Test. Melting and solidification of crystalline bodies(working with charts)
Option I
I. What was the body temperature when first observed?
1. Heating.
2. Cooling.
3. Melting.
4. Hardening.
1. Heating.
2. Cooling.
3. Melting.
4. Hardening.
IV. At what temperature did the melting process begin?
1. Increased.
2. Decreased.
3. Has not changed.
1. Heating.
2. Cooling.
3. Melting.
4. Hardening.
Option II
II. What process on the graph characterizes segment AB?
1. Heating.
2. Cooling.
3. Melting.
4. Hardening.
III. What process on the graph characterizes segment BC?
1. Heating.
2. Cooling.
3. Melting.
4. Hardening.
1. Increased.
2. Decreased.
3. Has not changed.
VII. What process on the graph characterizes the segment CD?
1. Heating.
2. Cooling.
3. Melting.
4. Hardening.
VIII. What was the temperature of the body when last observed?
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 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. Hardening.
III. What process on the graph characterizes segment BC?
1. Heating.
2. Cooling.
3. Melting.
4. Hardening.
IV. At what temperature did the melting process begin?
V. How long did it take for the body to melt?
VI. Did the body temperature change during melting?
1. Increased.
2. Decreased.
3. Has not changed.
VII. What process on the graph characterizes the segment CD?
1. Heating.
2. Cooling.
3. Melting.
4. Hardening
VIII. What was the temperature of the body when last observed?
Option IV
The figure shows a graph of the cooling and solidification of a crystalline body.
I. What temperature was the body when first observed?
II. What process on the graph characterizes segment AB?
1. Heating.
2. Cooling.
3. Melting.
4. Hardening
III. What process on the graph characterizes segment BC?
1. Heating.
2. Cooling.
3. Melting.
4. Hardening
IV. At what temperature did the hardening process begin?
V. How long did it take for the body to harden?
VI. Did your body temperature change during curing?
1. Increased.
2. Decreased.
3. Has not changed.
VII. What process on the graph characterizes the segment CD?
1. Heating.
2. Cooling.
3. Melting.
4. Hardening
VIII. What was the temperature of the body when last observed?
MUNICIPAL BUDGETARY EDUCATIONAL INSTITUTION
SECONDARY SCHOOL No. 3 village. ARZGIR
ARZGIRSKY DISTRICT OF STAVROPOL REGION
LESSON TOPIC:
SOLVING PROBLEMS ON THE TOPIC: “MELTING AND SOLIDIFICATION OF CRYSTAL BODIES
Physics teacher MBOU Secondary School No. 3
With. Arzgir, Arzgir district
Stavropol Territory
Kolesnik Lyudmila Nikolaevna
2016
Program section: “Changes in 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 students’ theoretical knowledge about the melting and solidification of crystalline bodies by solving problems
developmental: in order to develop students’ logical thinking, teach them to compare and identify common and distinctive features in the phenomena being studied
educational: show the knowability of the world and its patterns
Lesson type: Lesson in practical application of knowledge and skills
Lesson type: Problem Solving Lesson
Equipment: handouts, presentation
Methods and techniques: Verbal, visual, partially search
During the classes
Teacher's opening speech
Let's start a story about warmth,
Let's remember everything, summarize now
We won't let our brains melt
We train them until exhaustion!
We can overcome any challenge
And we can always help a friend!
Organizing time (readiness for the lesson, checking absences).The teacher introduces students to the topic of the lesson and 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 pronunciation by children.
Test: Melting and solidification of crystalline bodies.
1. The transition of a substance from a liquid to a solid state is calledA. Melting.
B. Diffusion.
B. Hardening.
D. Heating.
D. Cooling.
2. Cast iron melts at a temperature of 1200 0 C. What can be said about the solidification temperature of cast iron?
A. Can be anyone.
B. Equal to 1200 0 WITH.
B. Above the melting point
D. Below the melting point.
3. Which segment of the graph characterizes the process of heating a solid?
A. AB.
B. VS.
V.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 solidification of the body is ...
