Unit 2: How do chemical reactions shape the natural world?

Society is dependent on the work of chemists to analyse the materials and products in everyday use. In this unit students analyse and compare different substances dissolved in water and the gases that may be produced in chemical reactions. They explore applications of acid-base and redox reactions in society. Students conduct practical investigations involving the specific heat capacity of water, acid-base and redox reactions, solubility, molar volume of a gas, volumetric analysis, and the use of a calibration curve.

Throughout the unit students use chemistry terminology, including symbols, formulas, chemical nomenclature and equations, to represent and explain observations and data from their own investigations and to evaluate the chemistry-based claims of others.
A student-adapted or student-designed scientific investigation is undertaken in Area of Study 3. The investigation involves the generation of primary data and is related to the production of gases, acid-base or redox reactions, or the analysis of substances in water. It draws on the key science skills and key knowledge from Unit 2 Area of Study 1 and/or Area of Study 2.

Area of Study 1
How do chemicals interact with water
In this area of study students focus on understanding the properties of water and investigating acid-base and redox reactions. They explore water’s properties, including its density, specific heat capacity and latent heat of vaporisation. They write equations for acid-base and redox reactions, and apply concepts including pH as a measure of acidity. They explore applications of acid-base reactions and redox reactions in society.

The selection of learning contexts should allow students to develop practical techniques to investigate the properties of water and acid-base and redox reactions. Students develop their skills in the use of scientific equipment and apparatus. They may demonstrate their understanding of concentration using coloured solutions such as ammonium molybdate. Students explore pH: for example, by making their own indicators from natural materials, developing their own pH scale and comparing the accuracy of their indicators with commercial indicators. They may investigate redox reactions by comparing corrosion rates of iron in tap water and sea water or building simple cells to power a diode. They respond to challenges such as investigating the action of soda water on seashells and linking their findings to socio-scientific issues such as ocean acidification

Outcome 1
On completion of this unit the student should be able to explain the properties of water in terms of structure and bonding, and experimentally investigate and analyse applications of acid-base and redox reactions in society.
To achieve this outcome the student will draw on key knowledge outlined in Area of Study 1 and the related key science skills on pages 11 and 12 of the study design.

Properties of water

• trends in the melting and boiling points of Group 16 hydrides, with reference to the nature and relative strengths of their intermolecular forces and to account for the exceptional values for water

• specific heat capacity and latent heat including units and symbols, with reference to hydrogen bonding to account for the relatively high specific heat capacity of liquid water, and significance for organisms and water supplies of the relatively high latent heat of vaporisation of water.
Lesson 1 - Trends in MP of hydrides
Lesson 2 - hydrogen bonding
Lesson 3 - Heat capacity
Lesson 4 - Latent heat

Quiz 1 Solutions - trends in hydrides

Quiz 1a Solutions - Specific heat

Quiz 2 Solutions - latent heat

Quiz 3 Solutions - latent heat

Quiz 4 Solutions - latent heat

Quiz 5 Solutions - specific heat capacity, heat capacity.

Precipitation activity.

Quiz 1 Solutions (precipitates overall equations and ionic equations)

Quiz 2 Solutions ( overall equations and ionic equations)

Acid-base (proton transfer) reactions in water

• the Brønsted-Lowry theory of acids and bases, including polyprotic acids and amphiprotic species, and the writing of balanced ionic and full equations, with states, for their reactions in water
Lesson 1 - Video worksheet -definitions and terminology used in acid/base.
lesson 1a- conjugates
Lesson 2 - dilution

• the ionic product of water, the pH scale and the use of pH in the measurement and calculations of strengths of acids and bases and dilutions of solutions (calculations involving acidity constants are not required)
Lesson 3 (pdf) Lesson 3(doc)- Solutions
Lesson 3a - pH
Lesson 3b - pH calculations - Video worksheet

• the distinction between strong and weak acids and strong and weak bases, and between concentrated and dilute acids and bases, including common examples
Lesson 4 Solutions - Strong/weak acids
Lesson 4a - Video worksheet

• the reactions of acids with metals, carbonates and hydroxides including balanced full and ionic equations, with states
Lesson 5 - reactions with acids, some reactions covered are beyond the scope of the course
Lesson 5a - Video worksheet
Lesson 6 - ionic equations for acid reactions
Lesson 6a - ionic equations for salts - video worksheet

• neutralisation reactions to produce salts:
- reactions of acids with metal carbonates and hydroxides, including balanced full and ionic equations, with states
- types of antacids and their use in the neutralisation of stomach acid
Lesson 7a - Video worksheet of salts produced during neutralisation reactions taking place when antacids are ingested.

• accuracy and precision in measurement as illustrated by the comparison of natural indicators, commercial indicators, and pH meters to determine the relative strengths of acidic and basic solutions
Lesson 8 - Video worksheet on indicators and instrument resolution.

