*The Lesson Plan

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Lesson Plan

Topic: Atoms, Molecules and Stoichiometry Sub-topic: The Mole Concept Level: Lower Six Time: 40 mins


Upon completion of this lesson my students must be able to:

  • Explain the meaning of the term Mole.
  • State the relationship between mole and number of particles
  • Calculate the mass from the number of moles
  • Use stoichiometric ratio to calculate mass of reactants and products.

Prior Knowledge

The students must have a sound knowledge of atoms, molecules and compounds. They know how to balance equations. They are used to the concept of relative masses; relative atomic mass, relative molecular mass, relative isotopic mass and relative formula mass.

Teaching strategies

Questioning and activities leading to discovery learning.


Slides, OHP, Observation sheets, diagnostic testing sheets, worksheets, four identical books, four rulers.

Intro: first slide

An overview of what will be studied during this lesson.

The lesson

The mole concept.

Why the need to have relative mass instead of absolute mass in Chem?

expected answer : absolute mass of atom is too small and so is very difficult to measure

Absolute mass of individual atoms are too small to be used in calculations, instead the mass of atoms are compared ( x 10-31 kg).

Praise good answers and encourage reasoning.

For any comparison, a standard is required against which others are compared. The mass of atoms are compared against what?

expected answer 1/12th the mass of one atom of carbon-12

Pass diagnostic sheet and students to complete the definition of relative atomic mass, relative molecular mass, relative isotopic mass and relative formula mass.

Closely monitor students answers and making sure the students are on task, helping those having difficulties.

Correction of sheet

Avogadro’s idea was to have the mass of 1 atom, a microscopic particle. Is this practically feasible?

Activity 1.

Divide class into groups of four, distribute books and rulers. Ask students to fill in observation sheet. Collect value for thickness of 1 page. Can the thickness be obtained by the direct measurement of 1 page? Why?

How will you proceed to find the mass of 1 sand granule if you are provided with one spoon of sand.( Assume all sand granules have similar mass)

Avogadro’s decided to proceed similarly, taking the mass a group of atoms instead of 1 atom. He uses 6.02 x 1023 atoms and call that amount of substance a MOLE. Similar to the dozen or to the RAM of paper, 1 mole represents quantity of objects in a certain amount.

Why 6.0 x 1023?

Because that amount of particles will have a mass in gram equal to the Ar or Mr of the substance.

  • e.g 1 mole of carbon will have a mass of 12 g.
  • 12 g carbon will contain 6.02 x 1023 carbon atoms.

Molar mass: The mass of 1 mole of a substance = Ar or Mr gram Units g/mol

Define the mole using your own words

Walk among students helping them with the definition.

The formal definition

1 mole of a substance is that amount of substance which contains the same number of atoms as in 12 gram of carbon and will have a mass equal to the Ar or Mr of that substance

Make sure that all students can use calculators and exponential function. Encourage those with math difficulties.

Weighing 12 gram of carbon is equivalent to counting 6.02 x 1023 carbon atoms. The mole concept helps to count particles by weighing.

Complete worksheet


Consider the equation: CaCO3  CaO + CO2 A balanced equation interpreted in terms of moles will give the stoichiometric ratio. 1 mole calcium carbonate will give 1 mole calcium oxide and 1 mole carbon dioxide on heating. This can be converted into a mass ratio 100g calcium carbonate will produce 56 g calcium oxide and 44 g carbon dioxide. e.g what mass CaO will be obtained when 10 g CaCO3 is heated. Steps: Complete worksheet.

Summarizing lesson with concept map.