Topic 3 Walking into the Chemistry Laboratory

Topic 3

Walking into the Chemistry Laboratory

We already know that an important way to learn chemistry is through scientific inquiry. Experiments are an important means of scientific inquiry. To learn chemistry, one must enter the chemical laboratory, because this is an important place for scientific inquiry. There are many instruments and medicines waiting for us to use to explore the mysteries of substances and their changes.

When we walk into the chemical laboratory, we should first read the laboratory rules carefully. Do not take these rules lightly, as they are an important guarantee for conducting experiments safely and successfully! We should also know some commonly used instruments and medicines in experiments, and learn some basic operations of experiments, such as how to take chemicals and how to heat substances, etc., so that we can conduct experiments correctly, quickly and safely and obtain reliable experimental results .

Let's do a few experiments and learn some basic chemical

1、The use of chemicals

Many chemicals used in laboratories are flammable, explosive, corrosive or toxic. In order to ensure safety, carefully read the rules for taking medicines before the experiment.

1. Taking of solid medicine

Solid medicines are usually stored in jars, and the solid medicines are generally taken with a medicine spoon. Some blocky medicines (such as limestone, etc.) can be picked up with inserts. The used medicine spoon or setting should be wiped off with a clean paper immediately for the next use.

When putting dense lumpy medicine or metal particles into a glass container, the container should be placed horizontally first, and after the medicine or metal particles are put into the mouth of the container, the container should be erected slowly to make the medicine or metal particles slow down. Slide gently to the bottom of the container so as not to break the container.

When loading solid powder into the test tube, in order to prevent the drug from sticking to the tube mouth and the tube wall, the test tube can be tilted first, and the medicine spoon (or the paper slot folded with small paper strips) containing the drug can be carefully sent to the test tube. the bottom of the test tube and then stand the test tube upright.

2. Administering liquid medicines

Liquid medicines are usually contained in narrow-mouthed bottles, and are usually taken by pouring.

To take a certain amount of liquid medicine, the volume is usually measured with a graduated cylinder. When measuring liquid, the measuring cylinder must be placed flat, and the line of sight should be kept at the same level as the lowest point of the concave liquid surface of the liquid in the measuring stick, and then read the volume of the liquid.

A dropper can also be used when taking a small amount of liquid. After taking the liquid, keep the rubber cap on the dropper, and do not lay it flat or upside down to prevent the liquid from flowing backwards, contaminating the reagent or corroding the rubber cap; do not place the dropper on the test bench or other places to avoid contamination of the dropper. Tube. The used dropper should be rinsed with clean water immediately (do not rinse the dropper on the dropper with water) for reuse. It is strictly forbidden to use the unwashed dropper to draw other reagents.

1. How to use the alcohol lamp

When using alcohol lamps, pay attention to the following points:

(1) It is absolutely forbidden to add alcohol to the burning alcohol lamp to avoid fire;

(2)It is absolutely forbidden to ignite another alcohol lamp with an alcohol lamp;?

(3)After using the alcohol lamp, you must cover it with the lamp cap, and do not blow it with your mouth. (After the cover is off, lightly lift the lamp cap, and then cover it again)

(4)Don't knock down the alcohol lamp, if the spilled alcohol burns on the table, don't panic, cover it with a wet rag immediately.

2. To heat a substance

When heating liquid in a test tube with an alcohol lamp, pay attention to the following points:

(1)The outer wall of the test tube should be dry, and the liquid in the test tube should not exceed 1/3 of the test tube volume ;

(2)When clamping the test tube with the test tube clamp, it should be put on and removed from the bottom of the test tube;

(3)When heating, the bottom of the test tube should be heated evenly, and then fixed and heated with the outer flame of the alcohol lamp;

(4)Do not point the mouth of the test tube at yourself or others;

(5)The heated test tube cannot be exposed to or rinsed with cold water immediately.

3. Connect the instrument device

Correctly connecting the instrument and device is an important part of conducting chemical experiments. In junior high school chemical experiments, the operation of connecting glass catheters, rubber stoppers, rubber tubes, etc. is often used. After the device is connected, its airtightness is generally checked.

（1） Insert the glass tube into the rubber stopper with holes

Wet the mouth of the glass tube with water first, then align it with the hole on the rubber stopper and turn it slightly hard to insert it.

（2）Connect glass tube and rubber tube

Wet the mouth of the glass tube with water first, and then insert the glass tube into the rubber tube with a little force

（3）Rubber stoppers on container mouths

The rubber stopper should be slowly turned and inserted into the container mouth. Do not put the container on the table and then forcefully insert the stopper, so as not to crush the container.

（4）Check the airtightness of the device

hold the test tube tightly with your hand and observe whether there are bubbles coming out of the tube opening in the water. If there are air bubbles, it means that the device is not leaking; If there are no air bubbles, carefully find out the reason, such as whether the rubber stopper should be tightened or replaced, and the experiment can only be carried out after there is no air leakage.

4. Washing glass instruments

Clean instruments must be used for experiments, otherwise the experimental results will be affected. Now take the washing of test tubes as an example to illustrate the method of washing glass instruments.

First pour out the waste liquid in the test tube, then inject half of the test tube with water, pour out the water after shaking, then pour in water, shake and then pour out, and wash several times in this way. If there are substances that are not easy to wash off on the inner wall, use a test tube brush to scrub. When scrubbing, the test tube brush must be rotated or moved up and down, but the force should not be too strong to prevent damage to the test tube.

When the water attached to the inner wall of the washed glass instrument neither gathers into water droplets nor flows down in streams, it indicates that the instrument has been cleaned. Cleaned glass instruments should be placed in designated places.

After finishing this topic, you should know

1.The chemical laboratory is an important place for chemical experiments, and laboratory rules must be followed, with special attention to safety.

2.Learn some of the most basic experimental operation methods, such as taking chemicals, heating substances, connecting instruments, washing instruments, etc. Correct operation is an important guarantee for the success of experiments.