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>
Using dimensional analysis, we can find the moles of strontium by comparing the mass of strontium to it's atomic mass.
You can find the atomic mass of Sr on the periodic table:
Atomic Mass Sr = 87.62g/mol
In case you are not familiar, dimensional analysis works like this:
(what we know) x (conversion factor) = what we are looking for
The conversion factor compares the units of what we know to the units of what we are looking for. In this case, the conversion factor is:
1 mol/87.62g
The important thing to note about the conversion factor is that you want to be able to cancel out the units of your given measurement (in this case, it is the mass)
So, our full solution will be:
moles Sr = (175.24 g)x(1 mol/87.62 g)
(cancel out the mass units)
moles Sr = 175.24 x 1 mol/87.62
= 2.00 mol Sr
Hope this helped you!
I believe the answer is carbon dioxide. Because when carbon dioxide and water combine in the atmosphere it forms a very weak acid called carbonic acid, which falls to the Earth's surface as precipitation.
Answer:
- covalent bond
- polar covalent bond
- ionic bond
- metallic bond
Explanation:
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In chemistry, there are two types of change, they are chemical and physical changes. A chemical change is one in which new substance are formed and it is always irreversible while a physical change is one in which no new substance is formed and it is always reversible. There are many factors that can indicate that a chemical change has taken place, these include: energy transfer, formation of precipitation, gas production, etc. Fracture formation does not indicate chemical change. In fracture formation nothing changes, so it is a form of physical change.
