Advertisements
Advertisements
प्रश्न
A burning candle shows both physical and chemical changes. Explain ?
Burning of a candle is both a physical and chemical change.
Advertisements
उत्तर १
A burning candle produces wax vapours which solidify and form wax again is physical change. At the same time wax on burning produces water vapours and carbondioxide which escape into the atmosphere which are new substances with new properties. It is a chemical change.
Hence burning of candle shows both physical and chemcial changes.
उत्तर २
When a candle is lighted, some of the solid wax first melts and turns into liquid, then it turns into vapours to produce a flame. New substances CO2 and H2O vapours are formed along with the evolution of light and heat energy. This shows a chemical change. When some of the molten wax drops to the floor, it again solidifies. Which shows a physical change. Thus the melting of candle wax is a physical change and the production of CO2 and H2O represents chemical change.
संबंधित प्रश्न
Classify the following as chemical or physical change:
Cutting of trees
Classify the following as chemical or physical change:
Burning of paper and wood
Changes in which only ______ properties of a substance change are called physical changes.
When a candle burns, both physical and chemical changes take place. Identify these changes. Give another example of a familiar process in which both the chemical and physical changes take place.
State the differences between a physical change and a chemical change.
State whether the following is physical or chemical changes.
glowing of a bulb -
Tick (√) the correct alternative from the choice given for the following statement
Which one of the following is volatile in nature ?
Match the columns.
| Column A | Column B |
| 1. a change which cannot be easily reversed | a. man-made change |
| 2 a change that repeats itself at regular intervals | b. chemical chang |
| 3. a change that is made by humans | c. physical change |
| 4. a change in which the original substance cannot be obtained | d. periodic change |
| 5. a change where no new substance is formed | e. irreversible change |
| f . slow change |
Give two examples of periodic changes.
Give four difference between physical and chemical changes.
State whether the following statement is true or false. If false write the correct statement.
Melting of ice is an exothermic, irreversible chemical change.
Select the chemical changes from the following list of changes
Respiration in mammals.
Select the chemical changes from the following list of changes
The carbon cycle.
Select the correct answer from the choice given below to complete the sentence
A change in which a substance retains its identity is a
______ change.
Match the examples of changes in List I with the correct type of change in List II.
| List I | List II |
| 1. Burning of paper | A: Physical change |
| 2. The ringing of an electric bell | B: Chemical change |
| 3. Curdling of milk | |
| 4. Electric light is switched on | |
| 5. Melting of butter |
Name the following.
A form of energy required for a chemical change.
Paheli’s mother made a concentrated sugar syrup by dissolving sugar in hot water. On cooling, crystals of sugar got separated. This indicates a –
What kind of change is shown by tearing of paper?
Grinding of wheat grain changes its size. It is a ____________ change.
Keeping a stone in sunlight for few hours is ______.
