Category: Year 6 – 8 Science

Intermediate School Level

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More nitrogen than oxygen?

There are more nitrogen gases than oxygen gases in the air. Every living things on the earth need nitrogen to grow and repair. Despite, it is impossible to use these nitrogen by breathing. We gain nitrogen by eating and plants absorb nitrogen as nitrates. This is because nitrogens are slightly lighter than water or air so they tend to stay in the form of stable gases. If any one of these living things die, nitrogens are returned back to the soil and air by decomposers like bacteria and fungi. These decomposers are very important. They break down all the dead materials and releases essential elements and compounds (like nitrogen and carbon) back to it’s cycle.

Nitrogen cycle

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Nebulae

Combined X-Ray and Optical Images of the Crab Nebula

http://www.hubblesite.org/gallery/album/nebula/pr2002024a/

The word “nebula” is derived from the Latin word for “clouds”. Indeed, a nebula is a cosmic cloud of gas and dust floating in space. A nebula is a huge, diffuse cloud of gas and dust in intergalactic space. The gas in nebulae (the plural of nebula) is mostly hydrogen gas (H2).

More than one nebula are called nebulae. Nebulae are the basic building blocks of the universe. They contain the elements from which stars and solar systems are built.

They glow with rich colours of reds, blues and greens with swirls of light. Stars inside these clouds of gas cause them to glow in colours.

Most nebulae are composed of about 90% hydrogen, 10% helium, and 0.1% heavy elements such as carbon, nitrogen, magnesium, potassium, calcium, iron. These clouds of matter are also quite large. In fact, they are among the largest objects in the galaxy.

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How do we see and learn? (Part 3: Memory)


Everyone wants to learn faster and effectively.

One way is to understand how the learner’s brain processes in the learning environment. Learning is the process of taking new information in your working memory and integrating it with existing knowledge in your long-term memory.  Once it’s in long-term memory you can recall it and transfer the knowledge to the real world.


  • Working memory:  Your working memory is good at processing information, but it can only hold so much at one time.  All of your active thinking happens in the working memory.
  • Long-term memory:  Your long-term memory is your storage center and holds your existing knowledge.  In the learning process, you are connecting the new information to prior knowledge.  As you actively process information, you are swapping it between working and long-term memory.

The working memory is like a white board where you can do a lot of calculations and diagramming on the fly.  On the white board, you need space to both write down information (temporary storage) and do your problem-solving (active processing).

Often the problem is that you only have so much space.  As the white board gets cluttered with information, you run out of room to work.  That means you need to record the important information and free up space to do more work on the white board.

One way to capture the information is to create post-it notes (long-term memory) to record the information on the white board.  Once you you have the notes, you are free to erase the white board and do more work.  And, if you needed to recall what you did earlier, all you have to do is look at one of your notes.


As you go through an learning process, what you see and hear enters your working memory where it is temporarily stored.  Your brain actively processes the new information and integrates it with what you have stored in your long-term memory.

So, your brain is doing these things:

  1. Receiving new information
  2. Actively processing the information
  3. Integrating the information with long-term memory

(ref: http://www.articulate.com/rapid-elearning/2007/10/)

There are numerous ways been suggested by the researchers about effective ways to transfer information to the learners. These are used to promote clear processing and life long memory of the information and teachers in classroom happen to use coloured movie clips and pens. Most of the schools have recognized the importance in providing resources and been proved to be effective.

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How do we see? (Part1: The Eye)

In some ways the eye is like a camera: Its optical elements focus an image of some object on a light-sensitive “film – the retina – while ensuring the correct amount of light to make the proper “exposure”.

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When your eyelids are open, light enters your eye through a circular hole called the pupil and is focussed by a lens onto the light sensitive retina attached to the back of the eye.

The size of the pupil can be adjusted to allow more light to enter when the environment is dim, and less light when it’s bright.   There are about 126 million sensory cells in the retina, both cone-shaped cells which are color-sensitive and rod-shaped cells which aren’t color-sensitive but can detect low levels of light, useful for night vision.

