Presentation is loading. Please wait.

Presentation is loading. Please wait.

Boardworks GCSE Additional Science: Chemistry The Alkali Metals

Similar presentations


Presentation on theme: "Boardworks GCSE Additional Science: Chemistry The Alkali Metals"— Presentation transcript:

1 Boardworks GCSE Additional Science: Chemistry The Alkali Metals

2 Boardworks GCSE Additional Science: Chemistry The Alkali Metals

3 Where are the alkali metals?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals The elements in group 1, on the left of the periodic table, are called the alkali metals. Fr Cs Rb K Na Li lithium sodium potassium rubidium caesium francium These metals are all very reactive and are rarely found in nature in their elemental form.

4 What are the alkali metals?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals

5 Why are they called the ‘alkali metals’?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals The alkali metals are so reactive that, as elements, they have to be stored in oil. This stops them reacting with oxygen in the air. The alkali metals are unlike most other metals, which are usually hard and dense. Alkali metals are soft enough to be cut with a knife, and the most common alkali metals, lithium, sodium and potassium, all float on water. Photo credit: Dr John Mileham The elements in group 1 also react with water and form alkaline compounds. This is why they are called alkali metals.

6 What is the electron structure of alkali metals?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals The alkali metals all have one electron in their outer shell. This means that: lithium 2,1 They are found in group 1 of the periodic table. They have similar physical and chemical properties. sodium 2,8,1 They can readily lose the outer shell electron to form positive ions with a +1 charge and a full outer shell. potassium 2,8,8,1

7 How do you identify alkali metals?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals Teacher notes This virtual experiment illustrates how the alkali metals give off characteristic flame colours, and how they can be used to identify the presence of the metals. It could be used as a precursor to running the practical in the lab, or as a revision exercise.

8 Boardworks GCSE Additional Science: Chemistry The Alkali Metals

9 What are the properties of the alkali metals?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals The characteristic properties of the alkali metals are: They are soft and can be cut by a knife. Softness increases going down the group. They have a low density. Lithium, sodium and potassium float on water. They have low melting and boiling points. These properties mean that the alkali metals are different to typical metals. However, alkali metals do also share some properties with typical metals: Photo credit: Dr John Mileham Image is of sodium, freshly cut. Sodium tarnishes very quickly – within approximately 20 seconds. In this image, you can see how it is already tarnishing, starting from the right hand side. They are good conductors of heat and electricity. They are shiny. This is only seen when alkali metals are freshly cut.

10 What is the trend in density?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals The alkali metals generally become more dense going down the group, but the trend is not perfect because potassium is less dense than sodium. Element Density (g/dm3) lithium 0.53 sodium 0.97 potassium 0.86 rubidium 1.53 caesium 1.87 Water has a density of 1 g/dm3. Which elements in group 1 will float on water?

11 What are the trends in density?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals Teacher notes This animated graph could be used as a stimulus for either small-group or whole-class discussion on trend in density among the alkali metals.

12 What is the trend in melting and boiling point?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals The melting points and boiling points of alkali metals decrease going down the group. Element Melting point (°C) Boiling point (°C) lithium 181 1342 sodium 98 883 potassium 64 760 rubidium 39 686 caesium 28 671 The melting and boiling points decrease going down group 1 because the atoms get larger. In each metallic structure, the attraction between the positive metal ions and the delocalized sea of electrons gets weaker and so they become easier to melt, and to boil.

13 What are the trends in melting point?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals Teacher notes This animated graph could be used as a stimulus for either small-group or whole-class discussion on the melting points among the alkali metals.

14 What are the trends in boiling point?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals Teacher notes This animated graph could be used as a stimulus for either small-group or whole-class discussion on the boiling points among the alkali metals.

15 Properties of alkali metals quiz
Boardworks GCSE Additional Science: Chemistry The Alkali Metals Teacher notes This completing sentences activity provides the opportunity for some informal assessment of students’ understanding of the properties of alkali metals. Students could be asked to write down the missing words in their books and the activity could be concluded by the completion on the IWB.