A. To the workbody weight to the specific heat of fusion.
B. The ratio of the specific heat of fusion to body weight.
B. The ratio of body mass to specific heat of fusion.
1. The transition of a substance from solid to liquid is called
A. Cooling.
B. Hardening.
B. Diffusion.
D. Heating.
D. Melting.
2. Tin hardens at a temperature of 232 0 C. What can be said about its melting point?
A. Above the curing temperature
B. Can be anyone.
V. Ravna 232 0 WITH.
D. Below the curing temperature
3. Which segment of the graph characterizes the solidification process?
A. AB.
B. VS.
V.CD
4. 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 of a solid crystalline substance into liquid at the melting point.
B. Transformation at the melting point of a solid crystalline substance weighing 1 kg into a liquid.
5. Which formula is used to determine the amount of heat required to melt a substance?
A B C D.
Self-control.
Check to see if the test is running correctly -open answers on the board and put + or – next to the answers. Now give your rating according to the number of correct answers.Talk to who got 5,3,4 and what mistakes were made.
The second stage is working frontally with the class.
1. The figure shows a graph of heating and melting of a crystalline body.
I. What was your body temperature when you first observed it?
1 . 300 °C; 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. Hardening.
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 the 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. Hardening.
VIII. What was the temperature of the body when last observed?
50 °C; 2. 500 °C; 3. 550 °C; 4. 40 °C; 5. 1100 °C.
Two crucibles with the same amount of molten lead are cooled in different rooms: warm and cold. Which graph is built for a warm room and which for a cold one?
Third stage- physical education minute.Exercises to relieve visual fatigue.
1. Close your eyes. Open your eyes (5 times).
2. Circular movements with the eyes. Do not rotate your head (10 times).
3. Without turning your head, look as far to the left as possible. Don't blink. Look straight ahead. Blink a few times. Close your eyes and relax. 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 working with text from the OGE materials in groups (task 20,21 OGE in physics.).
Children from desk 3 sit on desks 1 and 2 in their row, and the group works with the text from the OGE materials on the spot. The text and questions are given on pieces of paper.
How do solutions freeze?
If you cool a solution of a salt in water, you will find that the crystallization temperature has decreased. Crystals will appear in the liquid only at a temperature several degrees below zero degrees. The crystallization temperature depends on the concentration of the solution. The higher the concentration of the solution, the lower it is. For example, when 45 kg of table salt is dissolved in 1 m3 of water, the crystallization temperature decreases to –3 °C. A saturated solution has the lowest temperature, i.e. a solution containing the maximum possible amount of dissolved salt. At the same time, the temperature decrease is quite significant. Thus, 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 consider how the crystallization process occurs. After the first ice crystals appear in the solution, the concentration of the solution will increase. The relative number of salt molecules will increase, interference with the water crystallization process will increase, and the crystallization temperature will decrease. If you do not lower the temperature further, crystallization will stop. As the temperature decreases further, 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 salt on some icy surface? The answer to the question is well known to 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 necessary, of course, that the freezing point of a saturated salt solution be lower than the air temperature. When ice and salt are mixed, the ice melts and the salt dissolves in the water. But melting requires heat, and ice takes it from its surroundings. As a result, the air temperature decreases. Thus, adding salt to ice causes the temperature to drop.
Assignments to the text
Questions in row 1:
What happens to the crystallization temperature of a solution as the concentration of the solute increases?
What happens to air temperature when ice melts?
Questions for row 2:
What happens when you mix ice and salt?
How does the solution freeze process?
Questions for row 3:
What prevents the process of freezing water in a solution?
What does the crystallization temperature of a solution depend on?
We discuss all the children's answers out loud
Fifth stage- problem solving.
1. Remember the types of melting problems.
2. Remember the algorithm for solving problems.
Algorithm for solving problems on thermal calculations
1. Carefully read the problem statement, write it down using generally accepted letter notations; Express all quantities in the SI system.
2. Find out: a) between which bodies heat exchange occurs; b) which bodies are cooled and which are heated during the heat exchange process; c) which processes described in the problem statement occur with the release and which with the absorption of energy.
