"Learning to Use Balances and Graduating Cylinders" Quality and Density PPT Courseware

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"Learning to Use Balances and Graduating Cylinders" Quality and Density PPT Courseware

【Experience 1】Using a scale

Activity 1: Observe that the graduation value of the weighing scale of the balance is _______ and the measuring range is _______.

Activity 2: After balancing the scale, measure the mass of a piece of chalk.

Tips: Activity 1.0.2g | 5g | Activity 2. Omitted

[Experience 2] Use of measuring cylinder

Activity 1: Observe the measuring cylinder as shown in the picture.

Activity 2: Use a measuring cylinder to measure the volume of water.

(1) In activity 1, the letters above the measuring cylinder are _______,

The graduation value of the measuring cylinder is _______, and the measuring range is _______.

(2) In activity 2, the volume of water measured is _______mL.

Tips: (1)mL　10mL　250mL　(2)110

pre-study questions

1. How to adjust and use the balance?

2. How to measure volume using measuring cylinders and measuring cups?

Explore 1 Balance

Combined with "experience", think about the following questions:

1. In Activity 2, how to adjust the scale to balance it before weighing the mass of chalk?

Reference answer: (1) Place the balance on a horizontal table; (2) Move the vernier to the "0" scale line at the left end of the weighing scale; (3) Adjust the balance nut so that the pointer points to the center line of the dividing plate .

2. How to measure the mass of chalk after the balance is adjusted?

Reference answer: Put chalk on the left pan of the balance, put a weight on the right pan, add the weight and move the slider to balance the balance. At this time, the sum of the mass of the weight and the value shown on the weighing scale is the mass of the chalk.

3. Fill in the following:

Read the "Pallet Balance Instructions for Use" and answer the following questions:

(1) Lay it flat: The balance should be placed on the __________ workbench when in use.

(2) Adjustment and balance: Before use, move __________ to the "0" scale line at the left end of the weighing scale, and adjust __________ so that the pointer points to the center line of the dividing plate.

(3) Weighing: The object is placed on the __________ plate of the balance, and the weight is placed on the __________ plate; by increasing or decreasing the weight and moving the position of the wandering scale on the weighing scale, until the beam returns to balance, at this time __________ and The sum of __________ on the weighing scale is the mass of the object being measured.

Reference answers: (1) Horizontal (2) Travel code Balance nut (3) Left and right

The mass of the weight indicates the value corresponding to the weight.

Explore 2 Measuring cylinders and cups

Combined with "experience", think about the following questions:

1. Looking at the picture below, please tell me what are the similarities and differences between measuring cylinders and measuring cups?

Tip: Graduated cylinders and cups are instruments that measure the volume of liquids. The upper and lower diameters of the measuring cylinder are the same, so the scale is uniform; the upper and lower diameters of the measuring cup are different, so the scale is uneven. The higher the measuring cup goes up, the thicker the diameter, and the smaller the height of the same volume, so the scale is tighter and the scale below is sparser. They have scales on them, numerical values ​​on them, and the letters "mL" on the top.

Reference answer:

2.Measure the volume

(1) Pour some water into the measuring cylinder, and you will see that the shape of the liquid surface is ______. When reading, your line of sight should be on the same level as the bottom of ______;

(2) Pour some mercury into the measuring cylinder. You will see that the shape of the liquid surface is ______. When reading, your sight should be on the same level as the top of ______.

Reference answers: (1) concave shape, concave surface (2) convex, convex surface

Knowledge summary

1. Pallet balance

1. Function: A common tool for measuring _____.

2.Use:

(1) Before use: Observe the _____ on the balance and the ________ on the weighing scale, and estimate the mass of the object to be measured.

(2) When in use: ①Put it flat: Place the balance on the _____ workbench.

②Zero adjustment: The cursor moves to the "0" mark of the weighing scale _____.

③Leveling: Adjust _________ so that the pointer points at the ________ of the index scale.

④Weighing: Place the object on the ___ plate of the balance, place the weight on the ___ plate, add the weight and move the weight so that the pointer is aligned with the _______ line of the graduated scale.

⑤Reading: ______________ is the mass of the object being measured.

(3) After use: After the measurement is completed, use _____ to put the weight back into the box and return the weight to zero.

2. Use of measuring cylinders and measuring cups

1. Purpose: A tool for measuring _________.

2. Unit: ___.

3. Reading: The line of sight should be at the same level as the bottom of _____ or the top of _____.

Test Points: Use of Scales

[Typical example] (2012 Weifang High School Entrance Examination) Xiaoqiang used a pallet balance to measure the mass of a piece of rubber. When adjusting the balance, he adjusted the scale to "0" and found that the pointer stopped on the right side of the index plate, as shown in the figure A shows. To balance the balance, move the balance nut at the right end toward ________. After the balance is balanced, place the rubber on the left pan and add the weight on the right pan. After moving the cursor to the right, the pointer stops at the center of the indexing pan. The value of the added weight and the position of the cursor are as shown in Figure B, then the rubber The mass is ________g. If you forget to adjust the scale to "0" when adjusting the balance, the rubber mass measured by him will be _________ than the true value.

