The concept of chemistry: chemistry is a science that studies the composition, structure, properties and changing laws of substances.

At present, there are only more than 100 elements discovered by human beings, but there are more than 30 million substances discovered and synthesized by human beings.

In modern times, British scientist Dalton put forward modern atomism; Italian physicist and chemist avogadro put forward the concept of molecule.

The establishment of atomism and molecular theory laid the foundation of modern chemistry.

1869, Russian chemist Mendeleev discovered the periodic law of elements and compiled the periodic table of elements.

Unit 1 Entering the Chemical World

Section 1 Changes and Properties of Substances

I. Physical and chemical changes

Physical change, chemical change

Changes that do not produce other substances are called physical changes, and changes that produce other substances are called chemical changes.

The state and shape of common substances may change, and there may be phenomena such as luminescence and exotherm, such as discoloration, outgassing and precipitation. And heat absorption, heat release and light emission.

The essential difference lies in whether new substances are produced.

Whether the molecules that make up the substance have changed.

Physical changes must occur in the connection at the same time as chemical changes, but chemical changes do not necessarily occur at the same time as physical changes.

The change from graphite to diamond is a chemical change.

"Purple smoke comes from the incense burner in Rizhao, and the waterfall hangs in front of the river in the distance" refers to physical changes.

Second, the physical and chemical properties

Physical properties chemical properties

The property of a substance without chemical change. Properties of substances in chemical changes.

Example colors, states and smells; Hardness, density, ignition point, boiling point, melting point, solubility, volatility, conductivity and other flammability, oxidation, reduction, stability, activity, acidity, alkalinity, toxicity and so on.

Do you need to undergo chemical changes to distinguish this property?

Nitrogen and rare gases can be used as protective gases. Although this does not contain chemical changes, it takes advantage of their chemical properties (stability).

Chemistry is a science based on experiments.

First of all, candles

Paraffin is insoluble in water and its density is less than that of water.

When a candle burns, the flame is divided into three layers, including outer flame, middle flame and inner flame.

Putting a matchstick flat into the flame, it is found that both ends carbonize first, indicating that the temperature of the external flame is the highest.

After lighting the candle, cover the flame with a dry and cold beaker, and water drops are generated on the inner wall of the beaker, indicating that the candle burns to produce water; Pour the clarified limewater into the beaker, and the clarified limewater becomes turbid, indicating that the candle burns to produce carbon dioxide.

The white smoke produced when the candle is extinguished is solidified paraffin vapor.

The form of candle burning is paraffin wax+oxygen and carbon dioxide+water C25H32+33O2 25CO2+ 16H2O.

Second, when doing the experiment of "exploring the air inhaled by human body and the gas exhaled by human body", the most important thing is to do a comparative experiment.

In the third quarter, I walked into the chemistry laboratory.

First, the use of pallet scale

1. The accuracy of the pallet balance is 0. 1g, that is, the mass of the object measured by the balance can only be accurate to one decimal point.

2. The pallet scale consists of a pallet, a pointer, a travel code, a scale, a dividing plate and a balance nut.

3. Physical use method (measuring the mass of an object):

A) Place the balance horizontally, put the travel code on the zero scale of the balance, and adjust the balance nut to balance the balance.

B) Put the object on the left plate and the weight on the right plate. The weight must be clamped with tweezers (to prevent the weighing error caused by the rust of the weight), first add the weight with large mass, then add the weight with small mass, and finally move the code until the balance is balanced.

C) Record the added weight and the quality of the mobile code.

D) After weighing, put the weight back in the weight box and move the roaming code back to 0.

4. Chemical use method (material-oriented):

A) Place the balance horizontally, put the travel code on the zero scale of the balance, and adjust the balance nut to balance the balance.

B) If the medicine is powder, put a piece of paper with the same size and quality on the left and right plates of the balance. If the medicine is deliquescent or corrosive, please put the glassware on the balance. You can put them first and then adjust the balance, so you don't have to record their quality. )

C) Take the weight with tweezers and put it on the correct plate, and move the code to make the reading of the balance equal to the quality of the medicine to be weighed.

D) Add medicine to the plate on the left to balance the balance. If the balance is unbalanced, you can only add or subtract drugs on the left plate, and you can't move weights or wander yards.

E) After weighing, put the weight back in the weight box and move the roaming code back to 0.

5. When "the left object is the right code", the mass of matter = the mass of weight+the index of wandering code; "Left yard and right things", the quality of material = the quality of weight-the index of wandering yard. Although the practice of "left yards and right things" can also measure the quality of matter, it is wrong.

