8_4_water

=Water=

The first astronauts who viewed the Earth from space commented on the beauty of our water-rich blue planet. Earth's position in the solar system enables its retention of water in solid, liquid and gaseous forms on and around its surface. The particular properties of the water molecule assisted the evolution of life and continue to support life processes by maintaining a narrow temperature range on the Earth’s surface. The concepts of bonding and intermolecular forces are used to increase understanding of the special nature of the water molecule. The chemistry of solutions is examined in greater detail.

(Resources)  || Evidence of Learning (Feedback) || // Students: // ||  ||   ||   || - a constituent of cells and its role as both a solvent and a raw material in metabolism - a habitat in which temperature extremes are less than nearby terrestrial habitats - an agent of weathering of rocks both as liquid and solid - a natural resource for humans and other organisms // Plan and perform an investigation to identify and describe the effect of anti-freeze or salt on the boiling point of water // ||  || Using teacher supplied reference texts/internet sites students construct a table to collate information related to the corresponding syllabus point.
 * Syllabus Content  ||   R   ||   Strategies
 * Students learn to:
 * Focus 1. ** Water is distributed on Earth as a solid, liquid and gas ** ||
 * Outline the significance of the different states of water on Earth in terms of water as:

Design an investigation using the teacher scaffold that allows valid and reliable data to be collected about the effect of anti-freeze and salt on the bp of water Select and draw appropriate graphs using EXCEL to show the effect of the above chemicals on the bp/freezing pt of water Identify and explain how this data supports the use of antifreeze/antiboil in car radiators and the use of salt to keep roads open in cold climates
 * (Skills – 12.1a, 12.2b ) **
 * (T3 pg 113-114) **
 * (Skills – 12.1a, 12.2c,131f, 14.1b,h ) **

2 Lessons ||  ||
 * Focus 2. **The wide distribution and importance of water on Earth is a consequence of its molecular structure and hydrogen bonding.** ||
 * Construct Lewis electron dot structures of water, ammonia and hydrogen sulfide to identify the distribution of electrons

// Process information from secondary sources to graph and compare the boiling and melting points of water with other similar sized molecules // Compare the molecular structure of water, ammonia and hydrogen sulfide, the differences in their molecular shapes and in their melting and boiling points Identify the water molecule as a polar molecule Describe the attractive forces between polar molecules as dipole-dipole forces Describe hydrogen bonding between molecules // Identify data and process information from secondary sources to model the structure of the water molecule and effects of forces between water molecules // Explain the following properties of water in terms of its intermolecular forces: - surface tension - viscosity - boiling and melting points // Choose equipment and perform first-hand investigations to demonstrate the following properties of water: // - // surface tension // - // viscosity // ||  || Round Table Activity for Lewis diagrams. Students working in groups pass a set of diagrams from student to student. The 1st draws the Lewis D. to match the formula. The next student either corrects the previous or draws a structural diagram. The group continues the cycle until the sheet is finished.
 * (W 2) **

Use teacher selected resources, graph mp & bp against column number(group) to compare the mp & bp of water with other similar sized molecules.
 * (T 3 pg 115-116) **
 * [Skills – 13.1f, 14.1f] **

Use teacher selected resources, notes and molecular model kits to compare the structure of water, ammonia, hydrogen sulphide. (Carbon dioxide could be used as an example of a linear molecule)
 * [Skills – 12.3c, 14.1f] **

Review electronegativity and relate this to unequal sharing of electrons in a polar covalent bond. Use the periodic table and a table of electronegativies to compare the relative polarities between H- N, H-O, H-S, C-O
 * [Skills – 14.3b] **

Use teacher selected resources and notes to develop an explanation of molecular shapes using the Valence Shell Electron Pair Repulsion Model(VSEPR). Use the information about the polarity of bonds and the shape of molecules to predict the polarity of water, ammonia, hydrogen sulfide 3 Lessons Use teacher selected resources and notes to list and describe the variety of intermolecular forces ie dispersion, dipole-dipole and hydrogen bonding
 * (W3) **
 * [Skills – 14.1d] **
 * [Skills – 14.3c ] **

Use the term dipole-dipole force to describe the attraction between polar molecules
 * (T1-pg 220-230, T2-pg187-191) **

