: “Different states of matter and their explanation based on molecular kinetic concepts”
Lesson in 7th grade: “Different states of matter and their explanation based on molecular kinetic concepts”
Date of_______________________
Lesson objectives:
Educational – to form ideas about some mechanical properties solids, liquids, gases.
Developmental – to develop students’ speech and thinking skills, the ability to analyze, and the ability to draw conclusions from the material studied.
Educational – to promote responsibility, the desire for success, to create conditions for increasing interest in the subject being studied.
Equipment: computer, multimedia projector.
During the classes:
I. Organizational moment.
II. Updating knowledge.
Everyone loves to do crossword puzzles. You and I will also solve a crossword puzzle, but a physical one (slide 1).
Horizontally: 1. The smallest “indivisible” particle. (atom)
2.Ancient Greek scientist who introduced the concept of the atom. (Democritus)
3. The process of canning vegetables and fish, which uses the phenomenon of diffusion (salting)
4. Diffusion proves ... molecules. (movement)
5. One of the types of molecular interaction (repulsion)
6. The phenomenon of spontaneous mixing of matter (diffusion)
7. Thin tubes through which liquid rises or falls due to the interaction of molecules (capillary)
8. A phenomenon that proves the interaction of molecules. (wetting)
III. Motivation.
We are surrounded different bodies. Bodies consist of various substances.
What substance do you see on slide 2? (Answer: Water)
When water freezes it forms... (ice) (slide 3)
Ice, what state of water is this? (solid)
Here, two different states of water exist simultaneously - liquid and solid. In the atmosphere, water is contained in a state invisible to the eye - steam. When there is a lot of steam, clouds form in the atmosphere. (slide 4)
What states can water be in? (solid, liquid, gaseous)
These states of matter are called aggregate states. This will be the topic of today’s lesson “Aggregative states of matter”. (slide 5,6) (further demonstration can be accompanied by music that is recorded in the presentation).
IV. Assimilation of new knowledge. ( Further transition to the slides is carried out using the link on slide 6)
IN various states substances have different properties. Most of the bodies around us are made of solids. These are houses, cars, tools, etc.
Give more examples of solids.
The shape of a solid body can be changed, but this requires effort. For example, to bend a nail, you need to apply quite a lot of force.
To give solids the desired shape and volume in plants and factories they are processed with special machines.
Which general property unites them?
(A solid has its own shape and volume ). (slide7)
The second state of matter is liquid. (Slide 8) Unlike solids, liquids easily change their shape. They take the shape of the vessel in which they are located.
For example, the milk that fills a bottle is shaped like a bottle. When poured into a glass, it takes the shape of a glass. But, changing shape, the liquid retains its volume.
IN normal conditions Only small droplets of liquid have their own shape - the shape of a ball. These are, for example, raindrops, or drops into which a stream of liquid breaks up.
The production of objects from molten glass is based on the property of a liquid to easily change its shape.
Let's conclude: Liquids easily change their shape but retain their volume. ( slide 9)
The air we breathe is a gaseous substance, or gas. Since most gases are colorless and transparent, they are invisible.
The presence of air can be felt when standing near open window moving train. Its presence in the surrounding space can be felt if there is a draft in the room, and can also be proven using simple experiments (slide 10).
Is it possible to fill a container with gas to half its volume? Why?
Conclusion: A substance in a gaseous state has no own form and volume.
V. Working with the textbook. Students read the paragraph and highlight necessary information and answer questions (slide 12). Then, together with the teacher, they summarize. (slide 11,13)
Gases. The distance between the molecules is many times greater than the molecules themselves; they hardly attract and move freely. Therefore, gases fill the entire provided volume, have no shape and are easily compressed. But if gases are strongly compressed or cooled, they turn into a liquid state.
Liquids. The molecules are located close to each other, the distance between them is comparable to the size of the molecules. They abruptly change their place - “jump”. Therefore, liquids do not retain their shape, they can flow, and are easy to pour. But it is difficult to compress them, since this brings the molecules closer together and repulsion occurs between them.
Solids. Molecules are located in in strict order the distance between molecules is comparable to the size of the molecules. Molecules vibrate around a certain point and cannot move far from it. Therefore, solids retain their shape and volume. Crystalline bodies.
VI. Independent work.
Students perform short test according to options. Checking the test. Slide 14.
Test. Option 1.
Which of specified properties belong to gases?
A. They have their own shape.
B. Maintain volume.
How are gas molecules arranged?
B. Located in in a certain order.
What state can mercury be in?
A. Only in liquid.
B. Only in solids.
Is it possible to fill an open vessel with gas to 40% of its capacity?
A. Yes, you can.
B. No, you can’t.
Q. There is no definite answer.
The water froze and turned into ice. Did the water molecules themselves change?
A. No, they haven’t changed.
B. Yes, they have changed.
Q. There is no definite answer.
Test. Option 2.
1. Which of the following properties belong to liquids?
A. They have their own shape and volume.
B. Easily change shape, but retain volume.
B. They do not have their own shape and constant volume.
2. How are molecules arranged in solids?
A. Moving randomly in all directions, they are almost not attracted to each other.
B. Do not diverge long distances.
B. Arranged in a certain (strict) order.
3. What condition can cast iron be in?
A. Only in liquid.
B. In liquid, solid, gaseous.
B. Only in solids.
4. The bottle contains water with a volume of 0.2 liters. It is poured into a flask with a capacity of 0.5 liters. Will the volume of water change?
A. It won't change.
B. Will increase.
B. Will decrease.
5. Rooms where medical ether is used usually smell strongly of it. What is the state of the ether in the room?
A. Only in liquid.
B. In liquid, solid, gaseous.
B. Only in gaseous form.
VII. Homework. Generalization of knowledge: fill out the table. Slide 15.
VIII. Lesson summary.
The teacher marks the most active students and assigns grades.
Characteristics of the gaseous state of a substance
Aggregate states of substances, their characteristics
Depending on external conditions (temperature and pressure), each substance can be in one of three states of aggregation: solid, liquid or gaseous.These states are called states of aggregation.Some substances are characterized by only two or even one state of aggregation. For example, naphthalene, iodine when heated under normal conditions from solid state pass into gaseous form, bypassing liquid form. Substances such as proteins, starch, and rubbers, which have huge macromolecules, cannot exist in a gaseous state.
Gases do not have a constant shape and constant volume. Liquids have a constant volume, but do not have a constant shape. Solids are characterized by constancy of shape and volume.
Characteristics of the gaseous state of a substance
Gases have the following properties:
Uniform filling of the entire provided volume;
Low density compared to liquid and solids and high diffusion speed;
Relatively easy to compress.
These properties are determined by the forces of intermolecular attraction and the distance between molecules.
In a gas, molecules are located at a very large distance from each other, the forces of attraction between them are negligible. At low pressures the distances between gas molecules are so great that compared to them the size of the molecules, and, consequently, the volume of molecules in total volume gas can be neglected. At large distances between molecules, there are practically no attractive forces between them. Gas in this state is called perfect.At normal conditions T=273 0 K (0 0 C) and p=101.325 kPa real gases, regardless of their nature, can be considered ideal and applied to them ideal gas equation of state (Claiperon-Mendeleev equation):
PV = n RT, (2.1)
where P– gas pressure,
V – volume of gas,
n – amount of substance,
R – universal gas constant (in SI units R =8.314 J/molK),
T – absolute temperature.
Real gases at high pressures And low temperatures do not obey the equation of state of an ideal gas, since under these conditions the forces of interaction between molecules begin to appear and it is no longer possible to neglect the intrinsic volume of the molecules compared to the volume of the body. For mathematical description behavior of real gases are used the equation van der Waals:
(р + n 2 a/V 2) (V – nb) = vRT, (2.2)
where a and b are constants,
a/V 2 – correction for mutual attraction,
b – correction for the intrinsic volume of molecules,
n is the number of moles of gas.
With increasing pressure and decreasing temperature, the distances between molecules decrease, and the interaction forces increase so that a substance can pass from a gaseous state to a liquid one. For each gas there is a limit critical temperature, above which a gas cannot be converted into a liquid at any pressure. The pressure required to liquefy the gas at critical temperature, called critical pressure, and the volume of one mole of gas under these conditions is critical volume.
Rice. 1. Isotherms of real gas
The state of the gas at critical parameters is called critical condition.In a critical state, the difference between liquid and gas disappears; they have the same physical properties.
The transition from gas to liquid can be shown graphically. Figure 1 shows the graphical relationship between volume and pressure at constant temperatures. Such curves are called isotherms. The isotherms can be divided into three sections: AB, BC, CD at low temperatures. AB – corresponds to the gaseous state, BC – corresponds to the transition of gas to liquid, CD – characterizes the liquid state. With increasing temperature, the section BC decreases and turns into an inflection point K, called critical point.
Solid has its own shape and volume.
Unlike solids, liquids easily change their shape. They take the shape of the vessel in which they are located.
Gases do not have their own shape and constant volume. They take the shape of the vessel and completely fill the volume provided to them.
2. The task of finding out the conditions for a body to float in a liquid.
If the force of gravity (mg) is less than the buoyant force, the body floats up
If the force of gravity (mg) is equal to the buoyant force, the body floats
If gravity (mg) is greater than the buoyant force - the body sinks
1. Mechanical movement. Speed. Path.
Mechanical movement is a change in the position of a body in space relative to other bodies.
For example, a car is moving along the road. There are people in the car. People move along with the car along the road. That is, people move in space relative to the road. But relative to the car itself, people do not move. This shows relativity mechanical movement . Next we will briefly consider main types of mechanical movement.
2. Problem of calculating the pressure of a solid body
GIVEN: SI: SOLUTION:
m= 35 kg F= mg
g= 10 N/kg F= 35*10= 350 N
S= 200cm 2= 0.02 m^2 p= F/ S
FIND: p p= 350N / 0.02 m ^2= 17500 Pa
ANSWER: 17.5k/Pa
1. Inertia.
ANSWER: A soccer ball is lying on the field. With a kick, the football player sets it in motion. But the ball itself will not change its speed and will not begin to move until other bodies act on it.
A bullet placed in a gun will not fly out until the powder gases push it out.
Thus, both the ball and the bullet do not change their speed until they are acted upon by other bodies.
2. Problem on determination of efficiency when lifting a body along an inclined plane.
According to the “Golden Rule” of mechanics, in the absence of friction we have:
1. Interaction of bodies. Weight of bodies
ANSWER: You already know that when uneven movement the speed of a body changes over time. A change in the speed of a body occurs under the influence of another body. The carts act on each other, i.e. they interact. This means that the action of one body on another cannot be one-sided; both bodies act on each other, i.e. interact. Also, the bullet is in relative position to the gun before it is fired. When interacting (during a shot), the bullet and the gun move in different sides. The movement of the gun is felt as recoil.
2. Problem on calculating pressure in liquids. (page 117)
1. Density of the substance.
ANSWER: The bodies around us consist of various substances: wood, iron, rubber, etc. The mass of any body depends not only on its size, but also on what substance this body consists of. Moreover, bodies having equal volumes, but made from different substances, have different masses.
m = ρV.
From two bodies of equal volume large mass has the body whose substance density is greater.
«
Three states of matter. The difference is molecular structure solids, liquids and gases»
Purpose of the lesson:
Educational - introduce the concept of a molecule, the three states of substances, the molecular structure of liquid, solid and gaseous substances; repeat the mutual attraction and repulsion of molecules;
Developmental – learn to apply knowledge about the molecular structure of substances in practice when solving problems;
Educational – to cultivate the ability to listen carefully to the opinions of others, to respect the answers of classmates.
Lesson stage 1:
Teacher: I will prove that for a whole year you have almost no time to study at school. There are 365 days in a year. Of these, 52 are Sundays, 10 other days of rest. 62 days are missing. Summer and the winter vacation– no less than 100. Minus another hundred days. They don't go to school at night, and nights make up half of the year, therefore another 183 days minus. There are 20 days left, but classes do not last all day, but not more than a quarter of the day. Only 5 days left. Is there much to learn here?
