When a candle burns, both physical and chemical changes occur, each identifiable by specific characteristics. Here's a breakdown of the changes and reasons that indicate which are physical and which are chemical:

Question

Physical Changes:
1. Melting of Wax:
o Observation: When the candle is lit, the solid wax melts and turns into liquid.
o Reason: This is a physical change because it involves a change of state from solid to liquid. The chemical composition of the wax remains unchanged; only its physical form changes.
2. Solidification of Wax:
o Observation: When the candle is extinguished, the melted wax cools and solidifies again.
o Reason: This is another physical change, as the wax changes back to solid form without altering its chemical structure.
3. Change in Size and Shape:
o Observation: As the candle burns, it gets shorter and may change in shape due to melting.
o Reason: The reduction in size is a physical change since the substance (wax) is still present; it is just in a different physical state and quantity.
Chemical Changes:
1. Combustion of Wax:
o Observation: The wick ignites, and the wax vaporizes and burns, producing light, heat, carbon dioxide, and water vapor.
o Reason: This is a chemical change because new substances are formed (carbon dioxide and water), and the original substances (wax and oxygen) cannot be easily reverted back to their original form. This process involves a chemical reaction (combustion) where energy is released.
2. Formation of Soot:
o Observation: Incomplete combustion can produce soot (carbon particles).
o Reason: The formation of soot indicates a chemical change because it results from the breakdown of wax molecules during combustion. This again produces different substances, which cannot revert to the original wax.

jumble up by creating two columns reason vs reasons and match them

Answer 1

Sure! Here’s a column format with the observations and reasons jumbled up, where you can match each observation with its corresponding reason.

Observations | Reasons

-------------------------------------------------|------------------------------------------------------

1. The wax melts and turns into liquid. | This is a physical change because it involves a change of state from solid to liquid.
2. The melted wax cools and solidifies again. | This indicates a chemical change because it results from the breakdown of wax molecules during combustion.
3. The candle gets shorter and may change shape. | The reduction in size is a physical change since the substance (wax) is still present; it is just in a different physical state and quantity.
4. The wick ignites, producing carbon dioxide. | This is a chemical change because new substances are formed, and the original substances cannot be easily reverted back to their original form.
5. Incomplete combustion produces soot. | This is another physical change, as the wax changes back to solid form without altering its chemical structure.

Instructions to Match:

• Match each observation in the left column with the correct reason from the right column.