16 Boardworks GCSE Additional Science: Chemistry The Alkali Metals

17 How do the alkali metals react with oxygen?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals All alkali metals react with oxygen in the air to form metal oxides. This produces a layer of dull oxide on the surface of the metal, called tarnish. The speed with which alkali metals react with oxygen in the air increases going down the group: lithium – tarnishes slowly sodium – tarnishes quickly Photo credit (top and bottom): Dr John Mileham Top image – uncut lithium, highly tarnished on the exposed surface. potassium – tarnishes very quickly. Why are alkali metals stored in oil? The oil prevents them from reacting with oxygen and tarnishing.

18 What is the equation for the reaction with oxygen?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals The reaction between an alkali metal and oxygen is an example of an oxidation reaction: alkali metal oxygen  alkali metal oxide The word and chemical equations for the reaction between lithium and oxygen are: 4Li (s) O2 (g)  Li2O (s) lithium oxygen  lithium oxide What are the word and chemical equations for the reaction that causes sodium to tarnish? 4Na (s) O2 (g)  Na2O (s) sodium oxygen  sodium oxide

19 How do the alkali metals react with water?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals Teacher notes This virtual experiment illustrates how each of the alkali metals reacts with water. It could be used as a precursor to running the practical in the lab, or as a revision exercise.

20 What does the reaction with water produce?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals All the alkali metals react vigorously with water. The reaction with water becomes more vigorous as you go down the group. It is an exothermic reaction as it releases a lot of heat. The reaction produces a gas that ignites a lighted splint with a squeaky pop. What is this gas? When green universal indicator is added to the reaction mixture, it turns purple. What does this tell you about the products of this reaction? Photo credit: Dr John Mileham Image of lithium in water, with universal indicator added. The indicator was green before the reaction, but has turned purple during the course of the reaction.

21 What is the equation for the reaction with water?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals This reaction creates alkaline hydroxide ions. This is why the group 1 elements are called the alkali metals. The general equation for the reaction between an alkali metal reacting with water is: 2M(s) H2O(l)  2MOH (aq) H2(g) alkali metal water  alkali metal + hydrogen hydroxide

22 How does lithium react with water?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals Lithium is the least reactive of the alkali metals. When added to water, it fizzes and moves around slowly across the surface of the water. What is the equation for this reaction? 2Li (s) H2O (l)  2LiOH (aq) H2 (g) lithium water  lithium hydrogen hydroxide Photo credit: Dr John Mileham

23 How does sodium react with water?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals When added to water, sodium fizzes more than lithium, and moves quickly across the surface of the water. The sodium melts as it reacts, and it becomes spherical and shiny, like a ball bearing. The hydrogen sometimes catches fire because of the heat from the reaction. What is the equation for this reaction? Photo credit (left and right): Dr John Mileham Left image – sodium reacting with water. It has created enough heat to melt the sodium to a round and spherical shape. Right image – in this image, sodium is reacting so strongly with the water that it has caught fire, burning with the characteristic sodium flame coloured. 2Na (s) H2O (l)  2NaOH (aq) H2 (g) sodium water  sodium hydrogen hydroxide

24 How does potassium react with water?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals When added to water, the potassium moves across the surface of the water very quickly. The reaction produces so much heat that the hydrogen given off catches alight. What colour would the flame be? Like sodium, it melts with the heat of the reaction. What is the equation for this reaction? Photo credit: Dr John Mileham 2K (s) H2O (l)  2KOH (aq) H2 (g) potassium water  potassium hydrogen hydroxide

25 How do alkali metals react with water?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals Which of the alkali metals will react most strongly with water? Teacher notes This illustration contains representations of how each alkali metal reacts with water. It can be used as plenary or revision exercise to the topic or as an introduction.

26 How does electron structure affect reactivity?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals The reactivity of alkali metals increases going down the group. What is the reason for this? The atoms of each element get larger going down the group. Li This means that the outer shell electron gets further away from the nucleus and is shielded by more electron shells. increase in reactivity Na The further an electron is from the positive nucleus, the easier it can be lost in reactions. K This is why the reactivity of the alkali metals increases going down group 1.

27 What is the order of reactivity?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals Teacher notes This ordering activity could be used as a plenary or revision exercise on the order of reactivity of the alkali metals. Mini-whiteboards could be used to make this a whole-class exercise.