3. Graphically depict the processes described in the task.
4. Write down an equation to calculate the amount of heat given and received.
5. Perform calculations and evaluate the reliability of the result obtained.
Note:
a) Before solving the problem, be sure to pay attention to the temperature at which the substance proposed in the problem statement is located. If the substance has already been takenat melting point , then the problem is solved in one action: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 OGE materials in physics (1 person solves it at the board)
Task. What amount of heat is required to melt a 2 kg piece of lead 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 melting lead is absorbed
warmth, where- specific heat of fusion of lead. When heated, heat is absorbedWhere- specific heat capacity of lead,t 2
=327
O C is the melting point of lead,t 1
=27
O C. Total heat 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 the horizontal section. Thus,
The correct answer is listed under number 1.
House. Job:
1. Repeat steps 12-15
2. Working with text from the OGE material in physics
Ice magic.
An interesting relationship is observed between external pressure and the freezing (melting) point of water. With an increase in pressure to 2200 atmospheres, it decreases: 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 increase: 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 when it freezes increases sharply (by about 11 %). In a confined space, such a process leads to the emergence of enormous excess pressure. When water freezes, it tears apart rocks and crushes multi-ton blocks. In 1872, the Englishman Bottomley first experimentally discovered the phenomenon of ice thinning. A wire with a weight suspended on it is placed on a piece of ice. The wire gradually cuts ice at a temperature of 0°C, but after passing the wire, the cut is covered with ice, and as a result, a piece of ice remains intact. For a long time it was thought that the ice under the blades of skates melts because it experiences strong pressure, the melting point of the ice decreases - and the ice melts. However, calculations show that a person weighing 60 kilograms, standing on skates, exerts a pressure of approximately 15 atmospheres on the ice. This means that under skates the melting temperature of ice decreases by only 0.11 ° C. This increase in temperature is clearly not enough for the ice to melt under the pressure of skates when skating, for example at -10 °C.
Assignments to the text
1. How does the melting temperature 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 “resolution” might mean.
4. During what process can heat be released that goes into melting 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 11. The amount of heat released during solidification of the body depends on...
A. The type of substance and its mass.
B. Body density and solidification temperature.
IN. Solidification temperatures and masses.
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. Which segment of the graph characterizes the process of heating the liquid?
A. AB.B. Sun.IN. CD.
A. 600 °C.B. 650 °C.IN. 700 °C.G. 750 °C.D. 900 °C.
A. 28 min.B. 10 min.IN. 6 min.G. 20 minutes.D. 14 min.
A. 185,000 J.
B. 185,000,000 J.
IN. 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 mass to specific heat of fusion.
B.
B.
The figure shows a graph of changes in body temperature over time. Body weight 150 g, specific heat of fusion
2. Which segment of the graph characterizes the solidification process?
A. AB.B. Sun.IN. CD.
3. At what temperature did curing end?
A.
1000 °C.
B. 1400 °C.
IN. 1450 °C.
G.
1500 °C.
D.
1600 °C.
A. 8 min.B. 5 minutes.IN. 13 min.G. 2 minutes.D. 15 minutes.
A. 0.005 J.
B. 45,000,000 J.
IN.
2,000,000 J.
G.
45,000 J.
D. 2000 J.
Graph of melting and solidification of crystalline solids
Option 3
1. When a crystalline substance hardens, it releases...
A. More heat than is absorbed by it during melting.B. The same amount of heat asis absorbed when it melts.
IN. Less 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?
A. AB.B. Sun.IN. CD.
3. At what temperature did melting end?
A.
30 °C.B.
140 °C.IN.
160 °C.G.
180 °C.D.
200 °C.
4. How long did the body take to melt?
A. 18 min.B. 42 min.IN. 30 min.G. 24 min.D. 8 min.
5. How much heat was spent on the melting process?
A. 0.58 J.
B. 1720 J.
IN.
107,500 J.
G.
1,720,000 J.
D. 107,500,000 J.
Graph of melting and solidification of crystalline solids
Option 4
1. The amount of heat spent on melting a body depends on...
A. Body density and melting point.
B. Body mass, melting point and type of substance.
IN. Melting point and mass.
