Урок по английскому языку на тему "Periodic Table. Groups I and VII"
план-конспект урока по английскому языку (9 класс)
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Lesson Plan: Year 10 (Higher Tier)
Title of the lesson: Group I and Group VII elements
Lesson 1: 11/04/08 Time: 09.15 – 10.15 a.m.
- Aims and Objectives
By the end of the lesson:
- Lesson Aim: Pupils will have a clear understanding of the trends/patterns of reactivity exhibited by elements within Group I and Group VII and will be able to write balanced equations for the reactions of the Group I metals with oxygen, water and the Group VII elements. Pupils will also be able to recall the displacement reactions of the Group VII elements and write balanced equations for these reactions
- Success Criteria: In order to successfully achieve the main aim of this lesson pupils will have revisited previous work on Group I and Group VII elements and will be able to explain the following points/complete the following:
🡪 Trends in boiling point, melting point and density within Group I and Group VII
🡪 Reactivity increases DOWN Group I and UP Group VII
🡪 Write balanced equations for the reactions of Group I metals with Group VII elements, oxygen and water
- Objectives: Pupils will be able to successfully compare the physical properties of elements within Group I elements and Group VII elements in order to establish trends within each group
- Pupils will be able to use any trends displayed by these two groups in order to make predictions as to the reactivity of the elements within each group
- Pupils will be able to recall that the melting points and boiling points decrease as you go down Group I, whereas melting/boiling points increase as you go down Group VII
- Pupils will be able to explain (using electron structure) the trends in melting points and boiling points observed within Group I and Group VII
🡪 Group 1: size of atom increases down Group I and therefore attraction between positive nucleus and the delocalised electrons is weaker (electrons are further away from the nucleus and therefore less heat energy is required in order for the atom to lose its outer electron)
🡪 Group VII: the size of the atom increases down Group VII and therefore the forces of attraction between molecules increases with size. More heat energy is needed to overcome these attractive forces in order that the elements may melt/boil
- Pupils will be able to recall that the density of the Group I metals increases down the group
🡪 Due to the large increase in mass of the atom compared to its size
- Pupils will be able to recall that reactivity of the elements increases down Group I due to the weakening forces of attraction between the nucleus and its surrounding electrons as the size increases
- Pupils will be able to recall that the melting points and boiling points of the elements increase as you go down Group VII
- Pupils will be able to explain (using electron structure) why the reactivity of the Group VII elements decreases down Group VII
- Pupils will be able to write balanced equations for the reactions of Group I metals with Group VII elements, oxygen and water
- Rationale for learning
- Pupils will carry out the work of this lesson in order to consolidate their knowledge of the topic of Group I and Group VII elements, and writing/balancing equations
- By carrying out the work of the lesson pupils will improve their abilities in comparing the physical and chemical properties of elements within Group I and Group VII
- By learning the content of today’s lesson pupils will gain confidence in identifying patterns/trends within Group I and Group VII, and will be able to use any trends identified to explain the reactions of elements in these two groups
- Links to previous learning
- KS3: Sc3 Materials and their properties – 1a, 1c, 1d, 1e, 1f, 3a, 3g
- WJEC GCSE Specification references
- Science – Chemistry 1: Atomic Structure, Elements and the Periodic Table – 1g, 1h
- Curriculum Cymreig
- Link topic of Group I and Group VII elements to the composition of seawater – possible to draw on several examples in the local area
- Introduction to the lesson
- Introduce myself and ask each pupil to write their name on a piece of card and place it in a prominent position
- Show PowerPoint slide of Aberystwyth North Beach – ask pupils to try to work out the link between seawater and today’s lesson
- Explanation of aims and objectives – have a pre-prepared PowerPoint document outlining the objectives in a way that can be understood by the pupils: see section 1 for aims/objectives
- Structure
5 minutes:
| 09.15 – 09.20 a.m. |
45 minutes:
🡪 pupils to discuss (pairs or groups of 3) any facts they remember about the elements of Group I and Group VII 🡪 3 minutes to write down 3 facts about Group I and 3 facts about Group VII
🡪 ensure open questioning throughout in order to elicit reasoned responses from pupils 🡪 pupils to use worksheet in conjunction with the PowerPoint slides to answer questions | 09.20 – 10.05 a.m. |
10 minutes:
🡪 Pupils given 3 minutes to design a slide containing their 3-point summary of the main ideas of the lesson 🡪 5 minutes: display lesson’s objectives and discuss how the pupils’ summaries compare to the objectives of the lesson
| 10.05 – 10.15 a.m. |
- Plenary
- Designing a slide to summarise the lesson
🡪 Pupils given 3 minutes to design a slide containing their 3-point summary of the main ideas of the lesson
🡪 5 minutes: display lesson’s objectives and discuss how the pupils’ summaries compare to the objectives of the lesson
- Assessment
- Questioning of pupils during the lesson will allow assessment of the extent of pupil learning during this session
- Safety Precautions
- No safety risks identified in this lesson
Key Questions
To be covered during the course of the lesson:
- Why are we interested in the Group I and Group VII elements?
