Science Eportfoilo term 2-3

Brownian Motion

As you can see in this picture, brownian motion is the constant and random motion of small solid particles.


According to the Kinetic Particle theroy, all matter is made up of discrete particles which are in constant random motion.

This can be shown by observing smoke particles under a microscope. When heat is supplied the smoke particles start to move more vigorously constantly and randomly.

Einstein said that the random motion of the smoke particles was the result of being hit by unseen fast air molecules.

 

Diffusion

Diffusion is the random motion of particles from a region of high concentration to lower concentration.

For example, if a building caught fire, you are able to smell smoke from a distance away. This is because the smoke particles travelled from the building to your nose. The spreading of molecules on their own accord without external aid is called diffusion.

Here is a periodic table of elements.

 

 

What is an element?

And element is a basic building block of matter that cannot be broken down into simpler substances by any known chemical methods. The elements in the periodic table are classified according to their properties. As you look at the periodic table from left to right, you can see a gradual change from metallic elements to non metallic ones.

 

Compounds

Compounds are substances that contain 2 or more elements joined together by a chemical reaction. A compound has different properties from its elements.

<--- These are examples of compounds.
The main component of wood is cellulose, which has the formula (C6H10O5)n The "n" is a variable. As cellulose is chemically joined by more than 2 elements, its a compound.

Process of making magnesium oxide. (oxygen + magnesium)

                                                                         Mixture

In a misture of elements, the atoms of the elements are not chemically combined. The above picture shows a mixtureof table salt and sand. A mixture does not have a fiexed composition. The percentage of each substance in a mixture is not always the same.

 

 

 

Solutions

 

All solutions are mixtures consisting of a solvent (a substance that the soltute dissolves in) and a solute (the substance that dissolves). A solution is homogenous when the colour, density, appearance,

other physical and chemical properties are the same in every part of the solution and light is able to pass though the solution.

 

 

 

A solution is hetrogenous when the insouluble particles are big enough to prevent light from passing through. This is called a suspension.

 

 

 

 

Seperation techniques

 

Different types of methods to separate constituents of a mixutre based on its properties:

 

• Filtration
• Evaporation to dryness
• Cystallizaton
• Seperating funnel
• Distillation and Fractional distillation
• Chromatography
• Magnetic attraction

Filtration

 Filtration is a simple method to separate a solid from a liquid.

 

 

 

 

 

Evaporation to dryness

 

Evaporation to dryness is the evaporation of the solvent to obtain the solute. In evaporation to dryness, any soluble impirities will be deposited along with the required solid so it is unable to separate a pure substance from its impure form.

 

 

 

Crystallisation

 

Crytallisation is the process of heating the solvent until most of the solvent evaporated, then letting the solvent cool. After a while, the cooled solution is poured off to obtain the solid crystals.

 

Magnetic Attraction

By using magnetic attraction, you can seperate magnetic objects from non-magnetic objects.

Distillation

Distillation is used to purify liquids. It is used to obtain a pure solvent from a solution of a solute.

 

 

Fractional Distillation

 

Fractional distillation is used to separate a mixture of miscible liquids using a fractional column.

 

 

Fractional distillation can also be used to obtaing pure oxygen and nitrogen from the air.

 

Separating Funnel

 

A separating funnel is used to separate mixtures that contain liquids which are not miscible. The tap is opened so that the lower layer of liquid runs out first into a beaker. The tap is closed when the last drop of the liquid leaves the funnel. The tap is opened again to run the upper layer of liquid into another beaker.



 

 



Chromatography

Chromatography is the method of separating and identifying mixtures. There are many types of chromatography such as paper chromataography. The most commonly used solvent for paper chromatography is ethanol.

Chromatography can also be used to separate and indentify colourlesss substances using a locating agent. A locating agent reacts with substances to produce a coloured product.

Reverse Osmosis
In this process, a semi-permeable membrane is used. Unlike normal osomosis, in reverse osmosis
pressure is applied on one side of the membrane , forcing water molecules to passs throught the membrane, leaving behind the undesirable substances like virus. Clean water is obtained on the other side of the membrane.

Diffusion and Osmosis

Lets recap on diffusion: Diffusion is the net movement of atoms or molecules from a region where they are at a higher concentraion to a region where they are at a lower concentration.

Diffusion continues until the particles are uniformly distributed throughout the system.

