This
dialogue is made based on the five approach theory, there are observe, ask,
analyze, try, and conclude.
On a sunny
morning, a chemistry teacher explains the material about the colligative nature
of the solution to her students in the classroom.
Teacher : Good morning Class!
All
student : Good morning, Miss!
Teacher : Today we will learn about the colligative nature of the solution.
The colligative nature of the solution is the nature of the solution that is affected by the amount
of solute particles and is independent of the nature of the solute. Does anyone know anything
that includes the colligative nature of the solution? Please raise your hand!
(Some students raised their hands. The teacher appoints one of the students to answer the question.)
Student 1 : The colligative nature of the solution comprises decreasing the vapor pressure of the solution,
the increase of the boiling point of the solution, the decrease in the freezing point of the solution
and the osmotic pressure.
Teacher : Exactly! The answer is right. So Class, now we will discuss its one by one. The first is a
decrease in the vapor pressure of the solution. The evaporation process is a change of a
substance from liquid to gas. The higher the temperature of the liquid, the more steam that is
above the liquid surface. This means the vapor pressure is higher. Evaporation of water is the
event of the release of water molecules from the water surface. But what if above the water
surface is blocked by solute particles? What will happen ?
Student 2 : Miss! (raise his hand)
Teacher : Yes, please!
Student 2 : I think if above the water surface is blocked by solute particles, the evaporation process will
be disrupted.
Teacher : That’s right! If above the water surface is blocked by solute particles, the evaporation process
will be disrupted. Consequently the amount of water vapor above the water surface becomes
reduced so that the vapor pressure will decrease. The magnitude of the decrease in water
vapor pressure due to the presence of solutes is called the decrease in the vapor pressure of
the solution. To find the amount of vapor pressure of the solution, you can see the formula at
page 10.
Student 3 : Miss, I don’t understand example on page 11.
Teacher : Oh, I am sorry about that. We will discuss all examples on tomorrow. Today we just discuss
the introduction of the material only. Okay Class, next we talk about the increase of the boiling
point of the solution. Have you ever heated the water until it boils ?
All student : Yes, I have.
Teacher : How do you say the water is boiling?
Student 4 : There is smoke from the kettle
Student 5 : The kettle is ringing
Student 6 : There is water vapor
Teacher : yes all of you is right! At a certain temperature, the vapor pressure of the liquid above the
surface of the substance will be equal to the outside air pressure. At which point the liquid boils.
Student 7 : I am sorry, Miss. I want to ask you, When I was holliday in the mountains , I heat up the water
but it feels like it boils faster than when I heat water at home. Why it can happen ?
Teacher : waw good question! As I mentioned earlier, the liquid will be boils if the vapor pressure of the
liquid above the surface of the substance be equal to the outside air pressure. So if the outside
air pressure is less than 1 atm, for example at the top of the mountain, the boiling point of
water is less than 100 degrees centigrade.
Well, the third is the decrease in the freezing point of the solution. What do you think people
in the four seasons do to clear the way from the falling snow ?
Student 8 : Miss! miss! miss!
Teacher : yes please!
Student 8 : I've seen movies, they clean the snow-covered streets by sprinkling salt into the street.
Teacher : yes it that’s true! The salt sown will cause the freezing point of water to decrease so the water
has not frozen at the temperature that should have caused the water to freeze. The freezing
process is the density of the liquid particles so that there will be very strong intermolecular
intermolecular forces and eventually form solids. The presence of solute will result in the
movement of solvent molecules blocked so that required a lower temperature to be able to
close the intermolecular distance for freezing process occurs. So can anyone deduce the effect
of solute in the freezing process of solution?
(All students answered simultaneously)
Teacher : Raise your hand, please!
(Teacher choose one of them)
Student 9 : The conclusion is that the presence of a solute in a liquid will result in a decrease in the freezing
point of the liquid.
Teacher : okay, well, I think all of you already understand what I said. For the next material we will
discuss next week. See you!
All student : Good bye, Miss. See you!
How to train our own skills especially teachers to get used to the method?
BalasHapusSteps to apply teaching methods with five aspects of a scientific approach:
Hapus1) observe (observe)
Let the teacher open widely and vary the learner's chance to observe through activities: seeing, listening, listening, and reading. Teachers facilitate learners to make observations, train them to watch (see, read, hear) the important things of an object or object.
