"Thermal Phenomena. Aggregate states of matter. Test. Melting and solidification of crystalline bodies (work with graphs) Tasks and exercises

"Thermal Phenomena. Aggregate states of matter "Grade 8.

Option 1.

A.1. Lead melts at a temperature of 327o C. What can be said about the solidification temperature of lead? 1) it is equal to 327o C;

2) it is below the melting point;

3) it is above the melting point;

A.2. At what temperature does mercury become crystalline?

1) 420o C; 4) 0o C;

2) -39o C;o C.

A.3. In the earth at a depth of 100 km, the temperature is about 1000 ° C. Which of the metals is in an unmelted state?

1) zinc; 2) tin; 3) iron.

A.4. The gas leaving the nozzle of a jet aircraft has a temperature of 500°C-700°C. Can the nozzle be made of aluminum?

1) can; 2) can't.

A.5. What was the body temperature at the first moment of observation?

A.6.

1) heating; 3) melting;

A.7

1) heating; 3) melting;

2) cooling; 4) hardening.

A.8. At what temperature did the melting process begin?

1) 50o C;o C;o C.

2) 100o C;o C;

A.9. How long did the body melt?

1) 8min; 3) 12min; 5) 7min.

2) 3min; 4) 16min;

A.10. Did the body temperature change during melting?

A.11.

1) heating; 3) melting;

2) cooling; 4) hardening.

A.12.?

1) 50o C;o C;o C.

2) 500оС; 4) 40o C;

A.13. Molecules in crystals are located:

A.14. When heating bodies average speed molecular movements:

A.15. What can be said about the internal energy of water with a mass of 1 kg. at a temperature

0o C and ice of 1 kg at the same temperature?

1) internal energy water and ice is the same;

2) ice has a large internal energy;

3) water has a large internal energy.

A.16. What energy is required to melt 1 kg of lead at 327°C?

1) 0.84*105J; 3) 5.9 * 106 J; 5) 2.1 * 106 J.

2) 0.25*105 J; 4) 3.9 * 106 J;

A.17. The aluminum, copper, and tin bodies are heated so that each is at its melting point. Which of them requires more heat to melt if their masses are the same?

1) aluminum; 3) copper.

2) tin;

A.18. During the ice drift near the river, the air temperature is……….. than away from it. This is explained by the fact that energy………..melting ice.

1) above ... ... stands out; 3) higher……absorbed;

2) below……. stands out; 4) below……absorbed;

A.19. What energy is required to melt 1 kg of iron at the melting temperature?

1) 2.5 * 105 J; 3) 8.4 * 105 J; 5) 3.9 * 105 J.

2) 2.7 * 105 J; 4) 5.9 * 105 J;

A.20. What energy is required to melt 5 kg of iron at the melting point?

1) 2.3*105 J; 3) 7.8 * 106 J; 5) 1.35*106 J.

2) 2.0*105 J; 4) 6.2*105 J;

A.21.Steel is obtained by melting iron scrap in open-hearth furnaces. What energy is required to melt iron scrap weighing 5 tons and having a temperature of 10°C? The melting point was taken to be 1460o C.

1) 4.05*106J; 4) 1.47 * 106 J;

2) 3.99*106J; 5) 4.90 * 106 kJ.

3) 1.97*106J;

A.22.Evaporation is called the phenomenon:

1) the transition of molecules into vapor from the surface and from inside the liquid;

A.23.Evaporation occurs:

1) at the boiling point;

2) at any temperature;

3) at a certain temperature for each liquid.

A.24. If there is no energy inflow to the liquid from other bodies, then when it evaporates, the temperature:

1) does not change; 2) increases; 3) decreases.

A.25. Internal energy during liquid evaporation:

1) does not change; 2) increases; 3) decreases.

A.26. In what state of aggregation will zinc be at the boiling point of mercury and normal atmospheric pressure?

1) in solid; 2) in liquid; 3) in gaseous.

A.27.Is the internal energy of water weighing 1 kg at a temperature of 100 ° C equal to the internal energy of water vapor weighing 1 kg at the same temperature?

2) the internal energy of steam is greater than the internal energy of water by 2.3 * 106 J;

3) the internal energy of steam is less than the internal energy of water by 2.3 * 106 J;

IN 1. Determine the amount of heat required to turn 8 kg of ether into steam,

taken at a temperature of 10°C.

IN 2. What energy will be released during the solidification of 2.5 kg of silver, taken at

melting temperature, and its further cooling to 160°C.

C.1. What final temperature will be established if 500 g of ice at a temperature

0°C, immerse in 4 liters of water at 30°C.

C.1.How much firewood must be burned in the stove, efficiency \u003d 40%, to get snow from 200 kg,

taken at 10°C, water at 20°C.

"Thermal Phenomena. Aggregate states of matter” Grade 8.

Option 2.

A.1. When a crystalline substance melts, its temperature is:

1) does not change; 2) increases; 3) decreases;

A.2. At what temperature can zinc be in a solid and liquid state?

