Answer:
Anhydrous sodium carbonate is stable to heat and does not decompose even when it is heated to redness. This is because sodium carbonate salt on heating with acids react to release carbon dioxide.
Physical Change: It is a type of change in which matter changes its physical state like shape, size but is not transformed into another substance. It is usually a reversible process.
Chemical Change: It is a type of change in which the rearrangement of atoms of one or more than one substance is involved. and it changes its chemical composition that is there is a formation of at least one new substance. It is usually an irreversible process.
Now, keeping in mind the definitions, we can easily classify the examples in the question as physical or chemical change.
7. Chemical Change
8. Chemical Change
9. Physical Change
10. Chemical Change
11. Physical Change
12. Physical Change
13. Chemical Change
14. Physical Change
15. Chemical Change
16. Physical Change
17. Chemical Change
18. Chemical Change
19. Physical Change
20. Physical Change
21. Chemical Change
22. Physical Change
23. Chemical Change
24. Chemical Change
25. Physical Change
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20. Answer is "it reflects sunlight".<span>
<span>The moon is </span>not a star<span> <span>as sun.
Hence, </span></span>moon can't produce light by itself<span>. The only reason that we can see the moon is </span>it reflects the sunlight<span>. According to the distance from the
sun to the moon, the light reflection can be varied.</span>
21. Answer is "Jupiter".
Asteroid
belt<span> <span>is
a </span></span>region which is located between
Mars and Jupiter and consists of asteroids and minor planets.<span> This asteroid belt has the </span>4%<span> <span>as the
mass </span>of our moon. Due to the </span>Jupiter's strong gravity<span>, it is </span>prevented a forming of new planet by this asteroid belt.
22.<span> Answer is "</span>they are equal".
The period of
revolution is
the time which is taken by a
mass to go completely one round around another mass. For moon, the period of revolution is 27 days.<span>
The period of
rotation</span> is
the time taken by a mass to complete
one round around its own axis. It is about 27 days for moon.
</span>23.<span> Answer is "</span>The moon is in Earth's shadow".
<span>Lunar eclipse happens when </span>Sun, Earth and moon are directly
aligned each other <span>and Earth is located in between the Sun and the
moon. </span>Then the moon is covered by the
Earth's shadow.
24.<span> Answer is "</span>In a solar eclipse, it is Earth that is caught in the umbra
of the moon. In a lunar eclipse, it is the moon that is caught in the umbra of
Earth".
In total lunar eclipse, Earth is located
between Sun and the moon and
they are directly aligned to each other. The moon is totally covered with the Earth's
shadow.
Total solar eclipse can be seen when the
moon is located between sun and Earth by completely covering the sun.
25. According
to the given choices, we can get "Apollo"<span> as the answer.
Apollo 8 is the first
manned mission to the moon. From
that there were several manned mission including <span>first
manned landing on the moon. The Apollo program was conducted by USA.</span> </span>
Answer:
The reaction between hydrogen and fluorine.
Explanation:
The balanced chemical equation of the reaction is:
From the balanced chemical equation, it is clear that:
1 mole of 
gas reacts with one mole of 
and forms 2 moles of HF(g).