28 How do alkali metals react with chlorine?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals Alkali metals burst into flames when heated and added to chlorine. They form metal chlorides. alkali metal chlorine  alkali metal chloride The word and chemical equations for the reaction between lithium and chlorine are: 2Li (s) Cl2 (g)  LiCl (s) lithium + chlorine  lithium chloride What are the word and chemical equations for the reaction that produces sodium chloride? 2Na (s) Cl2 (g)  NaCl (s) sodium + chlorine  sodium chloride

29 Boardworks GCSE Additional Science: Chemistry The Alkali Metals
True or false? Boardworks GCSE Additional Science: Chemistry The Alkali Metals Teacher notes This true-or-false activity could be used as a plenary or revision exercise on alkali metals, or at the start of the lesson to gauge students’ existing knowledge of the subject matter. Coloured traffic light cards (red = false, yellow = don’t know, green = true) could be used to make this a whole-class exercise.

30 Boardworks GCSE Additional Science: Chemistry The Alkali Metals

31 What are the uses of alkali metals?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals How many uses of alkali metals can you see below? Teacher notes This illustration contains several discussion points relating to the uses of alkali metals including: Man putting salt on his chips Using table salt, which is sodium chloride. Household goods in the shopping bag Sodium compounds are used in many household goods, including over cleaner and bicarbonate of soda. Batteries in a torch Lithium is used in batteries for many things, including torches. Street lamps Sodium is used in street lamps and causes the yellow glow. Fireworks Potassium compounds are used in fireworks. Aircraft Metal alloys of lithium are used to make the bodies of aircraft.

32 What are the uses of alkali metals?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals

33 What are the uses of alkali metals?
Boardworks GCSE Additional Science: Chemistry The Alkali Metals Teacher notes This drag and drop activity could be used as a plenary exercise to check students’ ability to recall the different uses of three of the alkali metals. Class voting or the use of coloured traffic light cards could be make this a whole-class exercise.

34 Boardworks GCSE Additional Science: Chemistry The Alkali Metals

35 Boardworks GCSE Additional Science: Chemistry The Alkali Metals
Glossary Boardworks GCSE Additional Science: Chemistry The Alkali Metals alkali metal – An element that belongs to group 1 of the periodic table. exothermic – A reaction that releases heat into its surroundings. metal chloride – The type of solid produced when an alkali metal is burned in chlorine gas. metal hydroxide – The type of alkali produced by the reaction between an alkali metal and water. metal oxide – The type of solid produced when an alkali metal reacts with oxygen. oxidation – The process by which a substance reacts and combines with oxygen. tarnish – The discolouration of metal after exposure to air caused by the formation of an oxide on the metal’s surface.

36 Boardworks GCSE Additional Science: Chemistry The Alkali Metals
Anagrams Boardworks GCSE Additional Science: Chemistry The Alkali Metals

37 Completing alkali metal equations
Boardworks GCSE Additional Science: Chemistry The Alkali Metals Teacher notes This drag and drop activity could be used as a plenary exercise to check students’ knowledge of alkali metal reactions. Class voting or the use of coloured traffic light cards could make this a whole-class exercise. Alternatively, students could be asked to complete the reactions in their books and the activity could be concluded by the completion on the IWB.

38 Comparing reactivity with water
Boardworks GCSE Additional Science: Chemistry The Alkali Metals Teacher notes This matching activity could be used as a plenary or revision exercise on alkali metals and their reaction with water. Students could be asked to complete the questions in their books and the activity could be concluded by the completion on the IWB.

39 Boardworks GCSE Additional Science: Chemistry The Alkali Metals
Multiple-choice quiz Boardworks GCSE Additional Science: Chemistry The Alkali Metals Teacher notes This multiple-choice quiz could be used as a plenary activity to assess students’ understanding of alkali metals. The questions can be skipped through without answering by clicking “next”. Students could be asked to complete the questions in their books and the activity could be concluded by the completion on the IWB.


Download ppt "Boardworks GCSE Additional Science: Chemistry The Alkali Metals"

Similar presentations


Ads by Google