Exploring Physical and Chemical Properties
by Celene Hernandez
10th Grade Chemistry Teacher
Classes are in full swing at Roberto Clemente Community Academy. This week, IB Chemistry students learned all about physical and chemical properties and changes. Physical properties of an element or compound can be observed without a chemical reaction of the substance. For example, a substance’s color, solubility, and density are physical properties. Chemical properties of an element or compound occur in chemical reactions. For example, sodium reacting explosively with water is a chemical property. Physical changes occur when substances undergo a change, are separated, or are combined – but are not altered chemically. Finally, chemical changes occur when substances are changed chemically and then display different physical and chemical properties.
Students began the week by learning new vocabulary, to build an understanding of chemical properties, physical properties, chemical changes, and physical changes. They then completed lab work through a rotation of stations, investing all of these concepts in action. The most debated station involved burning a candle and classifying their observations as related to chemical or physical change. While students on both sides articulated their arguments well, citing evidence form the observations and what they had learned in class, they ultimately realized that the burning candle represented both types of change – the wax melting was an example of a physical change while the candlewick burning was an example of a chemical change – which helped them realize the complexities of applying classroom knowledge to understand real-life scenarios.
Students then proceeded to design and complete an investigation to distinguish between physical and chemical properties. Students were provided with aluminum, salt, sugar, Alka-Seltzer tablets, ammonia, vinegar, matches, hydrogen peroxide, Popsicle sticks, paper, nails, and wax candles. From these materials, they design an exploration and recorded data on the physical and chemical properties of their choice, furthering their understanding through hands-on investigation.