1) 420o C; 4) 0o C;

2) -39o C;o C.

3) 1300o C -1500oC;

A.3. Which of the metals - zinc, tin or iron - will not melt at the temperature of copper?

1) zinc; 2) tin; 3) iron.

A.4. The temperature of the outer surface of the rocket during the flight rises to 1500oC-2000o C. What metal is suitable for making the outer skin of the rocket?

1) tin; 3) steel;

2) copper; 4) tungsten.

A.5. What was the temperature at the first moment of observation?

A.6. Which process on the graph characterizes segment AB?

1) heating; 3) melting;

2) cooling; 4) hardening.

A.7.What process on the graph characterizes the BV segment?

1) heating; 3) melting;

2) cooling; 4) hardening.

A.8. At what temperature did the curing process begin?

1) 80o C;o C;o C.

2) 350o C;o C;

A.9. How long does it take for the body to harden?

1) 8min; 3) 12min; 5) 7min.

2) 4min; 4) 16min;

A.10. Has body temperature changed during curing?

1) increased? 2) decreased; 3) has not changed.

A.11. What process on the graph characterizes the segment VG?

1) heating; 3) melting;

2) cooling; 4) hardening.

A.12. What temperature was the body at the last moment of observation ?

1) 10o C;oC;o C; 4) 40o C;o C.

A.13. Molecules in a molten substance are located:

1) in strict order; 2) in disarray.

A.14. Molecules in a molten substance move by………….forces of molecular attraction.

1) randomly, not staying in certain places;

2) near the equilibrium position, holding;

3) near the equilibrium position, not staying in certain places.

A.15. What can be said about the internal energy of molten and unmolten lead weighing 1 kg at a temperature of 327 ° C?

1) the internal energy is the same;

2) the internal energy of molten lead is greater than that of unmelted lead;

3) the internal energy of unmelted lead is greater than that of molten lead;

A.16. What energy will be released during the solidification of aluminum weighing 1 kg at a temperature of 660 ° C?

1) 2.7*105J; 3) 0.25*105 J; 5) 2.1 * 105 J.

2) 0.84 * 105 J; 4) 3.9 * 105 J;

A.17. Ice of the same temperature was introduced into a room with an air temperature of 0°C. Will the ice melt?

1) will be, since ice melts at 0°C;

2) will not be, since there will be no influx of energy;

3) will be, since the energy is borrowed from other bodies.

A.18. During a heavy snowfall in winter, the air temperature is……….., because when the water droplets formed from the clouds solidify…………..energy.

1) rises……….absorbed;

2) decreases……….. stands out;

3) rises………. stands out;

4) decreases………..absorbed.

A.19. What energy is required to melt 1 kg of tin at the melting temperature?

1) 0.25 * 105 J; 3) 0.84 * 105 J; 5) 3.9 * 105 J.

2) 0.94*105 J; 4) 0.59*105 J;

A.20. What energy is required to melt 4 kg of tin at the melting temperature?

1) 2.36 * 105 J; 3) 7.8 * 107 J; 5) 4.7 * 105 J.

2) 2.0*105 J; 4) 6.2*105 J;

A.21.What amount of heat is required to melt copper with a mass of 2 tons and a temperature of 25 ° C? The melting point of copper is taken about C

1) 5.29 * 107 kJ; 3) 1.97*105kJ;

2) 3.99*105 kJ; 4) 1.268*105k J; 5) 3.53 * 106 kJ.

A.22.Condensation is a phenomenon in which:

1) evaporation not only from the surface but also from the inside of the liquid;

2) the transition of molecules from liquid to vapor;

3) the transition of molecules from vapor to liquid;

A.23.Vapor condensation is accompanied by…………..energy.

1) absorption; 2) isolation;

A.24. At the same temperature, the amount of heat released during condensation………..the amount (amount) of heat absorbed during evaporation.

1) more; 2) less; 3) equal.

A.25. Water of the same mass was poured into a plate and a glass. From which vessel will it evaporate faster under the same conditions

1) from a plate; 2) from a glass; 3) the same.

A.26. Will water evaporate in an open vessel at 0°C?

1) yes, evaporation occurs at any temperature;

2) no, at 0°C water hardens;

3) does not evaporate, the formation of steam occurs when the liquid boils.

A.27.Specific heat of vaporization of mercury 0.3*106 J/kg. That means for……energy.

1) the conversion of mercury 0.3 * 106 kg into steam at the boiling point requires 1 J;

2) the conversion of 1 kg of mercury into steam at the boiling point requires 0.3 * 106 J;

3) heating to the boiling point and turning into mercury vapor weighing 1 kg

0.3 * 106 J is required.

IN 1. Determine the amount of heat released during cooling and further

crystallization of water weighing 2 kg. The initial water temperature is 30°C.

IN 2. What amount of heat is required to heat 1 g of lead, the initial

whose temperature is 27o C.

