Objectives (5 - 7 minutes)

1. Familiarize students with mass measurement units (kilogram, gram) and capacity (liter, milliliter) in a playful and practical way, so they can develop a basic understanding of these measurements and how they are used in everyday life.

2. Allow students to practice comparing mass and capacity measurements using concrete objects and interactive games. This will help reinforce measurement skills, as well as the understanding that different objects have different masses and capacities.

3. Encourage communication and collaboration among students through group activities involving discussion of answers and sharing of ideas. This will not only help improve students' oral communication skills but also promote a positive and collaborative learning environment.

Introduction (10 - 15 minutes)

1. Recalling concepts: The teacher starts the lesson by reminding students of basic math concepts covered in previous classes, such as numbers and operations. He may ask some review questions to assess students' understanding, such as 'What is the difference between addition and subtraction?' and 'What are even and odd numbers?'.

2. Problem-solving scenarios: Next, the teacher presents two problem-solving scenarios that will introduce the concepts of mass and capacity. First, he may ask: 'If I have two boxes full of toys, one full of teddy bears and the other full of marbles, which box do you think weighs more? Why?'. The second situation could be: 'If I have a glass full of water and another glass full of juice, which glass do you think has more liquid? Why?'.

3. Contextualization: The teacher then contextualizes the importance of mass and capacity concepts, explaining that these are measurements we use every day. For example, when buying fruits and vegetables at the market, weight is measured in kilograms or grams, and when drinking a cup of coffee or a bottle of water, we are using capacity measurements. He may even show some everyday objects that have their mass and capacity marked.

4. Introduction of the topic: To introduce the topic in an interesting and engaging way, the teacher can share some curiosities. For example, he can say that the kilogram is the standard unit of mass, defined as the weight of a cylinder of platinum and iridium kept in a laboratory in France. Similarly, he can explain that the liter is the standard unit of capacity and is approximately the size of a soda bottle. To make the curiosity more interactive, the teacher can bring a soda bottle and ask students to imagine how many of those would fit in a bathtub (which is measured in liters).

5. Capturing students' attention: Finally, the teacher can share two fun facts. The first is that the queen bee, which is the largest bee in a hive, weighs about 0.1 gram, while an adult male African elephant can weigh up to 6000 kilograms! The second curiosity is that a tablespoon is usually about 15 milliliters, and a standard bathtub has about 200 liters of capacity.

Development (20 - 25 minutes)

Activity 1: 'The Land of Weights and Measures' (10 - 15 minutes)

1. The teacher divides the class into groups of 4 or 5 students. Each group receives a box containing various everyday objects and a scale.
2. The teacher explains that they are in the 'Land of Weights and Measures' and their task is to arrange the objects in the box in ascending order of weight. They should use the scale to weigh the objects and line them up.
3. The teacher circulates around the room, guiding and assisting students as needed. He can ask questions to encourage critical thinking, such as 'Which object do you think weighs more? Why?' and 'How can you compare the weight of two objects without using the scale?'.
4. Once all groups have completed the activity, the teacher checks the answers with the class, discussing the findings and reinforcing the concepts of mass and weight comparison.

Activity 2: 'The Filling Challenge' (10 - 15 minutes)

1. The teacher proposes a new challenge to the students. They must use a graduated cylinder (or any other transparent container with markings) and a bowl of water to measure and compare the capacity of different objects.
2. The students, again divided into groups, receive a box with a variety of objects of different shapes and sizes. They should predict and record which objects they think have more or less capacity, and then test their predictions by filling the object with water from the bowl and measuring the amount of water used.
3. The teacher circulates around the room, assisting the students and asking questions to stimulate critical thinking, such as 'Which object do you think has more capacity? Why?' and 'How can you compare the capacity of two objects without using the graduated cylinder?'.
4. After completing the activity, the teacher gathers the class to discuss the results and reinforce the concepts of capacity and volume comparison.

