CLASS 7TH DAY 2
INTRODUCTION
PHASES OF MOON
The moon changes its shape almost every night. But why? The phases of the moon are caused by the light from the sun and the moon’s orbit around the Earth. From new moon through waxing crescent, quarter, gibbous, full moon, and waning back to new moon again, come learn about the cycle of shapes the moon takes (or rather, appears to take) as it travels around our planet.
The moon itself doesn’t emit any light like the sun. What we see when we see the moon is sunlight reflected off the moon. The phase of the moon is how much of the moon appears to us on Earth to be lit up by the sun. Half of the moon is always lit up by the sun, except during an eclipse, but we only see a portion that’s lit up. This is the phase of the moon.
Around once per month, every 29.53 days to be exact, the phases of the moon make a complete cycle. As the moon circles the Earth, we can only see a portion of the lit up side. When we can see 100% of the lit up side, this is a full moon. When we can’t see any of the lit up side, this is called a dark moon or new moon.
The phases of the moon starting with the New Moon are:
- New Moon
- Waxing Crescent
- First Quarter
- Waxing Gibbous
- Full Moon
- Waning Gibbous
- Third Quarter
- Waning Crescent
- Dark Moon
The New Moon and Dark Moon are pretty much the same phase happening at almost the same time.
Waxing or Waning?
As the New moon begins its orbit and we see more and more of the moon, this is called Waxing. After the moon gets to its Full phase, we start to see less and less of the moon. This is called Waning.
Lunar Calendar
A lunar calendar is one based on the orbit of the moon. A lunar month (29.53 days) is slightly shorter than an average standard month (30.44 days). If you only had 12 lunar months then you would end up around 12 days short of a year.
Eclipse
A lunar eclipse is when the Earth is exactly between the Moon and the Sun so none of the Sun’s rays can hit the moon. A solar eclipse is when the moon exactly blocks the Sun’s rays from hitting the Earth.
ACTIVITY: MELTING ICE FAST WITHOUT HEAT
1. Experiment procedure
Do you have any idea about the effect of adding salt in the process of melting ice? We will learn it with a simple experiment for which you will be needing ice cubes and table salt.
Now follow the given procedure to answer the question asked above:
1) Take 2 small bowls( bowl A and bowl B) filled with ice cubes.
2) Put some salt over the ice cubes of any one bowl (here bowl A)and now let ice in both the bowls melt.
3)Make observations which bowl’s ice melts faster.
2. Reason
What we have observed is that addition of salt makes the melting of ice faster. But let’s understand why is it so?
         Addition of temperature reduces the freezing temperature,(that temperature at which water freezes to ice). So, now that reduced temperature will be achieved first and hence it will turn to water first.
3. Uses
This addition of salt to make melting of snow faster is used where there is snow on the roads after heavy rainfall.
FUN ACTIVITY: Family Tree
A family tree is a chart representing family relationships in a tree like structure. It can trace our ancestry. Through this we could get to know about you great grandfathers, 5th or even more distant cousins.
So, here is an activity for you.Try to make your family tree at least to your great grandfather(grandfather’s father).