"Starting from Global Warming" Material Forms and Changes PPT Courseware 2

Description

"Starting from Global Warming" Material Forms and Changes PPT Courseware 2

learning target

1. Understand the concept of temperature and be able to name common temperature values ​​in daily life and natural environment

2. Know how to use a thermometer and be able to use it to measure temperature

3. Understand some methods of measuring temperature

Core test point: The reading of the thermometer.

Preview before class

1. ______________ is called temperature, and its common unit is _______, expressed in ____.

2. Under standard atmospheric pressure, the temperature of ___________ is specified as 0°C, and the temperature of _________ is specified as 100°C. Divide the two into 100 equal parts, each part is ____℃.

3. The highest temperature on the earth's surface is about 63°C, pronounced ______; the freezing point of mercury is -39°C, pronounced _____.

4. Before using a thermometer, please note:

①Observe its ________ and ________ and recognize its _______.

② When using, the glass bulb of the thermometer should be placed in the liquid to be measured and should not touch the container ________ or the container ________;

③ Wait for the thermometer to read ________ before reading;

④When reading, ________ should remain in the liquid being measured, and the line of sight should be level with the _________ of the liquid column in the thermometer.

Lectures in class

Knowledge point 1. Temperature

The degree of hotness or coldness of an object is called temperature. The degree of hotness and coldness is a relatively vague term. It varies depending on how people feel and is often inaccurate. To accurately measure temperature a thermometer is required.

The Celsius temperature scale was first formulated by the Swedish scientist Celsius. He defined the temperature of the ice-water mixture under normal circumstances as 0 degrees, and defined the temperature of water boiling under a standard atmospheric pressure as 100 degrees. The gap between 0 degrees and 100 degrees was divided into 100 equal parts, and each equal part is one degree Celsius. The unit is called 1 degree Celsius. Celsius is represented by the symbol ℃. Temperatures below 0°C and above 100°C expand outward with the same size of 1°C intervals. Celsius temperature is represented by the symbol t. Pay special attention to how to write and read when the temperature is below 0℃. The average temperature in November in the Northeast is recorded as "-18°C", which should be read as "minus 18°C" or "minus 18°C", not "minus 18°C". Don't miss the small circle in the upper left corner of the letter C when writing.

[Example 1] The weather announcer on the TV station said: "Today's lowest temperature in Beijing is minus 5 degrees." Student Zhang Hong's answer was incomplete. Do you think the correct and complete forecast should be "Today's lowest temperature in Beijing is ______."

【Exercise 1】The correct pronunciation of -20℃ is ( )

A. minus 20 degrees Celsius B. minus 20 degrees Celsius

C. minus 20 degrees Celsius D. minus 20 degrees Celsius

Test point 2. Thermometer

Thermometers are made by utilizing the thermal expansion and contraction properties of liquids.

The main part of a liquid thermometer is a glass tube with a very thin and uniform inner diameter. The lower end of the tube is a glass bubble, and an appropriate amount of liquid (mercury, alcohol or kerosene, etc.) is filled in the tube and bubble. When the temperature changes, due to thermal expansion and contraction, the position of the liquid level in the tube changes accordingly. The temperature value can be read from the scale reached after the liquid level stabilizes.

Because the temperature range that needs to be measured during experiments is relatively large, the scale range of the experimental thermometer is -20°C to 110°C. The minimum scale value is 1°C.

The red liquid column in the thermometer is alcohol. Alcohol will only condense at -117°C. Even in Antarctica, which has the lowest temperature on earth, an alcohol thermometer can be used.

How to use commonly used thermometers:

Before use: Observe its range to determine whether it is suitable for the temperature of the object to be measured; and recognize the graduation value of the thermometer, that is, recognize how many degrees Celsius each small grid on the thermometer represents for accurate readings;

When in use: the glass bulb of the thermometer is completely immersed in the liquid to be measured, and do not touch the bottom or wall of the container; the glass bulb of the thermometer is immersed in the liquid to be measured and wait for a while until the thermometer's indication stabilizes, that is, when the liquid column stops rising or Take a reading when it drops. When using a thermometer to measure the temperature of a liquid, the amount of liquid being measured should not be too small. At least it should be able to completely submerge the glass bulb of the thermometer, and a stirring rod (a thermometer cannot be used instead of the stirring rod) must be used to stir the liquid. , make the temperature of the entire liquid uniform before measuring;

When reading: the glass bubble should remain in the liquid being measured, and the line of sight should be level with the upper surface of the liquid column in the thermometer. Some thermometers have a triangular cross section, which is equivalent to a convex lens that can play a magnifying role (such as a thermometer), so when reading When counting, turn the thermometer to the position where the reading is clearest before reading.

[Example 2] There are four methods of measuring water temperature as shown in the figure, the correct one is ( )

[Exercise 2] (2014·Hulunbuir) Use the same thermometer to measure the temperature at noon and evening that day. The readings of the two thermometers are as shown in Figures A and B. The _______ picture is the temperature at night, and its reading is _______℃.

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For more information about the PPT courseware "Material Forms and Their Changes from the Global Warming Points", please click the Material Forms and Their Changes ppt from the Global Warming Points tab.

"Starting from Global Warming" PPT courseware of material form and its changes:

"Starting from Global Warming" PPT courseware on the form of matter and its changes Teaching objectives 1. Know that temperature is a physical quantity that expresses the degree of hotness and coldness of an object, and be able to tell common temperature values ​​in the living environment. 2. Understand the working principle of liquid thermometers and be able to use common thermometers to measure...

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Update Time: 2024-10-19

This template belongs to Physics courseware Guangdong and Shanghai version of eighth grade physics volume one industry PPT template

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