- By what names are the Group I and Group VII elements commonly known?
- How are the Alkali metals different to other metals, e.g. the Transition metals?
- What happens to the density as you go down Group I?
- Why do the first three elements in Group I float on water?
- What trends are present in the melting points and boiling points of Group I elements?
- How can this trend be explained?
- How does the reactivity of the Alkali metals change down Group I and how can this trend be explained?
- What trends are present in the melting points and boiling points of the Group VII elements as you go down the group?
- Using electron structure to explain your answer, why does the reactivity of the Halogens increase as you go down Group VII?
Предварительный просмотр:
Подписи к слайдам:
Where are the alkali metals? The elements in group 1, on the left of the periodic table, are called the alkali metals . These metals are all very reactive and are rarely found in nature in their elemental form. lithium sodium potassium rubidium caesium francium Fr Cs Rb K Na Li
Why are they called 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 elements in group 1 also react with water and form alkaline compounds. This is why they are called alkali metals . 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.
What are the properties of the alkali metals? The characteristic properties of the alkali metals are: They are shiny . This is only seen when alkali metals are freshly cut. They are good conductors of heat and electricity. 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:
What are the trends in density?
What is the trend in density? The alkali metals generally become more dense going down the group, but the trend is not perfect because potassium is less dense than sodium. Water has a density of 1 g/dm 3 . Element Density (g/dm 3 ) lithium potassium sodium rubidium caesium 0.53 0.97 0.86 1.53 1.87 Which elements in group 1 will float on water?
What are the trends in melting point?
What are the trends in boiling point?
What is the trend in melting and boiling points? The melting points and boiling points of alkali metals decrease going down the group. The melting and boiling points decrease going down group 1 because the atoms get larger. Melting points are lower than for typical, transition, metals, because alkali metals only have 1 electron in their outer shell. Not much heat energy is needed for this electron to be lost. Element Melting point ( °C ) lithium potassium sodium rubidium caesium 181 98 64 39 28 Boiling point ( °C ) 1342 883 760 686 671
Electron structure All alkali metals have 1 electron in their outer shell. This means that: lithium 2,1 sodium 2,8,1 potassium 2,8,8,1 They can easily obtain a full outer shell by losing 1 electron. They have similar physical and chemical properties. They all lose their outer shell electron in reactions to form positive ions with a +1 charge.
Electron structure and reactivity The reactivity of alkali metals increases down the group. What is the reason for this? Cs Rb K Na Li increase in reactivity The size of the element’s atoms, and the number of full electron shells, increases down the group. This means that, down the group, the electron in the outer shell gets further away from the nucleus and is shielded by more electron shells. The further away an electron is from the positive attraction of the nucleus, the easier it can be lost in reactions. This means that reactivity increases with the size of the atom.
Group 7 – the halogens The elements in group 7 of the periodic table, on the right, are called the halogens . fluorine chlorine bromine iodine astatine I Br Cl F At
Why are they called the ‘halogens’? Halogens are very reactive non metals. They are all toxic or harmful because they are so reactive. Before antiseptics, iodine was used to clean wounds as it is harmful to all things, including bacteria. They are also never found free in nature because of their reactivity – they are found as compounds with metals. These halogen-metal compounds are salts, which give halogens their name – ‘halo-gen’ means ‘salt-former’.
poisonous and smelly. brittle and crumbly when solid What are the general properties of the halogens? All the halogens are: They become darker in colour down the group: non-metals and so do not conduct electricity is pale yellow is yellow-green is grey is red-brown
Halogens – what do they look like? Chlorine Bromine Iodine
What is the physical state of the halogens? The melting and boiling points of the halogens increase down the group, as the molecules become bigger. What is the state of each halogen at room temperature? Halogen Relative size Melting point ( ° C) Boiling point ( ° C) State -220 -118 -101 -7 114 -34 59 184 gas gas liquid solid
Melting and boiling points of halogens
Halogen vapours Bromine and iodine are not gaseous, but have low boiling points. This means that they produce vapour at relatively low temperature. They are volatile . Bromine produces some red-brown vapour, seen here above the liquid bromine in the jar. When iodine is heated gently, it changes directly from a solid to a gas without first becoming a liquid. This is called sublimation .
