Primary school science experiment Put a small balloon on the mouth of the empty bottle. First put it in hot water, then put it in cold water

Primary school science experiment Put a small balloon on the mouth of the empty bottle. First put it in hot water, then put it in cold water

The balloon first expands and becomes larger, then it becomes the same after putting in cold water

Does the air in the experimental teaching plan of science grouping have weight

Experimental equipment: wood, string, balloon, needle. Steps: 1. Hang the balloon on the string at both ends of the wood; 2. Hang a string in the middle of the wood to balance it; 3. Puncture a balloon with a needle; 4. Observe the phenomenon: the balloon with air goes down. Conclusion: the air has quality

Contrast experiment
Two problems need to be paid attention to in comparative experiment: one is --- the other is --- two problems need to be paid attention to in comparative experiment

Two soybeans, one in good condition, one not full, placed in a suitable temperature place, there is an appropriate amount of water and air, found that good will sprout, the other does not
In other words, No. 2 is the control group

What kind of line segment can form a triangle

The sum of the two sides is greater than the third side