Thinking: Insert a chopstick into a cup filled with rice, and then lift the chopstick. Can chopsticks lift rice and cups?

Materials: a plastic cup, a rice cup and a bamboo chopstick.

Operation:

1. Fill the plastic cup with rice.

2. Press the rice in the cup by hand.

3. Hold the rice with your hands and put chopsticks between your fingers.

4. Gently lift chopsticks with your hands, and the cup and rice are lifted together.

Explanation:

Because of the extrusion between rice grains in the cup, the air in the cup is squeezed out, and the pressure outside the cup is greater than that inside the cup, so that chopsticks and rice grains are tightly combined and chopsticks can hold the rice cup.

★ bottle competition

Thinking: Two bottles of the same weight, one filled with sand and the other filled with water, roll down from a height. Who will reach the finish line first?

Materials: two bottles of the same size and weight, sand, water, a rectangular board and two thick books.

Operation:

1. Make a slope with a rectangular board and two books.

2. Pour water into another bottle and sand into the bottle.

3. Put two bottles on the board and let them roll down at the same starting height at the same time.

The bottle filled with water reaches the finish line earlier than the bottle filled with sand.

Explanation:

The friction between sand and the inner wall of the bottle is much greater than that of water, and there will be friction between sand, so its sliding speed is slower than that of a bottle filled with water.

Creation: change the substances in the bottle and let them compete!

★ paid newspaper

Thinking: Without glue, tape and other things, newspapers can stick to the wall without falling off. Do you know why?

Material: 1 pencil; 1 newspaper.

Steps:

1. Spread the newspaper and lay it flat on the wall.

2. After a few quick rubs on the newspaper with one side of the pencil, the newspaper won't fall off just like sticking to the wall.

3. Lift a corner of the newspaper, and then let go, and the lifted corner will be sucked back by the wall.

Take the newspaper off the wall slowly and pay attention to the static sound.

Description:

1. Wipe the pencil to charge the newspaper.

2. The charged newspaper was sucked to the wall.

When the indoor air is dry (especially in winter), if you take down the newspaper from the wall, you will hear the crackle of static electricity.

Creation: Please have a try. What else can be stuck to the wall by static electricity without glue?

★ Separation of pepper and salt

Thinking: I accidentally mixed the kitchen condiments: pepper and salt. How can I separate them?

Ingredients: pepper, salt, plastic spoon, small dish.

Operation:

1. Mix salt and pepper.

2. Stir well with chopsticks.

3. Rub the plastic spoon on the clothes and put it on the salt and pepper.

4. Pepper sticks to the spoon first.

5. Move the plastic spoon down slightly.

6. After salt, stick it on the spoon.

Explanation:

Pepper is electrostatically adsorbed earlier than salt because its weight is lighter than salt.

Create:

Can you separate other mixed materials in this way?

★ Inflatable balloon

Thinking: When will two balloons attract each other and repel each other?

Material: 2 inflatable balloons, 1 string, 1 cardboard.

Operation:

1 Inflate two balloons separately and tie a knot in your mouth.

Connect two balloons with a thread.

Rub the balloon on your hair (or sweater).

Lift the middle part of the rope and the two balloons will separate immediately.

Put the cardboard between two balloons, and the electricity on the balloons makes them attracted to the cardboard.

Explanation:

The electricity on one balloon repels the electricity on the other balloon.

The electricity on the two balloons attracts them to the cardboard.

Creation: Can other small experiments be used to illustrate that balloons are charged?

★ Lovely watermark

Thinking: The beautiful patterns on rice paper are not drawn, but how are they made?

Materials: 1 washbasin, 1-2 rice paper, 1 chopsticks, 1 cotton swab, 1 bottle of ink and water (about half a basin).

Operation:

1. Pour half a basin of water into the washbasin and gently touch the water surface with chopsticks dipped in ink to see the ink on the water surface.

Expand into a circle.

2. Wipe the scalp with a cotton swab for two or three times.

3. Then touch the center of the ink circle and see what happens.

4. Gently cover the calligraphy paper on the water, and then pick it up slowly. What patterns are printed on the paper?

Explanation:

1. When the cotton swab touches, the ink will swell into an irregular circular pattern.

2. A small amount of oil on the scalp rubbed by cotton swabs will affect the mutual pulling force of water molecules.

3. The watermark will present irregular concentric circles.

Create:

Try other methods to change the ink pattern on the water surface.