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. Which segment of the graph characterizes the process of cooling the liquid?
A. AB.B. Sun.IN. CD.
3. At what temperature did hardening begin?
A. 1200 °C.IN. 3400 °C.D. 4800 °C.
B.
3000 °C.G.
3500 °C.
4. How long did the body take to harden?
A. 24 min.B. 10 min.IN. 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 J.D. 37,000 J.
IN.
0.00108 J.
Graph of melting and solidification of crystalline solids
Option 5
1. The amount of heat released during solidification of the body is...
A. The product of body mass and specific heat of fusion.
B. The ratio of the specific heat of fusion to body weight.
IN. The ratio of body mass 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. Which segment of the graph characterizes the melting process?
A. AB.B. Sun.IN. CD.
3. At what temperature did melting begin?
A. 10 °C.B. 20 °C.IN. 250 °C.G. 270 °C.D. 300 °C.
4. How long did the body take to melt?
A. 6 min.B. 11 min.IN. 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.
IN.
125 J.
G.
20,000,000 J.
D. 125,000 J.
Graph of melting and solidification of crystalline solids
Option 6
1. 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. The transformation of a crystalline solid into a liquid at its melting point.
IN. Transformation of a solid crystalline substance weighing 1 kg into a liquid at the melting point.
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. Which segment of the graph characterizes the process of cooling a solid?
A. AB.B. Sun.IN. CD.
3. At what temperature did hardening begin?
A.
520 °C.B.
420 °C.IN.
410 °C.G.
400 °C.D.
80 °C.
4. How long did the body take to harden?
A. 6 min.B. 28 min.IN. 10 min.G. 12 min.D. 18 min.
5. How much heat was released during the curing process?
A. 160,000 J.IN. 160 J.D. 0.00626 J.
B. 90,000,000 J.G. 90,000 J.
Melting and solidification schedule
crystalline bodies
“Thermal phenomena. Aggregate states of matter" 8th grade.
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 higher than the melting point;
A.2. At what temperature does mercury acquire a crystalline state?
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 1000o C. Which metal is in an unmolten state?
1) zinc; 2) tin; 3) iron.
A.4. The gas leaving the nozzle of a jet aircraft has a temperature of 500oC-700oC. Can the nozzle be made of aluminum?
1) can; 2) it is impossible.
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 it take for the body to melt?
1) 8 min.; 3) 12 min; 5) 7 min.
2) 3min; 4) 16 min;
A.10. Did your 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) 500oC; 4) 40o C;
A.13. Molecules in crystals are located:
A.14. When bodies are heated, the average speed of movement of molecules is:
A.15. What can be said about the internal energy of water weighing 1 kg. at a temperature
0° C and ice weighing 1 kg at the same temperature?
1) the internal energy of water and ice is the same;
2) ice has high internal energy;
3) water has high internal energy.
A.16. What energy is required to melt 1 kg of lead at a temperature of 327o 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 ice drift, the air temperature near the river is……….. than far from it. This is explained by the fact that energy………..melting ice.
1) higher……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 its 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 its 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 produced by melting scrap iron in open hearth furnaces. What energy is required to melt scrap iron weighing 5 tons at a temperature of 10°C? The melting point of steel was set to 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 the phenomenon:
1) the transition of molecules into vapor from the surface and inside the liquid;
A.23.Evaporation occurs:
1) at boiling point;
2) at any temperature;
3) at a certain temperature for each liquid.
A.24. If there is no flow of energy to the liquid from other bodies, then during its evaporation 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. What state of aggregation will zinc be in at the boiling point of mercury and normal atmospheric pressure?
1) in solid; 2) in liquid; 3) in gaseous form.
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 2.3*106 J greater than the internal energy of water;
3) the internal energy of steam is 2.3*106 J less than the internal energy of water;
IN 1. Determine the amount of heat required to convert 8 kg of ether into steam,
taken at a temperature of 10°C.
AT 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.
S.1. What is the final temperature if 500g of ice is at
0°C immerse in 4 liters of water at a temperature of 30°C.
