casino singapore ban:casino,singapore,ban,锘縶,Keywor:锘縶Keywords}#Title Segmentation# First, science is at the side of science as an introduction to science. This section begins with some wonderful phenomena in nature. Through the doubts about these natural phenomena, students are stimulate
First, science is at the side of science as an introduction to science. This section begins with some wonderful phenomena in nature. Through the doubts about these natural phenomena, students are stimulated to explore and understand science. The essence of science - science is a discipline that studies various natural phenomena and finds the corresponding answers. Observation, experiment, and thinking are important methods of scientific inquiry. The continuous development of science and technology has changed the world, but we have to look at this issue dialectically. It has both positive and negative impacts on our lives, understanding the importance of learning scientific knowledge and making it better for humanity. Second, experiment and observation Observation and experiment are the basis of learning science, and experiment is the most important part of scientific research.
To conduct an experiment, it is necessary to understand some commonly used instruments and their uses and laboratory procedures.
Test tube: It is a reaction container for a small amount of reagents. It can be heated and used in a wide range of applications.
Use a test tube holder when heating the tube (long handle inward, short handle outward, and long handle).
When heating the liquid in the test tube, the volume of the liquid should not exceed 1/3 of the volume of the test tube, and the test tube clamp should be clamped at 1/3 of the distance from the test tube.
The tube should be tilted 45 degrees when heated.
, and then preheated evenly, and then heated in the concentrated part of the liquid.
The hot tube should not be quenched to prevent the tube from rupturing.
Stopwatch: Used to measure time, mainly to measure time interval.
balance and weight: used together to measure the quality of the object.
Ammeter: Determine the magnitude of the current.
Voltage meter: The magnitude of the voltage is measured.
Microscope: It is used to observe substances and changes in the microscopic world that cannot be observed by the naked eye.
Alcohol lamp: It is a commonly used heating instrument, the main heat source of the laboratory.
Use it to heat it with the outer flame.
Beaker: It can be used for reaction vessels with more reagents, and can be used to prepare and dilute solutions.
Surface plate: temporarily holds a small amount of solids and liquids.
Pill: used to take a small amount of solids.
Glass rod: It is mainly used for stirring, draining and transferring solid medicines.
Understanding the things of nature begins with observation.
First of all, we must have a correct attitude of observation. We must not observe for observation. We must clearly observe the purpose of observation, observe experimental phenomena comprehensively and meticulously, and accurately describe and record experimental phenomena through comparison and analysis.
Because of the limitations of human senses, the use of sensory observations 鈥?direct observations often fail to make reliable judgments about things.
In order to make accurate observations and make accurate judgments, we can use tools to expand the scope of observation and measure data.
Three, length and volume measurement and observation are the basic skills of our scientific inquiry.
The so-called measurement refers to the process of comparing a quantity to be tested with a recognized standard quantity.
According to different measurement requirements, the measurement object, we should be able to use the appropriate measurement tools and measurement methods, using the internationally recognized main unit as much as possible - the recognized standard quantity.
1. Measurement of length.
The internationally recognized length master unit is meters and the unit symbol is m.
Learn some common length units and get a sense of the conversion between them.
l km (km)=1000 m (m) 1 m (m) = 10 decimeters (dm) = 100 cm (cm) = 1000 mm (mm) = 106 渭m (m) = 109 nm (nm The basic tool used to measure length is the scale.
The correct use of the scale is the focus and difficulty of this section.
(1) Understand the construction of the scale.
Observation: Zero scale line minimum scale value: Read each large grid value and unit, and analyze the length and unit represented by each small grid, which is the minimum scale value.
Range: The maximum range that can be measured.
(2) When using the scale, do: * Put it correctly: The zero scale line is aligned with one end of the object to be measured, and the scale is close to the object to be measured (perpendicular to the object to be measured).
Thinking: What is the measurement result caused by the scale being skewed (the reading is too large) What should I do if the zero scale line is worn out? (Find a clear tick mark as the zero scale line, as shown in the figure, but pay attention when reading ) * Look right: the line of sight of the eye should be perpendicular to the ruler.
Thinking: What happens to the reading when the line of sight is to the left and to the right (the reading from the left is too large, and the reading to the right is too small) *Read correctly: Read the exact value of the length of the object before reading, that is, read the minimum scale Value, and then estimate the next digit of the minimum scale, which is the estimated value.
After the value, indicate the unit used - no unit value is meaningless.