Most cameras work in the same way as the eye – when the shutter is open, light enters a roughly circular hole called theaperture and is focussed by a lens onto a light sensitive medium at the back of the camera, either film or an electronic sensor.   Some types of camera, like a pinhole camera, don’t have a lens, and some digital cameras don’t have a shutter; nevertheless, understanding how these things work will help make your photographs better. (ref: Flying Kiwi)


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To understand how the eye forms clear images of objects on the retina, we must examine three processes:

  1. The refraction (bending) of light by the lens and cornea
  2. The change in shape of the lens
  3. Narrowing of the pupil

More information about vision – http://www.accessexcellence.org/AE/AEC/CC/vision_background.php

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Brains learns to see

When light rays traveling through a transparent substance pass into a second transparent substance with a different density, they bend at the junction between the two. This bending is called refraction. As light rays enter the eye, they are refracted at the anterior and posterior surface of the cornea. Both surfaces of the lens of the eye further refract the light rays so they come into exact focus on the retina. Images focused on the retina are inverted; they are upside down. The reason the world does not look inverted and reversed is that the brain “learns” early in life to co-ordinate visual images with the orientations of objects. The brain stores the inverted and reversed images we acquired when we first reached for and touched objects and interprets those visual images as being correctly oriented in space.

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Physiology of Vision: Photoreceptors and photopigments

The first step in visual transduction is absorption of light by a photopigment, a colored protein that undergoes structural changes when it absorbs light. The single type of photopigment in rods is rhodopsin. Three different cone photopigments are present in the retina, one in each of three types of cones. Colour vision results from different colors of light selectively activating the different cone photopigments.  All photopigments associated with vision contain two parts: retinal and opsin. Different opsins permit the rods and cones to absorb different colours (wavelength) of incoming light. Rhodopsins absorbe blue to green light(colour) most effectively, where as the three different cone photopigments most effectively absorb blue, green, or yellow-orange light(and colour).


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Sound

Sound is a form of energy. Being able to hear sound is one of our most important senses. Some of the sounds you hear are loud and some are soft. This is the intensity of the sound. Sounds can also be high or low. This is the pitch of the sound.

Sounds are made by something moving backwards and forwards. This is called vibrating. When you speak, vocal cords in your throat vibrate. When you play a guitar the strings vibrate to produce the sound.

Sound waves travel through the air. The air particles squash up and move apart! Sound can even travel through liquids and gases because the particles pass on the vibrations. Sounds travel fastest through solids, and slowest through gases.

  • Sound travels in all directions.
  • Sound travels in waves.

how the amplitude and frequency affects sound waves

  • Sound is made from vibrations.
  • Sound can be reflected, we call this an echo.
  • Sounds get louder as they closer and then fainter as they get further away.
  • Sounds travel to our ears.

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To learn about sounds in underwater visit http://www.divediscover.whoi.edu/expedition12/hottopics/sound.html

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Ionic bonding and Covalent bonding

Ionic bonding

Ionic bonding usually happens from reaction between metal and non-metal elements. You can see ionic bonding from a compound like NaCl (Sodium chloride). The forces of attraction between oppositely charged ions are called ionic bonds. As you can see in the diagram, Na+(Sodium ion) is a positive and Cl-(Chloride ion) is a negative ion. This is because sodium has lost one of its electron on it’s outer shell and chlorine has gained one electron from sodium element.

Sodium is an element but it becomes ion when it loses it’s electron from the outer shell. Chlorine is also an element – so it becomes negative ion as it gains a electron from the sodium.

An ionic bond (or electrovalent bond) is a type of chemical bond based on electrostatic forces between two oppositely-charged ions.

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Covalent bonding

Covalent bonds are forces that hold non-metal atoms together. The forces are formed when the atoms of a molecule share electrons.

As you may know, an atom is made of a tiny core called a nucleus, with tiny particles called electrons traveling about the nucleus. Sometimes when atoms come together, two electrons will start to travel about the nuclei of both atoms. The two atoms then share the pair of electrons.

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What is kinetic energy and potentional energy?

Kinetic energy

Kinetic Energy is energy that is in motion. Moving water and wind are good examples of kinetic energy. Electricity is also kinetic energy because even though you can’t see it happen, electricity involves electrons moving in conductors.

Energy makes change possible. We use it to do things for us. It moves cars along the road and boats over the water. It bakes a cake in the oven and keeps ice frozen in the freezer. It plays our favorite songs on the radio and lights our homes. Energy is needed for our bodies to grow and it allows our minds to think.

Scientists define energy as the ability to do work. Modern civilization is possible because we have learned how to change energy from one form to another and use it to do work for us and to live more comfortably.