• applications of acid-base reactions in society: for example, natural acidity of rain due to dissolved CO₂ and the distinction between the natural acidity of rain and acid rain, or the action of CO₂ forming a weak acid in oceans and the consequences for shell growth in marine invertebrates
Lesson 9 Solution - Video worksheet acid rain covering reactions between acidic gases and water as well acid reactions between metal carbonates, metal hydroxides and metal sulfides.

Quiz 1 Solutions - overall acid equations and ionic equations

Quiz 2 Solutions - pH, [H₃O⁺], [OH^-] , conjugates,
10^-14 = [H₃O⁺][OH^-], strong/weak acid,

Antacid activity - Measuring the concentration of the acitive ingredient of an antacid tablet. This is to be found towards the end of the video on acids.bases.

Redox (electron transfer) reactions in water

• oxidising and reducing agents, conjugate redox pairs and redox reactions including writing of balanced half and overall redox equations with states indicated
• the reactivity series of metals and metal displacement reactions including balanced redox equations with states indicated
• the causes and effects of a selected issue related to redox chemistry.

Lesson 1 - introduction to redox reactions.
Lesson 2 - Solution - half reactions, identifying oxidation and reduction reactions
Lesson 2a - Solution - half equations to balanced overall equation
Lesson 3 - the electrochemical series to predict spontaneous redox reactions and reactivity of metals.
Lesson 3a - metal displacement reactions
Lesson 4 Solutions - oxidation numbers
Lesson 5 - overall equations to half equations
Lesson 6 - from overall equation to galvanic cell design.
Lesson 7 - the electrochemical series as a tool.

Summary

Quiz 1 Solutions - introduction
Quiz 2 Solutions - writing balanced redox half equations and overall equations.
Quiz 3 Solutions- Identifying the oxidant and reductant using oxidation numbers and deriving oxidation and reduction half-equations.
Quiz 4 Solutions - drawing galvanic cells from an overall redox reaction
Quiz 5 Solutions- identifying redox reactions through oxidation numbers.
Quiz 6 Solutions - revision

Area of Study 2

How are chemicals measured and analysed?

In this area of study students focus on the analysis and quantification of chemical reactions involving acids, bases, salts and gases. 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. They quantify amounts in chemistry using volumetric analysis, application of the ideal gas equation, stoichiometry and calibration curves.
The selection of learning contexts should allow students to develop practical techniques to investigate substances that may be dissolved in water or found in soils, particularly salts, acids and bases, as well as gases. Students develop their skills in the use of scientific equipment and apparatus. They use precipitation reactions to purify water: for example, by using iron or aluminium compounds to precipitate and remove phosphorus from wastewater. They perform acid-base titrations, such as comparing the ethanoic acid concentrations of vinegar, mayonnaise and tomato sauce. They construct calibration curves to analyse unknown concentrations of substances, such as the amount of nitrates or phosphates in water or soil samples. Students respond to challenges such as determining the set of standards required in setting up
a calibration curve in colorimetry.

Outcome 2

On completion of this unit the student should be able to calculate solution concentrations and predict solubilities, use volumetric analysis and instrumental techniques to analyse for acids, bases and salts, and apply stoichiometry to calculate chemical quantities.
To achieve this outcome the student will draw on key knowledge outlined in Area of Study 2 and the related key science skills on pages 11 and 12 of the study design.

Key knowledge
Water sample analysis

• existence of water in all three states at Earth’s surface including the distribution and proportion of available drinking water
• sampling protocols including equipment and sterile techniques for the analysis of water quality at various depths and locations
• the definition of a chemical contaminant and an example relevant to a selected water supply.

Measurement of solubility and concentration
• the use of solubility tables and experimental measurement of solubility in gram per 100 g of water
• the quantitative relationship between temperature and solubility of a given solid, liquid or gas in water
• the use of solubility curves as a quantitative and predictive tool in selected biological, domestic or industrial contexts
• the concept of solution concentration measured with reference to moles (mol L^-1) or with reference to mass or volume (g L^-1, mg L^-1 , %(m/m), %(m/v), %(v/v), ppm, ppb) in selected domestic, environmental, commercial or industrial applications, including unit conversions.
Lesson 1 Solubility
Lesson 2 Solubility curves
Lesson 3 Solutions Constructing a solubility curve
Lesson 3-4 Unit conversion and concentration.
-ppm
-(v/v)%
-(w/v)%
-(w/w)%

Lesson 5-6 Molarity

Solubility curve of KNO₃ Solutions practical investigation.

