Page 24 - NCERT Science Class 10 English Medium

n Rinse both cloth strips with water and again check their odour.
n Note your observations.
n Now take some dilute vanilla essence and clove oil and check their
odour.
n Take some dilute HCl solution in one test tube and dilute NaOH
solution in another. Add a few drops of dilute vanilla essence to
both test tubes and shake well. Check the odour once again and
record changes in odour, if any.
n Similarly, test the change in the odour of clove oil with dilute HCl
and dilute NaOH solutions and record your observations.

Which of these – vanilla, onion and clove, can be used as olfactory
indicators on the basis of your observations?
Let us do some more activities to understand the chemical properties
of acids and bases.

2.1.2 How do Acids and Bases React with Metals?

Activity 2.3
Activity
Activity 2.32.3
Activity 2.3
2.3
Activity
CAUTION: This activity needs the teacher’s assistance.
n Set the apparatus as shown in Fig. 2.1.
n Take about 5 mL of dilute sulphuric acid in a test tube and add a
few pieces of zinc granules to it.
n What do you observe on the surface of zinc granules?
n Pass the gas being evolved through the soap solution.
n Why are bubbles formed in the soap solution?
n Take a burning candle near a gas filled bubble.
n What do you observe?
n Repeat this Activity with some more acids like HCl, HNO and
3
CH COOH.
3
n Are the observations in all the cases the same or different?

Figure 2.1
Figure 2.1
Figure 2.1
Figure 2.1 Reaction of zinc granules with dilute sulphuric acid and testing hydrogen
Figure 2.1
gas by burning
Acids, Bases and Salts 19

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