Students: No, not much.
Teacher: And we will try it in 40 minutes find out what three states substances are divided into and consider the differences in the molecular structure of solids, liquids and gases. But first, we must recall the material from the last lesson, for this we will consider the following tasks:
Why can’t we put a broken pencil back together so that it becomes whole again?
Why doesn't dust rise on the road after rain?
Why does it take a significant amount of time to separate sheets of paper wet with water? more effort than when turning over the dry pages of a book?
Why do they write on a blackboard with chalk and not with a piece of white marble?
Which substances (lead, wax, steel) have the greatest attraction between particles; least?
What do gluing paper and soldering metal products have in common?
Stage 2 (explanation of new material):
Teacher: What three groups can the following substances be divided into: water, sugar, air, tin, alcohol, ice, oxygen, aluminum, milk, nitrogen (these substances are given at room temperature). Slide 4
Students.
Teacher: All substances in nature are found in three states: liquid, solid, and gaseous. In different states, substances have different properties. Slide 5
A solid has shape and volume
The liquid easily changes its shape, but retains its volume.
Gases do not have their own shape and constant volume. They take the shape of the vessel and completely fill the volume provided to them.
Based on this, explain:
A closed bottle is half filled with mercury. Can we say that there is no mercury in the top half of the bottle?
Can they be in liquid state oxygen, nitrogen?
Can mercury, iron, and lead exist in a gaseous state?
Physical education minute.
They quickly stood up and smiled.
Higher, we reached higher.
Well, straighten your shoulders,
Raise, lower.
Turn right, turn left,
Touch your hands with your knees.
Sat down, stood up, sat down, stood up
And they ran on the spot.
These properties of substances can be explained if you know their molecular structure.
Molecule - This smallest particle, of this substance. All substances and bodies that exist on earth (solid, liquid, gaseous) consist of molecules. Molecules are usually depicted like this
If you split two water molecules, you get two oxygen atoms and four oxygen atoms. Every two hydrogen atoms can combine to form a hydrogen molecule, and every two oxygen atoms can combine to form an oxygen molecule. Slide 8.9
The different properties of a substance in all states are determined by the fact that its molecules are arranged differently and move differently. If a gas is compressed and its volume decreases, therefore, In gases, the distance between molecules is much greater than the size of the molecules themselves. Since on average the distance between molecules is tens of times larger size molecules, they are weakly attracted to each other. Therefore, gases do not have their own shape and constant volume.
Gas molecules, moving in all directions, are almost not attracted to each other and fill the entire container.
The molecules of a liquid are located close to each other. Distances between every two molecules smaller sizes molecules, so the attraction between them becomes significant.
The molecules of a liquid do not disperse over long distances, and the liquid under normal conditions retains its volume.
Since the attraction between the molecules of the liquid is not so strong, they can change their position abruptly. The liquid does not retain its shape and takes the form of a container. They are fluid and easy to pour from one vessel to another. A liquid is difficult to compress, since in this case the molecules come closer together at a distance when repulsion is noticeable.
In solids, the attraction between molecules (atoms) is even greater than in liquids. Therefore, under normal conditions, solids retain their shape and volume.
In solids, molecules (atoms) are arranged in a certain order. These are ice, salt, metals and others. Such bodies are called crystals. Slide 10.
Molecules or atoms of solids vibrate around a certain point and cannot move far from it. A solid therefore retains not only its volume, but also its shape.
Teacher: Guys, now let's look at the fairy tale about the Molyu molecule. (Slide No. 11)
To consolidate the material you have covered, I offer you the “Choose the correct answer” test. Points are awarded for the test. Slide 28
Teacher: Let's write it down homework No. 11, No. 12, questions, task 3 written in a notebook. Give grades for the lesson and comment on them.
Reflection Slide 46
Bad
Excellent
Guys, there are 3 “faces” in front of you, choose the one that matches your mood.
Indifferent