Quiz 1 Solutions concentrations %w/w,%w/v, %v/v, molarity, ppm.
Quiz 2a Solutions concentrations of ions

Quiz 2b Solutions calculating amount of solute

Concentration (ppm, %v/v, %w//v, %w/w) revision sheet solution

Quiz 3

Quiz 4 Solutions -more precipitation reactions overall and ionic equation

Revision 1 Solutions

Analysis for salts in water
• sources of salts found in water (may include minerals, heavy metals, organo-metallic substances) and the use of electrical conductivity to determine the salinity of water samples
• the application of mass-mass stoichiometry to gravimetric analysis to determine the mass of a salt in a water sample
Practical- Determination of Sulphate content in fertiliser

Gravimetric analysis

Sulphate content in fertiliser

Selection of Friday quizzes. The teacher can decide when to use these quizzes to gauge student progress.
Quiz 1 Solution

Quiz 2 Solution

Quiz 3 Solution

Quiz 4 Solution

Quiz 5 Solution

Quiz 6 Solution

Revision for gravimetric analysis (1) Solution
Revision for gravimetric analysis (2) Solution
Revision for gravimetric analysis (3) Solution

Gravimetric analysis from past exams.
2014 VCE
2013 VCE
2012 VCE
2011 VCE
2010 VCE
2010 HSC
2009 VCE
2008 VCE
2007 VCE
2007 NSW
2006 VCE
2005 VCE

UV-visible

Quiz 1 Solution
Quiz 2 Solution
Quiz 3 Solution
Quiz 4 Solution
Quiz 5 Solution

Atomic absorption

Quiz 1 Solution

Quiz 2 Solution

Atomic emission

Analysis for organic compounds in water
• sources of organic contaminants found in water (may include dioxins, insecticides, pesticides, oil spills)
• the application of high performance liquid chromatography (HPLC) including the use of a calibration curve and retention time to determine the concentration of a soluble organic compound in a water sample (excluding details of instrument).

Analysis for acids and bases in water
• sources of acids and bases found in water (may include dissolved carbon dioxide, mining activity and industrial wastes)
• volume-volume stoichiometry (solutions only) and application of volumetric analysis including the use of indicators, calculations related to preparation of standard solutions, dilution of solutions and use of acid-base titrations to determine the concentration of an acid or a base in a water sample.

Lesson 1 Solutions vol -vol stoichiometry -introduction to volumetric analysis
lesson 1 (word doc)
Lesson 2 - Titration and the glassware
Lesson 3 - indicators,equivalence point, end point and pH curves
Lesson 3a Solution- indicators
Lesson 3b Solution - dilution and titration
Lesson 3c Solution - dilution and titration
Lesson 3d Solution - dilution, titration and indicators
Lesson 4 Solution - dilution and titration
Lesson 5 Solution - dilution and titration
Lesson 6 - standard solutions, primary standard
Lesson 6a Solution - standard solution and titration
Lesson 7 Solution - errors and indicators in titration

Lesson 8 - virtual analysis of acetylsalicylic acid in an aspirin tablet.

Volumetric analysis summary sheet.

Quiz 1 Solution - pH

Quiz 2 Solution - excess calculation and pH

Quiz 3 Solution

Quiz 4 Solution

Quiz 5 Solution

Quiz 6 Solution

Quiz 7 Solution

Outcome 3

On completion of this unit the student should be able to design and undertake a quantitative laboratory investigation related to water quality, and draw conclusions based on evidence from collected data. To achieve this outcome the student will draw on key knowledge outlined in Area of Study 3 and the related key science skills on pages 10 and 11 of the study design.

Key knowledge
• the chemical concepts specific to the investigation and their significance, including definitions of key terms, and chemical representations
• the characteristics of laboratory techniques of primary qualitative and quantitative data collection relevant to the investigation: sampling protocols; gravimetric analysis, acid-base titrations and/or pH measurement; precision, accuracy, reliability and validity of data; and minimisation of experimental bias
• ethics of and concerns with research including identification and application of relevant health and safety guidelines
• methods of organising, analysing and evaluating primary data to identify patterns and relationships including identification of sources of error and uncertainty, and of limitations of data and methodologies
• observations and experiments that are consistent with, or challenge, current chemical models or theories
• the nature of evidence that supports or refutes a hypothesis, model or theory
• options, strategies or solutions to issues related to water quality
• the key findings of the selected investigation and their relationship to solubility, concentration, acid/base and/ or redox concepts
• the conventions of scientific report writing including chemical terminology and representations, symbols, chemical equations, formulas, units of measurement, significant figures and standard abbreviations.

Assessment

The award of satisfactory completion for a unit is based on a decision that the student has demonstrated the set of outcomes specified for the unit. Teachers should use a variety of learning activities and assessment tasks that provide a range of opportunities for students to demonstrate the key knowledge and key skills in the outcomes.

The areas of study, including the key knowledge and key skills listed for the outcomes, should be used for course design and the development of learning activities and assessment tasks. Assessment must be a part of the regular teaching and learning program and should be completed mainly in class and within a limited timeframe.

Revision Unit 2 2012

Solutions