okay i have a question which is on a key assesed piece
explain the physical and chemical changes when a candle burns using the big idea of energy?
what is the big idea of energy?
This is something I'd be interested in as well. What presicely energy is isn't clear so far. Scientists are argueing about this. So your science teacher is asking a rather ridiculous question, you can tell that.
However, the idea supposed to be used here is the concept of heat being a form of energy, i.e. the spoken-of energy, namely the heat, causes a chemical reaction so-to-speak: It breaks up the bondings between the molecules of the candles, i.e. the candle (the wax) turns liquid. Hence the liquid wax runs down the candle as it's got a bigger volme becaus of simply being liquid. Consequently, the candle's shape changes as the wax afterwards chills down again. The little wool thread in the candle turns black because the evoloving molecule causing this color is combined from carbo and dioxyde and other elements such as hydrogen. But it is not necessarily carbondioxyde which emerges and causes the coloring.
Thank you dongo you have made my life so much easier
The big idea of energy refers to the concept that energy can neither be created nor destroyed; it can only be transformed from one form to another. In the case of a burning candle, there are both physical and chemical changes taking place that can be explained through the lens of energy.
1. Physical changes:
When a candle burns, there are physical changes occurring. The solid wax undergoes a phase change from solid to liquid as it melts. This is known as a physical change because the substance itself is not changing at a molecular level, but rather its physical state is altered due to the absorption of heat energy from the flame. Additionally, the liquid wax is drawn up into the wick through capillary action, where it evaporates and forms a gas.
2. Chemical changes:
The chemical changes during candle burning are primarily related to the combustion process. The heat from the flame causes the hydrocarbon molecules in the wax (typically in the form of long carbon chains) to break apart through a process called pyrolysis. This results in the production of volatile hydrocarbon vapors, along with carbon dioxide and water vapor. The carbon atoms in these vapors react with oxygen from the air in a process known as oxidation or combustion. This chemical reaction releases a significant amount of energy in the form of heat and light.
In terms of the big idea of energy, we can observe the transformation of energy throughout this process. Initially, the candle has stored chemical potential energy in the wax. As the candle burns, this stored energy is released and transformed into other forms of energy, such as heat and light energy. This process is consistent with the principle that energy can be converted and transferred, but it cannot be created or destroyed.
To recap, when a candle burns, physical changes occur as the solid wax melts and evaporates, while chemical changes involve the breaking apart of hydrocarbon molecules and their subsequent reactions with oxygen. These changes demonstrate the conversion of the candle's stored chemical potential energy into heat and light energy, which aligns with the big idea of energy.