"Chemistry is a science based on experiments" Entering the World of Chemistry PPT Courseware 3

"Chemistry is a science based on experiments" Entering the World of Chemistry PPT Courseware 3

learning target

1. Know how to test oxygen and carbon dioxide

2. Learn how to use drainage to collect exhaled air

3. Learn how to compare the composition of the air exhaled by a person and the air inhaled

1. What information is provided in the textbook?

(1) ________ can make clear lime water turbid: the more turbidity, the more explanations (prerequisite: there is enough clear lime water).

(2) ________ can rekindle wood sticks with sparks; the more vigorously the wood sticks burn, it means _________. That is, ________ can support combustion.

(3) ________ can extinguish burning wood sticks, that is, ________ does not support burning.

(4) Air is mainly composed of _________ and _________, and also contains _________, _________, etc.

2. Based on the above information, think about ways to compare the contents of carbon dioxide, oxygen, and water vapor, and answer the following questions according to the textbook?

Step 1: What is the method for collecting human exhaled air?

Step 2: What is the experimental method for comparing oxygen levels?

Step 3: What is the experimental method for comparing carbon dioxide levels?

Step 4: What is the experimental method for comparing water vapor content?

(1) Does the oxygen content in the exhaled gas decrease?

Test with burning sticks

Step 3: Insert the burning sticks into a bottle of air and a bottle of exhaled gas respectively, observe the phenomenon and record it

(2) Is the carbon dioxide content in the exhaled gas increasing?

Step 4: Collect two bottles of air: Take two gas collecting bottles and cover the bottle mouths with glass pieces. Use clarified lime water to test: drop a few drops of clarified lime water into a bottle of air and a bottle of exhaled gas, and shake, observe and record the phenomenon.

(3) Is the water vapor content in the exhaled gas increasing?

Step 5: Take two dry glass pieces, exhale against one of them, observe the water vapor on the glass piece in the air, and compare it with the other glass piece placed in the air.

On-the-job training:

1. Use the drainage method to collect a bottle of exhaled gas. The method of taking out the gas collection bottle from the sink is ( )

A. Take out the gas collecting bottle directly from the water and place it on the table.

B. Take out the gas collecting bottle directly from the water, cover it with a glass piece and place it on the table

C. Cover the water with a glass piece, take out the water and place it on the table

D. Cover the water with a glass piece, take out the water and place it upside down on the table

2. A classmate discovered at home that biscuits exposed to the air for a period of time will become damp and soften. This phenomenon shows that the air contains _______. Please give two more examples based on your life experience or chemical knowledge to illustrate that the air contains this kind of _______. substance:

(1)_______________________________;

(2)_______________________________.

3. Plants not only perform photosynthesis, but also perform respiration. In order to compare the difference between the two, someone designed the following experiment: On a sunny morning, select two pots of the same plant of similar size, put a cup of clear lime water in each pot, and then put one of the pots (A) Cover it with a colorless and transparent plastic bag and place it in the sun; cover the other pot (B) with a black plastic bag and place it in a dark place. In the evening, cut a small opening in the plastic bag and insert a burning piece of wood. In the strip test, it was found that the wooden strips in A were brighter than the wooden strips in B, while the limewater in A remained clear and in B became turbid.

(1) The wood sticks in A burn more vigorously, which means that there are more _____ in A, which means that the plants mainly undergo ______ effects under sunlight.

(2) The lime water in A remains clear, while the lime water in B becomes turbid, indicating that there are more _________ in B, thus indicating that in the absence of sunlight, plants mainly undergo _____ effects.

(3) Many people like to go to the dense forest for morning exercises at dawn. Please share your opinion based on this experiment.

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