Energy is found in different forms including light, heat, chemical, and motion.

Potential Energy

Energy is measured in the amount of “work” it does. Potential Energy is stored energy. Examples of potential energy are oil sitting in a barrel, or water in a lake in the mountains. This energy is referred to as potential energy, because if it were released, it would do a lot of work.

Energy can change from one form to another. A good example is a Roller Coaster. When it is on its way up, it is using kinetic energy since the energy is in motion. When it reaches the top it has potential (or stored) energy. When it goes down the hill it is using kinetic energy again.

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Science fair help: Burning peanut experiment

Measuring Energy

burn a peanut and boil water to meaure its calorie content

This is a particular method that measures energy in a peanut. A peanut burns producing an impressive amount of flame for a long time. The flame is used to boil away water and count the calories contained in the peanut.

Equation for calculating the calories in a peanut: To raise the temperature of 10 grams of water from 20 °C to 100 °C it takes:

Q = mcDT

Or, use the following equation to calculate the calories per gram of the peanut:

calories per gram = (heat gained by water)/(mass lost when peanut burned)

This is another way of doing the experiment.

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To learn more about this experiment visit

http://www.exo.net/~pauld/activities/food/burnapeanut.html

http://www.chymist.com/energy%20of%20a%20peanut.pdf

http://www.cerlabs.com/experiments/10875406238.pdf

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Bacteria

Functions of major parts

  • DNA: Contains genetic information for the bacteria. Controls all the chemical reactions within the cytoplasm.
  • Capsule: Protects bacteria from heat and chemicals
  • Flagellum: For movement.
  • Fimbriae/Pilli: For attachment (eg. on the surface of stomach)
  • Cell wall: Maintains the shape of the bacteria.
  • Ribosomes: For making protein.
  • Cytoplasm: This is where all the chemical reaction happens (including making proteins).
  • Plasma-membrane/ cell membrane: Controls what comes in and goes out.

Uses of Bacteria :

ref http://hubpages.com/hub/Uses-and-Classifications-of-Bacteria

  • A bacterium breaks down the organic fertilizer (decomposed vegetables and animal matter) into material that can be used by plants.
  • Some species of soil bacteria convert nitrogen into nitrites, compounds that are readily absorbed by plants.
  • Different commercial processes also need certain bacteria, like Anaerobic bacteria that ferment certain substances are used in the production of vinegar and some drugs, and in the aging process of cheeses.


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RNA and DNA

Our body is made up of very complex proteins. In fact, it is not just us that is made up of very complex proteins. It is more accurate to say that all the living things are made up of very complex proteins. There are two kinds to proteins – functional protein and structural protein. What is the difference? Well, the functional protein helps with the chemical reactions in our cells – but the structural protein is like what you can see with your eyes and touch. You can touch your skin, finger nail, hair, skin… and organs inside your body!

Why am I talking about these things?

Because I am about to let you know that your cells contain all the information about these proteins. The information is used to make and control every single things which are inside and outside your cell. It is like an encyclopedia, written in the language that our body understands. Where can we find the information then? The famous DNA – inside the nucleus of a cell.

The DNA is a long double helix molecule. Helix is the shape of a twisted ladder.

May be you have seen this picture before. The DNA is made up of thousands and millions of a single unit called NUCLEOTIDE.

Nucleotides have another name – Nucleic acid. This is because we often have to see things from chemistry perspective to understand their property as a molecule.

DNA and RNA is all made up of nucleic acids. But only difference is that DNA is like a ‘REFERENCE COPY’ book in the library. As you know these REFERENCE COPY books cannot be taken out side the library. So, what do you do when you need an information from the book? You would photocopy the pages you need wouldn’t you? The RNA is like the photocopied pages which can take information from DNA in the nucleus to the cytoplasm to make proteins. This is because making protein needs big chemical reaction and this reaction can only take place in the cytoplasm.

This is how RNA and DNA looks like. As you can see RNA is single stranded and DNA is doubles stranded. The part you cannot see is the difference in length. DNA is way way longer than RNA because it contains whole information, unlikely, RNA is way way shorter than DNA because RNA only contains copy of a section in a DNA strand.

You will actually more things about RNAs and DNAs when you take senior Biology subject. Hope this helps for you to kick start! :)