"Water Cycle and Water Resources" Material Forms and Changes PPT Courseware

Description

"Water Cycle and Water Resources" Material Forms and Changes PPT Courseware

learning target

1. Some water cycle phenomena in nature can be explained by the three-state changes of water.

2. Understand the application of water in daily life and production technology, and understand the significance of water to human survival

3. Increase awareness of caring for the environment and saving water through activities such as investigating the use of local water resources

Core test points: changes in physical states in clouds, rain, snow, fog, frost and other phenomena in nature

Preview before class

1. The colorful clouds in the sky often arouse people's beautiful reverie, so how are clouds formed? When the air containing a lot of water vapor rises to a high altitude, the water vapor encounters cold _________ (the name of the change in the state of matter, the same below) and turns into small water droplets or ________ into small ice crystals, which are lifted up by the rising airflow, thus forming cloud.

2. Water is the source of life. Our earth is a huge water ball, but its fresh water resources only account for 3%. Our country is a country seriously short of water. The per capita amount of water resources is only one-quarter of the world average. .The water in oceans, rivers, and lakes is constantly changing into water vapor through ________. The water vapor rises to high altitudes with the air flow. When it encounters cold air, the water vapor will ________ or ________, forming rain or snow. , hail, etc. fall back to the surface, completing the atmospheric water cycle.

3. When water vapor encounters cold at high altitudes, some _________ turn into small water droplets, and some _________ turn into small ice crystals, forming various clouds.

Lectures in class

Knowledge point 1. Water cycle in nature

The water on the earth's surface evaporates to form water vapor that rises into the air. When it is cold, it releases heat and liquefies into small water droplets or condenses into small ice crystals, thus forming rain, snow, hail, dew, fog, and frost. Part of it absorbs heat and vaporizes or sublimates. It becomes water vapor, and the other part absorbs heat and melts into water, which flows into rivers, lakes, seas, or is absorbed by soil or plants, and then evaporates again to form water vapor and rises into the air, and so on.

Note: The water cycle is a problem we often encounter in study and life. It is necessary to understand the water cycle process and the changes in the physical state in each link to avoid making mistakes when solving practical problems.

[Example 1] The picture is a schematic diagram of the water cycle. In the figure, the physical state that occurs in process ① is _______, and is accompanied by _______ heat; the physical state changes that occur in process ② are sublimation and _______, and is accompanied by radiation. hot.

【Exercise 1】As shown in the figure is a schematic diagram of the water cycle phenomenon in nature. Water in rivers, rivers, lakes, seas and the surface of the earth continues to evaporate into water vapor. When air containing a lot of water vapor rises to a high altitude, the temperature of the water vapor decreases and condenses into small water droplets or small ice crystals. This is a cloud. Under certain conditions, small water droplets and small ice crystals in clouds will fall as they grow larger. In the process of falling, the "small ice crystals turn into small water droplets" and fall to the ground together with the original water droplets, forming rain.

(1) Please write down the names of the physical state changes in the above paragraphs in order: _________, _____________, _________.

(2) Among the above three physical state changes, the one that is endothermic is ________; the one that is exothermic is ________.

(3) Our country is a water-scarce country. Saving water starts with me. Please write down a measure to save water in your daily life: .

Test Point 2 Melting and Solidification (High Frequency Test Point)

Test point analysis: This test point is a high-frequency test point for the Guangdong High School Entrance Examination. Images related to melting and solidification are the focus of the test. In addition, choosing a thermometer based on the melting point and freezing point is also a test direction. When reviewing this test point, you must focus on learning to identify various melting and solidification Images. In physics, mathematical image methods are often used to express the relationship between physical phenomena or physical quantities. The changes in the state of matter that apply image analysis in this chapter include:

(1) Melting image. It also includes crystal melting image and amorphous melting image. The difference between the two is that in the crystal melting process, the temperature is first raised to the melting point, the starting melting temperature remains unchanged, and the temperature is raised again after melting. Amorphous materials melt while heating up, and there is no process in which the temperature remains constant.�

(2) Liquid boiling image. During the boiling process of a liquid, it first heats up to the boiling point and then begins to boil, while the temperature remains unchanged.�

(3) The solidification image is the opposite process of the melting image. When the crystal solidifies, it first cools down to the freezing point, solidifies and releases heat, and the temperature remains unchanged. After solidification, it cools down again; the amorphous crystal solidifies and cools down at the same time. Each image is as shown in the figure below. shows that the line segment parallel to the time coordinate corresponds to the melting (solidification) or boiling process, and the temperature corresponding to the line segment is the melting point (freezing point) or boiling point; the melting point and freezing point of the same crystalline material are the same, and the crystalline material may be solid or solid at the melting point temperature. Liquid or solid-liquid coexistence state.