2) ask
In observing activities, teachers open wider opportunities to learners to ask questions about what has been seen, listened to, read or viewed. Teachers need to guide learners to be able to ask questions: questions about which concrete object observations come to the abstract with regard to facts, concepts, procedures, or anything else more abstract
3) Gathering Information
The "information gathering" activity is a follow-up to asking questions. This activity is done by the teacher guiding the students to dig and gather information from various sources through various ways. For that learners can read more books, pay attention to phenomena or objects more thoroughly, or even doing experiments.
4) Associating / Processing Information / Reasoning
The "associate / process information / learning" activity in the learning activities is done by the teacher accompanying the students to process the information gathered from the collecting / experimental activity as well as the result of observing activities and gathering information activities.
5) Communicating
In the scientific approach the teacher is expected to give the learners the opportunity to communicate what they have learned. This activity can be done through writing or telling what is found in information seeking activities, associating and finding patterns.
Give me an example of the colligative nature of everyday life and please give me the explanation
BalasHapusApplication of the colligative nature of the solution in everyday life:
Hapus1) decrease of vapor pressure
Dead Sea is an example of a decrease in solvent vapor pressure by non-volatile solutes. This very high salt water is located in a very hot and dry desert region, and is not related to the free ocean, so the concentration of solute is higher.
At the time of swimming in the dead sea, we will not drown because of the concentration of its very high solute. This of course, can be used as a means of entertainment or recreation for humans. Application of the same principle with the dead sea we can find in some tourist attractions in Indonesia in the form of floating pool.
2) decrease of freezing point
Animals living in cold climates, such as polar bears, utilize the principle of the colligative nature of frost reduction solutions to survive. The blood of marine fish contains antifreeze substances that can lower the freezing point of water to 0.8oC. Thus, marine fish can survive in winter where temperatures reach 1.9oC because the antifreeze they contain can prevent ice crystals from forming in their tissues and cells. Other animals whose bodies contain antifreeze substances include insects, amphibians, and nematodes. Insect body contains glycerol and dimethyl sulfoxide, amphibians containing glucose and blood glycerol while nematodes contain glycerol and trihalose.
In an area that has winter, every snowfall occurs, the streets are filled with snow ice. This of course makes the vehicle difficult to drive. To overcome this, the snowy streets are sprinkled with a mixture of NaCl and CaCl2 salts. Sowing of the salt can melt the snow. The more salt that is sown, the more snow will melt
3) osmotic pressure
Blood Washing Machine
Patients with kidney failure should undergo dialysis therapy. Therapy uses the dialysis method, which is the process of moving small molecules such as urea through a semipermeable membrane and into another liquid, then discarded. Membranes can not be penetrated by large molecules like proteins that will remain in the blood.
Food Preservation
Before the cooling technique to preserve food is found, salt is used to preserve food. Salt can kill the microbes that cause rotten food on the surface of food.
Eradicate Leeches
Kitchen salt can eradicate soft animals, such as leeches. This is because the salt sprinkled on the surface of the leech body is able to absorb water in the body so that the leech will lack water in the body.
Why in the learning process teachers should have a good approach to students?
BalasHapusIn order to achieve the learning objectives set out in the curriculum, teachers need to undertake a range of learning activities from planning, strategy determination, material selection and learning methods, to assessment. A series of learning activities in order to achieve these educational goals is often referred to as the approach taken by the teacher or the learning approach.
HapusSo it can be concluded that the approach of teachers to students aims to create an effective and efficient learning process. In teaching, teachers must be good at using the approach wisely and wisely, the teacher's view of the students will determine the attitude and deeds.
Komentar ini telah dihapus oleh administrator blog.
BalasHapusKomentar ini telah dihapus oleh pengarang.
Hapuswhat is the different in coligative proporties of electrolyte and non-electrolyte?
BalasHapusThe difference is that at the same concentration, the colligative nature of electrolyte solution has a value greater than the colligative nature of non-electrolyte solution. The number of solute particles of the ionization reaction of the electrolyte solution is formulated in Van't Hoff factor.
Hapus