Key points of primary school science

The length, direction and size of an object's shadow under the illumination of light are related to the position, direction and distance of the light source.

during the day, the shadows of objects in the sun will change with the position and direction of the sun.

light travels in a straight line.

When light meets an object, it will change its propagation direction and be reflected back. This phenomenon is called light reflection.

the temperature of an object in the sun is related to the intensity of light received by the object. The stronger the light, the higher the temperature of the object.

People use concave mirror and convex lens to converge light to form strong light and high temperature.

The temperature of an object in sunlight is related to the color of the object, the smoothness of the surface and the angle of illumination.

the lighter the color, the smoother the surface and the more oblique the angle of illumination, the lower the temperature.

the solar water heater is an energy-saving device designed by using various scientific principles such as heat absorption and heat preservation of materials.

a magnifying glass is a convex lens, which can enlarge the image of an object.

A simple microscope is composed of two convex lenses with different magnifications.

The invention of the microscope enables people to observe very small objects and their fine structures.

3. Electricity

Friction can transfer charge from one object to another, thus making the object electrostatic.

when the current flowing from the power supply passes through the filament, the small light bulb will glow.

the wire, battery (power supply) and small light bulb (electrical appliance) can form a simple circuit.

the current flows from one end of the battery through the wire, passes through the small light bulb and returns to the other end of the battery, forming a complete circuit, which is called a circuit.

an object that is easy to conduct electricity is called a conductor; Objects that do not conduct electricity easily are called insulators.

a switch is an element that controls the on-off of electricity in a circuit.

according to different needs, the circuit can be connected in series or in parallel.

4. Heat

The degree of heat and cold of an object is called temperature, which is usually expressed in degrees Celsius (℃).

the rise or fall of the temperature of an object indicates that the heat of the object is increasing or decreasing.

normally, the body temperature is 37℃, the freezing temperature of water is ℃, and the boiling temperature of water is 1℃.

when water is heated, its volume expands, but when it is cooled, it shrinks. This property of water is called expansion with heat and contraction with cold.

air, as well as many liquids and solids, have the property of expanding with heat and contracting with cold.

heat always travels from the hot end to the cold end, which is called heat transfer.

different objects have different heat transfer performance. Metal has better heat transfer performance.

different materials have different heat absorption and dissipation capacities.

5. Magnetism

The property that a magnet can attract iron is called magnetism, and a magnet can also attract iron through some objects.

the strongest part of a magnet is called a magnetic pole, and a magnet has two magnetic poles.

the north pole is called the north pole, and the guide pole is called the south pole. Like poles of magnets repel each other, but opposite poles attract each other.

when a plurality of magnets are combined together, the magnetic force of the magnets will change.

a compass is an instrument that uses magnets to indicate the direction. Compass is one of the four great inventions in ancient China.

a magnet rubbing against a steel needle can make the steel needle magnetic.

6. Energy conversion

The electrified wire will generate magnetic force, which can deflect the magnetic needle of the compass.

an electromagnet is composed of a coil and an iron core. The north and south poles of the electromagnet are related to the winding direction.

the magnetic force of electromagnet can be changed, and it can be enhanced by increasing the number of coils and batteries.

the motor generates power by using the principle that electricity generates magnetism and the interaction between magnetic poles.

sound, light, electricity, heat and magnetism are all forms of energy. Various forms of energy can be transformed into each other.

a generator is a mechanical device that converts other forms of energy into electrical energy.

coal was formed by complex changes of plants hundreds of millions of years ago, which can be inferred from the characteristics of coal and strata.

the energy stored in coal, oil and natural gas comes from the sun.

(4) the earth and the universe

1. the atmosphere and its changes

there is air around us, and the air will flow.

air will occupy space, and the size of the space occupied by air can be changed.

air can be compressed, and compressed air is elastic.

the weather refers to the atmospheric conditions in the area where we live at a certain time.

a weather calendar is a table that records various weather phenomena every day.

the wind direction refers to the direction in which the wind blows, and the wind direction can be measured by a weather vane.

Wind speed refers to the distance that the wind travels every second. Wind speed can be measured by anemometer or expressed by wind speed grade.

precipitation is a basic feature of weather, and rain, snow and hail are the main forms of precipitation.

the amount of precipitation is often measured by rain gauge.

The clouds floating in the sky are actually composed of thousands of small water droplets or small ice crystals in Qian Qian.

in a period of time, temperature, precipitation, wind and cloud cover will change.

2. rocks and minerals

different rocks have different characteristics. According to the characteristics of rocks, the types of rocks can be identified.

minerals rarely exist alone in nature, but are usually mixed together to form rocks.

