrode materials. Electrolysis Electrolysis is using an electric current to break up an ionic compound to form elements. Covalent compounds can t be split up by electrolysis. Terms used in electrolysis: Electrolyte - the