Chasing 200. Summary of Physical and Chemistry Experiments for College Entrance Examination

Collection of High School Chemistry Experiment Poems

1. The use of pallet balances

The screw vernier scale and the pointer scale have pallets. Adjust the screw to achieve balance, and the object codes are separated on the left and right sides.

You need to use tweezers to pick up the code, first large and then small. Medicines cannot be placed directly and must be restored after weighing.

Explanation:

1. Screw vernier scale, pointer scale with pallet: These two sentences describe the main components of the pallet balance: (to adjust the zero point) screws, vernier scale , scale, pointer, tray (divided into two left and right).

2. Adjust the screw to achieve balance: This means that you should first check whether the balance is in a balanced state before weighing. If it is not balanced, adjust the screws to balance it.

3. The object codes are separated on the left and right sides: "object" refers to the substance being weighed; "code" refers to the weight of the balance. This means that the object to be weighed should be placed in the left pan and the weight should be placed in the right pan.

4. Use tweezers to pick up the weight: This sentence means that when picking up the weight, you must not take it with your hands, but must use tweezers.

5. Big first, then small. Remember: when adding weights, you should clamp the weight with large mass first, then the weight with small mass (and finally move the weight).

6. Medicines cannot be placed directly: This means that the weighed medicines cannot be placed directly on the tray (association: You can put a piece of paper of the same size on each of the two trays, and then put the weighed medicines on the tray. The weighed drugs are placed on the paper, and wet or corrosive drugs must be weighed in a watch glass or beaker).

7. Restore after weighing: This means that after weighing, the weight should be put back into the weight box and the balance should be moved back to zero to restore the balance to its original state.

2. Filtration operation experiment

The bucket holder, beaker, glass rod, filter paper and funnel have the same angles. Let it stand before filtering. Don’t forget to keep the three and two low.

Explanation:

1. The bucket rack, beaker, glass rod, and filter paper have the same funnel angles: "bucket" refers to the funnel; "frame" refers to the funnel stand. These two sentences explain the instruments required for filtration operation experiments: funnel, funnel stand, beaker, glass rod, filter paper, and emphasize that the folding angle of the filter paper should be the same as the angle of the funnel (so that the filter paper can be tightly attached to the funnel wall).

2. Let the liquid stand for a while before filtering: This means that the liquid must be allowed to stand for a while before filtering to fully separate the solid and liquid.

3. Don’t forget three points and two low points: This means don’t forget three points and two low points when filtering. "Three leans" means that the end of the funnel neck should lean against the wall of the beaker that receives the filtrate, the glass rod should lean against the filter paper, and the mouth of the beaker holding the filtrate should lean against the glass rod; "two lows" means This means that the edge of the filter paper should be slightly lower than the edge of the funnel, and the liquid level of the poured filtrate should be slightly lower than the edge of the filter paper.

3. Distillation operation experiment

The heating and cooling tube separated by a mesh is tilted, and the upper edge and the lower edge are flat. It is necessary to add broken porcelain to prevent sudden boiling, and the hot air and cold water flow in the opposite direction.

Explanation:

1. The heating and cooling pipe is separated by a network: the "cold pipe" is the condenser pipe. This means that when heating the distillation flask, it should be separated by asbestos mesh (to prevent the distillation flask from cracking due to uneven heating), and when installing the condenser tube, it should be tilted downward.

2. The upper edge and lower edge are parallel: This means that the upper edge of the mercury bulb of the thermometer should be exactly on the same horizontal line as the lower edge of the branch pipe interface of the distilling bottle.

3. Hot air and cold water flow in the opposite direction: This means that the cooling water must continuously flow from bottom to top, in the opposite direction to the flow of hot steam.

4. Extraction operation experiment

The original solutions of the extraction agents are insoluble in each other and have different degrees of solubility. Shake it thoroughly and then let it stand until it is clearly cut.

Explanation:

1. The original solutions of extraction agents are insoluble in each other, and the degree of solubility is different: "extraction agent" refers to the extraction agent; "quality" refers to the solute. The meaning of these two sentences is that in the extraction operation experiment, the principle of selecting the extraction agent is: the extraction agent and the solvent in the solution must be immiscible with each other, and the solubility of the solute in the extraction agent and the original solvent must be different (in the extraction agent The solubility in the solution is greater than the solubility in the original solution).

2. Fully shake and then let stand: This means that the extraction process should be fully shaken to ensure sufficient extraction, and then let stand to allow the solution to stratify.

3. Put it down and pour it down clearly: This sentence means that the lower liquid of the separatory funnel should be released from the funnel foot, while the upper liquid should be poured from the funnel mouth

5. Substance Calculate the amount and concentration of the solution in the preparation step. Calculate and weigh the solution, dissolve, transfer and then adjust the volume. Don’t forget to wash at room temperature, shake the label and you’re done.

Explanation:

1. Calculate and weigh, take the steps to clear, dissolve, transfer and then set the volume: The meaning of these two sentences illustrates the steps for preparing molar solutions: calculation, weighing, (or measure), dissolve, transfer, and dilute to volume.

2. Do not forget to wash at room temperature: "room temperature" means that the temperature of the solution often rises due to the heat of dissolution during dissolution, so it must be cooled to room temperature before transferring to a constant volume. "Wash" means that after pipetting, the beaker and glass rod must be washed with distilled water (2-3 times), and the washing liquid must be combined into the volumetric flask, and then diluted to volume.

3. Shake well and the label is ready: "Shake well" means to fix the bottle stopper after adjusting the volume, hold the stopper with your index finger, and hold the bottom of the bottle with the fingers of the other hand. Invert and shake the volumetric flask several times to mix the solution evenly; "labeling" means attaching a label to indicate the concentration of the solution and the date of preparation.

