Advertisements
Advertisements
Question
A chemical reaction is often accompanied by external indications or characteristics which include –
- Colour change
- Effervescence or gas evolved
- Evolution or absorption of heat
- Formation of a precipitate.
With reference to each of the above indications, state the external indication seen during – Addition of water to quicklime.
Advertisements
Solution
Addition of water to quick lime: Hissing sound accompanied by a lot of heat (boiling).
APPEARS IN
RELATED QUESTIONS
How do the following help in bringing about a chemical change?
heat.
What are (i) positive catalysts and (ii) negative catalysts? Support your answer with one example for each of them.
Name three biochemical catalysts found in the human body.
Give reason.
Acidic soil is treated with quick lime.
FILL IN THE BLANK
Positively charged ions are called ........
Fill in the blank:
The substances formed as a result of a chemical reaction are called _______
Explain the following reaction with one suitable example of Combination reactions .
Distinguish by heating the following in dry test tubs.
Copper Sulphate and copper carbonate
Give examples of exothermic reactions i.e. heat evolved in each of the following:
(a) reaction between a solid and a liquid
(b) reaction between two gases
Give two examples of exothermic reactions seen in everyday life.
Give a word equation for the following reaction.
Two gases which combine to give a solid.
Give balanced equation for the following conversion affected by heat alone on the substance:
Hydrated copper sulphate to sulphur dioxide
Complete the table given below.
| Flame test for calcium chloride | Acid used for flame test |
Name the solid residual product formed reaction and state its colour during – thermal decomposition of the following substance.
Calcium hydroxide.
NPK are the primary nutrients for plants.
Which of the following is not an “element + element → compound” type reaction?
______ is a natural indicator.
Which of the following is/are true when milk changes into curd?
- Its state is changed from liquid to semi solid.
- It changes colour.
- It changes taste.
- The change cannot be reversed.
Choose the correct option from below:
Match the following:
| Column I | Column II | ||
| 1. | Burning of coal | a. | Rusting |
| 2. | Painting of a surface | b. | Evaporation |
| 3. | Dipping iron in the water | c. | Chemical change |
| 4. | Salt from seawater | d. | Prevention of rusting |
Assertion (A): Cutting paper into very small pieces is an irreversible change.
Reason (R): Physical changes are always reversible.
What is the difference between reactants and products?