*Record correctly: Recorded value = accurate value + estimated value + unit The accuracy with which the measurement can be achieved is determined by the minimum scale value of the scale.
According to the actual measurement requirements and measurement objects, the appropriate measurement tools and measurement methods will be selected.
Understand the use of tape measure and tape measure.
Knowing the finger distance and step size can roughly measure the length of the object. Sonar, radar, and laser can also be used for ranging.
(3) Special measurement method for length.
*Accumulation and averaging method: Indirect measurement is performed by using a method of reducing the amount of accumulation and measuring more.
For example: measuring the thickness of a piece of paper, the quality of a stamp, the diameter of a thin wire, etc.
*Roller method: When measuring the length of a longer curve, the circumference of one wheel can be measured first.
When the wheel rolls from one end to the other along the curve, note the number of turns the wheel rolls.
Length 2 weeks X laps.
For example: measuring the perimeter of the playground.
*Resolve the straight method: measure the length of a shorter curve. Use a soft cotton thread with no elasticity or elasticity to be placed at one end of the curve and gradually place it along the curve to make it completely coincide with the curve. , make the end mark on the cotton thread.
Use the scale to measure the distance between two points, which is the length of the curve.
For example: Measure the distance between two points on the map.
*Combination method: Measure the diameter of the object with a ruler and a triangle ruler.
2. Measurement of volume.
Volume is the amount of space occupied by an object.
The common unit of solid volume is cubic meters (m3), and there are smaller volume units, such as cubic decimeter (dm3), cubic centimeters (cm3), cubic millimeters (mm3), and the like.
The usual units for liquid volume are liters (L) and milliliters (ml).
The conversion relationship between them is: 1 cubic meter = 103 cubic meters = 106 cubic centimeters = 109 cubic millimeters 1 liter = 1 cubic centimeter = 1000 milliliters = 1000 cubic centimeters We sometimes hear 'cc' , lcc = lcm3 For the measurement of some regular object volume, such as cube, cuboid volume measurement, based on the length measurement, can be directly measured, using the formula to obtain.
If measuring the volume of liquid, it can be measured directly with a measuring cylinder or measuring cup.
When using the measuring cylinder and measuring cup, be careful: 1) Put it steady: Place the measuring cylinder and the measuring cup on the horizontal table.
2) Observe the range and the minimum scale value.
3) Correct reading: When reading, the line of sight should be perpendicular to the wall of the tube and level with the lowest point in the center of the concave liquid level.
When looking down, the reading is too large; when looking up, the reading is too small.
For the measurement of irregular object volume, such as small stones, it can be measured indirectly using the measuring cylinder and the measuring cup.
3. Measurement of area.
The area measurement of a regular object is the same as the measurement of the regular object volume, based on the length measurement.
The area measurement of irregular objects includes the cut-and-shoot method, the square method, and the like.
Grid method to measure the area of 鈥嬧€媔rregular objects: 1) Measure the length and width of each square, and use the length and width to find the area of 鈥嬧€媏ach square.
2) Count the number of squares occupied by irregular objects: the number of squares above the half-square is less than half of the grid.
3) Area = area of 鈥嬧€媏ach square 脳 total number of squares.