C.1.How much wood needs to be burned in the stove, efficiency = 40%, to get 200 kg of snow,
taken at a temperature of 10°C, water at 20°C.
“Thermal phenomena. Aggregate states of matter" 8th grade.
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 metal - 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 a rocket during flight rises to 1500°C-2000°C. What metal is suitable for making the outer skin of a rocket?
1) tin; 3) steel;
2) copper; 4) tungsten.
A.5.What was the temperature at the first moment of observation?
A.6. What process on the graph characterizes segment AB?
1) heating; 3) melting;
2) cooling; 4) hardening.
A.7.What process on the graph characterizes the segment BV?
1) heating; 3) melting;
2) cooling; 4) hardening.
A.8. At what temperature did the hardening 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) 8 min.; 3) 12 min; 5) 7 min.
2) 4min; 4) 16 min;
A.10. Did your body temperature change during curing?
1) has it increased? 2) decreased; 3) has not changed.
A.11. What process on the graph characterizes the VG segment?
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. The molecules in the 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) chaotically, not staying in certain places;
2) near the equilibrium position, holding;
3) near the equilibrium position, without holding 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 327o C?
1) the internal energy is the same;
2) the internal energy of molten lead is greater than that of unmolten lead;
3) the internal energy of unmolten lead is greater than that of molten lead;
A.16. What energy will be released when 1 kg of aluminum solidifies 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 brought into a room with an air temperature of 0°C. Will the ice melt?
1) will be, since ice melts at 0°C;
2) there will be no, since there will be no influx of energy;
3) will be, since energy is borrowed from other bodies.
A.18. During heavy snowfall in winter, the air temperature……….., because when the water droplets formed from the clouds solidify…………..energy.
1) increases……….absorbed;
2) decreases………..stands out;
3) increases……….stands out;
4) decreases………..absorbed.
A.19. What energy is required to melt 1 kg of tin at its 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 its melting point?
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 weighing 2 tons at a temperature of 25°C? The melting point of copper is taken to be 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 inside the liquid;
2) transition of molecules from liquid to vapor;
3) transition of molecules from vapor to liquid;
A.23.Condensation of steam 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 solidifies;
3) does not evaporate; vapor is formed when the liquid boils.
A.27.The specific heat of vaporization of mercury is 0.3*106 J/kg. This means that for......energy.
1) transformation of mercury 0.3 * 106 kg into steam at boiling point requires 1 J;
2) converting 1 kg of mercury into steam at the boiling point requires 0.3 * 106 J;
3) heating to boiling point and turning mercury weighing 1 kg into vapor
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.
AT 2. What amount of heat is required to heat 1g of lead, initial
whose temperature is 27o C.
S.1. What amount of heat is required to melt 3 kg of ice having
initial temperature - 20°C, and heating of the resulting water to a temperature
C.2.1 kg of centigrade
water vapor. After some time, the temperature in the vessel reached 20°C.
Determine the mass of water initially contained in the vessel.
Testing in 8th grade based on 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 part C-3 points; in this case, the solution of problems can be assessed in parts of 1 point (formulas are written correctly, processes are named, process graphs are depicted, 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.
Goals and objectives of the lesson: improving skills in 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, blackboard, 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 the presentation "F5 key", stop - "Esc key".
Changes of all slides are organized by clicking the left mouse button (or using the right arrow key).
Return to previous slide "left arrow".
I. Repetition of the studied material.
1. What 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 the presence of a substance in various states of aggregation in nature. (Slide 3)
4. What practical significance are the phenomena of the transition of a substance from one state of aggregation to another? (Slide 4)
5. What process corresponds to the transition of a substance from a liquid 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 molecules of a substance change when transitioning from a liquid to a solid state?
II. Learning new material
In this lesson we will study the process of melting and crystallization of a crystalline substance - paraffin, and build a graph of these processes.
In the course of performing a physical experiment, we will find out how the temperature of paraffin changes when heated and cooled.
You will perform the experiment according to the descriptions for the work.
Before performing work, I would like to remind you of the safety rules:
Be careful and careful when performing laboratory work.
Safety precautions.
