Square dance teaching in the spring season

(1) Because the particles that make up the substance are constantly moving, the particles of floral fragrance can be emitted into the surrounding air through movement, so in the spring season, people can often smell pleasant floral fragrance in the park.

(2) In order to facilitate transportation and use, liquefied petroleum gas is usually stored under pressure in steel cylinders, indicating that there is a certain gap between the particles that make up liquefied petroleum gas, and the gap becomes smaller when pressurized;

(3) straw, coal, cotton yarn, etc. Are flammable. If they are stacked unreasonably and the air is not circulated, they will slowly oxidize and generate heat. If the ignition point is reached for a long time, it may cause spontaneous combustion, which is spontaneous combustion.

(4) According to the nature that vitamin C is relatively stable in acidic environment and easily destroyed by heating, vinegar and cold salad can be used to make full use of the rich vitamin C in cucumber.

(5) Because the freezing point of the mixture is lower than that of pure substances, sprinkling salt on snow or ice is to lower the freezing point of water and accelerate the melting of snow or ice.

So the answer is: (1) molecules are constantly moving; (2) There are gaps between molecules; (3) nature; (4) adding vinegar and cold salad; (5) Reduce the freezing point of water.