You helped me with my observations yesterday, but I need help with my questions as well. I tried to answer as many as I could by myself, but I'm having difficulties understanding some. Pointing me towards the right direction would be helpful, thanks.
Questions:
Which changes that u noted in step 4 were physical? which were chemical?
I wrote: Changes in step 4 which were physical were the candle melting and the flame growing. Changes in step 4 which were chemical were the oxygen and the wick burning.
I am kind of having troubles identifying which changes are chemical and which are physical so I'm not sure which other occured changes were physical and which were chemical.
What evidence showed the release of energy? what forms of energy were produced by the burning candle? where was this energy in the unlit candle?
I wrote:
The flame growing hotter and hotter; heat is given off. This energy was in the wick --Please correct me if I'm wrong, thanks
based upon your analysis of your observations in Part 3, what are 2 substances produced by the combustion of the candle?
-I don't get this question-- i don't know the answer. i'll guess and say that bubbles were produced.
How does the mass of the candle change during combustion, explain this change in mass.?????????????????
Is it because of the wax starting to melt?
is there any evidence that the candle needs something from the air to help it burn? what might this something be?
- I don't get the first part but is the second one oxygen and hydrocarbon?
You did not read my response.
Physical changes: wax melted, then wax vaporized.
CHemical change: wax vapor and oxygen in air changes to combustion products. THe cobalt paper tested for water vapor in the "fumes", and the limewater tested for carbon dioxide. So the output of the combustion was water and carbon dioxide.
The mass of the candle changes because it is consumed in the burning. As for a evidence that something in the air was contributing to the burning, didn't the candle smother, or at least reduce the burn rate, when you put the coil down over it to shut off the air?
Sara -- if you expect us to help you, you must thoroughly read all responses. It's discouraging for us to post an answer -- only to find that the student has ignored it.
sorry Ms. Sue, sorry bobpursley for that inconvenience.
big words...
I'm glad to hear that I could help you with your observations! Let's work through your questions step by step:
1. Which changes that you noted in step 4 were physical? Which were chemical?
To identify whether a change is physical or chemical, you need to consider whether the substances involved undergo a chemical reaction or if they only experience a change in their physical properties. In step 4, you correctly identified that the candle melting and the flame growing were physical changes. The candle melting is a physical change because it changes from a solid to a liquid state, while the flame growing is also a physical change because it involves the increase in size and temperature of the flame. The oxygen and wick burning, however, are chemical changes since they involve a chemical reaction in which new substances are formed.
2. What evidence showed the release of energy? What forms of energy were produced by the burning candle? Where was this energy in the unlit candle?
In step 4, the flame growing hotter and hotter is evidence of the release of energy. The forms of energy produced by the burning candle include light and heat. The energy in the unlit candle was stored in the chemical bonds of the wax and the wick, which are released as heat and light during combustion.
3. Based on your analysis of your observations in Part 3, what are two substances produced by the combustion of the candle?
In Part 3, you need to review your observations to identify the substances produced by the combustion of the candle. Bubbles were not mentioned in your observations, so we cannot conclude that they were produced. Examples of substances that are typically produced during combustion are carbon dioxide and water vapor. Check your observations again, and see if you can spot any evidence of these substances being produced.
4. How does the mass of the candle change during combustion? Explain this change in mass.
The mass of the candle decreases during combustion. This is because the wax is being transformed into gases, such as carbon dioxide and water vapor, and released into the air. As these gases escape, the overall mass of the candle decreases.
5. Is there any evidence that the candle needs something from the air to help it burn? What might this something be?
Yes, there is evidence that the candle needs something from the air to burn, and that something is oxygen. One piece of evidence is the fact that the flame grows bigger when more oxygen is supplied to it. Another piece of evidence is the observation that the candle cannot burn if it is covered or placed in an area with low oxygen levels. Oxygen is one of the key reactants required for the chemical reaction of combustion to occur.