★ Switch water flow

Thinking: Why does a stream of water become a stream when you touch it with your hand?

Material: a tin can, awl, water.

Operation:

1. Drill five holes in the bottom of the empty iron box with nails (the spacing between the holes is only about 5 mm).

2. Fill the water tank with water, and five streams of water flow out from five small holes.

Twist these streams together with your thumb and forefinger.

When the hand is removed, the five streams of water will merge into one.

If you wipe the small hole in the jar with your hand again, the water will become five strands again.

Explanation:

The surface tension of water makes the water flow on and off.

★ Floating needle

Thinking: Why does the needle float on the water?

Materials: a bowl of water, needles, tweezers and detergent.

Operation:

1, pour a glass of water in the cup.

2, with children, carefully put a needle on the water.

2. Remove the piston slowly and the needle will float on the water.

Drop a drop of detergent into the water and the needle will sink.

Explanation:

1, it is the surface tension of water that supports the needle so that it will not sink. Surface tension is the cohesive connection formed by water molecules. This cohesive connection is due to the fact that some molecules are attracted together and the molecules squeeze each other to form films. This kind of film is called surface tension, which can hold the object that should sink.

2, detergent reduces the surface tension, the needle will not float.

Attention: The needle is dangerous, please ask parents to help you operate it.

In the experiment 1, the sound is generated by poking the comb teeth.

The sound made by sparse teeth is low, and the sound made by thin teeth is high. The sound generated by the comb can be amplified by the "horn" of the paper roll or something hard.

Experiment 2 compares the difference between vibration and sound with a water cup.

In order to enhance comparability, you can only use a cup or a bottle-instruct students to tap the mouth of the cup with a small wooden stick in the process of adding water to the cup to compare different sounds. Experimental results-With the increase of water in the cup, the sound becomes lower and lower. Tip: In order to prevent bubbles from forming in the process of adding water, it is best to use cold boiled water. )

In experiment 3, the vibration phenomenon of * * * was observed with the materials around us.

To use two cups, first add one-third of water to one cup, and tap the mouth of the two cups with a pencil to see if the two cups make the same sound. Then slowly add water to the second cup (knock on the mouths of both cups at the same time) until the two cups make the same sound (at this time, the two cups reach the state of * * * vibration). Then, stick a metal wire to the mouth of the second cup with tape, and knock on the mouth of the first cup, and you will find that the metal wire is vibrating gently. As you keep knocking, make the cup with wire slowly close to the first cup, you will find that the vibration amplitude of the wire is getting bigger and bigger until it finally falls. (Related story: A long time ago, a czar's army went out to train. With the officer's orders, the soldiers marched in neat steps. When the troops were walking on a wooden bridge, the wooden bridge suddenly shook up and down and finally collapsed with a bang. After inspection, it was found that the collapse of the wooden bridge was caused by the marching rhythm of the soldiers. From then on, the army crossed the bridge and never dared to March forward with neat steps. )

Experiment 4: Make a "tape recorder" with the materials around you.

Active materials: jar (or round paper box) without cover, round paper, glue, nails, thick iron wire, thin iron sheet with tip, long glass and candles.

Activity steps:

(1) Cut off the bottom of the can with a suitable tool, and the can becomes a short and thick cylinder.

(2) Cut a round piece of paper and stick it on one end of the can with glue instead of the cut bottom.

(3) After the glue is dry, spray paper with water.

(4) Punch two small holes with the same height on the side of the cylinder with nails.

5] Insert the wire into the shape shown in the figure with a vice and insert it into the two holes.

[6] When the bottom of the paper is soaked with water and becomes dry and tight like a drum skin, drop a drop of glue in the center of the paper, stick a thin iron sheet (one end of the iron sheet is as sharp as a needle) on the glue, and set it aside until it is dry.

Once, light a candle and bake the glass on the flame until the glass turns black.

⑻ Turn the glass rod over and put the blackened side on the table.

(9) Bring the cylinder to the front so that the tip of the iron sheet just reaches the blackened glass plate.

⑽ Pull the glass sheet and observe the movement track left by the needle tip on the blackened glass sheet. (Corresponding to the different sounds made by the surrounding objects, the needle tip will leave different tracks. In order to avoid recording confusion, a blackened glass plate should be changed every experiment, and the sound should be controlled one at a time. )