Review materials of science in the first volume of the fourth grade of People's Education Press (no test paper)

Fourth grade, the first volume of scientific review materials.

1, weather unit

Scientific concept:

Weather features mainly include cloud cover, precipitation, wind and temperature. The weather is constantly changing, which can be observed and predicted. Some animals or plants can be our special "meteorologists". Observe the weather at the same time and place every day. A month's weather change cannot represent this year's climate characteristics.

Clouds can be regarded as fog in the sky. Different clouds indicate different weather is coming. Cloud amount is the standard to distinguish sunny (less than 1/4), cloudy (about 7/ 10) and cloudy (more than 9/ 10). Clouds are divided into cumulus clouds (it rains lightly, just like cotton piles), stratus clouds (it rains, rains and snows in Mao Mao) and cirrus clouds (it is slender and feathery and consists of ice crystals, but it doesn't rain).

Temperature is an important record data in the weather calendar. Thermometers can be used for measurement, and the unit is 0℃. The temperature of an area should be measured in a ventilated and cool place outside. The lowest temperature is around 6 o'clock in the morning and the highest temperature is around 14 o'clock in the afternoon. During the morning to afternoon 14, the temperature gradually rose, and after the afternoon 14, the temperature began to fall gradually. When water freezes, the temperature should be below 0℃. When water is boiling, the temperature should be 100℃

Wind vane is an instrument for measuring wind direction, and the arrow points to the direction in which the wind blows. The wind has power. The wind is divided into 13 in the wind scale table. The anemometer can detect the level and speed of the wind, and the wind speed is calculated by how many meters the wind travels per second. The wind level in the weather calendar can also be represented by simplified flags: no wind, breeze and strong wind. (See page 10 of the Science Book for the wind rating table. )

Rain gauge is a device for measuring precipitation (rainfall), which detects the precipitation within 24 hours a day (there are many kinds of precipitation, such as rain, snow, hail and so on). The diameter of the rain gauge does not affect the accuracy of the data. It is light rain below 10mm, moderate rain below10-25mm, heavy rain below 25-50mm, heavy rain below 50-100mm and heavy rain above 200mm. ..

Scientific experiment:

1. Measurement and comparison of indoor and outdoor temperatures.

Precautions for using thermometer:

Hold the thermometer in your hand for about one minute until the liquid column no longer changes, and then read it correctly.

When reading, you should look directly at the top of the liquid level in the thermometer, and you can't look down or up.

2. The team will make a weather calendar, then observe the weather for one month and make records.

The weather calendar should include: cloud cover, precipitation, wind speed and direction, temperature and other weather phenomena (with learned weather symbols). Date cannot be less than.

Short answer questions:

1. The influence of weather on our life can be represented by a network diagram. (page 3 of science books)

2. What methods are used to classify weather conditions such as sunny, cloudy, cloudy and foggy? (drawing)

Do you know which eight directions can be used to describe the wind direction? (Can be expressed in words or pictures)

4. Be able to count weather information and analyze data. For example, the "Science Exercise Book" on page 7.

I can draw a line graph (curve) or histogram of temperature change and analyze the data in the graph.

2. Dissolving device

Scientific concept:

Dissolution characteristics: Dissolution means that the substance is evenly and stably dispersed in water, and will not settle by itself, and the substance cannot be separated from water by filtration or precipitation.

Potassium permanganate is dissolved in water to form a purple transparent solution, which is often used for disinfection and antisepsis.

Water can dissolve solids (such as salt and potassium permanganate). ), liquid (such as alcohol, white vinegar, etc. ) and gases (such as oxygen, carbon dioxide, etc. For example, animals and plants in water breathe air dissolved in water.

Dissolution of substances can be accelerated by stirring, heating and crushing.

The amount of salt dissolved in a certain amount of water is certain, and it is impossible to dissolve indefinitely. The amount of salt dissolved in water is related to the amount of water. Generally 100ML water can dissolve about 36 grams of salt. If there is some insoluble salt at the bottom of a cup of concentrated brine, you can increase the amount of dissolved salt by adding water.

Salt dissolved in water can be separated by evaporation, which is widely used in life.

The flame of alcohol lamp consists of outer flame (maximum temperature), inner flame and flame core.

Scientific experiment:

1, filtration experiment

Required materials: square bracket, funnel, filter paper, beaker, glass rod.

Key points of operation: "one stick", "two lows" and "three inclinations"

"One paste" means that the filter paper soaked with water should be close to the funnel wall;

"Two lows" means that ① the filter paper edge is slightly lower than the funnel edge ② the filtrate level is slightly lower than the filter paper edge;

"Three leanings" means ① the beaker is close to the lower part of the funnel, ② the glass rod is slightly close to the edge of the three-layer filter paper, and ③ the end of the funnel is close to the inner wall of the beaker.

2. How to accelerate dissolution?

(1) Key points of comparison between stirred and non-stirred conditions:

Ingredients: two portions of salt, two beakers, glass rods and water.