1. The calorimeters contain water at 60°C, be careful.
2. Be careful when working with glassware.
3. If you accidentally break the device, then inform the teacher; do not remove the fragments yourself.
III. Frontal physical experiment.
On the students’ desks there are sheets with a description of the work (Appendix 2), on 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 paraffin in the solid state is heated to a temperature of 50? C, the temperature increases.
During the melting process, the temperature remains constant.
When all the paraffin has melted, the temperature increases with further heating.
As liquid paraffin cools, the temperature decreases.
During the crystallization process, the temperature remains constant.
When all the paraffin has hardened, 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 | Laws | Application |
| When a crystalline body melts, the temperature does not change. When a crystalline body solidifies, the temperature does not change |
When a crystalline body melts, the kinetic energy of the atoms increases and the crystal lattice is destroyed. During hardening, the kinetic energy decreases and a crystal lattice is built. |
A solid body is a body whose atoms are material points, arranged in an orderly manner (crystal lattice), interact with each other by forces of mutual attraction and repulsion. | Q - amount of heat Specific heat of fusion |
Q = m - absorbed Q = m - highlighted |
1. To calculate the amount of heat 2. For use in technology and metallurgy. 3. thermal processes in nature (melting glaciers, freezing of rivers in winter, etc. 4. Write your own examples. |
The temperature at which the transition of a solid to a liquid occurs is called the melting point.
The crystallization process will also occur 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 releases it into the environment.
Different melting temperatures determine the areas of application of various solids in everyday life and 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-g;
The graph shows observations of temperature changes in two
crystalline substances. Answer the questions:
a) At what points in time did observation of each substance begin? How long did it last?
b) Which substance began to melt first? Which substance melted first?
c) Indicate 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 cold pole, where the lowest temperature was recorded - 88 degrees Celsius?
6. The combustion temperature of powder gases is about 3500 degrees Celsius. Why doesn't a gun barrel 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 the 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 combustion of gunpowder does not allow the gun barrel to heat up to the melting temperature.
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 when first observed?
1. 300 °C; 2. 600 °C; 3. 100 °C; 4. 50 °C; 5. 550 °C.
II. What process on the graph characterizes segment AB?
III. What process on the graph characterizes the segment BV?
1. Heating. 2. Cooling. 3. Melting. 4. Hardening.
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 the body temperature change during melting?
VII. What process on the graph characterizes the VG segment?
1. Heating. 2. Cooling. 3. Melting. 4. Hardening.
VIII. What was the temperature of the body when last observed?
1. 50 °C; 2. 500 °C; 3. 550 °C; 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 when first observed?
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. Hardening.
III. What process on the graph characterizes the segment BV?
1. Heating. 2. Cooling. 3. Melting. 4. Hardening.
IV. At what temperature did the hardening process begin?
1. 80 °C; 2. 350 °C; 3. 320 °C; 4. 450 °C; 5. 1000 °C.
V. How long did it take for the body to harden?
1. 8 min; 2. 4 min; 3. 12 min;-4. 16 min; 5. 7 min.
VI. Did your body temperature change during curing?
1. Increased. 2. Decreased. 3. Has not changed.
VII. What process on the graph characterizes the VG segment?
1. Heating. 2. Cooling. 3. Melting. 4. Hardening.
VIII. What temperature was the body at the time of 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: "melting ice at t<0C?"
Student reports on industrial applications of melting and crystallization.
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 8th grade. - M.: Bustard.2009.
- Kabardin O. F. Kabardina S. I. Orlov V. A. Assignments for the final control of students’ knowledge in physics 7-11. - M.: Education 1995.
- Lukashik V.I. Ivanova E.V. Collection of problems in physics. 7-9. - M.: Education 2005.
- Burov V. A. Kabanov S. F. Sviridov V. I. Frontal experimental tasks in physics.
- Postnikov A.V. Testing students' knowledge in physics 6-7. - M.: Education 1986.
- Kabardin O. F., Shefer N. I. Determination of the solidification temperature and specific heat of crystallization of paraffin. Physics at school No. 5 1993.
- Videotape "School physics experiment"
- Pictures from websites.