[Concise Lecture and Analysis] This question tests the use of a balance. The pointer stops on the right side of the index plate, indicating that the mass on the right end is too large, so the balance nut should be adjusted to the left; the mass of the object being measured is equal to the sum of the mass of the weight and the number displayed on the scale, that is, m=30g+ 3.2g=33.2g; when adjusting the balance balance, if you forget to adjust the scale to "0", the final measured total mass will be greater than the actual mass, and the larger mass is equal to the indication of the scale before adding the weight.

Answer: Left 33.2 large

[Method Summary] Six things to note when using pallet balances

(1) When adjusting the balance nut, follow the principle of "turn left to right, turn right to left", that is, when the pointer deviates to the left of the central scale line of the index plate, adjust the balance nut to the right and the pointer deviates to the central scale line of the index plate. to the right, adjust the balance nut to the left.

(2) When the pointer swings with equal amplitude to the left and right of the central scale line of the index plate, it is also called beam balance.

(3) When reading, refer to the corresponding scale line on the left side of the travel code.

(4) The balance nut cannot be adjusted during the measurement process. The beam balance can only be adjusted by moving the wandering code or increasing or decreasing the weight.

(5) A balance that has been adjusted and balanced can measure the mass of an object multiple times in a row. After the position of the balance moves, it must be readjusted before use.

(6) When weighing the mass of an object, averaging multiple times can reduce the error.

1. The following are some ways that Xiao Ming uses the scale. The correct one is ()

A. Place the balance on a level table before measuring

B. When adjusting the balance of the beam, the wandering code does not need to be at the zero mark.

C. Add and subtract weights directly by hand

D. The mass of the measured object can exceed the maximum measurement value of the balance

[Analysis] Choose A. This question tests the use of a pallet balance. When measuring, the balance is placed on the horizontal workbench, A is correct; when adjusting the balance of the beam, move the vernier to the zero mark of the scale and then rotate the balance nut to adjust the balance, B is wrong; when adding or subtracting weights, it is necessary to Use tweezers, not hands, C is wrong; the mass of the object being measured cannot exceed the maximum measurement value of the balance, D is wrong.

2. (2012 Nanning High School Entrance Examination) Before using a pallet balance to measure the mass of an object, when adjusting the balance of the beam, you find that the pointer is pointing to the left of the center line of the index plate. At this time, you should ()

A. Move the game code to the left

B. Turn the balance nut on the right end a little to the left

C. Move the game code to the right

D. Turn the balance nut on the right end to the right some more

[Analysis] Choose D. This question examines the adjustment of a pallet balance. During the process of adjusting the balance of the balance beam, the position of the wandering code cannot be adjusted; the pointer is biased to the left side of the index plate, and the mass on the left side of the beam is large, so the balance nut should be adjusted to the right.

3. In order to measure the mass of a bottle of oil, a student used the following steps: (1) Move the balance nut to balance the beam; (2) After pouring oil into the bottle, weigh the total mass of the oil and the bottle; (3) The total mass of the bottle Place the left plate and weigh the bottle; (4) Arrange the balance; (5) Put the

Place the balance on a horizontal platform; (6) Place the slider at the left end zero position. Which of the following statements is correct ()

A. There is no shortage of steps, the order is (5)(6)(1)(3)(2)(4)

B. There is no shortage of steps, the order is (4)(5)(6)(1)(3)(2)

C. Missing step "(7) The mass of oil is equal to the mass of bottle and oil minus the mass of bottle", the order is (4)(5)(6)(1)(3)(2)(7)

D. Missing step "(7) The mass of oil is equal to the mass of bottle and oil minus the mass of bottle", the order is (5)(6)(1)(3)(2)(7)(4)

[Analysis] Choose D. This question examines the method of measuring liquid quality. When using a balance to weigh the mass of a liquid, in order to make the measurement result accurate, the mass of the container is generally weighed first and then the total mass of the liquid and the container. The mass of the liquid is obtained by subtracting the mass of the container from the total mass of the liquid and the container.

Find out where you tend to go wrong?

How to measure the mass of a glass of water using a scale?

[Students’ own answers]

(1) Measure the mass m1 of the cup and water;

(2) Pour out the water and measure the mass m2 of the cup;

(3) The mass of water is m1-m2.

[Teacher Comments]

Error: The influence of error is not considered. This measurement method will make the water in the cup not poured cleanly and the error will be large.

【correct answer】

(1) Measure the mass m2 of the empty cup;

(2) Pour water into the cup and measure the mass m1 of the cup and water;

(3) The mass of water is m1-m2.

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"Learning to Use Balances and Graduating Cylinders" Mass and Density PPT Courseware 2:

"Learning to Use Balances and Graduating Cylinders" Mass and Density PPT Courseware 2 How to adjust the balance nut as shown in the picture? The left end of the beam is too heavy, and the nuts at both ends should be adjusted to the right. The right end of the beam is too heavy, and the nuts at both ends should be adjusted to the left. Thought 1: Which side should be used when reading the travel code? ..

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Update Time: 2024-09-10

This template belongs to Physics courseware Shanghai Science Edition 8th Grade Physics industry PPT template

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