Topic: Hydrates

Target group

High school / technical school student

Core curriculum:

New core curriculum:

High school and technical high school – basic level:

XI. Applications of selected inorganic compounds. Pupil:

5) write the formula of hydrates and anhydrous salts (CaSO Indeks dolny 4₄, (CaSOIndeks dolny 4₄) 2 · HIndeks dolny 2₂O and CaSO Indeks dolny 4₄ · 2HIndeks dolny 2₂O); gives their mineralogical names; describes the differences in the properties of hydrates and anhydrous substances; predicts hydrate behavior during heating and verifies its predictions experimentally; lists the applications of gypsum rocks; explains the hardening process of gypsum mortar; writes the appropriate reaction equation.

High school and technical high school – extended level:

XI. Applications of selected inorganic compounds. Pupil:

5) write the formula of hydrates and anhydrous salts (CaSO Indeks dolny 4₄, (CaSOIndeks dolny 4₄) 2 · HIndeks dolny 2₂O and CaSO Indeks dolny 4₄ · 2HIndeks dolny 2₂O); gives their mineralogical names; describes the differences in the properties of hydrates and anhydrous substances; predicts hydrate behavior during heating and verifies its predictions experimentally; lists the applications of gypsum rocks; explains the hardening process of gypsum mortar; writes the appropriate reaction equation.

Old core curriculum:

High school and technical high school – basic level:

XI. Applications of selected inorganic compounds. Pupil:

1) writes formulas of hydrates and anhydrous salts (CaSOIndeks dolny 4₄, (CaSOIndeks dolny 4₄Indeks dolny 2₂·HIndeks dolny 2₂O i CaSOIndeks dolny 4₄·2HIndeks dolny 2₂O); gives their common names; describes the differences in the properties of hydrates and anhydrous substances; predicts the behavior of hydrates during heating and verifies its predictions experimentally; mentions the use of gypsum rock; explains the hardening process of gypsum mortar; he writes the appropriate equation of reaction.

General aim of education

The student will explain the importance of hydrates and the properties and use of gypsum rock

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• to write down formulas and create hydrates nomenclature ;

• to interpret differences in the properties of hydrates and anhydrous substances;

• to describe the hardening process of gypsum mortar and to note down the appropriate reaction equation ;

• to discuss the use of gypsum rock;

• to justify why calcined gypsum is used in medicine.

Methods/techniques

• activating

  • discussion.

• expository

  • talk.

• programmed

  • with computer;

  • with e‑textbook.

• practical

  • exercices concerned.

• exposing

  • exposition.

Forms of work

• individual activity;

• activity in pairs;

• activity in groups;

• collective activity.

Teaching aids

• e‑textbook;

• notebook and crayons/felt‑tip pens;

• interactive whiteboard, tablets/computers.

Lesson plan overview

Introduction

1. The teacher hands out Methodology Guide or green, yellow and red sheets of paper to the students to be used during the work based on a traffic light technique. He presents the aims of the lesson in the student's language on a multimedia presentation and discusses the criteria of success (aims of the lesson and success criteria can be send to students via e‑mail or posted on Facebook, so that students will be able to manage their portfolio).

2. The teacher together with the students determines the topic – based on the previously presented lesson aims – and then writes it on the interactive whiteboard/blackboard. Students write the topic in the notebook.

3. Health and safety – before starting the experiments, students familiarise themselves with the safety data sheets of the substances that will be used during the lesson. The teacher points out the need to be careful when working with them.

Realization

1. The teacher refers students to the abstract and asks for familiarization with the content of the topic „Types of plaster rock”, and then to put questions to the text read (work with the text). After the work, the volunteers present prepared questions, others provide answers. The teacher controls the correctness of the question - answer process.

2. The teacher explains the construction of hydrates. Indicates the difference between anhydrous substances and hydrates; gives examples of anhydrous salts and hydrates; informs that the same salt may form several different hydrates, e.g. sodium carbonate. Next, he displays on the multimedia board an illustration of „Ways of creating hydrate names” and discusses the nomenclature rules, paying attention to the creation of current systematic names.

3. The teacher informs students that they will watch the film „Heating of crystalline gypsum”. Before this happens, they have to formulate a research question and hypotheses, and then write them down in the abstract. The observations made during the material issue and discussed on the forum as well as jointly determined conclusions remain to be recorded.

4. At the end of the lesson, the teacher asks students to do interactive exercises - individual work.

Summary

1. The teacher asks the students to finish the following sentences:

   • Today I learned ...

   • I understood that …

   • It surprised me …

   • I found out ...