4. Temperature measurement The degree of heat and cold of an object is expressed by temperature.
The usual unit of temperature is Celsius and the unit symbol is 掳C. The temperature of the ice-water mixture is artificially set to 0 掳 C, and the temperature of boiling water at a standard atmospheric pressure is 100 掳 C. Divided into 100 cells between 0 掳 C and 100 掳 C, then each cell is 1 掳 C. Usually we think that cold objects have low temperatures and hot objects have high temperatures. However, it is easy to make an error by judging the temperature of the object by the feeling, and it is not possible to objectively reflect the temperature of the actual object. At this time, a thermometer is needed. The thermometer is made according to the principle of liquid expansion and contraction. There is a scale on the top, the inner diameter is very thin, but the thickness is even. There is a glass bubble underneath, filled with liquid. Commonly used liquid thermometers include mercury thermometers, alcohol thermometers, and kerosene thermometers. When using a liquid thermometer, pay attention to the following points: 1) Select a suitable thermometer before measuring. Do not exceed its range. 2) When holding, hold the hand above the thermometer. The glass bulb of the thermometer should be in full contact with the object being measured, but it should not touch the wall of the container. After the glass bulb of the thermometer is immersed in the measured liquid, it cannot be read immediately, and the liquid column is stabilized before reading. 3) When reading, the thermometer cannot be taken out of the liquid to be tested. The line of sight should be level with the liquid level in the thermometer. 4) When recording, the unit should be written after the data. A thermometer is a special type of thermometer. The measurement range is from 35 掳 C to 42 掳 C. The glass bubble has a large volume and a very small inner diameter. When the temperature changes slightly, the height of the mercury column changes significantly. Since there is a special thin bend in the middle of the pipe diameter, the mercury in the thin pipe will be broken after the thermometer leaves the human body, so it can express the temperature of the human body after leaving the human body. After using the thermometer, the thermometer should be rubbed a few times to return the mercury to the glass bubble. With the continuous development of technology, more advanced temperature measuring instruments and methods are also emerging. Such as electronic thermometers, metal thermometers, ribbon thermometers, photometric thermometers (playing a huge role during SARS), radiation thermometers, satellite remote sensing temperature measurement, spectral analysis, etc. V. Measurement of quality In daily life, we have to touch a large number of objects, all of which are composed of substances. The amount of matter contained in an object is called mass. The quality of an object is determined by the object itself. The more substances it contains, the greater its quality. Quality has the following properties: it does not change with the shape, state, temperature, and position of the object. The main unit of quality in the world is kilograms, and the unit symbol is kg. Commonly used units are tons, symbol t; gram, symbol g; milligram, symbol mg. The conversion between them is: 1 ton = 1000 kg I kg = 1000 g = 106 mg The conversion relationship between the commonly used mass unit and the traditional Chinese quality unit is: 1 kg = 1 kg 1 kg = 500 g 1 two = 50 g measurement Common tools for quality are electronic scales, steel scales, scales, etc. (Spring scales are not a tool for measuring quality) A pallet balance is often used in the laboratory to measure quality. Understand the basic structure of the pallet balance: indexing plate pointer pallet beam beam ruler travel code weight base balance nut Note the following when using the pallet balance: (1) leveling: put the pallet balance on the horizontal table. (2) Leveling: Dial the travel code to the 鈥?鈥?scale line. Adjust the balance nut so that the pointer is aligned with the center mark of the indexing plate, or the pointer swings in the small range from the left and right sides of the center mark. Thinking: How to adjust the balance nut when the pointer is deflected? The pointer is to the left and the balance nut is adjusted to the right (outer); the pointer is to the right and the balance nut is adjusted to the left (inside). (3) Weighing: The quality of the left disc object = the total mass of the right disc weight code + the mass value indicated by the travel code plus the weight, first estimate, use the dice to increase from large to small, and adjust the game code until the balance is balanced. Do not place wet items or chemicals directly on the balance tray (two or two pieces of glass of equal size and mass can be placed in both trays). (4) Finishing equipment: Use the tweezers to put the weight back into the weight box and move the code back to the 鈥?鈥?tick mark. Thinking: If the position of the object and the weight is reversed, how do you determine the actual quality of the object? The above formula is changed to the mass value of the left disk weight quality = right disk object mass + travel code indication. 6. Measurement of time In nature, any periodic motion can be used to measure time. In ancient times, people used the methods of sundial, incense, and hourglass to time. Nowadays, people use advanced instruments such as clocks and watches to measure time. The main unit of time is seconds and the unit symbol is s. Commonly used units are minutes, hours, days, months, and years. The basic conversion relationship of time is: I day = 24 hours l hour = 60 minutes = 3600 seconds The time usually contains two layers of meaning: time and time interval. The moment refers to a point of time, such as 10:00; the time interval refers to a period of time, such as 10 minutes of break between classes. The tools commonly used in the laboratory for timing are stopwatches, mechanical stopwatches and electronic stopwatches. The exact value of the electronic stopwatch can reach seconds. When the mechanical stopwatch is reading, read the points (small disk: 15 minutes) and seconds (large disk: 30 seconds) and add them. Its exact value is seconds. Seven, scientific inquiry to understand the nature of science, its core is to explore. Know the basic process of scientific inquiry: asking questions 鈥?building guesses and assumptions 鈥?making plans 鈥?getting facts and evidence 鈥?testing and evaluation 鈥?cooperation and communication can complete simple scientific inquiry design and process implementation. The general review of junior high school science knowledge (24 articles) Next post: The second chapter of the seventh chapter observation... pay attention to more health information, pay attention to the health of the South Window.
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