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प्रश्न
What is the difference between dissolution of sugar and burning of sugar ?
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उत्तर
1. Dissolution of sugar:
- When sugar is dissolved in water it disappears. It we taste the solution, the sugar is still present in dissolved form.
- If water is evaporated we get back the sugar.
- So it is a physical and reversible change.
2. Burning of sugar:
- Fire activates a chemical reaction between sugar and oxygen. The oxygen in the air reacts with the sugar as the chemical bonds broke.
- Energy is released in the form of smoke.
- So, burning a sugar is a chemical change.
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संबंधित प्रश्न
Tick the most appropriate answer.
3. Physical changes are
- permanent.
- periodic,
- temporary
- irreversible.
True or false
Change of seasons is a non-periodic change.
Make a list of different types of changes with example.
Which of the following are physical changes ?
- melting of iron metal
- rusting of iron metal
- bending of an iron rod
- drawing a wire of iron metal
Classify the following as a physical or a chemical change.
Burning of coal
Fill in the blank.
The process of a liquid changing into a solid is called ________
Fill in the blank with the appropriate word of the statement given below:
If a change is permanent and irreversible it is considered a _________ change.
Potassium chloride is added to water and stirred. A salt solution is obtained, which is then boiled, leaving behind a residue.
- Is the above change physical or chemical?
- Name the residue which remains behind after the salt solution is boiled.
- Is the change reversible or not reversible?
- Are the composition and properties of the original substance altered?
- Give a reason why the above experimentation would not be possible if calcium carbonate was taken in place of potassium chloride.
State whether the following statement is true or false:
Anaerobic bacteria digest animal waste and produce biogas.
Match the items of Column I with the items of Column II.
| Column I | Column II | ||
| (a) | Large crystals | (i) | Turns lime water into milky |
| (b) | Depositing a layer of zinc on iron | (ii) | Physical change |
| (c) | Souring of milk | (iii) | Rust |
| (d) | Carbon dioxide | (iv) | Sugar candy (Mishri) |
| (e) | Iron oxide | (v) | Chemical change |
| (f) | Dissolving common salt in water | (vi) | Galvanisation |