C.1. How much heat is needed to melt 3 kg of ice

initial temperature -20оС, and heating of the formed water up to the temperature

C.2.In a vessel with water, having a temperature of 0 ° C, they let in 1 kg of centigrade

water vapor. After some time, the temperature of 20°C was established in the vessel.

Determine the mass of water initially in the vessel.

Testing in grade 8 following the results of the 1st half of the year is designed for 2 academic hours.

The test consists of three parts:

1) part A - choose the correct answer;

2) part B - solve the problem;

3) part C - solve a problem of increased complexity.

Evaluation criteria:

1) for each correctly completed task in part A-1 point;

2) for a correctly solved problem in part B-2 points;

3) for a correctly solved problem in the part C-3 points; at the same time, the solution of problems can be evaluated in parts of 1 point (the formulas are written correctly, the processes are named, the graphs of the processes are shown, etc.)

	Option 1	Option-2

Grade "5"- from 32 to 38 points;

"4"- from 24 to 31 points;

"3"- from 16 to 23 points;

"2"- 15 points.

MUNICIPAL BUDGET GENERAL EDUCATIONAL INSTITUTION

SECONDARY EDUCATIONAL SCHOOL № 3 with. ARZGIR

ARZGIR DISTRICT OF STAVROPOL KRAI

TOPIC OF THE LESSON:

SOLUTION OF PROBLEMS ON THE TOPIC: "MELTING AND HARDENING OF CRYSTALLINE BODIES

physics teacher MBOU secondary school №3

With. Arzgir, Arzgir region

Stavropol Territory

Kolesnik Ludmila Nikolaevna

2016

Program section: "Changing the Aggregate States of Matter"

Lesson topic: “Solving problems on the topic “Melting and solidification of crystalline bodies”.

Lesson Objectives:

educational: to deepen and consolidate the theoretical knowledge of students about the melting and solidification of crystalline bodies by solving problems

developing: in order to develop the logical thinking of students, teach them to compare and identify the common and distinctive in the studied phenomena

educational: to show the cognizability of the world and its patterns

Lesson type: Lesson practical application knowledge and skills

Type of lesson: Problem solving lesson

Equipment: handout, presentation

Methods and techniques: Verbal, visual, partially search

During the classes

Introductory speech of the teacher

Let's start the story about warmth,
Let's remember everything, summarize now
We will not bring brains to melting
We train them to the point of exhaustion!
We can overcome any challenge
And we can always help a friend!

Organizing time (readiness for the lesson, checking absentees).The teacher introduces the students to the topic of the lesson, the objectives of the lesson.

May this lesson bring you joy from communicating with each other, with me, and may your good answers and your knowledge of physics bring joy to everyone.

The first stage is testing and self-examination and speaking from a place by children.

Test: Melting and solidification of crystalline bodies.

1. The transition of a substance from a liquid state to a solid state is called

A. Melting.

B. Diffusion.

B. Hardening.

G. By heating.

D. Cooling.

2. Cast iron melts at 1200 0 C. What about the solidification temperature of cast iron?

A. Can be anyone.

B. Equal to 1200 0 WITH.

B. Above melting point

D. Below melting point.

3. What segment of the graph characterizes the process of heating a solid body?

A. AV.

B. Sun.

B. CD

4. In what units is the specific heat of fusion measured?

A. J / kg B. J / kg∙ O WITH V. J G. kg

5. The amount of heat released during the solidification of the body is ...

A. The workbody mass per specific heat of fusion.

B. The ratio of the specific heat of fusion to body weight.

B. The ratio of body weight to specific heat of fusion.

1. The transition of a substance from a solid to a liquid state is called

A. Cooling.

B. Hardening.

B. Diffusion.

G. By heating.

D. Melting.

2. Tin hardens at a temperature of 232 0 C. What can be said about its melting point?

A. Above curing temperature

B. Can be anyone.

V. Ravna 232 0 WITH.

D. Below curing temperature

3. Which segment of the graph characterizes the curing process?

A. AV.

B. Sun.

B. CD

4. The specific heat of fusion is the amount of heat required for ...

A. Heating a solid crystalline substance weighing 1 kg to the melting point.

B. Transformation into a liquid of a solid crystalline substance at the melting point.

B. Transformations at the melting temperature of a solid crystalline substance weighing 1 kg into a liquid.

5. Which of the formulas determines the amount of heat required to melt a substance?

A B C D.

Self control.

Check the correctness of the test yourself -open answers on the board and put + or - next to the answers. And now put the mark - according to the number of correct answers.Speak from who received 5,3,4 and what mistakes were made.

The second stage is work frontally with the class.

1. The figure shows a graph of heating and melting of a crystalline body.

I. What was the body temperature at the first observation?

1 . 300 °С; 2. 600 °C; 3. 100 °C; 4. 50 °C; 5. 550 °C.

IIAB?

