Short scientific trivia

Brief scientific information:

1. Raw dumplings sink, boiled dumplings float, because hot air is lighter than cold;

2. Adding salt can make potatoes and eggs pop. Adding salt increases density of water.

3. A parachute made of plastic film can stay in air for a relatively long time, because there is an updraft near a high-rise building;

4. We can see blue skies because blue light has strongest penetrating power of sunlight;

5. A magnifying glass can burn paper because a convex lens can focus;

6. The compass can point way, since south is north pole of geomagnetic field;

7. Iron chains wrap around snowmobile wheels to increase friction;

8. At night, there are fewer and fewer stars because universe is still expanding;

9. Plants produce oxygen, absorb dust and noise, reduce ambient temperature, resist wind and sand, and fix soil and water, so a variety of trees and grasses should be planted;

10. Air conditioners, car exhausts, concrete floors and a large number of houses are main culprits of greenhouse effect.

Little knowledge: what interesting scientific knowledge should elementary school students know?

1. Why is it difficult for an ostrich to fly?

A species of camel and bird with huge growth, but it is not easy for them to fly into sky! This is not because their wings are useless, but because their feathers are too soft and their wings are too small to fly at all. In addition, muscles of ostrich are poorly developed, and shoulder blades are medium, which does not help navigation. Ostriches live in Africa, since they have lived in desert for a long time, their bodies have gradually evolved into what they are today in order to adapt.

2. Why are foods in canned fruit not easily affected?

Lunchtime canned meats, dace tempeh, beans with tomato sauce, etc. are all delicious canned fruit ingredients that can be stored for a long time without being easily affected. This is due to fact that canned food is airtight, so bacteria cannot get inside.

When we make canned fruit, we remove all air from canned fruit and then seal it. In absence of air, even if food inside is colored by a small amount of microbes, they cannot survive or reproduce!

3. Why don't you feel itchy when you scratch?

When others scratch, we feel itchy and continue to laugh, however, when we scratch ourselves, we not only laugh, but also feel less itchy. According to our thoughts, which we have prepared in advance, brain will send a message that there is no risk, and nervous system will also relax accordingly, so it will not laugh and scratch!

4. Why do you have goosebumps?

In our body, hair grows on surface of skin, and under each pore there is a muscle that straightens hair. When nervous withthe system is stimulated (such as anger, anxiety, coldness, etc.) body will fall and muscles that straighten hair will contract and hair will stand on end, resulting in goosebumps. In addition to function of keeping warm, this physiological system can also make animal seem larger than it actually is, thereby scaring off enemy.

5. Why do fallen leaves appear?

When autumn comes, more water evaporates from fallen leaves than in summer, but tree trunk absorbs less moisture than in summer. To reduce water loss of flowers and trees, cells of leaf stems begin to form a separating layer. After nutrients have completely left fallen leaves, separating layer will protect fallen leaves and tree stems, and then fallen leaves will fall off.