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प्रश्न
A burning candle shows both physical and chemical changes. Explain ?
Burning of a candle is both a physical and chemical change.
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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
Try segregating the things around you as pure substances or mixtures.
Which of the following are chemical changes?
- Growth of a plant
- Rusting of iron
- Mixing of iron fillings and sand
- Cooking of food
- Digestion of food
- Freezing of water
- Burning of candle
Changes in which only ______ properties of a substance change are called physical changes.
Tick the most appropriate answer
2. Melting of ice is a
- reversible change
- irreversible change
- chemical change
- none of these
State whether the following is physical or chemical changes.
growing of a piglet into a pig —
State whether the following is physical or chemical changes.
mixing oil with water —
Write true or false
Earthquake is a desirable change.
Write true or false
Melting of ice is a physical change.
Tick the most appropriate answer.
Photosynthesis requires
Given reason:
Cutting of a cloth piece is a physical change, though it cannot be reversed.
Change is the law of nature and occurs in our everyday life, at all times and in all places.
Differentiate between the following change with a suitable example.
Slow and fast change.
State what is meant by the term – interconversion of matter. Is interconversion of matter a physical change or a chemical change.
Give a reason why – Heating a platinum wire is a reversible change but, heating a magnesium wire is an irreversible change.
Give a reason why rusting of iron is a chemical change but, the magnetization of iron is a physical change.
Give the reason why the following is considered as chemical changes.
A piece of magnesium strip is dropped into a beaker containing dilute hydrochloric acid.
When a woolen yarn is knitted to get a sweater, the change can be classified as ____________.
Sublimation of Iodine is a ______.
Ice, water and water vapour look different and display different ______ properties but they are ______ the same.
Fill in the blanks in the following statements using the words given in the box.
| rusted, colourful, substance, chemical, physical, reversible, iron oxide, object |
- Making sugar solution is a ______ change.
- A physical change is generally ______.
- Grinding of wheat grain changes its size. It is a ______ change.
- Iron benches kept in lawns and gardens get ______. It is a ______ change because a new ______ is formed.
Mention a few physical properties of a substance.