Use appropriate secondary sources to visualise the formation of hydrogen bonds between molecules such as water, ammonia, hydrogen fluoride


 * [Skills – 12.3a-d ] **

In a Round Table activity (Students take turns in describing the effect of ….) assess the reliability of information by comparing several sources to describe and analyse the effect of forces between water molecules in determining the following properties of water: - surface tension - viscosity - boiling and melting points In the same groups, using the teacher directed scaffold choose equipment and perform a first-hand investigation to demonstrate the following properties of water: - surface tension - viscosity In their groups analyse the implications ONE of these properties of water for plants or animals by - establishing the validity and relevance of the information in identified data sources - summarise and collate from the identified range of resources about the implications of the selected property of water on the plant or animal.
 * ( T1 pg184, T2 pg231-234) **
 * [Skills – 11.1e, 12.3a-d ] **

- establish and describe cause and effect relationships between the selected property of water and the implications to plants and/or animals.
 * [Skills – 12.3a-d ] **

(4 Lessons) || Students present cause effect relationships to class - a soluble ionic compound such as sodium chloride - a soluble molecular compound such as sucrose - a soluble or partially soluble molecular element or compound such as iodine, oxygen or hydrogen chloride - a covalent network structure substance such as silicon dioxide - a substance with large molecules, such as cellulose or polyethylene // Perform a first-hand investigation to test the solubilities in water of a range of substances that include ionic, soluble molecular, insoluble molecular, covalent networks and large molecules // Analyse the relationship between the solubility of substances in water and the polar nature of the water molecule ||  || Review prior knowledge through brainstorming about ionic, covalent and covalent network compounds. Identify the relationship between the solubility of substances in water and the molar nature of water. With teacher guidance and class discussion develop a model, with regards to bonding , that explains why some compounds dissolve and others do not.
 * (Peer discussion) **
 * [Skills – 12.3a-d ] ** ||
 * Focus 3. ** Water is an important solvent ** ||
 * Explain changes, if any, to particles and account for those changes when the following types of chemicals interact with water:
 * [Skills – 14.1f ] **

An assignment based on most of these dot points forms an **ASSESSMENT OF LEARNING** project where students produce models of particular compounds and their ability to go through the dissolution process.


 * [Skills – P2; P6;12.3a; 14.1b,f,h;14.3b] **

Carry out a teacher planned procedure to test the solubility of substances in water including ionic, soluble covalent, insoluble covalent covalent network and large molecules.
 * [Skills – 12.3a-d ] **

2 Lessons ||  || Process information from secondary sources to visualise the dissolution in water of various types of substances and solve problems by using models to show the changes that occur in particle arrangement as dissolution occurs ||  ||   ||   || Identify some combinations of solutions which will produce precipitates, using solubility data Describe a model that traces the movement of ions when solution and precipitation occur // Construct ionic equations to represent the dissolution and precipitation of ionic compounds in water // // Present information in balanced chemical equations and identify the appropriate phase descriptors (s), (l), (g), and (aq) for all chemical species // Identify the dynamic nature of ion movement in a saturated dissolution Explain why different measurements of concentration are important Describe the molarity of a solution as the number of moles of solute per litre of solution using: // Carry out simple calculations to describe the concentration of given solutions, given masses of solute and volumes of solution //
 * Focus 4. ** The concentration of salts in water will vary according to their solubility, and precipitation can occur when the ions of an insoluble salt are in solution together. ** ||
 * // Perform a first-hand investigation, using micro-techniques, to compare the solubility of appropriate salts in solution through precipitation reactions //

// Perform a first-hand investigation to make solutions to specified volume-to-volume and mass-to-volume specifications and dilute them to specified concentrations //

// (cV = constant) // // Calculate mass and concentration relationships in precipitation reactions as they are encountered // ||  || Safely carry out a planned procedure, minimising hazards and resource wastage, to compare the solubility of a variety of salts using micro-techniques. With teacher assistance and using a provided solubility table, determine the name of the precipitate formed Drawing on the Assessment of Learning Task re models of dissolution students, with teacher assistance describe the movement of ions in a precipitation reaction With teacher assistance and using a provided solubility table, write balanced ionic equations using phase descriptors
 * (T3 pg133-135) **
 * [Skills – 12.3a-d ] **
 * [Skills – 14.1a ] **
 * [Skills – 14.1f,g,h ] (T1 pg252) **


