I, Thermometers
1, Thermometers
(1) The concept of temperature: the degree of hotness or coldness of an object is called temperature.
(2) Measuring tool of temperature: thermometer.
(3) Range: the highest and lowest temperatures that can be measured.
(4) Graduated value: the value represented by a smallest cell.
(5) The most basic note: the temperature of the object to be measured can not exceed the range of the thermometer.
2, the temperature:
(1) Celsius temperature: symbol t, unit symbol ℃, Celsius temperature regulations: the temperature of the ice-water mixture for 0 ℃, 1 standard atmospheric pressure under the temperature of boiling water for 100 ℃, 0 ℃ - 100 ℃ between the divided into 100 equal parts, each equal part of 1 degree Celsius.
(2) The body temperature of a normal person is 37°C.
3, thermometer:
(1) thermometer glass bubble and straight glass tube between a section of thin tube, mercury contraction, shrinkage of mercury first automatic disconnect, straight tube of mercury can not return to the glass bubble. Therefore, before each use of the thermometer should be thrown back to the glass bubble mercury.
(2) The range of the thermometer is 35--42℃, and the index value is 0.1℃.
4, the use of thermometers to measure the temperature of the liquid
(1) the thermometer's glass bubble all invade the measured liquid, do not touch the bottom of the container and the container wall.
(2) thermometer glass bubble into the measured liquid, to be stabilized after reading.
(3) The glass bubble of the thermometer should be left in the liquid when reading, and the line of sight should be level with the upper surface of the liquid column in the thermometer. Reminder: thermometers can be read away from the body, and ordinary thermometers cannot be read away from the object being measured.
Two, melting and solidification
1, melting and solidification: substances from solid to liquid is called melting, from liquid to solid is called solidification. Such as ice into water is melting; water into ice is solidified. Reminder: melting and dissolution should not be confused, the former indicates that the substance has a solid state into a liquid state; the latter indicates that some solutes dissolved in the solvent process.
2, melting point and freezing point
(1) crystals and amorphous: crystals have a fixed melting point, such as seawater, ice, quartz, crystals, salt, naphthalene, a variety of metals, etc.; amorphous has no fixed melting point, such as rosin, glass, asphalt and so on.
(2) melting point and freezing point: crystals have a certain melting temperature, called the melting point; solidification temperature is called the freezing point. The freezing point of the same crystalline substance is the same as its melting point.
Exercise: the following groups of substances, all belong to the crystal (C)
A sea wave, quartz, glass B salt, naphthalene, asphalt C sea wave, ice, crystals, D rosin, glass, asphalt
3, melting absorbs heat, solidification of exothermic
(1) the characteristics of melting crystals: the process of melting absorbs heat, the temperature (melting point) remains constant. Melting conditions: ① temperature to the melting point; ② constantly absorbing heat from the outside world.
(2) non-crystalline melting properties: the melting process absorbs heat, the temperature gradually increases.
(3) crystal solidification characteristics: solidification process exothermic, the temperature (freezing point) remains unchanged. Conditions: ① temperature reaches the freezing point; ② constantly exothermic to the outside world.
(4) non-crystalline solidification characteristics: exothermic, the temperature decreases.
Three, vaporization and liquefaction
1, the phenomenon of vaporization and liquefaction
(1) Vaporization: the process of changing substances from liquid to gas is called vaporization; such as sprinkled water on the ground, after a while dry; wet clothes after the sun's irradiation became dry.
(2) liquefaction: the process of changing a substance from a gaseous state to a liquid state is called liquefaction. For example, in winter, you can see outdoor people constantly exhale "white gas"; boil water often see the "white gas" and so on.
2, the phenomenon of boiling
(1) boiling: the internal and surface of the liquid at the same time the phenomenon of intense vaporization.
(2) boiling point: the temperature at which a liquid boils. Different liquids have different boiling points.
(3) boiling conditions: ① 1 standard atmospheric pressure, the boiling point of water is 100 ℃. ② liquid boiling to keep boiling, the liquid must be heated, but the boiling process does not increase the temperature of the liquid.
3, evaporation:
(1) the conditions of evaporation: anywhere, at any temperature can occur.
(2) Characteristics of evaporation: evaporation is a vaporization that occurs only on the surface of a liquid.
(3) factors affecting the speed of evaporation: ① liquid temperature. The higher the temperature of the liquid, the faster the evaporation. ② surface area of the liquid. Then the larger the area, the faster the evaporation. ③ liquid surface air flow speed: the faster the flow, the faster the evaporation.
(4) control evaporation methods: speed up evaporation: increase the temperature of the liquid; increase the surface area of the liquid; accelerate the flow of air on the surface of the liquid. Slow down evaporation: use the opposite measures.
(5) Evaporation has a cooling effect: evaporative heat absorption process, which leads to a decrease in the temperature of the liquid and itself.
Exercise: the following measures can make evaporation faster (C)
A wrap vegetables in plastic wrap and put them in the refrigerator B put a cap on an ink bottle C dry wet hair with a hairdryer D put fresh citrus in a plastic bag
4, liquefaction
(1) Two ways to liquefy: ① lower the temperature; ② compress the volume.
(2) Liquefaction is exothermic. Liquefaction is the inverse process of vaporization, vaporization absorbs heat, liquefaction is exothermic.
5, the judgment of the liquefaction phenomenon
(1) "white gas" "fog" is the phenomenon of liquefaction. Such as: fog is the water vapor in the air is cold and the formation of fog, is exothermic process.
(2) "sweat" is the phenomenon of liquefaction. For example: a layer of water beads hanging on the surface of the tap water pipe, is an exothermic process.
Four, sublimation and condensation
1, the phenomenon of sublimation: solid substances directly into a gaseous state is called sublimation, sublimation absorbs heat. Such as the stage shrouded in white fog, is due to the sublimation of dry ice into a gas. Sublimation absorbs heat, so that the nearby air in the vaporization of water into small droplets - white fog.
2, condensation phenomenon: substances from the gas state directly into a solid state called condensation, condensation exothermic. Such as the winter tree branches on the "freezing fog" phenomenon, the window of the inner surface of the ice phenomenon, etc. 3 sublimation and condensation phenomenon of judgment