I urgently want a few small experiments in the China Science and Technology Museum, and I want ,,, n

Two different metals are put into a suitable electrolyte and connected by wires to generate an electric current. Of course, it is possible to put two metals into the same cup of electrolyte, or to put two metals into different electrolytes, and then connect the two electrolytes with a salt bridge.

This is because the metal becomes an electrode after being put into the electrolyte, and different types of electrodes have different electrode potentials (related to the metal type, electrolyte type, electrolyte concentration, and temperature).

Connecting two different metals in the electrolyte with wires is equivalent to connecting two different electrodes, and because the potentials of the two electrodes are different, that is, there is a potential difference (voltage) between the electrodes, and an electric current is generated.

Guess the reason is the above, I think there should be an explanation.

Unclear discussion.

Categories: Education, Science, >> Science & Technology.

Problem description: Science and technology museums generally have a device: from the same position on the high place to the same place on the ground, there are three tracks with different curvatures for the ball to roll down, and the ball on it can be released downward at the same time. What is it used for? The result? Write out the process of conjecture and experimentation.

Analysis: This should demonstrate the most rappelling line problem. That is, the object lands fastest in the orbit between two points only under the action of gravity. At that time, Newton, Bernoulli and other university grinders gave different answers.

The chain of the most downhill line is officially the roller line, which is the trajectory of a wheel at any point on the wheel in pure rolling. So the result is the fastest one for the roller line.

The variational method has been extended from the problem of the fastest descending line, which has been widely used in mathematics, physics and engineering.

Categories: Education Academic Exams >> High School Entrance Examination.

Analysis: Rolling bottles.

The Leaning Tower of Pisa experiment is one of the most famous experiments in the history of science, in which Galileo Galilei proved that the speed of falling objects is independent of weight with the help of two iron balls of different weights. So, does an object of the same weight have to fall at the same velocity? Now let's do a little experiment on rolling friction, and maybe the results will surprise you.

Take a rectangular board and use a few books to raise and secure one end and lay the other end flat on the table. Find two round glass bottles of the same texture, the same size, and the same weight, fill them with the same weight of fine sand and water, and close the caps. To prevent water and sand from leaking out of the bottle when it rolls, you can stick a little beeswax to the mouth of the bottle.

Now place the two bottles on the board and roll them down at the same starting height. Theoretically, if two bottles weigh the same weight and slide on the same plank, then the external frictional resistance of both bottles should be the same, and because they both slide from the same height at the same time, then both bottles should reach the table at the same time. But in reality, you'll find that the bottle with water will reach the end earlier than the bottle with sand.

Why is this so?

In fact, the energy that the bottle has at the starting position is the potential energy, when it begins to slide, the potential energy will be converted into kinetic energy and the heat energy generated by friction, although the friction between the two bottles and the wooden board is the same, but the friction of the sand on the inner wall of the bottle is much greater than the friction of the water on the inner wall of the bottle, and there will be friction between the sand, the heat energy generated by these frictions is greater than the heat energy of the internal friction of the bottle filled with water, according to the law of conservation of energy, the kinetic energy of the bottle containing sand is naturally less, As a result, it slides more slowly than a bottle filled with water.

chemfans/huaxveshihua

There are some interesting little experiments in chemistry on this website.

Tools Raw Materials:

1 cup of hot and cold water, 1 color of ink (pigment).

1. Material preparation: 1 cup of hot and cold water, 1 color of ink (pigment).

2. Pour hot water into one of the cups and cold water in the other.

3. Drip ink into the cup of cold water first, and then drip ink into the cup of hot water. (At the same time drops will be better contrasts).

4. We can observe that the pigments in the cup filled with hot water begin to diffuse, and the ink stains in the cup filled with cold water are still condensed together, and the color of the hot water is also stronger.

Experimental principle

Due to the high temperature of the hot water and the violent movement of the molecules, if you drop two drops of ink into the cold water cup and the hot water cup, you will see that the ink in the hot water spreads quickly.

This suggests that the irregular motion of the molecule is related to the temperature, and the higher the temperature, the more intense the irregular motion of the molecule. Because the water molecules of hot water move faster than cold water. The water molecules in the hot water can run into the ink relatively quickly and merge with the ink.

Turning over a set of good stuff this afternoon, what is it? Haha, it's a science experiment package.

This is a baby, the first thing I took out was a small test strip, but I didn't bring a contrast color card, what can I do? Ask Mom.

Mom, you see, this inferior product was only given a test strip, not a contrast color card. ”

Hehe, I knew that this wonderful mother, at the critical moment, would definitely be useless.

So what to do, there is some knowledge, if you don't understand it, you don't understand. Oh yes, back to the textbook, this is the matching school bag, and the knowledge is definitely in the textbook.

Haha, sure enough, the color card is clearly printed on the textbook, and it also explains the use of these test strips in detail. That's going to be easy, it.

I prepared white vinegar, laundry detergent, tap water, purified water, baking soda, cucumber juice and apple juice, as well as sodium acetate and calcium lactate.

And guess what? This solution of sodium acetate and calcium lactate turned out to be alkaline, what about the acid? Bullying small children.

That white vinegar and apple, needless to say, are acidic. Laundry detergent and baking soda are definitely alkaline. There is still a difference between tap water and pure water, the tap water in our community is weakly acidic, and pure water is really nothing, it is neutral. Cucumber juice does not react, it should also be neutral.

The second experiment is the most interesting, one that proves that air really exists. That's interesting. Prepare a candle, a plate, an empty bottle of mineral water, a little water.

Light the candle and stick it to the bottom of the plate, then pour water into the plate and cover the candle with an empty mineral water bottle.

And then a miracle happened!

Haha, after a while, the candle went out, and the water on the plate poured into the bottle with a clatter, and the candle floated up. It startled me at the time, and then I burst out laughing. It turns out that air really exists, and when the candle burns, it really consumes some of the air, which is oxygen.

Then the air pressure inside and outside the bottle changed, and the water poured in, and it turned out that we could see the air in this way, which was so interesting.

Now you know why I didn't use a glass but a mineral water bottle, right? Because the mouth of the mineral water bottle is very thin, the water is particularly obvious when it pours in, which makes it shocking and the memory clearer, right?

I must not let my mother hear this, and when she hears it, she will say that I am talking nonsense. Because the reason why I used the mineral water bottle was because I couldn't find the glass, and I didn't expect it to have an unexpected effect.

Of course, we also did some other small experiments, but I didn't think it was a big deal, so I won't mention it.

It seems that the science is still quite interesting, and you can play it later.

Think: Why, eggs can get in from a bottle smaller than yourself.

Experimental materials: 1 hard-boiled egg, 1 fine-mouthed bottle, several pieces of paper, 1 box of matches.

Hard-boiled eggs: Bottles:

A number of pieces of paper: matches:

Operation: 1Peel the shell of the hard-boiled eggs.

3.Leave the note still in the bottle after it is lit.

4.As soon as the fire is extinguished, immediately hold the egg to the mouth of the bottle and immediately remove your hand.

Answer: 1When the finger of the paper is just burned, the bottle is hot.

2.After the egg is buckled at the mouth of the bottle, the temperature of the pin in the bottle gradually decreases, and the pressure inside the bottle becomes smaller.