There are 206 bones and more than 600 muscles in the human body, and the muscle weight accounts for 40% of the body weight.

2. Bones play the role of movement, support, and protection. The movable connections between bones are called joints. Various movements of the human body are realized by the contraction and relaxation of muscles driving the bones and joints.

3. The benefits of regular exercise are: improving body flexibility; enhancing cardiac muscle and lung capacity; developing muscles; having sufficient physical strength; delaying aging; and having a well-proportioned body.

4. The main nutrients that people need are: protein, carbohydrates, fats, vitamins, and minerals.

5. The types of food we eat every day include: grains, vegetables and fruits, fish, meat and eggs, soy milk, oil, salt and sugar. What I eat the most is grain. The ones you eat the least should be oil, salt and sugar.

6. The main digestive organs of the human body include the mouth, esophagus, stomach, small intestine, large intestine, and anus.

7. In order to eat safely, fruits and vegetables should be fully soaked and washed. Eat more green foods and less pickled foods.

8. When buying processed foods, pay attention to the production date and shelf life.

9. No food contains all the nutrients the human body needs, so the food we eat must be diversified and comprehensive.

10. Fruits cannot replace vegetables.

Air

1. Air is mainly composed of nitrogen, oxygen, a small amount of carbon dioxide, water vapor and other gases. If harmful substances are added to the air, the air will be polluted, and the flow of air will form wind. The ancient Chinese invented the Kongming Lantern based on the principle of hot air rising.

2. Combustion must meet three conditions at the same time: combustibles, oxygen, and a certain temperature.

3. Air is also the source of life, but people’s activities are the main cause of air pollution. Some measures to prevent air pollution include planting trees, saving energy, driving fewer cars, improving automobile fuel, banning straw burning, and using fluorine-free refrigerators.

4. You can feel the presence of air by fanning it with your hands or putting it in a plastic bag. Air is a colorless, odorless and tasteless transparent gas.

5. Tighten the funnel with the rubber stopper on the mouth of the bottle and pour water into the funnel. Will the water flow into the bottle?

Why? (Water cannot flow into the bottle because the space in the bottle is occupied by air. The rubber stopper seals the mouth of the bottle and the air cannot come out, so the water in the funnel cannot flow in.)

6. When cooling food with ice, should the food be placed on or under the ice? Why? (Food should be placed under the ice cubes, because the air around the ice cubes will sink quickly when cold, and the sinking air surrounds the object to be cooled, thereby achieving the purpose of cooling as quickly as possible.)

< p>7. Air can be compressed, and compressed air is elastic. Why can't bicycle tires be filled with enough air in hot summer? (Air has the property of thermal expansion and contraction. In summer, because the temperature is too high, the air in the tire is exposed to high temperatures, and its volume will inevitably increase quickly, generating a lot of pressure. When the tire cannot withstand such a large pressure, it will (expanded)

Astronomy

1. The position of the sun in the sky can be expressed by its direction and height. We see the phenomenon of the sun rising in the east and setting in the west during the day and night. In fact, it is formed by the rotation of the earth from west to east. It’s just that we live on the earth and use the earth as a reference, so it looks like it rises in the east and sets in the west

2. The sun is in the east, the object’s shadow is in the west, the sun is in the south, and the object’s shadow is in the north , the position of the sun is in the west and the shadow of the object is in the east. A sun clock is formed based on the change of the direction of the shadow of an object under sunlight. The sun clock in the Palace Museum is called a sundial, which is an equatorial sundial. The sundial kept by the Nanjing Purple Mountain Observatory is called a horizon sundial.

3. The bright part of the moon The image is called the moon phase.

4. The new moon refers to the invisible moon in the sky. The crescent moon at the beginning of the month means that the sun has just set on the horizon, and the moon phase we see is facing the sun. The crescent moon at the end of the month means that when the sun is about to rise, the moon phase you see is also facing the sun.

5. When you see the moon from the first to the fifteenth day of the lunar month at sunset, you will find that: the crescent moon is in the west, the first quarter moon is in the southern sky, the gibbous moon is east of the center, and the full moon is in the east. It can be seen that the direction of the moon's rotation around the earth is from west to east.

6. Look at the moon from the 16th to the end of the month at sunrise. You will find that the 16th moon is in the west, the waning moon is in the southern sky, the waning moon is in the east of the center, and the crescent moon is in the east.

7. The moon rises in the east and sets in the west throughout the day. This is caused by the earth's rotation from west to east. The moon is a satellite of the earth, and one revolution of the moon around the earth is one month in the lunar calendar.

Motion and force

1. When we ride a bicycle, the wheels are making linear motion and rotation.

2. The speed of a truck is related to its own weight, pulling force, and road surface.

3. The unit of force is Newton.

4. When using a dynamometer, keep the pointer at 0 and not exceed the maximum measurement range.

5. When an object is subjected to an external force, its shape or volume will change, and it can return to its original shape or volume after the external force is removed. This property is called elasticity, and this force is called elasticity.

6. Everything on the earth has vertical downward gravity. This force is due to Earth's gravity.

7. Judgment:

Force can change the motion state of an object. (True)

The elasticity of an object is infinite (False)

When an object passes through liquid or air, friction will also occur (True)

8 , Friction can generate heat, and the formation of meteors is related to friction. Car tires on the highway in hot summer will get hot; there are many things in life that increase beneficial friction (such as patterns on tires, handlebars, etc.) Patterns) and reducing harmful friction (adding lubricating oil and ball bearings to mechanical moving parts).