6. Oxygen production experiment

In the experiment, first check the air tightness and tilt the test tube evenly when heated. Collect common drainage methods, remove the pipe first and then move the lights.

Explanation:

1. In the experiment, first check the air tightness and tilt the test tube evenly when heated. "Test tube tilting" means that when installing a large test tube, the test tube should be slightly tilted, that is, the mouth of the test tube should be lower than the bottom of the test tube. This can prevent the small amount of moisture contained in the medicine from turning into water vapor when heating and reaching the mouth of the tube. It condenses into water droplets and flows back, causing the test tube to rupture. "Heating evenly" means that when heating the test tube, the test tube must be heated evenly (association: the method is to hold the alcohol lamp with your hand when heating is just started, move it back and forth, wait for the test tube to be heated evenly, and then fix the heating. This can prevent the test tube from being heated evenly. Exploded due to local heating).

2. Commonly used drainage methods for collection: This means that when collecting oxygen, the drainage and gas collection method should be used (association: If both the drainage method and the exhaust method can be used to collect a certain gas, then it is generally used. Drainage method. Because the gas collected by the drainage method is higher than the exhaust method. Oxygen is heavier than air. Although the upward exhaust method can be used, it is not as good as the drainage method.)

3. Remove the catheter first and then move the lamp. This means that when stopping the production of oxygen, you must first remove the air conduit from the water tank, and then remove the alcohol lamp (association: if you remove the alcohol lamp first, the temperature in the test tube will decrease, the air pressure will decrease, and the water will flow along the test tube) The catheter sucks into the hot test tube, causing the test tube to rupture due to rapid cooling).

7. Methane production experiment

Sodium acetate alkali gray water has no shadow, and the operation and collection are the same as oxygen. Be sure to check the purity when lighting, and cover the beaker with water drops.

Explanation:

1. Sodium acetate and alkali ash water are shadowless: "sodium acetate" refers to sodium acetate; "alkali ash" refers to soda lime. This sentence means that methane must be produced by reacting anhydrous sodium acetate with dry soda lime (otherwise if sodium acetate crystals or lime are not dried, almost no methane gas will be produced). [Lenovo: You cannot directly react sodium hydroxide with anhydrous sodium acetate. On the one hand, sodium hydroxide easily absorbs moisture in the air; on the other hand, pure sodium hydroxide has a corrosive effect on glass test tubes when heated].

2. The operation and collection are the same as those for oxygen: This means that the operation precautions and collection methods of this experiment are exactly the same as those for oxygen.

3. Be sure to check the purity when igniting: This means that when igniting methane, you must first check its purity (just like igniting hydrogen) [association: if methane is impure and mixed with some air, there will be a risk of explosion] .

4. Cover the beaker with water droplets: This means that if you cover a beaker over the flame, you will soon see water droplets forming on the inner wall [association: turn the beaker over and inject a small amount into the beaker Clear lime water shakes, and lime water becomes turbid.

8. Ammonia production experiment

The ammonium salt is converted into ammonia by heat, and the device has a stable oxygen core. When the alkali ash is dry and the exhaust is exhausted, the pipe opening needs to be plugged with a ball of cotton.

Explanation:

1. Thermal conversion of sludge ammonium salt into ammonia: "slaked ash" refers to slaked lime. This means that ammonia gas is commonly produced in the laboratory by mixing and heating slaked lime and ammonium salt.

2. The device has the same oxygen core: it means that the device is the same as the oxygen-producing device (the implication is that the relevant precautions are also the same).

3. Exhaust air under drying of soda ash: "Soda ash" refers to soda lime. "Soda ash drying" means that when drying ammonia in the experiment, the produced ammonia is usually dried through soda lime. "Downward exhaust" means that the collection of ammonia must use the downward exhaust air collection method (because ammonia is easily soluble in water and is lighter than air). [Lenovo: (1) In order to obtain relatively pure ammonia quickly, the air tube must be extended into the bottom of the test tube; (2) The method to check whether the ammonia gas has filled the test tube is: "Ammonia turns red when it encounters phenolphthalein", "When two acids meet ammonia, they emit white smoke." ]

4. The mouth of the test tube that collects ammonia needs to be blocked with a ball of cotton: This means that the mouth of the test tube that collects ammonia gas needs to be blocked with a ball of cotton. of moisture; (2) Increase the density of ammonia in the test tube. ]

9. Experiment on the reduction of copper oxide by hydrogen

Incline the hydrogen purity test tube, pass the hydrogen gas first and then light the lamp. Black water turns to red water droplets appear, turn off the light and then stop the hydrogen.

Explanation:

1. Test tube for hydrogen purity test: "Hydrogen purity test" means that the purity of the hydrogen passed into the large test tube must be checked first, otherwise there is a risk of explosion; "Tilting the test tube" means that the test tube must be tilted (making the tube mouth lower than the bottom) in order to prevent the generated water vapor from cooling back at the test tube mouth and causing the test tube to rupture.

2. Pass the hydrogen gas first and then light the lamp: This means that when doing this experiment, you must first pass the hydrogen gas for a while, and then light the alcohol lamp after the air in the test tube is exhausted. Otherwise, the hydrogen and air will be mixed during heating. An explosion may occur under such conditions.

3. Black turns to red water droplets: This means that when all the black powder (copper oxide) turns into bright red (copper powder), and a large number of water droplets appear at the mouth of the tube, it indicates a reaction. Complete, the experiment is now stopped.

4. Turn off the lamp and then stop the hydrogen: This means that when you start the experiment, you must first turn off the alcohol lamp, and then wait for the test tube to cool down before stopping the hydrogen gas. Otherwise, air will enter the test tube, and the reduced copper will undergo an oxidation reaction with the oxygen in the air under heated conditions to regenerate copper oxide, causing the experiment to fail.