Chemistry Unit 2: What Makes Water Such a Unique Chemical?
Students are advised to complete the Year 10 Chemistry course and Chemistry Unit 1 before undertaking Chemistry Unit 2. Mathematical Methods is strongly recommended.
Water is the most widely used solvent on Earth. In this unit students explore the physical and chemical properties of water, the reactions that occur in water and various methods of water analysis.
Students examine the polar nature of a water molecule and the intermolecular forces between water molecules. They explore the relationship between these bonding forces and the physical and chemical properties of water. In this context students investigate solubility, concentration, pH and reactions in water including precipitation, acid-base and redox. Students are introduced to stoichiometry and to analytical techniques and instrumental procedures, and apply these to determine concentrations of different species in water samples, including chemical contaminants. They use chemistry terminology including symbols, units, formulas and equations to represent and explain observations and data from experiments in a wide variety of contexts and analyse selected issues with substances dissolved in water.
Areas of Study
How Do Substances Interact with Water?
Students explore the special properties (chemical and physical) of water which make it so important to living things and relate the properties to chemical bonding characteristics. The key knowledge includes:
- role of water in maintaining life in the environment;
- acids and bases: proton transfer; common reactions of acids; strong and weak acids and bases; polyprotic acids; amphiprotic substances;
- calculations including mass-mass stoichiometry and concentration and volume of solutions; pH of strong acids and of strong bases;
- redox reactions in aqueous solution including writing balanced equations for oxidation and reduction reactions, for example metal displacement reactions, corrosion of iron.
- Properties of water.
- Water as a solvent.
- Acid-base (proton transfer) reactions in water.
- Redox (electron transfer) reactions in water.
How are Substances in Water Measured and Analysed?
In this area of study students focus on the use of analytical techniques, both in the laboratory and in the field, to measure the solubility and concentrations of solutes in water, and to analyse water samples for various solutes including chemical contaminants.
Students examine the origin and chemical nature of substances that may be present in a water supply, including contaminants, and outline sampling techniques used to assess water quality. They measure the solubility of substances in water, explore the relationship between solubility and temperature using solubility curves and learn to predict when a solute will dissolve or crystallise out of solution.
The concept of molarity is introduced and students measure concentrations of solutions using a variety of commonly used units. Students apply the principles of stoichiometry to gravimetric and volumetric analyses of aqueous solutions and water samples. Instrumental techniques include the use of colorimetry and/or UV–visible spectroscopy to estimate the concentrations of coloured species in solutions, atomic absorption spectroscopy data to determine the concentration of metal ions in solutions and high performance liquid chromatography data to calculate the concentration of organic compounds in solution.
- Water sample analysis.
- Measurement of solubility and concentration.
- Analysis for salts in water.
- Analysis for organic compounds in water.
- Analysis for acids and bases in water.
Substances that are dissolved in water supplies may be beneficial or harmful, and sometimes toxic, to humans and other living organisms. They may also form coatings on, or corrode, water pipes. In this area of study students design and conduct a practical investigation into an aspect of water quality. The investigation relates key knowledge and skills developed in Area of Study 1 and/or 2 and is conducted by the student through laboratory work and/or fieldwork.
The investigation requires that students develop a question, plan a course of action that attempts to answer the question, undertake the investigation to gather primary qualitative and quantitative data, organise and interpret the data and reach a conclusion in response to the question.
|How do substances interact with water?
Tasks are selected by the teacher from the following:
- Annotations of a practical work folio of activities and investigations.
- A report of a practical activity or investigation.
- A modelling activity.
- Media response.
- Problem solving involving chemical concepts, and/or issues.
- A reflective learning journal/blog related to chosen activities or in response to an issue.
- Data analysis.
- A test comprising multiple choice and/or extended response.
|How are substances in water measured and analysed?
||A report of a student designed quantitative laboratory investigation using an appropriate format, for example digital presentation, oral communication, scientific poster or written report.
Overall Final Assessment
End of Semester Examination – 1.5 hours.
Information can be obtained from the Victorian Curriculum and Assessment Authority, Victoria, Australia: www.vcaa.vic.edu.au