All halogens have seven electrons in their outer shell. This means that: What is the electron structure of the halogens? fluorine 2,7 chlorine 2,8,7 bromine 2,8,8,7 They can easily obtain a full outer shell by gaining one electron. They have similar chemical properties. They all gain an electron in reactions to form negative ions with a -1 charge.
How does electron structure affect reactivity? The reactivity of alkali metals decreases going down the group. What is the reason for this? The atoms of each element get larger going down the group. This means that the outer shell gets further away from the nucleus and is shielded by more electron shells. The further the outer shell is from the positive attraction of the nucleus, the harder it is to attract another electron to complete the outer shell. This is why the reactivity of the halogens decreases going down group 7. decrease in reactivity F Cl Br
How do halogen molecules exist? All halogen atoms require one more electron to obtain a full outer shell and become stable. Each atom can achieve this by sharing one electron with another atom to form a single covalent bond . This means that all halogens exist as diatomic molecules: F 2 , Cl 2 , Br 2 and I 2 . + F F F F
Reactions of the Group I and Group VII elements
How do the alkali metals react with oxygen? 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: Why are alkali metals stored in oil ? lithium – tarnishes slowly sodium – tarnishes quickly potassium – tarnishes very quickly. The oil prevents them from reacting with oxygen and tarnishing.
What are the word and chemical equations for the reaction that causes sodium to tarnish? What is the equation for the reaction with oxygen? The reaction between an alkali metal and oxygen is an example of an oxidation reaction: alkali metal + oxygen alkali metal oxide 4Na (s) + O 2 (g) 2Na 2 O (s) sodium + oxygen sodium oxide The word and chemical equations for the reaction between lithium and oxygen are: 4Li (s) + O 2 (g) 2Li 2 O (s) lithium + oxygen lithium oxide
All the alkali metals react vigorously with water. The reaction produces a gas that ignites a lighted splint with a squeaky pop. What is this gas? What does the reaction with water produce? It is an exothermic reaction as it releases a lot of heat. When green universal indicator is added to the reaction mixture, it turns purple. What does this tell you about the products of this reaction? The reaction with water becomes more vigorous as you go down the group.
2M(s) + 2H 2 O(l) 2MOH (aq) + H 2 (g) alkali metal + water alkali metal + hydrogen hydroxide This reaction creates alkaline hydroxide ions. The general equation for the reaction between an alkali metal reacting with water is: What is the equation for the reaction with water? This is why the group 1 elements are called the alkali metals.
Lithium with water
How does lithium react with water? Lithium is the least reactive of the alkali metals. 2Li (s) + 2H 2 O (l) 2LiOH (aq) + H 2 (g) lithium + water lithium + hydrogen hydroxide When added to water, it fizzes and moves around slowly across the surface of the water. What is the equation for this reaction?
Sodium with water
How does sodium react with water? When added to water, sodium fizzes more than lithium, and moves quickly across the surface of the water. 2Na (s) + 2H 2 O (l) 2NaOH (aq) + H 2 (g) sodium + water sodium + hydrogen hydroxide What is the equation for this reaction? The hydrogen sometimes catches fire because of the heat from the reaction. The sodium melts as it reacts, and it becomes spherical and shiny, like a ball bearing.
Potassium with water
How does potassium react with water? When added to water, the potassium moves across the surface of the water very quickly. 2K (s) + 2H 2 O (l) 2KOH (aq) + H 2 (g) potassium + water potassium + hydrogen hydroxide What is the equation for this reaction? Like sodium, it melts with the heat of the reaction. The reaction produces so much heat that the hydrogen given off catches alight. What colour would the flame be?
Alkali metals burst into flames when heated and added to chlorine. They form metal chlorides . How do alkali metals react with chlorine? 2Li (s) + Cl 2 (g) 2LiCl (s) lithium + chlorine lithium chloride What are the word and chemical equations for the reaction that produces sodium chloride? 2Na (s) + Cl 2 (g) 2NaCl (s) sodium + chlorine sodium chloride alkali metal + chlorine alkali metal chloride The word and chemical equations for the reaction between lithium and chlorine are:
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