Lesson plan of Gases: Relationship between Mol and Volume at STP

Objectives (5-7 minutes)

• Understand the concept of a mole and its relationship to the volume of a gas, especially at Standard Temperature and Pressure (STP).
• Develop skills in using the ideal gas law equation (PV = nRT) to calculate the volume of a gas from its moles, pressure and temperature.
• Apply this understanding to solve real-life problems involving the mole to volume relationship of gases at STP.

Secondary Objectives

• Promote critical thinking by analyzing and solving problems related to the topic.
• Encourage active student participation through practical activities and group discussion.
• Support self-directed learning by prompting students to find solutions for complex problems.

Introduction (10-15 minutes)

• The teacher begins the class by reviewing the basic concepts of gases. This could include reviewing the definition of a gas, its properties and gas laws, as well as Standard Temperature and Pressure (STP) - this could be through a short quiz or class discussion.

• Next, the teacher will introduce two problem scenarios that serve to engage the interest of the student, for example:

  1. Imagine you have a balloon filled with helium that contains exactly 1 mole of particles. If the temperature of the balloon is increased, will its volume increase? Explain your answer.
  2. Now imagine you have a sealed glass container of an unknown gas, if you know its pressure and temperature can you determine how many moles of gas it contains and therefore what its volume will be? If you can, explain how you would do it.

• The teacher explains that these are situations the class will be addressing during the lesson and encourages the students to think about the problems and attempt to form their own hypothesis.

• In order to provide context to the importance of this topic the teacher can include some real world examples, for instance, the use of the ideal gas law in the chemical industry or by meteorologists in order to predict gas behavior in different circumstances.

• The teacher could also share a fun fact or anecdote to engage the class with the topic, for example:

  1. Fun Fact: The concept of the mole was first introduced by Italian scientist Amedeo Avogadro back in 1811. Avogadro suggested that "equal volumes of gases under the same conditions of temperature and pressure have the same number of molecules", regardless of the type of gas. His work, however, was only widely recognized after he passed away.

  2. Historical Anecdote: During World War 2 the U.S. Air force used large hot air balloons to carry microwave antennas for long distance communication, these balloons needed to be filled with a gas that was lighter than air, like Helium in order for them to float. Understanding the mole to volume ratios of gases would have been essential to the success of this operation.

Development (20-25 minutes)

Activity 1: The Mole Race Game (10-12 minutes)

• Divide the students into groups of up to 5 and give each team a selection of different coloured balloons (to represent different gases) and rulers.

• The aim of the race is for the teams to fill their balloons with a set volume of air (representing the number of moles) then measure the volume that this takes up.

• Give students a formula they can use to work out the volume of one mole of a gas from the measured radius of their balloon (this can be measured with the ruler).

• Each group will select a particular gas (colour of balloon) and be given a designated "number of moles" of this gas which they must then inflate their balloons to.

• Once they have inflated their balloons the students need to measure the radius of their balloon, they can then work out the volume that one mole of their sample gas takes up.

• The group with the most accurate volume (closest to the theoretical volume calculated from their formula) will win the race.

• The teacher will circulate the room, checking in with teams and encouraging discussions around strategies.

Activity 2: The Mystery Container Challenge (10-12 minutes)

• Give students groups a "mystery container" which is a glass jar that is completely sealed and a means to measure pressure, such as the column of a syringe.

• Select a gas (this could be any non-flammable gas that is available at the school such as air, carbon dioxide, or helium).

• The teams are then tasked with determining how many moles of their mystery gas are inside their container and subsequently working out what volume of the container this gas occupies.

• In order to achieve this they must use the pressure gauge to measure the pressure of the gas inside their container as well as using a thermometer to determine the room temperature, then using the ideal gas law (PV=nRT) they can work out how many moles of their gas they have which they can then use to calculate its volume.

• Again, the team with the most accurate volume calculation (closest to the actual volume of the container provided by the teacher) wins.

• Again, the teacher should circulate the classroom checking in on groups and encouraging discussion of their strategies.

• The teacher will bring the class back together to discuss their solutions to these problems, addressing any difficulties they encountered, and summarizing the learning that took place.

Debrief (8-10 minutes)

• Begin the Debrief by encouraging students to share the methods and conclusions from their groups. Each team will be given up to 3 minutes to present back to the class, during their presentations, encourage discussion and questions from other class members, this will promote higher order thinking of the topics.

• After group presentations encourage the discussion of how these different methods used by the groups related back to the theory that was discussed in the introduction, emphasize the use of the Ideal Gas Law (PV = nRT) in both situations to work out the volume of a mole of gas.

• Finally, ask students to recall the original Lesson Objectives and ask what they learnt that helped them meet these objectives, this could be through open class discussion or a short quiz.

• Check in with the class and establish whether there is any topic content they are unsure of, this will help identify areas for further support and plan future lessons to address any difficulties.

• Conclude the lesson by giving a brief summary and reiterating the importance of the mole to volume relationship in gases and how this can be calculated using the ideal gas equation. Remind the students of any homework, or further reading or research tasks that will help to reinforce their understanding.

Conclusion (5-7 minutes)

• Summarize the key points of the lesson, revisiting the concepts of a mole, the ideal gas law (PV=nRT), and the mole-volume relationships of gases at STP. Highlight the skills students have gained, such as the ability to apply the theory learnt to real-world situations and problem solving.

• Link the theoretical knowledge to the activities they did and emphasize how these activities illustrated the practical application of the theoretical concepts. For example, how the "Mole Race" activity gave the students a visual representation of the volume to mole relationship and the "Mystery Container Challenge" had them applying the ideal gas law to determine the volume of gas inside a sealed container.

• Encourage further learning and engagement by suggesting students undertake a home task review activity, this could be reading a chapter in the textbook, revising lesson notes or taking a short online quiz, encourage them to research anything they are still unsure of.

• Emphasize how this topic has relevance in the world, for example the ideal gas law has many applications in industries like meteorology (to predict the weather), the pharmaceutical industry (for the development of drugs) and the automobile industry (to design more efficient engines).

• Finish by giving a brief overview of what will be expected in the next lesson, this creates a sense of anticipation as well as giving the students a chance to start the next lesson prepared, encourage students to think ahead and prepare for the next class by doing the relevant reading or background research.