Same conditions: the water quantity, water temperature, salt quantity and observation time are the same.

Different conditions: one cup with stirring and one cup without stirring.

(2) Comparison of key points under heating and non-heating conditions:

Ingredients: two servings of salt, two beakers and water (hot water and cold water).

The same conditions: the amount of water, salt and observation time are the same, without stirring.

Different conditions: one cup is heated and one cup is not heated.

(3) Compare the key points under crushing and non-crushing conditions:

Ingredients: two parts salt (one part crude salt and one part refined salt), two beakers and water.

The same conditions: water quantity, water temperature and observation time are the same, and no stirring is required.

Different conditions: a cup of fine salt, a cup of strong salt.

3. Dissolution of liquid and gas.

Key points: When the syringe is pulled out, the air pressure decreases and bubbles (bigger and more) are precipitated.

When the syringe is pushed back, the air pressure increases, the bubbles disappear (become smaller until they disappear), and the gas dissolves in water.

4. How much salt can a glass of water dissolve?

Instrument preparation: measuring cylinder, balance, medicine spoon, glass rod, salt and record sheet.

Process: 1. Take 100 ml of water with a measuring cylinder. 2. Separate 2g of salt with a balance. 3, put salt, stir to speed up the dissolution, dissolve one and then put down another. 4. Keep it until it looks insoluble. Count the salt and subtract the insoluble salt.

Conclusion: 100 ml water can dissolve about 36 grams of salt.

5. Salt water separation experiment.

Experimental instruments: asbestos net (heated evenly), alcohol lamp (heated), evaporating dish, tripod (supported).

The precipitated salt can't taste. Test method: the precipitated crystal can be dissolved in water again, which proves that it is salt.

6, the use of alcohol lamp matters needing attention:

When lighting the alcohol lamp, you must use burning matches, not burning alcohol lamps.

When putting out the fire, you can't blow it out with your mouth, but cover it with a lamp holder, and then cover it after covering it.

Alcohol is a liquid that is easy to volatilize and burn. If spilled alcohol burns outside the lamp, don't panic. You can put it out with a wet rag or sand.

Short answer questions:

1. Is the flour dissolved?

It can be separated by filtration, so it does not dissolve. Answer whether salt and sand dissolve in the same way.

2. How did seawater become salt?

When seawater is introduced into the salt field, the water in seawater is evaporated by the heat of the sun, and finally salt can be precipitated.

3. How to separate salt and water from brine?

Evaporation or exposure (can write simple steps)

Both alcohol and salt are soluble in water. Please judge according to the experimental results you have done: Can they be infinitely soluble in water?

Alcohol can be infinitely soluble in water, and water can be infinitely soluble in alcohol. The dissolution of salt in a certain amount of water is certain, and its dissolution depends on the amount of water. More water will dissolve more, less water will dissolve less, so salt can't dissolve in water indefinitely.

3. Sound unit

Scientific concept:

Tuning fork is a kind of generating musical instrument, which is used to debug musical instruments and measure pitch.

Sound is produced by the vibration of objects, and the sound varies in size. The vibration of an object can be observed by the changes of other objects. People make sounds through vibrating sound belts.

The strength of sound can be described by volume. The greater the amplitude, the stronger the sound, and the smaller the amplitude, the weaker the sound. The unit of volume is decibel.

The level of sound can be described by pitch, which is a quantity describing the vibration speed of an object. The faster an object vibrates, the higher its sound is, and the slower it vibrates, the lower its sound is. The position of the pitch is Hertz.

Sound travels in waves. When sound waves meet an object, it will cause the object to vibrate. It can spread in gas, liquid and solid, and sound can't spread without matter. There is no air in a vacuum, so you can only see the vibration and not hear the sound. So on the moon, because there is no air, two people can't talk to each other even if they are not far apart, so you must use radio equipment.

The human ear can be divided into three parts: outer ear, middle ear and inner ear. The ear canal transmits sound to the inner ear, the eardrum converts sound waves into vibrations, the ossicles transmit vibrations to the inner ear, the cochlea converts vibrations into auditory signals, and the auditory nerve transmits auditory signals to the brain. Frequent use of MP3 and other items will damage the ears, and both children and adults may have hearing problems, so protect your hearing organs.

Common sense:

1. Knock two tuning forks of different sizes with the same force, do you hear different volumes or different pitches?

A: The pitch is different.

2. Knock two tuning forks with different sizes with the same force, which tuning fork emits pitch?

A: The big tuning fork has a low pitch and the small tuning fork has a pitch.

Erhu has two strings, and the sound is high and low when the empty string is played. What is the reason?

Answer: The thickness of the rope.

