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Solar Energy (2) – Grade 7 Science Worksheets

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The Sun

The sun is a huge shining star which is about one hundred million times the size of Earth. Suppose Earth was a mustard seed, the sun would be roughly the size of a basketball. It is again just an assumption of how big it is than the Earth. Truth is its unimaginable coz no one ever got very close to it ever. It is in the centre of the Milky Way galaxy, our galaxy and holds all the planets in its position.

solar

Credit: https://www.calacademy.org/planet-watch-0

The sun is a very huge hot ball of gas. Its surface is estimated to be 6,000 degrees Celsius, and the sun is even hotter the further towards its center. This is because nuclear fusion takes place at the center of the sun. Hydrogen (70%) and helium (28%) are the gases which make up most of the sun.  Nuclear fusion is a process which happens when small nuclei are fused together to form a bigger and heavier nuclei. This gives off lot of heat energy.

solar1

Credit: http://denebstar.weebly.com/nuclear-fusion-in-stars.html

The word ‘nuclear’ refers to the nucleus of an atom, and the word ‘fusion’ means merging together. Nuclear fusion is fusing together of nuclei, which releases of large amounts of extreme heat and energy.

 

What is the source for solar energy?

Solar is a Latin term for the sun. Solar energy simply means energy that radiates from the sun.

solar2

Credit: https://www.flickr.com/photos/11304375@N07/2819311727

The core of the sun is where the nuclear fusion takes place, followed by the radiative zone, he then convection zone, the outer part of the sun is termed as the corona.
The Sun is the closest of all the stars. It is a huge sphere of very hot gas in space which emits heat and light in all directions. It is the primary source of energy. All the planets, including our home, the Earth, revolve around the Sun in an elliptical orbit.

 

The Sun is immensely necessary:

  • Sun helps to restore and continue life on earth (for the simple reason plants prepare food in the presence of sunlight and all living beings directly or indirectly depend on plants for food and energy.
  • Sun is one of the most important renewable energy sources. Because we very well know the sun is coming up tomorrow without fail.
  • It provides us with heat and light.
  • Its movement across the sky causes day and night.
  • The change of seasons, climate and weather.

 

Every planet takes its own time period to rotate around its axis and so they have different lengths of days. For example Venus is the slowest of all; it takes 243 days to complete one rotation.

We say that the Sun rises in the east and sets in the west but that is just a way of saying. It doesn’t mean that the sun is moving. The Sun is constant and all the planets of the Milky Way galaxy revolve around it. It is a vital source of energy to all the planets but since life exists on Earth we know how essential it is to us.

The Earth’s rotation about its axis causes day and night. One half of the Earth has daylight, the other half has nights. As the Earth spins we move from light to shadow and back to light again over the course of one day (24 hours).

During the night we cannot see the Sun move across the sky, but when we look carefully we notice that the stars move across the sky, just like the Sun does.

 

Earth’s Rotation
It takes the Earth 24 hours to make one complete turn (called a rotation) on its axis, so an Earth day is 24 hours long.

solar3

Earth’s Revolution

The Earth revolves around the Sun in a circle, and it takes 365 ¼ days for one revolution to complete. The Earth revolves around the Sun it also rotates (spins) on its axis at the same time. The earth’s revolution around the sun causes the seasons.

What is solar energy and how is it used?

Plants prepare their own food with the help of chlorophyll in the presence of sunlight. The Sun’s energy is processed and stored in the form of food so that it can be used later. In photosynthesis the energy from the Sun is used to change carbon dioxide and water into carbohydrates (forexample cellulosestarch or glucose). The carbohydrates are stored in fruits, leaves, wood or bark. When we eat a plant product, for example an apple, our bodies are able to utilize the energy stored in the apple in the form of carbohydrates, vitamins etc. In the same way animals, for example cows, use the Sun’s energy when they eat the grass.

We all living beings directly or indirectly depend on plants on photosynthesis for our energy. Earlier we learnt about energy transfer between producers, for example grass, and consumer: example a lion. Plants play a vital role in life on Earth as they form the basis of food chains. Without plants, life on Earth would not be possible. As we depend on plants so does plants depend on the Sun for survival and would die without its energy which allows them to photosynthesize.

 

Stored Solar Energy      

Earlier we learnt about renewable and non-renewable energy sources.

Fossil fuels are examples of non-renewable energy sources.

We know that plants store the Sun’s energy and we are able to use that energy later on. But when plants die what happen to their stored energy? They get stored in the Earth in different forms. Like

  • Fossil Fuels
  • Coal
  • Crude oil
  • Natural gas

Check Point

  1. What is the approximate surface temperature of the Sun?
  2. What is nuclear fusion?
  3. Why is the sun very important?
  4. What do you mean by the Earth’s Rotation?
  5. What do you mean by the Earth’s Revolution?
Answer Key
  1. The sun is a very huge hot sphere of gas. Its surface is estimated to be 6,000 degrees Celsius.
  2. Nuclear fusion is a process which happens when small nuclei are fused together to form a bigger and heavier nuclei.

The Sun is immensely necessary:

  • Sun helps to restore and continue life on earth (for the simple reason plants prepare food in the presence of sunlight and all living beings directly or indirectly depend on plants for food and energy.
  • Sun is one of the most important renewable energy sources. Because we very well know the Sun is coming up tomorrow without fail.
  • It provides us with heat and light
  • Its movement across the sky causes day and night.
  • The change of seasons, climate and weather.
  1. The process of the earth spinning on its own axis causing day and night is called the Earth’s rotation.
  2. The Earth revolves around the Sun in a circle, and it takes 365 ¼ days for one revolution to complete.

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Solar Energy 2 ultima modifica: 2018-07-10T06:03:07+00:00 da Ashima