Activity 3: 'What's My Mass?' (5 - 7 minutes)

1. The teacher proposes a mass guessing game for the class. He brings a handheld scale and a series of objects of different masses, all hidden in paper bags.
2. Challenging the class to guess the mass of each object, the teacher goes from student to student, allowing each student to feel the weight of the object hidden in their bag.
3. After each student makes their guess, the teacher weighs the object on the scale and reveals the answer. This creates an opportunity for students to compare their estimates with the actual mass of the object and reflect on what they learned in previous activities.
4. The teacher concludes the activity by reinforcing the concepts of mass and the importance of accurate measurement.

The suggested activities are interactive and playful, providing a fun and engaging way for students to learn about mass and capacity measurement units. The teacher can choose one or more activities, depending on the available time and the class's progress.

Feedback (10 - 15 minutes)

1. Group discussion: The teacher gathers all students for a group discussion on the solutions and findings from the activities. Each group is invited to share their conclusions, challenges encountered, and how they solved the problems. The teacher can ask questions to stimulate reflection and participation from everyone, such as 'Which objects did you find most difficult to compare? Why?' and 'Do you think an object's mass is always related to its size? Why?'.

2. Connection to theory: After discussing the activities, the teacher connects the practical experiences to the theory, reinforcing the concepts of mass and capacity. He may ask: 'Based on the activities we did, what does it mean to say that one object has more mass than the other?' and 'How can we compare the capacity of two objects without using a graduated cylinder?'.

3. Individual reflection: Next, the teacher proposes a moment of individual reflection. He asks two simple questions for students to reflect on what they learned in the lesson. The questions are:

   • 'What is the unit of measurement we use to weigh an object and to measure the amount of liquid in a container?'.
   • 'What did you discover today about the mass and capacity of objects that you didn't know before?'.

4. Review of objectives: To conclude the lesson, the teacher reviews the objectives set at the beginning. He asks students if they were able to achieve these objectives and if they have any remaining doubts or difficulties. The teacher reinforces that understanding mass and capacity measurement units is an ongoing process and that they will have more opportunities to practice and improve these skills in the upcoming classes.

Feedback is a crucial part of the lesson plan as it allows the teacher to assess students' progress, identify any gaps in understanding, and adjust instruction as needed. Additionally, it helps students consolidate what they have learned, make connections to the real world, and reflect on their own learning process.

Conclusion (5 - 10 minutes)

1. Summary and Recap: The teacher begins the conclusion by recapping the key points covered during the lesson. He summarizes the mass measurement units (kilogram and gram) and capacity (liter and milliliter) and how they are used in daily life. He also recalls the practical activities carried out, emphasizing the discoveries and conclusions made by the students.

2. Connection between Theory and Practice: Next, the teacher reinforces the connection between theory and practice, explaining how the practical activities helped illustrate the theoretical concepts concretely. He highlights how the experience of weighing and measuring real objects helped make the concepts of mass and capacity more tangible and understandable for the students.

3. Extra Materials: The teacher suggests extra materials for students who wish to deepen their knowledge on the subject. He may recommend children's math books that address measurement topics, online educational games involving measurement practice, or even activities to do at home, such as weighing ingredients in the kitchen or measuring the capacity of different containers with water.

4. Importance in Daily Life: Finally, the teacher emphasizes the importance of mass and capacity concepts in everyday life. He explains that understanding these measurements is essential for a variety of daily activities, such as cooking, shopping, filling a glass of water, and much more. He also encourages students to observe and question measurements in their surroundings, fostering critical thinking and a greater awareness of the importance of mathematics in their lives.

5. Closure: The teacher concludes the lesson by reinforcing that learning is an ongoing process and that they will have more opportunities to explore and deepen their knowledge of measurements in the upcoming sessions. He congratulates the students on their work and active participation, and motivates them to continue to be engaged and curious in their mathematical learning journeys.