 * [Skills – 14.2c ] **

Review the particle theory of matter again and identify the dynamic nature of particle movement in a mixture of a solid and its ions Relate the dynamic nature of precipitation and dissolution to a saturated solution and use the term equilibrium to describe the condition when both are occurring at the same rate. 3 Lessons Use teacher selected notes to identify and explain why there are situations where measurements of concentrations of solutions are used. Through class discussion, research and teacher assistance if necessary, explain using examples such as food labels, liquid cleaners found in supermarkets, why different measurements of concentration may be important /used.
 * [Skills – 14.1f, 14.3b ] **
 * (T1-pg 257-260) [Skills – 14.2a, 14.3d ] **
 * [Skills – 14.3d ] **

Describe the molarity of a solution, use the formula to calculate the molarity of given and required solutions
 * [Skills – 12.4b ] **

Measurements of concentration With teacher guidance, calculate the concentration of dilute solutions by recognising that when dilution occurs, the no. of moles remains constant (cV = constant) and the equation c1V1 = c2V2 may be applied to dilutions.
 * (T3 pg142 -144) **
 * [Skills – 12.b ] **
 * [Skills – 12.a ] **

Safely carry out a planned procedure, minimising hazards and resource wastage, to prepare solutions to specified volume to volume and mass to volume concentrations
 * (T3 pg150-151) **
 * [Skills – 12.b ] **

3 Lessons || Students complete worksheet on writing balanced ionic equations


 * [P6, P10, 14.2c ] **

Complete worksheet on a variety of

c1V1 = c2V2 calculations Compare the specific heat capacity of water with a range of other solvents Explain and use the equation // Choose resources and perform a first-hand investigation to measure the change in temperature when substances dissolve in water and calculate the molar heat of solution //
 * [ P6, P10,Skills – 12.ab ] ** ||
 * Focus 5. ** Water has a higher heat capacity than many other liquids ** ||
 * Explain what is meant by the specific heat capacity of a substance

// Process and present information from secondary sources to assess the limitations of calorimetry experiments and design modifications to equipment used //

Explain how water’s ability to absorb heat is used to measure energy changes in chemical reactions Describe dissolutions which release heat as exothermic and give examples Describe dissolutions which absorb heat as endothermic and give examples Explain why water’s ability to absorb heat is important to aquatic organisms and to life on earth generally Explain what is meant by thermal pollution and discuss the implications for life if a body of water is affected by thermal pollution || || Use teacher selected notes to explain what is meant by the specific heat of water.

With teacher guidance suggest /predict a reason for the smaller temperature range between land and water. Access information from a range of sources to compare the specific heat of water with other substances of similar molecular size and/or weight and with a range of other solvents.
 * (T-pg272 ,T2- pg 222 ) **
 * [Skills – 12.b ] **

Investigation: Measuring the Heat of Solution Use data loggers and Temp probes to show the difference in the using the computer generated equipment ant thermometers.
 * (T4 pg156) **
 * [Skills – 12.2a,12.4c ] **

Evaluate the validity of the data collected in relation to the heats of solution compared with the standard values given. Generate plausible explanations for the differences in obtained and theoretical results, thus identifying the limitations of calorimetry investigations. Identify and explain the nature of the problem with calorimetry investigations. Redo Investigation using the changes to the investigation to obtain more valid results.
 * [Skills – 12.4d, 14.1d, 14.2a ] **
 * [Skills – 11.b,d ] **

3 Lessons

Identify that during the processes occurring when an ionic substance dissolves Participate in class discussion to predict scenarios in which the temperature of natural bodies of water my rise. Discuss the possible outcome of such temp. changes on living things in these environments Use teacher identified resources to explain what is meant by thermal pollution and identify situations in which thermal pollution may occur.
 * the braking of ionic bonds as the substance absorbs energy
 * making bonds between water molecules and the separated ions during hydration releases energy
 * the net energy product can be measured as temperature increase or decrease
 * use the terms endothermic and exothermic to describe the above reactions.
 * (T1-pg228-229 T2-pg226-227) **

1 Lesson ||  ||
 * [Skills – 14.3b, 12.3d ] **