6. When weighing dry solids, put a piece of paper with the same size and quality in each tray on both sides and weigh it on the paper. Wet or corrosive drugs (such as sodium hydroxide) are weighed in covered glassware (such as small beakers and watches).

Second, the connection of the instrument

1. Insert the glass tube into the rubber plug with holes: first wet the end of the glass to be inserted into the rubber plug with water, and then rotate it slightly to insert it.

2. Connect the glass tube with the rubber tube: first wet the glass tube with water, and then insert the glass tube into the rubber tube with a little force.

3. Plug the rubber plug into the container mouth: slowly turn the rubber plug and plug it into the container mouth. Never put the container on the table and force it into the plug to avoid crushing it.

Everything that requires strength should be done by the right hand.

Three, the provisions of the laboratory to obtain drugs

1. Don't touch the medicine with your hands, don't put your nose to the mouth of the container to smell the medicine, and don't taste any medicine.

2. Pay attention to saving medicines. Drugs should be taken in strict accordance with the dose prescribed in the experiment. If there is no prescribed dose, the minimum amount of liquid (1~2mL) should be taken. The solid only needs to cover the bottom of the test tube.

3. The remaining drugs in the experiment can't be put back into the original bottle, can't be discarded at will, and can't be taken out of the laboratory, but should be put into the designated container.

Four. Obtain solid medicine

1. Solid drugs are usually kept in jars.

2. Solid powder is generally taken with a spoon or paper trough. When operating, tilt the test tube, carefully send the medicine spoon to the bottom of the test tube, and then make the test tube stand upright. ("one tilt, two feeds, three uprights")

3. Bulk drugs are generally picked up with tweezers. In operation, the container is placed horizontally, the medicine or metal particles are put into the mouth of the container, and then the container is slowly erected, so that the medicine or metal particles slowly slide to the bottom of the container to avoid the container from breaking. ("one horizontal, two horizontal and three vertical")

4. Used medicine spoons or tweezers should be wiped with clean paper immediately.

Verb (abbreviation for verb) to obtain liquid medicine

Liquid drugs are usually packed in narrow-mouthed bottles. Wide-mouth bottle, narrow-mouth bottle, etc. Have been frosted to increase the air tightness of the container.

1. Take an indefinite amount (more) of liquid-pour it directly.

Precautions in use (for operation purposes in brackets):

A. Bottle stoppers of narrow-mouth bottles must be placed upside down on the table to prevent drugs from corroding the testing platform or polluting drugs;

B the bottle mouth must be close to the test tube mouth and poured slowly to prevent the loss of liquid medicine;

C. The labeled side of the narrow-mouth bottle must face the palm of your hand to prevent the liquid medicine from splashing corrosive labels;

D. Immediately after pouring out the liquid, close the cork, put the bottle back in its original place, and put the label outward to prevent the medicine from deliquescence and deterioration.

2. Take an indefinite amount (less) of liquid-use a rubber-tipped dropper.

Precautions in use (for operation purposes in brackets):

A. it should be dropped vertically above the container; Don't touch the container wall with rubber dropper to avoid polluting the test tube or reagent;

B. After taking the liquid, the dropper should keep the rubber cap on the floor, and should not be placed flat or upside down to prevent the liquid from flowing back, polluting the reagent or corroding the rubber cap;

C used test tubes should be washed with clear water immediately; But the dropper on the dropper bottle can't be washed with water and can't be used interchangeably.

3. Take a certain amount of liquid-use a measuring cylinder.

Matters needing attention when using:

A. When the liquid poured into the measuring cylinder approaches the required scale, stop pouring, and use a rubber dropper to drop the rest to the required scale;

B. When reading, the measuring cylinder must be placed smoothly. If the line of sight and the lowest part of the concave liquid level in the measuring cylinder keep horizontal reading, the reading will be low. When reading, if you look down, the reading is on the high side-when you look up when you pour the liquid, you measure more liquid; Looking down when pouring the liquid, the measured liquid is less.

Six, the heating of materials

1. Precautions when using alcohol lamp (for operation purposes in brackets)

A it is absolutely forbidden to add alcohol to the burning alcohol lamp to prevent fire;

B, it is absolutely forbidden to use alcohol lamp to light another alcohol lamp, and use matches to prevent fire;

C. After using the alcohol lamp, be sure to cover the lamp cap, and do not blow it with your mouth, so as to avoid alcohol burning in the lamp and causing danger;

D if spilled alcohol burns on the table, immediately wipe the cover with a wet rag.

