Changes are All Around
In this How the World Works unit, we have had done some experiments related to our topic “Physical and Chemical Changes”. We have visited and conducted experiments in the Science Laboratory in the Secondary Department twice and we invited two parents as our resource speakers. In the first meeting, we did “MYSTERY POWDERS” experiment. Here, we explored the physical and chemical properties, changes and reactions.
The five mystery powders in this activity have different physical properties, though they are all white. We tested all five powders with iodine, water, vinegar, sense of taste (except for the plaster of Paris) and heat. In the first test, we put some drops of iodine to the powders, powder B turned brown and powder D turned black. Then, we put some water to the powders. Powder B and C dissolved, powder E became sticky. Next, when added vinegar, powder A was fizzing, powder E was foamy. After that, they tasted powder A – D. The last treatment, we heated them all. Powder B caramelised and powder D turned black.
After that, we had Burning Candle. When the wax was heated, it changed its state into liquid and when it was cooled, it reversed back into solid. It was physical change in candle. What happened with its string? The string got burnt and could not reverse back into its original shape, it was a chemical change. We learnt that in burning candle we could see that physical and chemical changes happened all together.
After we finished with the treatment to those powders, the students guessed the name of the powder. Most of the answers were correct for powder A – D but no one could answer powder E correctly. Powder A was baking soda, powder B was sugar, powder C was salt, powder D was corn starch and powder E was plaster of Paris.
We have conducted some more challenging experiments in our second visit to the secondary department laboratory. Why were they challenging? Because some of the experiments did not work as we planned. Good thing, we discovered new idea about experiments. When we had pH checking by adding universal indicator, we could see the different colour of the substance. From it, we could classify whether the substance is acidic, base or neutral one. We did this experiment because we wanted to know chemical substances in our beverages.
Next experiment, we had Melting Chocolate where we saw the changes on the states from solid to liquid and back to solid. The chocolate changed its state when we add or remove heat (physical change). Some of the chocolate we heated got caramelised and even burnt. It was because it contained sugar. It could not reverse, then it was a chemical change.
Then, we did Camphor Sublimation. In this experiment, we needed to crush a mothball into powder. Then we heated it. The funnel on the evaporating dish became foggy then we it cooled, we could see the clear crystal of camphor in the funnel. It was a sight to see. We learnt that solid can change into gas and reverse into solid that we call it as sublimation. It was a physical change.
After we sublimated camphor, we had Salt Separation. We heated salt solution to prove whether we could reverse it back into salt or not. We could see white crystal at the edge of the evaporating dish. It was the salt that underwent change.
Last but not the least, we conducted Elephant’s Toothpaste. All of the six groups have discovered new ideas in this experiment. It seemed that the tubes we used were not clean or contaminated with other substance, that was why the substances did not work well. Then, we decided to make the new one and we did it. We could see that the substances we added could release heat when they changed to other state. We also learnt about decomposition reaction, in this experiment, hydrogen peroxide became water and oxygen.
To see the practical applications of physical and chemical changes, we were helped by Mrs. Tracy Mondoringin and Mrs. Hasna Becher. We made 5 minutes DIY ice cream and chocolate cake. It was so fun when we made ice cream. We just added all the ingredients and we shook it for 5 minutes. Then, voila! We had our own ice cream. Everybody screamed for ice cream. We did not need freezer because the rock salt added to ice cube was decreasing the temperature of the ice cube. We also made chocolate cake. We could see the physical change when the ingredients were blended. The chemical change could be seen when the cake batter was put in the oven. It was rising slowly but surely. After 30 minutes in the oven, we could enjoy our chocolate cake.
Through these learning experiences, we understand that materials can undergo changes that may provide challenges and benefits for the society and the environment.