   The teacher can use the interactive whiteboard in the abstract or instruct students to work with it

2. The student indicated by the teacher sums up the lesson, telling what he has learned and what skills he/she has been practicing.

Homework

1. Listen to the abstract recording at home. Pay attention to pronunciation, accent and intonation. Learn to pronounce the words learned during the lesson.

2. Make at home a note from the lesson using the sketchnoting method.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Hydrates

Gypsum rock is a sedimentary rock along with limestone and chalk. Their main ingredient is calcium sulphate building the minerals such as gypsum and anhydrite. Deposits of gypsum flower (${\text{CaSO}}_{\text{4}}{\text{· 2H}}_{\text{2}}\text{O}$), which is an example of a hydrate, were formed during the evaporation of saline waters of lakes and rivers at a temperature lower than 42°C. Gypsum flower can also create a variant called alabaster (${\text{CaSO}}_{\text{4}}{\text{· 2H}}_{\text{2}}\text{O}$). However, anhydrite crystallizes at higher temperatures (c${\text{CaSO}}_{\text{4}}$), anhydrous calcium sulphate, Latin an – without and hydro – water, so‑called anhydrous gypsum.

Gypsum flower creates beautiful crystals in various colours: red, grey, white, but most often it is colourless in natural conditions. It has a characteristic silky, pearly or glassy gloss. Its hardness in the Mohs scale of mineral hardness is 2, so it is soft and fragile mineral. The density of this mineral is approx. 2.3 g/cmIndeks górny 3³.

Alabaster is a translucent, white or slightly coloured material, e.g. yellowish, greenish, pinkish. Gypsum alabaster can be easily scratched with a fingernail. In the natural conditions calcite alabaster can be found. The hardness distinguishes it from gypsum alabaster because it is much more difficult to be scratched – it can be done only with a sharp knife of good quality steel. The range of density of calcite alabaster is 2.7–2.8 g/cmIndeks górny 3³.

Anhydrite can also be found in various colours: white, grey, blue or colourless. It always is transparent with a characteristic glassy or pearly gloss. Its Mohs hardness is 3–3.5, and the density is about 2.9–3.0 g/cmIndeks górny 3³.

Hydrates are hydrated salts. These are chemical compounds that contain water molecules built into the crystal structure. Water contained in hydrates is called water of crystallization or hydration. There are five molecules of water for one copper(II) cation and one sulphate anion in the copper(II) sulphate pentahydrate. Often, the same substance may form several different hydrates, for example sodium carbonate (${\text{Na}}_{\text{2}}{\text{CO}}_{\text{3}}{\text{· 10H}}_{\text{2}}\text{O}$, ${\text{Na}}_{\text{2}}{\text{CO}}_{\text{3}}{\text{· 7H}}_{\text{2}}\text{O,}$${\text{Na}}_{\text{2}}{\text{CO}}_{\text{3}}{\text{· H}}_{\text{2}}\text{O}$).

The symbolic notation of the presence of water in hydrates is a dot, which does not represent the sign of multiplication, but indicates the presence of water in the crystal structure. The hydrate names are created in several ways. The systematic name recommended by the PTCh Nomenclature Commission (based on IUPAC recommendation) includes: the name of anhydrous salt, a long line, the word „water” and mutual proportions of ingredients in this compound contained in brackets.

Some anhydrous salts may differ from their hydrates by colour. An example may be the so‑called bluestone, i.e. ${\text{CuSO}}_{\text{4}}{\text{· 5H}}_{\text{2}}\text{O}$ [copper(II) sulphate–water (1/5)], which is formed from blue crystals. While heating it, the blue colour gradually turns white. The salt used to detect water ${\mathrm{CoCl}}_2$ behaves in a similar way because it changes its colour in a characteristic way depending on the number of molecules of water of crystallization, i.e. the anhydrous cobalt(II) chloride is blue, dihydrate – pink and hexahydrate – red.

• Gypsum rock contains calcium sulphate.

• The calcined gypsum is formed as a result of gypsum flower’s calcinating in the 120°C. When the temperature is higher than 180°C, the anhydrous calcium sulphate is formed.

• Gypsum flower and calcined gypsum are examples of hydrated salts (hydrates). Anhydrite is an example of anhydrous salt.

• Hydrates are unstable and, during heating, are transformed into anhydrous salts or salts with lower degree of hydration.

• Gypsum mortar is an example of hydraulic lime mortar.

• Gypsum rock is used in construction, medicine, agriculture and in the ceramic, food, chemical industry. It is also a valuable material in the hands of artists.