Ó Sivchenko E.I., physics teacher, Secondary School No. 5, Svetly

7th grade. Section 2. Lesson 2. L. r. No. 2 “Measuring the sizes of small bodies”

7th grade

Section 2. Initial information about the structure of matter.

Lesson 2. Laboratory work No. 2 “Measuring the sizes of small bodies.”

Continue to form ideas about methods scientific knowledge;

Fostering a culture of mental work: working in pairs, keeping notes when taking measurements.

Equipment:

1. Presentation “7th grade L.R. No. 2. " Measuring the sizes of small bodies."

2. Laboratory equipment: ruler, peas, millet, needle textbook.

Lesson progress

I . Repetition.

– What do you know about the structure of matter?

– What observations, phenomena, facts indicate that all substances consist of tiny particles, between which there are gaps? (Give examples with explanation)

– Why do bodies seem solid to us?

– Can molecules be seen?

II . Setting a learning task.

When conducting experiments, scientists take measurements.

For example, having received a photo of molecules using electron microscope, they measure the size of a single molecule.

Lesson objective: learn to determine the sizes of small bodies, including molecules.

III . New material.

Slide 2.

The measuring tool in our work will be a ruler. You can easily determine the price of its division. Typically, the ruler division price is 1 mm.

Let's define simple measurement using a ruler to determine the exact size of a small object, such as a grain of rice.

If you simply apply a ruler to the grain (see figure), then you can say that its diameter is more than 1 mm and less than 2 mm. This measurement is very inaccurate.

Our task is to obtain a more accurate measurement using the same ruler. To do this, you can do the following. Let's place a certain number of grains along the ruler so that there are no gaps between them. Count the number of grains in a row, measure the length of the row in mm. The grains have approximately same size. Therefore, to get the size of one grain, you need to divide the length of the row by the number of grains. This method is called the row method.

Slide 3.

In a similar way, we determine the size of the molecule in the photograph.

Since the photo was taken with a magnification of 70,000 times true size the molecules will be 70,000 times smaller than in the photograph

IV. Performing laboratory work “Determining the sizes of small bodies using the row method.”

1. Work with the textbook pp. 160-161 and prepare notes for the report.

Purpose of work: learn how to measure using the row method.

Devices and materials:

Measurement table.

Conclusion.

2. Getting the job done

V . Summing up.

Questions:

Are the sizes of small particles measured in this way absolutely accurate? Why?

2. What determines the accuracy of measuring the sizes of small bodies using the row method?

3. To measure the sizes of which bodies is the microphotography method used?

VI . Homework:

§§ 7, 8 – repeat.

Purpose of work: learn how to measure using the row method.

The measuring tool in this work is a ruler. You can easily determine the price of its division. Typically, the ruler division price is 1 mm. It is impossible to determine the exact size of any small object (for example, a grain of millet) by simple measurement using a ruler.

If you simply apply a ruler to the grain (see figure), then you can say that its diameter is more than 1 mm and less than 2 mm. This measurement is very inaccurate. To get more exact value you can use another tool (for example, a caliper

or even a micrometer). Our task is to obtain a more accurate measurement using the same ruler. To do this, you can do the following. Let's place a certain number of grains along the ruler so that there are no gaps between them.

This way we measure the length of the row of grains. The grains have the same diameter. Therefore, to obtain the grain diameter, you need to divide the length of the row by the number of grains of its components.

27 mm: 25 pcs = 1.08 mm

It can be seen by eye that the length of the row is slightly longer than 27 millimeters, so it can be considered 27.5 mm. Then: 27.5 mm: 25 pcs = 1.1 mm

If the first measurement differs from the second by 0.5 millimeters, the result differs by only 0.02 (two hundredths!) of a millimeter. For a ruler with 1 mm divisions, the measurement result is very accurate. This is called the row method.

Example of doing the job:

Calculations:

where d is diameter

l - row length

n - number of particles in a row

LESSON PLAN
Lesson No. 7 Lesson topic: Laboratory work No. 2 “Measuring the sizes of small bodies”

Full name: Chilikova Daria Andreevna

Place of work: Municipal educational institution "Secondary school No. 2 UIP named after. V.P. Tikhonov" Saratov, Saratov region

Position: Physics teacher

Subject: physics

Class: 7a, 7b

Lesson type: workshop lesson, laboratory lesson

Laboratory work No. 2 “Measuring the sizes of small bodies”

Basic tutorial

A.V. Peryshkin, “Physics”, 7, Bustard, 2014

Objective of the lesson:

introduce students to methods of measuring the sizes of small bodies, their calculation

repeat the conversion of units of measurement.

Tasks

educational:

developing:

educational:

formulate the concept of measuring the sizes of small bodies, find out using specific material how to correctly calculate quantities;

continue to develop the skills to observe and explain physical phenomena, summarize and compare the results of the experiment;

form elements creative search based on the generalization technique, continue to work on developing the skills to compose, analyze, and draw conclusions;

develop the ability to analyze educational material;

develop students' interest in physics using experimental tasks;

develop skills and abilities teamwork;

promote the formation ideological ideas cognizability of phenomena and properties of the surrounding world.