Granite is composed of Shi Ying, feldspar and mica.

when identifying minerals, the stripe color of minerals is more reliable than the color of mineral appearance.

the color, shape, transparency, luster, streaks and hardness of minerals are important basis for identifying minerals.

the distinctive features of minerals are the basis for effective description and identification of minerals.

rocks and minerals are important substances that make up the earth, and they are also valuable resources for people's production and life.

3. The Earth's surface and its changes

The topography of the Earth's surface is varied. Land, sea, plateau, mountains, basins and canyons are all common landforms.

Earthquakes and volcanoes are caused by internal movements of the earth.

the internal movement of the earth makes the surface morphology change constantly, some of which are very violent, while others are very slow.

due to the action of water, atmosphere, temperature or animals and plants, rocks are broken, which is called weathering.

Soil is a mixture of sand, pebbles, clay, humus, water and air.

due to the erosion of rain, soil or some substances in the soil are lost with the water flow, which is erosion.

weathering and erosion have changed the topography of the earth.

The slope of the land, whether there is plant cover or not, and the rainfall will affect the degree of soil erosion.

4. Time measurement

The ancients used the position of the sun in the sky and the shadow of objects in the sun to time.

according to different timing methods, water clocks can be divided into two types: water-receiving water clocks and water-discharging water clocks.

the dripping speed of the water clock is related to the size of the dripping hole and the water level of the water outlet container.

the same pendulum takes the same time for each swing.

the speed of pendulum swing is mainly related to the length of cycloid.

the change of pendulum position will affect the length of cycloid, thus affecting the speed of pendulum.

The pendulum moves the pointer through the pendulum gear manipulator.

5. Earth Movement

Ptolemy put forward the theory of geocentric theory, and Copernicus put forward the theory of Heliocentrism.

Foucault pendulum takes advantage of the fact that the pendulum keeps its swinging direction unchanged, which proves that the earth is rotating.

people divide the earth into 24 time zones based on the meridian of the earth.

the earth rotates from west to east around its axis. When the earth rotates, its axis always points to Polaris.

the earth keeps moving around the sun from west to east, which is called revolution. The revolution period of the earth is one year.

the phenomena of four seasons, extreme day and extreme night are caused by the fact that the earth's axis always tilts towards Polaris when the earth revolves.

6. Explore the universe

The moon is a satellite of the earth, and it keeps moving around the earth.

the moon's various shapes during the change of the round and short periods are called moon phases.

the change of the moon phase is regular, and the formation of the moon phase is related to the revolution of the moon.

the biggest feature of the lunar landscape is that there are many craters of different sizes.

during the revolution of the moon, when the sun, the earth and the moon are in the same straight line, there will be a solar eclipse or a lunar eclipse.

A celestial system with the sun as the center and including eight planets, satellites, dwarf planets and small celestial bodies revolving around it is called the solar system.

The eight planets in the solar system are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

for easy identification, people divide the starry sky into different regions, which are called "constellations".

The Milky Way is actually a shining band of stars.

light year is the distance traveled by light in a year, and it is a unit of length used to measure the distance between stars.

(5) Scientific inquiry skills

1. Understanding of scientific inquiry

Real observation is purposeful.

continuous observation and field investigation can help us to know more about plant changes.

It is a good way to observe small animals by field observation and investigation without disturbing them.

characteristics are particularly obvious signs that distinguish one thing from other things.

In scientific observation, we can't know the characteristics of unknown objects by tasting.

to exclude an inappropriate explanation, we need sufficient evidence, not just subjective will.

scientific inquiry involves the process of asking questions, analyzing hypotheses, making plans, experimental verification and drawing conclusions.

there is a certain gap between the results of scientific inquiry such as simulation experiment and speculation and the objective truth.

the development of science and technology will have a positive or negative impact on human life and changes in the earth's environment.

2. Scientific inquiry skills

Being able to observe the external characteristics of simple things by using sensory organs such as eyes, ears, nose, tongue and hands.

Be able to observe the characteristics of things carefully with a magnifying glass and a microscope.

Be able to use measuring tools such as ruler, thermometer and dynamometer to observe things and obtain data.

leaf specimens can be made by rubbing.

can make simple anatomical specimens of plant flowers.

simple switch circuit can be assembled.

Be able to dissect flowers, fruits and seeds of plants correctly.

fat and starch in food can be detected by simple methods.

can use alcohol lamp to heat objects.

can make nails and electromagnets.

be able to draw simple structural drawings and design drawings and explain them with words and symbols.

venn diagram, network diagram, bubble diagram, column diagram and line diagram can be used to organize information.