III. What process on the graph characterizes the segmentBV?

1. Heating. 2. Cooling. 3. Melting. 4. Curing.

IV. At what temperature did the melting process begin?

1. 50 °C; 2. 100 °C; 3. 600 °C; 4. 1200 °C; 5. 1000 °C.

V. How long did it take for the body to melt?

1. 8 min; 2. 4 min; 3. 12 min; 4. 16 min; 5.7 min.

VI. Did body temperature change during melting?

1. Increased. 2. Decreased. 3. Has not changed.

VII. What process on the graph characterizes the segmentVG?

1. Heating. 2. Cooling. 3. Melting. 4. Curing.

VIII. What temperature was the body at the last observation?

50 °С; 2. 500 °C; 3. 550 °С; 4. 40 °C; 5. 1100 °C.

Two crucibles with the same amount of molten lead cool down in different rooms: warm and cold. In which of the graphs is built for a warm room and which one for a cold one?

Third stage- physical education minute.Exercises to relieve visual fatigue.

1. Close your eyes. Open eyes (5 times).

2. Circular eye movements. Do not rotate your head (10 times).

3. Without turning your head, look away as far to the left as possible. Don't blink. Look straight ahead. Blink several times. Close your eyes and rest. The same to the right (2-3 times).

4. Look at any object in front of you and turn your head to the right and left without taking your eyes off this object (2-3 times).

5. Look out the window into the distance for 1 minute.

The fourth stage is work with the text from the materials of the OGE in groups (task 20.21 of the OGE in physics.).

Children from the 3rd desk sit down on the 1st and 2nd desks of their row, the group works with the text from the OGE materials on the spot. Tex and questions are given on leaflets.

How solutions freeze

If a solution of any salt in water is cooled, it will be found that the crystallization temperature has decreased. Crystals will appear in the liquid only at a temperature a few degrees below zero degrees. The crystallization temperature depends on the concentration of the solution. It is the lower, the higher the concentration of the solution. For example, when 45 kg of table salt is dissolved in 1 m3 of water, the crystallization temperature decreases to -3 °C. The lowest temperature has a saturated solution, i.e. a solution containing the maximum possible amount of dissolved salt. In this case, the decrease in temperature is quite significant. So, a saturated solution of table salt in water crystallizes at a temperature of -21 ° C, and a saturated solution of calcium chloride - at a temperature of -55 ° C. Let's see how the crystallization process goes. After the first ice crystals appear in the solution, the concentration of the solution will increase. The relative number of salt molecules will increase, the interference with the water crystallization process will increase, and the crystallization temperature will decrease. If the temperature is not lowered further, crystallization will stop. With a further decrease in temperature, water crystals will continue to form, and the solution will become saturated. Further enrichment of the solution with the dissolved substance (salt) becomes impossible, and the solution solidifies immediately. If we consider the frozen mixture in , you can see that it consists of ice crystals and salt crystals. Thus, the solution freezes differently than a simple liquid. The freezing process extends over a large temperature interval.

What happens if you sprinkle some icy surface with salt? The answer to this question is well known to the janitors: as soon as the salt comes into contact with the ice, the ice will begin to melt. For the phenomenon to take place, it is, of course, necessary that the freezing point of a saturated salt solution be below the air temperature. When ice is mixed with salt, the ice melts and the salt dissolves in water. But melting requires heat, and ice takes it from its surroundings. As a result, the air temperature drops. Thus, adding salt to ice causes the temperature to drop.

Assignments to the text

Questions in the 1st row:

What happens to the crystallization temperature of a solution as the concentration of the solute increases?

What happens to air temperature when ice melts?

2nd row questions:

What happens when ice is mixed with salt?

How does the freezing process take place?

3rd row questions:

What prevents the freezing of water in solution?

What determines the crystallization temperature of a solution?

We discuss all the answers of the children aloud

Fifth stage- problem solving.

1. Recall the types of tasks for melting.

2. Recall the algorithm for solving problems.

Algorithm for solving problems for thermal calculations

1. Carefully read the condition of the problem, write it down using generally accepted letter designations; Express all quantities in the SI system.

2. Find out: a) between which bodies heat exchange occurs; b) which bodies in the process of heat exchange are cooled and which are heated; c) which processes described in the condition of the problem occur with the release, and which - with the absorption of energy.

3. Draw graphically the processes described in the tasks.

4. Write down the equation for calculating the given and received amount of heat.

5. Perform calculations and evaluate the reliability of the result.

Note:

a) Before solving the problem, be sure to pay attention to the temperature at which the substance proposed in the condition of the problem is located. If the substance has already been takenat melting point , then the problem is solved in one step:Q = λ m .

b) If the substance is takennot at melting point , then the problem is solved in three steps:

1) first you need to determine how much heat is needed to heat the substance from the initial temperaturet 1 up to melting pointt 2 according to the formula:

Q 1 = c m ( t 2 – t 1 );

2) then calculate the amount of heat required to melt the substance already at the melting point:Q 2 = λ m ;

3) determine the total amount of heatQ general = Q 1 + Q 2

3. Solving problems from the materials of the OGE in physics (1 person solves it at the blackboard)

Task. What amount of heat is needed to melt a piece of lead weighing 2 kg, taken at a temperature of 27 °C? (λ=0.25×10 5 J/kg, s=140J/(kg× O WITH))

1) 50 kJ

2) 78 kJ

3) 84 kJ

4) 134 kJ

Solution.

