Junior 3 chemical changes Physical changes

1 Physical change is a change in the state of water without the formation of new substances2 Physical change is a change in the state of water, no new substances are formed3 Chemical changes Iron becomes rust and new substances are formed.

4 Chemical changes Copper turns into patina, and new substances are formed.

The process of candle burning, the process of paraffin dissolving and solidification is a physical change, and the process of burning paraffin wax produces carbon dioxide and water, forming a new substance, which is a chemical change.

Physical changes"1..3..

Chemical changes"2..4..

Two. Where there is a chemical change, there must be a physical change. If there is combustion, it must be a chemical change.

I'm a chemistry teacher.

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The physical change is 1,2

The chemical change is 3,4

The process of dissolving and solidifying paraffin wax burned by candle is a physical change, and the process of burning paraffin wax to produce carbon dioxide and water, forming a new substance, is a chemical change.

1. Physical change, water changes from gaseous to liquid, and no new substances are formed.

2. Physical change, water changes from solid to liquid, and no new substances are formed.

3 Chemical changes, rust is a substance that is different from iron.

4 Chemical changes, patina is also a new substance relative to copper.

The process of lighting a candle, melting the candle, vaporizing is a physical change; The burning of candles produces water and carbon dioxide, which is a chemical change.

What is new is a chemical change, and what is not something new is a chemical change.

The transformation of ice into water is a physical change.

Chemical changes: alkaline noodles are added to the dough, laundry detergent washes the stolen goods, photosynthesis and filial piety for plant growth, AB glue is mixed with sticky things, food deteriorates, gasoline burns, candles burn, stain remover rubs dirt, amaranth juice mixes noodles, chemical fertilizer acts on the soil, food becomes feces, pus grows on the body, grain wine, vinegar, manure fertilizer, imitation biogas.

The changes in junior high school physics are mainly about the changes in the state of matter, while the changes in chemistry are divided into synthetic and chemical combinations.

The physical changes of the junior high school Yula are as follows

1. Melting: Ice and snow melting, summer popsicles dripping, burning candles and candles flowing down, drinks with ice. Slow feast solidification: freezing, ice hanging under the eaves after rain in the cold winter in the north, molds made of molten iron, a few jars of water in the vegetable cellar in the northern winter, and molten steel cast into wheels.

2. Vaporization: evaporation phenomenon (clothes drying, hair drying, water sprinkled on the ground is gone, fog is dispersed), boiling. Liquefaction:

In the summer, there is "white gas" around the popsicle, and in the morning, small water droplets and liquid on the grass and trees in the summer, the outer layer of the water tank "sweats", and the dense fog and dew form in the morning.

3. Sublimation: The filament (or tungsten filament) becomes thinner, in winter, the frozen clothes outside the vertical skating room are dried, the mothballs (or sanitary balls) in the suitcase gradually become smaller, the iodine is heated at high temperature, the volume of iodine becomes smaller, the snowman piled up becomes smaller in the cold winter, and the sublimation of dry ice (solid carbon dioxide) is used to create a stage effect, and can also be used for artificial rainfall.

4. Temperature: refers to the degree of heat and cold of the object. The measuring tool is a thermometer, which is made according to the principle of thermal expansion and contraction of liquids.

The unit of Celsius temperature ( ) is Celsius. 1 degree Celsius regulation: the temperature of the ice-water mixture is specified as 0 degrees, the temperature of boiling water at a standard atmospheric pressure is specified as 100 degrees, and it is divided into 100 equal parts between 0 and 100 degrees, and each equal is divided into 1.

1.When a substance changes, no other matter is formed, and a change is called a physical change.

For example, damp clothes are dried out by the sun; porcelain bowls are broken; Put a ball of snow in a warm room on a snowy day and the snow melts.

Wait. 2.When a substance changes, there is a change in the formation of other substances, which is called a chemical change, also known as a chemical reaction.

For example, copper produces patina in moist air; paper burning; Iron rust, etc. 3.The properties of matter that manifest themselves in chemical changes are called chemical properties.

For example, food is digested in the human body and can eventually be turned into water, carbon dioxide, etc.; The amount of food can be used as raw material to make wine; Carbon dioxide can make clarified limestone cloudy; Alcohol burns.

Wait. 4.The property that a substance exhibits without a chemical change is called a physical property.

For example, air is a gas with no color and no smell; When water boils, it can turn into water vapor; The density of copper is.

g/cm^3

The melting point is 1083

Alcohol is volatile.

Wait. 100% right! ~！

Chemical properties: flammability of oxygen, strong reducing properties of K, NA, CA, strong oxidation of LCL2, strong stability of silver, gold, Ba, strong oxidation and dehydration of concentrated sulfuric acid.

Chemical changes: combustion of carbon, rusting of iron, burning of paraffin, brewing of wine, vinegar, acid-base reaction, sodium reaction with water, hydrogen**, physical changes: paraffin wax melts by heat, ice becomes water, water becomes ice, water becomes water vapor, dry ice sublimation, iodine sublimation, chemical properties: carbon can burn, iron is easy to rust, paraffin can burn, oxygen can support combustion, physical properties: diamond is hard, graphite is soft, sodium is silvery-white, sulfur is solid, carbon dioxide is gas, graphite can conduct electricity, hydrogen density is small, mercury is liquid,......

Chemical properties: oxygen can support combustion, physical properties: color, odor, state, hardness.

Chemical changes: iron rusts, paraffin burns.

Physical Properties: Ice turns into water.

From a microscopic point of view, the essence of a chemical reaction is that the molecule is broken into atoms, and the original molecule is reconstituted into a new molecule, and the type and number of atoms before and after the chemical change remain unchanged, and the type of molecule must change. The change produced by the presence of a new substance is a chemical change, and the process of chemical change is always accompanied by a physical change.

Chemical change refers to the process of conversion or transfer of atoms or electrons between molecules in contact with each other to form new molecules accompanied by changes in energy, which is essentially the breaking of old bonds and the formation of new bonds. Chemical changes are generally divided into four types: chemical and chemical reactions, decomposition reactions, displacement reactions, and metathesis reactions.

Chemical Change: Changes in other substances are generated.

2. Physical change: no change in other substances.

3. Physical properties: the properties of Chuntuanxiang that do not need to undergo chemical changes.

Such as: color, state, density, odor, melting point, boiling point, hardness, water or dissolubility, etc.) 4. Chemical properties: the properties of substances in chemical changes.

Such as: flammability, flammability, oxidation, reduction, acidity and alkalinity, stability of the beat, etc.).

Most of them are quite easy to distinguish, but a few are somewhat easily confused, the ** of the atomic bomb, graphite to diamond. The former is physics, and the latter is chemistry or rent.

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