Test point 3 Vaporization and liquefaction (high frequency test point)

Analysis of test points: This test point is a high-frequency test point, and the test is relatively difficult. The judgment of vaporization and liquefaction phenomena, the relationship between the boiling point of water and atmospheric pressure, and the application of vaporization endotherm and liquefaction heat release are the focus of the test. During review It should be noted: (1) The process of a substance changing from a liquid state to a gaseous state is called vaporization. The methods of vaporization include evaporation and boiling, both of which absorb heat. (2) The process of a substance changing from a gaseous state to a liquid state is called liquefaction, and liquefaction releases heat. Methods for gas liquefaction include: compression volume and cooling. (3) Under a standard atmospheric pressure, the boiling point of water is 100°C. The higher the pressure, the higher the boiling point. The lower the pressure, the lower the boiling point. Boiled eggs on high mountains will not be cooked properly. , because the higher the altitude, the lower the air pressure, the lower the air pressure, and the lower the boiling point. The pressure cooker works on the principle of increasing the air pressure to increase the boiling point. (4) The factors that affect the speed of evaporation are: ① the temperature of the liquid, ② the surface area of ​​the liquid, ③ The speed of air flowing above a liquid.

1. (2010 Guangdong, 4, 3 points) According to relevant reports: The current global daily production of seawater desalination is about 35 million cubic meters, 80% of which is used for drinking water, solving the water problem of more than 100 million people. There are many methods of seawater desalination currently used, one of which is the distillation method, which evaporates the water in the seawater to leave the salt, and then condenses the water vapor into liquid fresh water. The above process involves changes in the physical state of water ( )

A. Vaporization Solidification B. Sublimation Sublimation C. Liquefaction Condensation D. vaporize liquefy

2. (2013 Guangdong, 13, 3 points) Use the same heat source to heat a certain mass of water. The relationship between temperature and time is shown in line a in the figure. If other conditions remain unchanged,

(1) Only increases the mass of water; (2) Only increases the atmospheric pressure on the liquid surface; (3) Both increases the mass of water and decreases the atmospheric pressure on the liquid surface.

Then in the three cases, the relationship between temperature and time corresponds to _____, _____, and _____ respectively (select "a", "b", "c" or "d" in the picture)

Test point 4 Sublimation and sublimation (high frequency test point)

Analysis of test points: The focus of this test point is the phenomenon of sublimation and condensation (for example, the ends of a fluorescent lamp will "turn black" after being used for a long time), and the physical state changes involved in clouds, rain, snow, fog, frost and other phenomena in nature.

Clouds, rain, snow, fog, frost and other phenomena in nature are all formed by changes in the physical state of water, which is a difficult point in learning. The following will focus on the physical properties of clouds, rain, snow, fog, frost and other phenomena in nature. state changes.

Ice is formed by the solidification of water.

Dew occurs when the water vapor in the air encounters cooler leaves, flowers and plants before early morning when the weather is hot, and liquefies into small water droplets that adhere to their surfaces. This is a liquefaction phenomenon.

Fog is water vapor that liquefies into small water droplets when it encounters cold in the air. These small water droplets are suspended in the air near the ground, so fog is the liquefaction phenomenon of water vapor.

Clouds are water vapor that rises to high altitudes and liquefies into small water droplets when encountering cold air currents or condenses into small ice crystals, which are suspended in the air. Therefore, clouds include the liquefaction and sublimation phenomena of water vapor.

Frost and snow are both phenomena of condensation of water vapor.

Frost is water vapor on the ground surface that condenses directly into a solid state at temperatures below zero degrees Celsius.

Snow occurs when the weather is cold and the temperature in the air is below zero degrees Celsius. Water vapor condenses into a solid state in the air and becomes hexagonal ice crystals (or snowflakes), which combine with each other to form snow flakes or snow clumps as they fall.

Hail is an ice ball, and its formation is complicated. Water droplets in the cloud are carried by updrafts to high altitudes where the temperature is below 0°C, and condense into small ice droplets. When the small ice droplets fall, their outer layers are heated and melt into water, and Combining with each other, the ice beads become larger and larger. If the updraft is strong, they will rise to high altitude and condense a layer of ice shell on their surface. After many times of up and down rolling, they can combine into larger ice beads. When they rise, When the airflow cannot support it, the ice beads fall to the ground and form hailstones.

"Rime" and frost are caused by water vapor directly condensing into small ice crystals when it is cold. Similarly, in cold winter, ice flowers often appear on people's window glass in some places in northern my country.

Keywords: material form and its changes teaching courseware, water cycle and water resources teaching courseware, Guangdong and Shanghai version eighth grade physics PPT courseware download, eighth grade physics slide courseware download, material form and its changes PPT courseware download, water cycle and water resources PPT courseware download, .PPT format;

For more information about the PPT courseware "Material Forms and Their Changes Water Cycle and Water Resources", please click the Material Forms and Their Changes ppt Water Cycle and Water Resources ppt tag.

"Water Cycle and Water Resources" Material Forms and Changes PPT Courseware 2:

"Water Cycle and Water Resources" Material Forms and Changes PPT Courseware 2 Teaching Objectives 1. The three-state changes of water availability explain some water cycle phenomena in nature. 2. Understand the water resources situation in our country and local areas, and know the water resources crisis faced by mankind. 3. Pass...

File Info

Update Time: 2024-09-01

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

Preview