3. Is the vibrating object long or short, which is louder than the long sound? A: Short.

4. The vibrating objects are coarse and fine. Which is louder, thick or thin? A: Good.

5. There are large and small vibrating objects. Which is louder, the big one or the small one? A: Small.

6. The vibration speed is fast and slow. Which sound is louder than fast or slow? A: Quick.

7. In sound intensity, sound size and sound weight, which one refers to pitch? What do you mean by volume?

A: Sound intensity, sound size and sound intensity all refer to volume.

Scientific experiment:

1, an experiment to explore the change of ruler pitch.

(1). Predict the change of pitch and its reasons first. (2) Experiment to determine the change of pitch when the ruler sticks out of the desktop for different lengths, such as high, high, low and low. (3) Record every pitch change. (4) Collate the collected data and draw a conclusion.

2. The propagation of sound in different substances.

(1), first predict which substance the sound propagates fast, (2) experiment, listen carefully and feel the vibration of the tuning fork, (3) record the data, (4) sort out the collected data and draw a conclusion.

3. Control the sound of the sounding tank.

How to change the sound: increase the volume, and the sounding object is close to the generator fuel tank.

Mitigation methods: reduce the volume, keep the sounding object away from the generator, cover the sounding groove with an object, cover it with your hand, etc.

Short answer questions:

1, what do the earth telephone and stethoscope use to spread sound respectively?

The answering phone transmits sound through a tight cotton thread, and the stethoscope transmits sound to the ear through a connected hose.

2. How do people control noise?

Control the volume of sounding objects, plant trees and make protective screens.

3. Four identical glasses,No. 1, No.2, No.3 and No.4, are filled with tap water respectively (as shown in the figure below), and tap the glass mouth with a small stick. Please judge: What's the difference between the sounds made by glasses?

High, high, low, low.

Step 4 draw pictures

5. How do we hear the sound?

Vibrating objects will make the surrounding air vibrate, and the vibrating air will reach our ears and cause the eardrum to vibrate. Then the ossicle in the ear will transmit the vibration to the cochlea, which will convert the vibration into auditory signals, and the auditory nerve will transmit the signals to the brain, so that we can feel the sound.

4. Our bodies

Scientific concept:

Every part of the human body has a special function. In life activities, the parts are closely coordinated.

The appearance of human body can be divided into four parts: head, neck, trunk and limbs.

The body movement of human body is completed by bones, joints and muscles, and different forms of movement will involve different bones, joints and muscles. Bones support the body and protect the internal organs.

People's breathing is actually the exchange of gases, allowing oxygen to enter the blood and carbon dioxide and other waste gases to be discharged. It is known that human respiratory organs include nasal cavity, trachea, bronchus, lung and diaphragm. When we are calm, our breathing is generally about 20 times per minute, and our heartbeat is about 80 times per minute.

Oxygen needed by the human body enters the blood after being inhaled by the lungs, and then is transported to all parts of the body by the heart through blood vessels, and waste such as carbon dioxide is collected and excreted.

With the increase of physical exercise, people need more oxygen, and their breathing and heartbeat are gradually accelerated to transport more nutrients and oxygen.

Regular exercise will make your heart stronger, increase your vital capacity and provide more oxygen for your body.

The energy needed for human exercise comes from the absorption of nutrients in food by digestive organs, which mainly include mouth, esophagus, stomach, small intestine and large intestine.

Food will digest some starch in the mouth, and then be transported to the stomach through the esophagus, where it will be further ground and decomposed to digest some protein. Most of the nutrients will be absorbed in the small intestine and then transferred to the large intestine. Food will absorb a small amount of water and cellulose in the large intestine and then be excreted.

Oral cavity is the place where food digestion begins, which is completed by teeth, tongue and saliva. Teeth are divided into incisors (8 teeth), canines (4 teeth) and molars (20 teeth) according to their shapes. Old people often say

The principle of "chewing slowly" is that teeth grind food to facilitate the digestion of food in the body.

Scientific experiment:

Selecting an activity will use a bubble chart to indicate which parts of the activity are involved. See page 65 of the science book.

Describe the cooperative relationship of human organs with simple words and charts. See pages 78 and 79 of science books.

Short answer questions:

1. Why do we breathe more every minute after exercise?

With the increase of physical activity, people need more oxygen, and in order to transport more oxygen, breathing is gradually accelerated.

2. Why does our heart beat faster every minute after exercise?

With the increase of physical activity, people need more oxygen, and their heartbeat is gradually accelerated to transport more fresh blood.

Write down some benefits of exercise to our health?

Regular exercise will make your heart stronger, increase your vital capacity, provide more oxygen for your body and enhance your physique.

Strong bones, developed muscles, more flexible joints, etc.

4. Give examples to illustrate the relationship between various organs of the human body.

The respiratory organs provide oxygen for the motor organs and digestive system, and the digestive system provides nutrition for the motor organs and respiratory organs.

If food is well digested in the body, we will absorb more nutrients and provide nutrients for the growth of bones and muscles. Bad teeth will affect digestion and affect the movement of the whole body. When you digest food, you also consume oxygen.