Small science experiments that third graders can do include: triboelectricity, garlic sprouting experiment, punch-proof paper experiment, ice fishing, bouncing eggs , the non-wet paper, the toothpick speedboat, the rainbow bridge, the bottle of anger.
Experiment 1: Bouncing Bubbles
Experimental Principle: The bubbles in stage 1 are prone to explosion due to water evaporation. After adding glue, they will become very sticky and the water will become very sticky. cannot be easily removed. As it evaporates, the resistance of the bubble wrap increases so it can jump onto the back of our hands.
Experiment 2: Automatic rise of water
Experimental principle: When the candle is extinguished, the water in the glass rises gradually and stops after reaching a certain level . Because the candle burns, it consumesme the oxygen contained in the glass and the reduced oxygen is filled with water.
Experiment 3: Color changes
Experimental principle: Purple cabbage contains anthocyanins. When it encounters substances of different acidity and alkalinity, a chemical reaction occurs, so that it changes color overall. , it appears red when it encounters acidic substances, blue when it encounters alkaline substances, and purple when it encounters neutral liquids.
There is a physical experiment, please hero, please explain its physical principles.
1. Cut the lemon (orange) in half (you can also cut it into four pieces if the fruit is not enough), insert small copper plates and small zinc plates at both ends (be careful not to leave the copper and the zinc come into contact). Repeat four times to get four pieces of fruit with copper and zinc plates,then use the belt tightening wire to tighten the adjacent copper and zinc plates of the two pieces of fruit at once.
2. Do not connect the last two remaining wires yet. Connect one end of the two wires to the small bulb (or LED), the other to the sensitive ammeter, and insert a new wire. the middle to connect the small bulb (or LED) and the ammeter.
3. After the connection is completed, the experimental results: the small bulb (or LED) emits dim light and the display on the sensitive galvanometer can be read After the experiment is completed, wash and. recover the experimental materials.
Physical knowledge about water
Generally, when water is heated, its volume increases, its density decreases, and it flows upward, then cold water flows downwards, forming “convection” because it is hot. water only flows upwards. After flowing, it is heated and flows again towardsthe top, so that the “convection” of hot and cold water occurs only in the ascending zone of the heated part and the change in water temperature below the heating point. depends on the "heat conduction" of water, and the "heat conduction" ratio of water convection has a much smaller effect on temperature, so the water temperature changes very slowly by thermal conduction alone. So the water above boils, but there is no change below.
The three modes of heat transfer are thermal conduction, convection and thermal radiation.
Physical knowledge related to water
1 Mechanical research is closely related to water
Water is a colorless liquid, odorless and transparent with a density of 1.0 ×103kg/m3.
(1) If the volume of water is known, its mass and gravity can be calculated, which is useful for calculating buoyancy, the presession, etc. generated by water.
(2) The volume of the container can be calculated with water and measured using the drainage methodThe volume of an irregular object.
(3) The density of a human being is similar to that of water. The volume of a human being can be calculated based on the mass of the human being.
(4) Since sea water contains salt, its density is greater than that of pure water. As a ship navigates oceans and rivers, the volume of water displaced by the hull changes.
(5) Water pressure increases with depth, so the dam is designed to be wide at the bottom and narrow at the top.
(6) Water produces buoyancy on objects submerged in it, and the magnitude of the buoyancy is F float = ρ displacement gV of the water.
(7) One-tenth of the volume of ice floating on water must be exposed to water, and after the ice melts, the height of the water surface remains unchanged.
2 Water is themain research object in thermal science
(1) Water has the largest specific heat capacity, its value is 4.2 × 103 J/(kg·℃), and the specific heat capacity of all other substances is lower than this. Taking advantage of this characteristic of water, we often use hot water for heating in our lives. This is also the role of water in nature in regulating the climate.
(2) The freezing point of water is 0℃. When water solidifies, it is called ice and it is a crystal.
(3) Water vaporizes in two ways: by evaporation and by boiling. At standard atmospheric pressure, the boiling point of water is 100°C. The boiling point of water is related to atmospheric pressure. The pressure cooker in daily life uses the method of increasing pressure to increase the boiling point of water to cook food faster.
(4) The blurard, dew and "white gas" observed in life are small water droplets formed by the liquefaction of water vapor, snowflakes and ice flakes are the result of condensation of water ; steam.
3 Water and acoustics
Water can transmit sound. The speed of sound propagation in water is about 1,500 meters/second, and the water surface can also reflect sound.
4 Water in optical research
(1) The surface of still water acts like a plane mirror and can form a virtual image.
(2) Light will be reflected and refracted as it bends from the air to the water surface, and the angle of refraction is always smaller than the angle of incidence when a scuba diver sees the trees on the shore, they will become taller.
(3) Light also undergoes refraction when it passes from water into air. At this time, the angle of refraction is always greaterr to the angle of incidence, so rods inserted into water will bend and light will be refracted. the pool water will appear shallower than it actually is.
(4) Ice melts when exposed to fire, but ice lenses can capture fire. It’s an unexpected creation.
5 Water and electricity
(1) Pure water is not a conductor and ordinary water is also a poor conductor of electricity, but wet objects (filled of water) can conduct electricity. ! Do not use wet hands to turn on the switch and the insulation should be kept dry.
(2) Large hydroelectric power plants must build very high dams, which can increase the gravitational potential energy of water, thereby increasing the power generation power of generators.
6 Water Experiments
Experiments involving water include: (1) Using a thermometer for measuring water temperature (2) Observe water boiling; (3) Study; liquid pressure; (4) Verify Archimedes’ principle.