When melted, lead is absorbedwarmth, where- specific heat of fusion of lead. When heated, heat is absorbedwhereis the specific heat capacity of lead,t 2 =327 O C is the melting point of lead,t 1 =27 O C. In total, heat will be released during melting and heating:

0.25×10 5 ×2+140×2×(327-27)=50000+84000=1340000J.

Answer: 4.

Additional task. The figure shows a graph of the dependence of temperature on the amount of heat received for a substance weighing 2 kg. Initially, the substance was in a solid state. Determine the specific heat of fusion of the substance.

1) 25 kJ/kg

2) 50 kJ/kg

3) 64 kJ/kg

4) 128 kJ/kg

Solution.

The specific heat of fusion is the amount of energy required to melt a unit mass. On the graph, melting corresponds to a horizontal section. In this way,

The correct answer is number 1.

House. Work:

1. Repeat steps 12-15

2. Working with text from the OGE material in physics

Ice magic.
An interesting relationship is observed between the external pressure and the freezing (melting) point of water. With an increase in pressure to 2200 atmospheres, it drops: with an increase in pressure per atmosphere, the melting point decreases by 0.0075 ° C. With a further increase in pressure, the freezing point of water begins to rise: at a pressure of 3530 atmospheres, water freezes at 17 ° C, at 6380 atmospheres - at 0 ° C, and at 20,670 atmospheres - at 76 ° C. In the latter case, hot ice will be observed. At a pressure of 1 atmosphere, the volume of water increases sharply upon freezing (by about 11 %). In a closed space, such a process leads to the emergence of a huge overpressure. Water, freezing, breaks rocks, crushes multi-ton blocks. In 1872, the Englishman Bottomley was the first to experimentally discover the phenomenon of ice thinning. A wire with a load suspended on it is placed on a piece of ice. The wire gradually cuts ice at a temperature of 0°C, but after passing through the wire, the cut is covered with ice, and as a result, the piece of ice remains intact. For a long time it was thought that the ice under the blades of the skates melts because it is under strong pressure, the melting point of the ice drops - and the ice melts. However, calculations show that a person weighing 60 kilograms, standing on skates, exerts a pressure of about 15 atmospheres on the ice. This means that under the skates, the melting temperature of ice decreases only by 0.11 ° C. Such an increase in temperature is clearly not enough for the ice to begin to melt under the pressure of the skates when skating, for example, at -10 ° C.

Assignments to the text
1. How does the melting point of ice depend on external pressure?
2. Give two examples that illustrate the occurrence of excess pressure when water freezes.
3. Try to explain in your own words what the term “relationship” might mean.
4. In the course of what process can heat be released, which is used to melt ice when skating?

3. What amount of heat will be released during the crystallization of 2 kg of molten tin, taken at the crystallization temperature, and its subsequent cooling to 32 ° C?

1) 210 kJ 2) 156 kJ 3) 92 kJ 4) 14.72 kJ

Reflection.

Option 1

1. The amount of heat released during the solidification of the body depends on ...

A. The type of substance and its mass.

B. Body density and solidification temperature.

V. Curing temperatures and weights.

G. Body mass, solidification temperature and type of substance.

The figure shows a graph of changes in body temperature over time. Body weight 500 g, specific heat of fusion . After looking at the picture, answer questions 2-5.

2. What segment of the graph characterizes the process of heating the liquid?

A. AB.B. Sun.V. CD.

A. 600 °C.B. 650 °C.V. 700 °C.G. 750 °C.D. 900 °C.

A. 28 min.B. 10 min.V. 6 min.G. 20 minutes.D. 14 min.

A. 185,000 J

B. 185,000,000 J.

V. 740 J.

G. 740,000 J

D. 0.00135 J.

Option 2

1. The amount of heat transferred to the body during melting is ...

A. The ratio of body weight to specific heat of fusion.
B.

The figure shows a graph of changes in body temperature over time. Body weight 150 g, specific heat of fusion

2. Which section of the graph characterizes the curing process?

A. AB.B. Sun.V. CD.

3. At what temperature did curing end?
A. 1000 °C.

B. 1400 °C.

V. 1450 °C.

G. 1500 °C.
D. 1600 °C.

A. 8 min.B. 5 minutes.V. 13 min.G. 2 minutes.D. 15 minutes.

A. 0.005 J

B. 45,000,000 J.

V. 2,000,000 J
G. 45,000 J

D. 2000 J.

Graph of melting and solidification of crystalline bodies

Option 3

1. When a crystalline substance solidifies, ...

A. More heat than is absorbed by it during melting.B. The same amount of heat asswallowed when it melts.

V. Less amount of heat than is absorbed by it during melting.

The figure shows a graph of changes in body temperature over time. Body weight 250 g, specific heat of fusion . After looking at the picture, answer questions 2-5.