 

Osmosis

 

Osmosis is the net movement of water molecules throught a partially permeable membrane, from a rgion of higher concentration of water molecules to a region of lower concentration of water molecules. Similar to diffusion, osmosis continues until the water concentraion is uniformly distributed between 2 solutions.

 

 



There are 3 types of solutions:

• Isotonic solution (equal water concentration)
• Hypotonic solution ( higher concentration of water; lower concentration of solute)
• Hypertonic solution (lower concentration of water; hight concentration of solute)

Osmosis is very important for all living things as its is used in transporting food waste and other substances in and out of the cells through a partially permeable membrane.

CELLS (here comes my fav topic!!!)

Cells are the basic unit of life. All living things are made up of one or more cells. A human being like us is made up of millions of cells whereas living things like amoeba only have one cell. Thus amoeba is a unicellular organsim and a human is a multi-cellular organism.

An Euglena is a unicellular organism.

Whereas a human being, is a multicellular organism.

 

 

 

 

 

 Animal cell

 

Plant cell

 

 

The main difference between a typical plant cell and a typical animal cell is that a plant cell has chloroplasts and a cell wall but an animal cell does not.

 

 

Different cells of the same type work together to form tissues. Different tissues that carry out different functions work together to from an organ. Different organs that carries out different functions work together to from a system. An differnt systems that carry out different functions work together to from an organism! That is LIFE :D

 

EVEN PLANTS HAVE ORGANS!!!!

 

 

Examples of plant organs are:

 

Flowers, roots, leaves, stems.

 



 

Microscopes

 

Just because u can see something, doesnt mean its not there!!! A microscope allows us to see things that cannot be seen with the naked eye, such as cells and bacteria.

This is a basic stero light microscope.

This is a electron microscope, capable of magnifying 1000,000x!



This concludes what i have learnt so far for term 2-3!!!

 







 

 

 

 



Science eportfolio

In the learning of science in hci, I faced problems such as how to read and measure the scales of the micro screw gauge. I overcame this problem by asking the teacher for help. I also learnt some scientific concepts such observation, prediction, recording and organising, measurement, hypothesising, inference, estimation, classification, analysing. These concepts would help me do experiments, make things in order, etc. I learnt observations skills during the candle video, the reaction of chemical such as sodium chloride, and reaction of other chemicals such as limewater, etc.

My target for the next science test is A1

I plan to read my science notes regularly 2 weeks before the test.

I need to improve my critical thinking skills, and not be so careless. I shall read and write the questions and answers slowly and not hastily do everything at once.

There is some part of the lesson which I don't really understand such as the reason for strike back. I would check the internet to help me answer my questions. I have different ways to solve the problems such as asking my parents/teachers/elder brother, or checking reference books and checking the internet.

From the activities (science experiences, laboratory sessions, fieldwork and excursion) , I learnt the safety precautions of doing experiments such has during heating of chemicals, u must wear safety goggles. I like doing the experiments the most and seeing the reaction of chemicals the best. There is nothing i least like about the activity. i learn that my partner is careful and i should learn from him.

Obesity:

Who is responsible? Why?

Reviewed at 13 March 2012 11:17pm:

Obesity is caused by oneself. Obesity means having too much body fat. It is not the same as being overweight, which means weighing too much. A person may be overweight from extra muscle or water, as well as from having too much fat.

Taking in more calories than you burn can lead to obesity because the body stores unused calories as fat. Obesity can be caused by, eating more food than your body can use, drinking too much alcohol, no regular exercise, eating food on a daily basis that are unhealthy or contain too much calories. (Such as McDonalds, Coke, Pepsi, Beef Steak, etc)

There are some factors that affect our weight: Our habit of eating when we are young; (The way we eat as children may affect the way we eat as adults. It affects the amount of food we eat, the type of food we eat and the time of the day we eat) the fact that most people nowadays have no time to plan a healthy and balanced meal; most people do desk jobs not outdoor/active jobs; people have less free time to exercise due to heavy work.

Excessive smoking can also cause an increase in weight. Stress, distress, anxiety can also cause an increase in weight.

The main reason why some people become fat is due to excessive eating of unhealthy and high calories foods. A frequent trip to a fast food restaurant will most likely make you grow fat.

Tips to avoid obesity:

Avoid eating unhealthy food often. Exercise often on a regular basis. You can ask your family member to get you to exercise with them; this will also strengthen the family bonds. Ask your family members to help you plan a healthy and balanced diet.