Contextualization
Theoretical Introduction
State changes are physical phenomena that occur daily and are present in various aspects of our daily lives. For example, when ice melts and turns into liquid water, or when water evaporates and becomes vapor, we are witnessing state changes.
They occur when a substance changes from a solid to a liquid state (melting), from a liquid to a gaseous state (boiling or vaporization), from a solid state directly to a gaseous state (sublimation), and vice versa (resublimation). Additionally, we also have condensation (from the gaseous state to the liquid state) and solidification (from the liquid state to the solid state).
These different types of state changes occur due to variations in temperature and pressure to which the substance is subjected. Each substance presents a characteristic behavior that defines at what temperature and pressure each state change will occur.
Contextualization
State changes play a fundamental role in various industrial and natural processes. They are responsible for the formation of clouds and rain, the operation of air conditioning and refrigeration systems, the production of energy in thermoelectric power plants, among others.
Furthermore, state changes are essential for life on Earth. Through the water cycle, for example, water evaporates from the oceans, condenses in the atmosphere forming clouds, precipitates as rain, and returns again to the oceans and rivers. In this cycle, evaporation, condensation, and precipitation are examples of state changes that allow the distribution of water throughout the planet.
Understanding state changes is therefore indispensable for our lives and for the maintenance of the planet. Through an in-depth study of these processes, it is possible to develop technologies and strategies to use them efficiently and sustainably.
Practical Activity
Activity Title: Changes of State - The Water Cycle in a Bottle
Project Objective
The main objective of this activity is to provide students with the opportunity to observe and analyze state changes of matter in practice, more specifically the water cycle: evaporation, condensation, and precipitation.
Detailed Project Description
Each group of 3 to 5 students will create a simple model of the water cycle using a plastic bottle, soil, plants, and water. By carrying out the activity, it is expected that students will be able to understand how state changes occur in practice and thus build a more solid understanding of these chemical concepts.
Required Materials
- A transparent plastic bottle (2 liters)
- Soil
- Water
- Two small plants
- Scissors
Detailed Step-by-Step for the Activity
- Cut the top part of the plastic bottle, creating an opening.
- Fill the bottle with soil until it reaches about 1/4 of the total volume.
- Plant the two small plants in the soil inside the bottle.
- Add enough water to moisten the soil, but without soaking it.
- Put the top part of the plastic bottle back, creating a 'closed terrarium'.
- Place the bottle in a location where it receives sunlight, but without direct exposure to the sun.
- Observe daily what happens inside the bottle for a week.
Project Deliverables
At the end of the week, each group must write a report on the project, covering the following topics:
1. Introduction:
Students must contextualize the theme, explaining the concept of state change and its importance in the real world. They must also present the project's objective and explain why they chose to carry out the proposed activity.
2. Development:
Students must explain the theory behind state changes and the water cycle. Then, detail how the activity was carried out, including the materials used and the step-by-step process followed. Finally, they must present and discuss the results obtained, explaining what they observed during the week in the bottle and how this illustrates the water cycle and state changes.
3. Conclusion:
Students must conclude the work by summarizing their main points, explaining what they learned from the project, and what conclusions they were able to draw from the practical activity carried out.
4. Bibliography:
Students must indicate the sources consulted to carry out the project, whether books, websites, videos, etc.
The report should be written clearly, containing images of the bottle throughout the week and graphs or tables, if appropriate. It must be submitted in digital format and must have at least twice the number of pages as the number of group members. For example, a group with 4 students must submit a report of at least 8 pages.