E the alcohol content in the alcohol lamp should not be less than 1/4 of the capacity of the alcohol lamp, nor should it be more than 2/3 of the capacity of the alcohol lamp.

2. Heating equipment

Liquid: test tube, evaporating dish, conical bottle, beaker and flask (the three need asbestos mesh when heating after use).

Solid: test tube, evaporating dish, burning spoon.

3. Precautions for heating test tubes (used for the operation in brackets)

A there should be no water on the outer wall of the test tube to prevent the test tube from bursting;

B. there should be a test tube clamp when heating. When clamping the test tube, the test tube clamp should be sleeved upward from the bottom of the test tube, and the clamping position is close to the test tube mouth 1/3. Hold the long handle of the tube clamp, and don't press your thumb on the short handle.

C. If the solid is heated, the test tube mouth should be slightly inclined downward to prevent the condensed water from flowing back to the bottom of the hot test tube, causing the test tube to burst; If the liquid is heated, the mouth of the test tube should be inclined upward at an angle of 45 with the table top.

D if the liquid is heated, the volume of the liquid should not exceed 1/3 of the volume of the test tube to prevent the liquid from overflowing when it is boiling.

E. Preheat before heating, and let the test tube move on the flame. After the test tube is heated evenly, the flame is fixed at the part containing the medicine and heated to prevent the test tube from bursting.

F don't touch the wick of the alcohol lamp at the bottom of the test tube to prevent the test tube from bursting;

G. The hot test tube cannot be washed with cold water immediately to prevent the test tube from bursting;

H. Don't point the test tube in the direction of someone when heating to prevent the liquid from overflowing when boiling.

1. After heating, take the test tube clamp out of the test tube mouth;

Seven, washing utensils

1. Washing method: First, pour the waste liquid in the test tube into the waste liquid tank, then pour it into the test tube volume of 1/2, shake it well, then pour out the water, and repeat the washing several times. If the inner wall is attached with substances that are not easy to wash off, scrub it with a tube brush.

2. Tube brush: When brushing, the tube brush should rotate or move up and down, but the force should not be too strong to prevent damage to the test tube.

3. Standard for cleaning the instrument: When the water attached to the inner wall of the cleaned glass instrument neither gathers into water droplets nor flows down in strands, it means that the instrument has been cleaned.

4. After cleaning, the instrument should not be misplaced, but should be inserted upside down in the test tube rack to dry.

5. Special circumstances

If grease is attached to the glass instrument, first clean it with hot soda solution or washing powder, and then rinse it with clean water.

If water-insoluble alkali, basic oxide and carbonate are attached to the glass instrument, it should be dissolved with dilute hydrochloric acid first, and then washed with water.

Eight, the method of smelling gas: gently fan the bottle mouth with your hands, so that only a very small amount of gas enters the nostrils.

Nine, the storage of several drugs

1. White phosphorus in water.

Some people say that white phosphorus should be put in a narrow-mouthed bottle because there is water, which is wrong.

2. Concentrated sulfuric acid and concentrated hydrochloric acid should be ground and covered tightly. The brown grinding bottle cap of concentrated nitric acid is tight.

Concentrated sulfuric acid has water absorption, concentrated hydrochloric acid and concentrated nitric acid are volatile, and concentrated nitric acid is easy to decompose when exposed to light.

3. Silver nitrate solution is stored in brown reagent bottle. (Silver nitrate solution is easily decomposed by light. )

4. Solid sodium hydroxide and potassium hydroxide should be sealed in dry containers and sealed with rubber plugs instead of glass plugs.

Solid sodium hydroxide and potassium hydroxide have water absorption and are easy to deliquesce. Alkali will react with glass, and it is difficult to open the bottle with a glass stopper.

5. Metal potassium, sodium and calcium are stored in kerosene. Metal potassium, sodium and calcium are very active and can react with oxygen in the air.

X. accident handling

1. Fire: Cover it with a wet rag or sand.

2. If concentrated sulfuric acid accidentally touches clothes or skin, it should be washed with plenty of water immediately, and then coated with 3%~5% sodium bicarbonate solution.

Dilute sulfuric acid should also be treated when it comes into contact with clothes or skin, otherwise the water in dilute sulfuric acid will evaporate and become concentrated sulfuric acid.

3. If the lye drops on the skin carelessly, wash it with more water and then apply boric acid solution.

4. When quicklime touches the skin, wipe it off with a cloth first, and then rinse it with plenty of water.

Eleven, pay attention to the specific operation and precautions of the experiment! There is always such a problem in the exam: give some pictures of experimental operations, and then distinguish right from wrong.