2. Which segment of the graph characterizes the process of heating a solid body?

A. AB.B. Sun.V. CD.

3. At what temperature did the melting end?
A. 30 °C.B. 140 °C.V. 160 °C.G. 180 °C.D. 200 °C.

4. How long did the body melt?

A. 18 min.B. 42 min.V. 30 minutes.G. 24 min.D. 8 min.

5. How much heat was spent on the melting process?

A. 0.58 J

B. 1720 J.

V. 107 500 J.
G. 1,720,000 J

D. 107,500,000 J.

Graph of melting and solidification of crystalline bodies

Option 4

1. The amount of heat spent on melting the body depends on ...

A. Body density and melting temperature.

B. Body mass, melting point and type of substance.

V. Melting points and masses.

G. The type of substance and its mass.

The figure shows a graph of changes in body temperature over time. Body weight 200 g, specific heat of fusion . After looking at the picture, answer questions 2-5.

2. What segment of the graph characterizes the process of liquid cooling?

A. AB.B. Sun.V. CD.

3. At what temperature did curing begin?

A. 1200 °C.V. 3400 °C.D. 4800 °C.

B. 3000 °C.G. 3500 °C.

4. How long did the body harden?

A. 24 min.B. 10 min.V. 18 min.G. 6 min.D. 8 min.

5. How much heat was released during the curing process?

A. 37,000,000 J.G. 925 J.

B. 925,000 JD. 37,000 J

V. 0.00108 J

Graph of melting and solidification of crystalline bodies

Option 5

1. The amount of heat released during the solidification of the body is ...

A. The product of the mass of the body and the specific heat of fusion.

B. The ratio of specific heat of fusion to body weight.

V. The ratio of body weight to specific heat of fusion.

The figure shows a graph of changes in body temperature over time. Body weight 400 g, specific heat of fusion . After looking at the picture, answer questions 2-5.

2. What segment of the graph characterizes the melting process?

A. AB.B. Sun.V. CD.

3. At what temperature did melting begin?

A. 10 °C.B. 20 °C.V. 250 °C.G. 270 °C.D. 300 °C.

4. How long did the body melt?

A. 6 min.B. 11 min.V. 4 min.G. 7 min.D. 14 min.

5. How much heat was spent on the melting process?

A. 0.008 J

B. 20,000 J

V. 125 J.
G. 20,000,000 J.

D. 125,000 J

Graph of melting and solidification of crystalline bodies

Option 6

1. The specific heat of fusion is the amount of heat required for ...

A. Heating a solid crystalline substance weighing 1 kg to the melting point.

B. Transformation into a liquid of a solid crystalline substance at a melting point.

V. Transformation at the melting temperature of a solid crystalline substance weighing 1 kg into a liquid.

The figure shows a graph of changes in body temperature over time. Body weight 750 g, specific heat of fusion . After looking at the picture, answer questions 2-5.

2. What segment of the graph characterizes the process of cooling a solid body?

A. AB.B. Sun.V. CD.

3. At what temperature did curing begin?
A. 520 °C.B. 420 °C.V. 410 °C.G. 400 °C.D. 80 °C.

4. How long did the body harden?

A. 6 min.B. 28 min.V. 10 min.G. 12 min.D. 18 min.

5. How much heat was released during the curing process?

A. 160,000 JV. 160 J.D. 0.00626 J.

B. 90,000,000 JG. 90,000 J

Melting and hardening chart

crystalline bodies

Test. Melting and solidification of crystalline bodies(work with charts)

Option I

I. What was the body temperature at the first observation?

1. Heating.

2. Cooling.

3. Melting.

4. Curing.

1. Heating.

2. Cooling.

3. Melting.

4. Curing.

IV. At what temperature did the melting process begin?

1. Increased.

2. Decreased.

3. Has not changed.

1. Heating.

2. Cooling.

3. Melting.

4. Curing.

Option II

II. What process on the graph characterizes segment AB?

1. Heating.

2. Cooling.

3. Melting.

4. Curing.

III. What process on the graph characterizes segment BC?

1. Heating.

2. Cooling.

3. Melting.

4. Curing.

1. Increased.

2. Decreased.

3. Has not changed.

VII. What process on the graph characterizes segment CD?

1. Heating.

2. Cooling.

3. Melting.

4. Curing.

VIII. What temperature was the body at the last observation?

Option III

The figure shows a graph of heating and melting of a crystalline body.

I. What temperature was the body at the time of the first observation?

1. 400°C. 2. 110°C. 3. 100°C.

4. 50°C. 5. 440°C.