Lesson type laboratory work using ESM.

Forms of student work: conversation, frontal work

Required technical equipment worksheet, materials for experiments: ruler, millet, peas, thread, hair, thin wire.

LESSON PROGRESS:

Organizational moment.(Welcome students, check readiness for lesson)

Hello guys! Sit down. Let's start the lesson.

State the topic and purpose of the lesson.

Today we will do laboratory work. There are worksheets on your desks.

Let's read the topic and purpose of the lab. Look at the equipment, check that everything is on the tables.

Execution of work:

1. Completing tasks:

__________________________________________________________________________________________________________________________________________________________
_____________________________________________________________________________

Temperature m/s

Speed ​​m

Area m3

Volume. kg

1. Working with equipment.

2. Determine the diameter of millet, peas, thread, hair, needle, thin wire.

Look at the photo of the molecule in the textbook. Determine the particle sizes if the magnification is 70,000 times, the number is 10 molecules and they occupy a length of 2.8 cm.

Experimental task.
__________________________________________________________________________________________________________________________________________________________

Summing up.

Answer the security questions.

Security questions:

Draw a conclusion from your work.

Conclusion of the work:
V. Turn in the worksheets. The lesson is over.

7th grade
Worksheet to laboratory work
Determining the size of small bodies.
Equipment: ruler, millet, peas, thread, hair, thin wire.
Training tasks and questions:
1. How can you use a ruler to measure the diameter of a hair, thread, or thin wire? Give an example.
_____________________________________________________________________________
__________________________________________________________________________________________________________________________________________________________
2. A stack of coins consists of 30 pieces, the length of the stack is 32 cm. What is the thickness of the coin? (mm, cm, m)
__________________________________________________________________________________________________________________________________________________________
_____________________________________________________________________________

3. Match physical quantities and their units:

Temperature m/s

Speed ​​m

Area m3

Volume. kg

WORK PLAN:

I. Working with equipment.

1. Determine the price of dividing the ruler C.d.=_____ mm
2. Determine the diameter of millet, peas, thread, hair, thin wire.
3. For each type of small body, take measurements at least 2 times. To do this, make rows with different amounts particles.
4. For each small body, calculate the average value of the measured quantity using the formula (1st value + 2nd value)/2
5. Write down the measurement and calculation data in the table:

CALCULATIONS:________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
6. Look at the photo of a molecule in the textbook. Determine the particle sizes if the magnification is 70,000 times, the number is 10 molecules and they occupy a length of 2.8 cm.
Number of particles in a row _________pcs.
Row length __________ mm = ______________cm = ________________ m

Particle diameter in the photo ___________ mm = ___________ cm = _____________ m
Magnification when photographing __________ times
Actual particle size ________mm ​​= ______________ cm = ______________ m
Experimental task.
How can you measure the thickness of a sheet of paper in a book?
_______________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Security questions:
1. What is the significance of the sizes of small particles, exact or approximate? Why?
_______________________________________________________________________________________________________________________________________________________________________________________________________________________________________

2. What determines the accuracy of measuring the sizes of small bodies?
_______________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Conclusion of the work: _____________________________________________________________________________
__________________________________________________________________________________________________________________________________________________________

Rating: _________Date:__________Work checked by:___________

« Measuring the sizes of small bodies ».

Objective of the lesson: P -r develop skills practical activities, consolidate the skill of determining the sizes of small bodies, draw conclusions based on the results of the work;

D - naw teach students how to handle measuring instruments and be able to prepare a report on laboratory work;

IN - develop mutual understanding when working in pairs and respect for equipment.

Lesson plan.

Download:

Preview:

Laboratory work No. 2

"Measuring the sizes of small bodies."

Objective of the lesson: P - develop practical skills, consolidate the skill of determining the sizes of small bodies, and draw conclusions based on the results of the work;

D - teach students how to use measuring instruments and be able to prepare a report on laboratory work;

IN - develop mutual understanding when working in pairs and respect for equipment.

Lesson plan.

1. Checking homework.

2. Safety briefing.

3. Performing laboratory work.

1. Knowledge test:

1. How to determine the sizes of small bodies?

3. Is it possible to measure the dimensions of small bodies accurately? Why?

1. Measuring the sizes of small bodies.

Purpose of the work: learn to take measurements using the row method.

Devices and materials:ruler, fraction (or peas), needle.

Directions for use

1. Place several (20-25 pieces) pellets (or peas) in a row close to the ruler. Measure the length of the row and calculate the diameter of one pellet.

2. Determine the size of a millet grain (or poppy seed) in the same way. To make it more convenient to place and count the grains, use a needle. The way you determine your body size is called method of rows.

3. Determine the diameter of the molecule using the photograph using the row method (Fig. 199, magnification 70,000).

4. Enter the data from all experiments and the results obtained into the table.

5. Determine and record measurement errors.

Error: absolute -Δ d = Δi d + Δо d = ... (cm)

relative - ε = Δ d / d pr. *100% = ... % (d pr = d )