Matter and Its Properties · SHS1 Chemistry

Lesson notes

Learning Objectives

Indicator: 1.1.1.LI.5 - Explain why gases show deviation from ideal behaviour and suggest how the ideal gas equation could be modified to describe gas behaviour more accurately.

By the end of the lesson, learners can:

State the assumptions of the kinetic theory of matter that underlie the ideal gas equation (PV = nRT) and identify which assumptions break down for real gases.
Explain qualitatively, in terms of intermolecular forces and molecular size, why real gases deviate from ideal behaviour at high pressure and at very low temperature.
State the conditions under which a real gas (such as oxygen, nitrogen or carbon dioxide) most closely approaches ideal behaviour.
State the Van der Waals equation, explain the meaning of each correction term (a and b), and describe how it modifies the ideal gas equation to account for molecular size and intermolecular attractions.
Discuss real-life applications of the Van der Waals equation, including in the design of gas cylinders and in understanding the liquefaction of gases such as LPG.

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Curriculum details

Strand: Physical Chemistry (Strand 1)
Sub-strand: Matter and Its Properties (1.1)
Content standard: 1.1.1.CS.3 - Demonstrate understanding of the use of the kinetic theory of matter to explain the behaviour of solids, liquids and gases under different conditions and describe the laboratory preparation of gases as well as their uses in everyday life. 1.1.1.LO.1 Use the knowledge and understanding of the scientific practices in Chemistry to explain the structure of the atom as well as the stability of its nucleus. 1.1.1.LO.2 Use the mole concept to determine the amount and quantity of various substances involved in chemical reactions. 1.1.1.LO.3 Write mole ratios for chemical equations and apply it in quantitative analysis. 1.1.1.LO.4 Use the kinetic theory of matter to explain the behaviour of solids, liquids and gases under different conditions and describe the laboratory preparation of gases as well as their uses in everyday life.
Indicator: 1.1.1.LI.5 - Explain why gases show deviation from ideal behaviour and suggest how the ideal gas equation could be modified to describe gas behaviour more accurately.
Suggested placement: Semester 2, Week 2 (Week 22 of the year)
Our suggestion, laid out in curriculum order across three terms of twelve weeks. NaCCA does not fix the week, so follow your school's scheme of learning.
Curriculum reference: NaCCA curriculum document, p. 40

Exemplars (from the NaCCA curriculum)

Project-Based Learning:
- Through various sources such as the internet, videos or books, explain qualitatively in terms of intermolecular forces and molecular size: a. The conditions necessary for a real gas to approach ideal behaviour. b. The limitations of ideality at very high pressure and very low temperature.
Talk for Learning: In a whole class discussion, State and explain Van der Waals equation and discuss its applications.
Teaching and Learning Materials:
- apparatus * Chart to illustrate the behaviour of particles * [Simulations (PHET), video, virtual laboratory can be used here] * Graph board * Graph sheets * Long cylindrical transparent glass tube * Small wads cotton wool * Forceps or bungs (to fit into the ends of the glass tube) * Conc. HCl and Conc. NH
- 3
- * Protective gloves * * Retort stand with clamps * Strip of universal indicator paper * *
- Calculator * Worksheets with steps for the calculation
- Gas preparation kits
- Wooden splint
- water * Marble chips
- Hydrochloric acid * Magnesium ribbon
- Calcium hydroxide * Ammonium chloride etc.
- Universal litmus paper
Assessment (1.1.1.AS.5). The document marks these depth-of-knowledge levels for this indicator: Level 3 Strategic reasoning.