II. What process on the graph characterizes segment AB?

1. Heating.

2. Cooling.

3. Melting.

4. Curing.

III. What process on the graph characterizes segment BC?

1. Heating.

2. Cooling.

3. Melting.

4. Curing.

IV. At what temperature did the melting process begin?

V. How long did the body melt?

VI. Did body temperature change during melting?

1. Increased.

2. Decreased.

3. Has not changed.

VII. What process on the graph characterizes segment CD?

1. Heating.

2. Cooling.

3. Melting.

4. Curing

VIII. What temperature was the body at the last observation?

Option IV

The figure shows a graph of cooling and solidification of a crystalline body.

I. What temperature was the body at the first observation?

II. What process on the graph characterizes segment AB?

1. Heating.

2. Cooling.

3. Melting.

4. Curing

III. What process on the graph characterizes segment BC?

1. Heating.

2. Cooling.

3. Melting.

4. Curing

IV. At what temperature did the curing process begin?

V. How long did the body harden?

VI. Did body temperature change during hardening?

1. Increased.

2. Decreased.

3. Has not changed.

VII. What process on the graph characterizes segment CD?

1. Heating.

2. Cooling.

3. Melting.

4. Curing

VIII. What temperature was the body at the last observation?

Goals and objectives of the lesson: improving the skills of graphical problem solving, repetition of basic physical concepts on this topic; development of oral and written speech, logical thinking; activation of cognitive activity through the content and degree of complexity of tasks; generating interest in the topic.

Lesson plan.

During the classes

Necessary equipment and materials: computer, projector, screen, whiteboard, Ms Power Point program, for each student : laboratory thermometer, test tube with paraffin, test tube holder, glass with cold and hot water, calorimeter.

Control:

Start presentation "F5 key", stop - "Esc key".

Changes of all slides are organized by clicking the left mouse button (or by pressing the right arrow key).

Return to the previous slide "left arrow".

I. Repetition of the studied material.

1. What aggregate states of matter do you know? (Slide 1)

2. What determines this or that state of aggregation of a substance? (Slide 2)

3. Give examples of finding a substance in various states of aggregation in nature. (Slide 3)

4. What is the practical significance of the phenomena of the transition of matter from one state of aggregation to another? (Slide 4)

5. What process corresponds to the transition of a substance from a liquid state to a solid state? (Slide 5)

6. What process corresponds to the transition of a substance from a solid state to a liquid? (Slide 6)

7. What is sublimation? Give examples. (Slide 7)

8. How does the speed of the molecules of a substance change during the transition from a liquid to a solid state?

II. Learning new material

In the lesson, we will study the process of melting and crystallization of a crystalline substance - paraffin, and plot these processes.

In the course of performing a physical experiment, we will find out how the temperature of paraffin changes during heating and cooling.

You will perform the experiment according to the descriptions for the work.

Before starting work, I will remind you of the safety rules:

By doing laboratory work be attentive and careful.

Safety engineering.

1. Calorimeters contain water 60? C, be careful.

2. Use caution when handling glassware.

3. If the device is accidentally broken, then inform the teacher, do not remove the fragments yourself.

III. Frontal physical experiment.

On the tables of the students there are sheets with a description of the work (Appendix 2), according to which they perform the experiment, build a graph of the process and draw conclusions. (Slides 5).

IV. Consolidation of the studied material.

Summing up the results of the frontal experiment.

Conclusions:

When heated paraffin in the solid state to a temperature of 50? C, the temperature increases.

During melting, the temperature remains constant.

When all the paraffin has melted, the temperature increases with further heating.

When liquid paraffin is cooled, the temperature decreases.

During crystallization, the temperature remains constant.

When all of the paraffin has solidified, the temperature decreases with further cooling.

Structural diagram: "Melting and solidification of crystalline bodies"

(Slide 12) Work according to the scheme.

Phenomena

Scientific facts

Hypothesis

Ideal object

Quantities

The laws

Application

When a crystalline body melts, the temperature does not change.

When a crystalline solid solidifies, the temperature does not change.

When a crystalline body melts, the kinetic energy of atoms increases, the crystal lattice is destroyed.

During solidification, the kinetic energy decreases and the crystal lattice is built.

A solid body is a body whose atoms are material points arranged in an orderly manner (crystal lattice), interacting with each other by forces of mutual attraction and repulsion.

Q is the amount of heat

Specific heat of fusion

Q = m - absorbed

Q = m - stands out

1. To calculate the amount of heat

2. For use in engineering, metallurgy.

3. thermal processes in nature (melting of glaciers, freezing of rivers in winter, etc.)

4. Write your examples.

The temperature at which a solid changes to liquid state, is called the melting point.

The crystallization process will also proceed at a constant temperature. It is called the crystallization temperature. In this case, the melting temperature is equal to the crystallization temperature.

Thus, melting and crystallization are two symmetrical processes. In the first case, the substance absorbs energy from the outside, and in the second - it gives it to the environment.

Different melting temperatures determine the applications of different solids in everyday life, technology. Refractory metals are used to make heat-resistant structures in aircraft and rockets, nuclear reactors and electrical engineering.

