Physics works!Walter Lewin demonstrates that the period of a pendulum is independent of the mass hanging from the pendulum
Lewin rides a tricycle powered by a fire extinguisherDemonstration is the first aspect of any experiment. For pupils’ safety, some experiments are simply not suitable for them to try their hand at unaided. In such cases, teachers or pupils in upper grades will demonstrate the experiment for them. For example, inhaling helium gas alters the human voice, which indicates that the frequency of vocal cords is related to mediums. Helium is a kind of inert gas without toxicity, but it will dilute the oxygen content in the body of anyone who inhales it. Under such circumstances, it is preferable for the science teacher to assume this (extremely moderate) risk and provide a risk-free demonstration for their pupils. A Van de Graaff generator makes your hair stand on end and can scatter tinsels, which shows how electrostatic phenomena of two objects of like charge will repel each other. Demonstrators in this experiment have to obey strict instructions to avoid getting an electric shock. A steam engine model can be used to as a power plant to demonstrate energy transformation and its efficiency. In order to generate steam, the little boiler is heated to high temperature. Demonstrators need to be very cautious to avoid being scalded. Such dramatic experimental demonstrations are invariably successful in attracting pupils’ attention and motivating them to learn more. They are also conducive to explaining scientific principles and deepening pupils’ understanding and retention of relevant theories. Such experiments have high safety requirements, and all are demonstrated by our experienced teachers, particularly for pupils in lower grades.
ManipulatingHowever, it is not particularly satisfying to merely watch demonstrations. If possible, it is better to let everyone try it for themselves. This principle introduces the second aspect of experiments at Huili — manipulating. During Huili science lessons, we will make the best use of every opportunity to create hands-on activities for pupils while ensuring that they remain entirely safe. For example, pupils recently made a colourful ‘volcano’ by combining materials such as vinegar, sodium bicarbonate and pigment. When bubbly ‘magma’ erupted from it, pupils could observe that solid sodium bicarbonate mixed with liquid vinegar created a new state of matter — gas, a sign of chemical changes (compared to physical changes). Pupils also put out candles with carbon dioxide. Through this experiment, they obtained a deeper understanding of the density and conditions that burning requires. Heavier carbon dioxide sinks to displace oxygen and isolate it from the flame. Thus, the flame finally goes out. Pupils wove a vivid and stereoscopic food web with ribbons. After intense discussion and trying various means to connect them altogether, pupils definitely acquired a better understanding of feeding relationships and interdependent relationships of different species. In a (staged) murder mystery experiment, pupils used powder to collect fingerprints from a murder weapon and compared them to that of the suspects’, allowing them to find out the identity of the murderer. This experiment trained pupils’ discernment and insight, helping them to understand the importance of evidence. Pupils discovered how to put a egg that is larger than the diameter of a bottleneck through the bottle and take it out again, whole and unbroken. In this experiment, they observed how the pressure of the contained gas changed with the temperature and the amount of gas molecules. All of these experiments have strengthened pupils’ safety awareness and manipulative abilities while familiarising them with the correct usage of laboratory apparatus. Hands-on processes like these can stimulate thought and discussion, contributing to developing their problem-solving abilities. For example, pupils were encouraged to consider the following: