Target:development of practical skills in working with physical equipment.

move lesson

I. Organizing time

II. Repetition of what has been learned.

Checking homework

After checking the completion of the tasks solved at home and listening to the answers to § 36, the teacher can ask the class a number of more questions to repeat what has been learned, for example:

- Give examples of the transformation of mechanical energy into

internal and internal to mechanical.

- Give examples of the transfer of energy from one body to another.

- What experience shows that during the transition internal energy from

one body to another its meaning is preserved?

III. Laboratory work

Before starting work, students should briefly familiarize themselves with the safety rules. Glass, thermometers and hot water are used in the work, therefore, to avoid burns, the temperature of hot water should not exceed 60 ° C.

If mercury thermometers are used during work, then after measuring the temperature, the thermometers are immediately put into the case. The working position of the measuring cylinders is horizontal.

The work must be mobile enough. This will reduce the errors in the calculations. Thermometer readings can be taken 15-20 seconds after the start of temperature measurement. This time is sufficient to establish thermal equilibrium "thermometer-liquid".

Since the work is related to the application measuring instruments, then before taking measurements, it is necessary to determine and write down in the notebook the division value of the measuring cylinder and thermometer. Usually for school appliances C\\u003d 1 cm / div, and C g\u003d 1 ° С / div.

The main content of the work is the verification of the law of conservation of thermal energy in a closed system.

In this case, the amount of heat given off by hot water when mixed with cold water must be equal to the amount of heat received by cold water:

Watd ~~ Do the floor

where t\ - mass of hot watert\ - initial hot water temperature, t 2 - mass of cold watert 2 - initial temperature of cold water, in- mixture temperature. But in practice, most students with correct calculations d td F Q aan.

Therefore, in the conclusions on the work, it is necessary to note those reasons that lead to the violation of the equality

If there is not enough equipment in the school laboratory, you can split the class into two groups. First, one group does the work directly, and the second one solves one or two simple tasks on the topic. Then the groups change places. The scope of this work allows you to organize the work in this way.

Task 1

How will the temperature of 200 g of water change if a copper ball of mass 50 g heated to a temperature of 150 ° C is lowered into water. The initial water temperature is 10 °C.

Task 2

When will the water in the vessel be heated to higher temperature: if an iron ball heated to a temperature of 100 ° C is lowered into it, or an aluminum ball heated to the same temperature? The masses of the balls are the same.

Homework .

Repeat what you have learned

Presentation for performing laboratory work, explains the order of execution, helps children correctly calculate the amount of heat and draw a conclusion on the work done. Helps the teacher to carry out laboratory work.

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Slides captions:

Laboratory work No. 1 _____________________ date Comparison of the amount of heat when mixing water different temperatures. Lab #1

Purpose: Checking the Equation heat balance(compare the amount of heat given off by hot water and received by cold water, and explain the result). Equipment: calorimeter, beaker, thermometer, vessel with cold water, hot water.

Safety regulations. Carefully! Hot water! Glass! Be careful when working with hot water. Do not spill water - burns are possible. Be careful when working with glassware (thermometer, glass, beaker). Remember, glass is a brittle material, easily cracked by impacts and sudden changes in temperature. The mercury contained in the thermometer is poisonous! Take data without taking the thermometer out of the liquid! There should be no foreign objects on the table. I have read the rules and agree to abide by them. ____________________________ Student Signature

Progress: Measure out 100 ml of cold water with a beaker. Mass of cold water m1 \u003d 100 g Measure the temperature of cold water t 1 \u003d ______ ºС with a thermometer. Use a beaker to measure out 100 ml of hot water. Mass of hot water m 2 \u003d 100 g. Pour hot water weighing 100 g into the inner glass of the calorimeter. Measure the temperature of hot water t 2 \u003d _______ ºС with a thermometer. Pour cold water into the hot water calorimeter. Carefully stirring the water, measure the temperature of the resulting mixture t = __________ ºС.

7. Calculate the amount of heat Q 2 given away by hot water according to the formula: Q 2 \u003d c m 2 (t2 - t) Q 2 \u003d __________________________________________________________________________ J. 8. Calculate the amount of heat Q 1 received by cold water according to the formula: Q 1 \u003d c m 1 (t - t 1) Q 1 \u003d __________________________________________________________________________ J.

9. Record the results of measurements and calculations in the table. Mass of cold water m 1, kg Initial temperature cold water t 1, ºС Temperature of the resulting mixture t, ºС Amount of heat received by cold water Q 1, J Mass of hot water m 2, kg Initial temperature of hot water t 2, ºС Amount of heat given off by hot water Q 2, J

10. Compare the amount of heat Q 1 and Q 2. Draw the appropriate conclusion. CONCLUSION: _______________________________________________________________ ______________________________________________________________________________________________________________________________________________ ______________________________________________________________________________________________________________________________________________

CONTROL QUESTIONS: How is heat transferred from hot water to cold water? ____________ ________________________________________________________________________________________________________________________________ What is called the heat balance equation? ___________________________ ________________________________________________________________________________________________________________________________________________________________________________________________ When spontaneous mixing of cold and hot water occurs faster: if hot water is poured into cold water, or cold water is poured into hot water in the same proportion? ___________________________________________________ ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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