Consolidation of knowledge and preparation for independent work.

1. The figure shows a graph of heating and melting of a crystalline body. (Slide)

2. For each of the situations listed below, select a graph that most accurately reflects the processes occurring with the substance:

a) copper is heated and melted;

b) zinc is heated to 400°C;

c) melting stearin is heated to 100°C;

d) iron taken at 1539°C is heated to 1600°C;

e) tin is heated from 100 to 232°C;

f) aluminum is heated from 500 to 700°C.

Answers: 1-b; 2-a; 3-in; 4-in; 5 B; 6-d;

The graph reflects observations of the change in temperature of two

crystalline substances. Answer the questions:

(a) At what time did the observation of each substance begin? How long did it last?

b) Which substance began to melt first? Which substance melted first?

c) State the melting point of each substance. Name the substances whose heating and melting graphs are shown.

4. Is it possible to melt iron in an aluminum spoon?

5.. Is it possible to use a mercury thermometer at the Pole of Cold, where the lowest temperature was recorded - 88 degrees Celsius?

6. The combustion temperature of powder gases is about 3500 degrees Celsius. Why doesn't the barrel of a gun melt when fired?

Answers: It is impossible, since the melting point of iron is much higher than the melting point of aluminum.

5. It is impossible, since mercury will freeze at this temperature, and the thermometer will fail.

6. It takes time to heat and melt a substance, and the short duration of the combustion of gunpowder does not allow the gun barrel to heat up to the melting point.

4. Independent work. (Appendix 3).

Option 1

Figure 1a shows a graph of heating and melting of a crystalline body.

I. What was the body temperature at the first observation?

1. 300 °C; 2. 600 °C; 3. 100 °C; 4. 50 °C; 5. 550 °C.

II. Which process on the graph characterizes segment AB?

III. What process on the graph characterizes the BV segment?

1. Heating. 2. Cooling. 3. Melting. 4. Curing.

IV. At what temperature did the melting process begin?

1. 50 °C; 2. 100 °C; 3. 600 °C; 4. 1200 °C; 5. 1000 °C.

V. How long did the body melt?

1. 8 min; 2. 4 min; 3. 12 min; 4. 16 min; 5.7 min.

VI. Did body temperature change during melting?

VII. What process on the graph characterizes the segment VG?

1. Heating. 2. Cooling. 3. Melting. 4. Curing.

VIII. What temperature was the body at the last observation?

1. 50 °C; 2. 500 °C; 3. 550 °С; 4. 40 °C; 5. 1100 °C.

Option 2

Figure 101.6 shows a graph of cooling and solidification of a crystalline body.

I. What temperature was the body at the first observation?

1. 400 °C; 2. 110°C; 3. 100 °C; 4. 50 °C; 5. 440 °C.

II. Which process on the graph characterizes segment AB?

1. Heating. 2. Cooling. 3. Melting. 4. Curing.

III. What process on the graph characterizes the BV segment?

1. Heating. 2. Cooling. 3. Melting. 4. Curing.

IV. At what temperature did the curing process begin?

1. 80 °C; 2. 350 °C; 3. 320 °С; 4. 450 °C; 5. 1000 °C.

V. How long did the body harden?

1. 8 min; 2. 4 min; 3. 12 min;-4. 16 min; 5.7 min.

VI. Did body temperature change during hardening?

1. Increased. 2. Decreased. 3. Has not changed.

VII. What process on the graph characterizes the segment VG?

1. Heating. 2. Cooling. 3. Melting. 4. Curing.

VIII. What temperature was the body at the time of the last observation?

1. 10 °C; 2. 500 °C; 3. 350 °C; 4. 40 °C; 5. 1100 °C.

Summing up the results of independent work.

1 option

I-4, II-1, III-3, IV-5, V-2, VI-3, VII-1, VIII-5.

Option 2

I-2, II-2, III-4, IV-1, V-2, VI-3, VII-2, VIII-4.

Additional material: Watch the video: "Ice melting at t<0C?"

Student reports on the use of melting and crystallization in industry.

Homework.

14 textbooks; questions and tasks for the paragraph.

Tasks and exercises.

Collection of problems by V. I. Lukashik, E. V. Ivanova, No. 1055-1057

Bibliography:

Peryshkin A.V. Physics grade 8. - M.: Bustard. 2009.
Kabardin O. F. Kabardina S. I. Orlov V. A. Tasks for the final control of students' knowledge in physics 7-11. - M.: Enlightenment 1995.
Lukashik V. I. Ivanova E. V. Collection of problems in physics. 7-9. - M.: Enlightenment 2005.
Burov V. A. Kabanov S. F. Sviridov V. I. Frontal experimental tasks in physics.
Postnikov AV Checking students' knowledge in physics 6-7. - M.: Enlightenment 1986.
Kabardin OF, Shefer NI Determination of solidification temperature and specific heat of paraffin crystallization. Physics at school No. 5 1993.
Video cassette "School physical experiment"
Pictures from sites.