"What's in the Soil" Earth's surface and its changes PPT courseware

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"What's in the Soil" Earth's surface and its changes PPT courseware

1. Life in the soil - soil organisms

⑴First of all, you can see the roots of many plants - absorbing various nutrients in the soil;

⑵ Small animals: such as earthworms, etc.

⑶Microorganisms: bacteria, fungi, actinomycetes, etc.

We call microorganisms, animals and plants living in the soil soil organisms.

2. Non-living substances in soil

Experiment: When soil is immersed in water, what phenomena are found? What does it mean?

It means there is air in the soil. The soil is loose and the gaps are filled with air.

[Experiment 1] Measuring the volume fraction of air in the soil

Requirements: Choose dry soil - dry soil contains more air, and the experimental effect is obvious. In moist soil, many spaces have been occupied by water, and the air content will become less.

Thinking: 1. In the experiment, why do the volumes of the soil and iron blocks have to be the same?

2. The two large beakers used to hold soil and iron must be consistent in shape or volume. What is the purpose of this?

discuss:

1. Why are the amounts of water added to the same volume of iron and soil different?

Answer: The soil is loose and the iron is dense. Water can penetrate into the soil but cannot penetrate into the iron.

2. According to your experimental results, what is the approximate volume fraction of air in the soil to the volume of the soil?

Answer: In soil, air accounts for about 15% - 35% of the soil volume.

3. Given a metal container, an appropriate amount of water, and a large enough measuring cylinder, how do you measure the approximate volume fraction of air in the soil?

Method 1. Metal container measurement method (water injection method)

① Use a metal container to dig out a piece of soil that just fills the container.

② Use a measuring cylinder to fill the container with water until it is level with the mouth of the metal container. The volume of water injected is V1 (equivalent to the volume of air in the soil)

③ Pour out the soil from the metal container, fill it with water, and the volume of water injected is V2. (V2 is equivalent to the volume of a metal container and the volume of soil)

④ Calculate the volume fraction of air in the soil: V1 / V2 ×100%

Method 2: Graduated cylinder measurement method (difference method)

① Use a metal container to dig out a piece of soil that just fills the container.

②Inject a certain volume of water into the measuring cylinder and record the volume as V1

③Pour the soil in the container into the measuring cylinder and write down the total volume as V2 (V2-V1), which is the volume of the non-air part of the soil.

④ Pour out the soil from the metal container, fill it with water, and the volume of water injected is V3. (V3 is equivalent to the volume of a metal container and the volume of soil)

⑤Calculation: V air in soil = V3-(V2-V1)=V3+V1-V2

summary

The formation from rock to soil is an extremely complex process involving the interaction of multiple natural factors over a long period of time. That is, there is the process of rocks growing from large to small and the accumulation of organic matter in rock particles.

1. Weathering: natural external forces - wind, water flow, and water forming ice;

Thermal expansion and contraction - sudden drops in heat cause rocks to burst

The role of plants and animals

2. The corpses and excrement of plants and animals accumulate between rock particles and are an important source of soil humus and organic matter.

3. Soil formation is still proceeding normally, and the speed of soil formation is extremely slow - pay attention to protect cultivated land.

protect soil

(1) Soil pollution

①Industrial "three wastes" pollution: Toxic and harmful substances in waste gas, waste liquid and waste residue discharged from industry have direct or indirect harm to the soil.

② A large amount of chemical fertilizers and pesticides are used in agricultural production, which damages the soil structure or pollutes the soil.

③ Domestic waste is discarded at will. The plastic and rubber in it cannot be decomposed by soil organisms, destroying the soil structure and causing white soil pollution.

(2) Rational utilization of soil: Soil should be utilized rationally, and the development and use of soil should be based on the premise of benefiting human development.

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Update Time: 2024-10-02

This template belongs to science courseware Fifth Grade Science Volume 1, Textbook Edition industry PPT template

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