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Learn from an expert tutor. Book a free class! Solution 5: When a candle burns, both physical and chemical changes occur. Physical Changes: On heating, candle wax gets melted.
Since it again turns into solid wax on cooling. So, the melting of wax and vapourisation of melted wax are physical changes. Chemical Changes : The wax near flame burns and gives new substances like carbon dioxide, carbon soot, water vapour, heat and light. LPG is another example of a familiar process in which both the chemical and physical changes take place.
LPG is present in liquid form in the cylinder. When it comes out of the cylinder, it converts into gaseous form which is a physical change. It undergoes chemical change when gas burns in air. Set your child up for success with Lido, book a class today! Maths Class 6 Class 7 Class 8. Science Class 6 Class 7 Class 8. Selina Question Bank. A physical candle is composed of wax surrounding a wick. Describe the wicking process in the burning candle, and be sure your description includes the physical state of the wax and the wick.
As a candle burns, the wax gradually disappears from sight. Is there a physical change in the wax that would account for this disappearance If the wax was simply undergoing physical change, would you expect the candle to produce heat and light as it does when a candle burns? The process of burning as opposed to evaporating is a chemical reaction, a chemical change. The wax molecules are undergoing a chemical change; they are changing into different molecules by reacting with a substance in the air.
What is this substance in the air that a candle needs to burn? Part Two. We can represent the combustion of a candle like this:.
If less oxygen is available, one possible outcome in the combustion of wax is. What do you observe on the bottom of the beaker? What could this substance be and where did it come from? How does this provide evidence that a chemical reaction is taking place? Wipe the bottom of the beaker clean and place an ice cube inside it.
Hold the beaker several centimeters above not in the flame and allow the candle to burn. Can you see a substance forming on the bottom of the beaker? Could it have come from the melting ice inside the beaker? Consider the flame itself.
Is the flame a substance produced by the candle? What observations lead you to think that the flame is matter? In what ways does the flame seem like energy? Part Three. Reflecting on the Investigation. What phase is the wax in when it mixes with oxygen in the air and undergoes a chemical change? Based on your observations, in which phase solid, liquid, or gas is the wax most likely to undergo a chemical change? Explain why this is the case based on your sketches of wax in solid, liquid, and gas phases.
Look back at your diagrams of the candle flame. Can you identify the region where the wick itself is undergoing combustion? Where is this region? What is fire? Is it matter or is it energy?
Explain your answer. In a short paragraph, summarize the changes that a candle undergoes when it burns. Incorporate the following words into the paragraph in a meaningful way: wax, wick, phase change, chemical reaction, vaporize, melt, transforms, solid, liquid, gas, energy, light, and heat. Back to the top. Please login with the same password. Encyclopedia of academic concepts Articles and project ideas Expert opinion on doubts Sample papers, board papers and exam tips Latest updates from education sector.
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