9. The shape of an object is related to the amount of friction it experiences. For example, the falling speed of a parachute is related to the size of the umbrella surface.

Water

1. Water is the source of life. Water is a colorless, odorless, tasteless, transparent liquid. Water has three states: solid, liquid, and gas. Clouds, fog, rain, dew, and frost are all formed by condensation of water in the air.

2. Commonly used methods to understand objects include seeing with your eyes, smelling with your nose, tasting with your tongue, and touching with your hands. Never smell or taste random objects that you don’t understand. What is the method to identify water, salt water, sugar water, milk, and white vinegar in a cup?

3. Water has the force to shrink its surface as much as possible. This is called the surface tension of water.

4. Iron blocks will sink in water, but why can steel ships float on the water? (Because the steel ship has a large space, it is lighter than the same volume of water, so it floats on the water.)

5. Most of the water on the earth is salt water in the ocean, with only a very small amount Most of the fresh water is only stored in the glaciers of the Antarctic and Arctic. There is a small amount of invisible water vapor in the atmosphere. Only the water in rivers, lakes and shallow strata is available for human use. The fresh water available for human use has been polluted to varying degrees. If humans do not pay attention to protecting water resources, there will be no clean water available on the earth.

6. Solids have a certain shape. The separation of solids, such as separating beans from rice, and separating coarse sand from fine sand, will make the volume smaller after mixing two different solids. For example, after mixing soybeans and rice, the volume becomes smaller, but the weight remains unchanged. When the liquid is mixed with water, some are soluble in water and some are insoluble in water. Some float on water and some sink under water, but this is not absolute. When conditions change, liquids that are insoluble in water may also be soluble in water.

Biology

1. The structure of seeds: cotyledons, radicle, and embryo. The embryo will grow into stems and leaves, and the radicle will grow into roots.

2. Plant growth needs: sunlight, water, air, soil, suitable temperature, and nutrients.

3. A flower, such as rapeseed, has: petals, sepals, pistils, and stamens.

Bees and some insects can pollinate some flowers. There are seeds inside the fruit. "Seedless melon" is artificially cultivated. It is still a fruit. Radish is not a fruit.

4. The main components of soil are: sand, clay, humus, etc.

5. Silkworms, dragonflies, ants, crickets, etc. all belong to the category of insects. Their adult bodies are divided into three parts: head, thorax and abdomen. There is a pair of tentacles on the head and three pairs of legs on the chest. The antennae of silk moths are feathery. Insects go through metamorphosis in their lives, and silkworms go through four stages in their lives: silkworm eggs, silkworms, silkworm pupae, and silkworm moths. China was the first country in the world to grow mulberry and raise silkworms to produce silk fabrics.

6. Fish live in water all their lives. Fish come in various shapes and have scales on their bodies. Some fish, such as eels and slimy fish, have no scales. The pattern of fish scales is like the growth rings of trees. Fish also have ears, but they are hidden in the skull. Fish use their gills to get oxygen from the water. Fish can change their own volume by adjusting the amount of gas in their swim bladders, thereby adjusting their specific gravity and obtaining different buoyancy. Fast-moving sharks don't have swim bladders. A fish relies on its tail to move forward, and its slow movement relies on its pelvic fins or gills to drain water. Expanding its pectoral fins can stop the moving fish, and its lateral lines can determine the direction and sense the water temperature.

7. We must be kind to animals, love animals, and protect animals that are closely related to our lives. Such as cows, bees, and bug-eating birds. Rare animals must also be protected. Where can we start? (For our middle schools that live in urban areas for a long time, we need to care for birds, trees, and the environment where small animals live. To protect animals in the water, we must protect water sources. During the breeding season of birds, we must work together with parents to Make "artificial bird nests" for birds, and be civilized spectators at the zoo and care for all kinds of animals)

8. Animals have different living habits. Most birds are active during the day, and owls are for hunting. Rats are the main species, and rats like to be active at night, so owls are also active at night. Its sleeping time is from morning to afternoon. The snail likes to live in a dark and humid environment, and its active time is also at night.

Thermal Science

1. The degree of hotness and coldness of an object is called temperature. Heat always travels from high to low.

2. The main method of heat transfer in solids is conduction. The heat transfer method in liquids and gases is by convection. The heat from the sun radiates to the earth.

3. When most objects are heated, their volume will expand and when they cool, their volume will shrink. This property is called thermal expansion and contraction.

4. Because dark-colored objects absorb radiant heat more easily than light-colored objects, we like to wear light-colored clothes in summer and dark-colored clothes in winter.

5. What effects will changes in temperature have on objects? (Wires stretch in summer, water pipes freeze and burst in cold winter, etc.)

6. What are the applications of heating and cooling objects in daily life? (Sometimes the pickle bottle cap cannot be unscrewed. You can use a hot towel to wrap the bottle cap. The bottle cap will expand easily when heated. There are also connections for plastic water pipes, steelmaking, popsicle making, candle making, etc.) < /p>

7. Why are pot handles made of plastic? Is the pot made of metal? (Plastic is not good at transferring heat, so a pot handle made of plastic will not burn your hands. Because metal is good at transferring heat, the pot body is made of metal.)

8. Draw a diagram of heat transfer in a water pot. Show. (omitted)

Sound

1. Sound is produced by the vibration of objects. Any sound that people don't need is noise. Noise harms people's physical and mental health and is one of the four major public hazards in today's society.

2. Structure of the human ear: auricle, external auditory canal, tympanic membrane, ossicles, cochlea, auditory nerve

3. Sound cannot propagate in a vacuum.