Elements, Mixtures and Compounds

This topic covers elements, mixtures and compounds.

Reflections: This topic was rather much a HUGE headache for me. First of all, as I had previously said, I am a TERRIBLE memorizer ( pardon the English). There were 20 elements to memorize and i also had to remember the groups and periods. Well, I did it eventually but that was not even close to the hard part. The hard part was the mixtures and compounds. I had to differentiate between a compound and a mixture, and also to remember which mixtures were mixed from what and which compounds were formed from which elements. This is kind of hard, considering the fact that there are 16 million organic (carbon-containing) compounds in the world. And those are only the carbon containing ones. Also, as I did research on this topic, unexpectedly I learnt something very interesting. Somehow, I saw the wiki page on elements had the link 'Matter', so I clicked on the link and read the page. I learnt that not everything in the world is made up of matter. In fact, less than only 17%of matter in the universe is made up of ordinary matter. The rest are a mysterious kind of matter called dark matter which naturally accounts for 83%.

Acknowledgements

Information used in this blog are from various websites. The credits go to Wikipedia, Google Images, YouTube and the powerpoint slides in the Secondary 1 science wiki.

Personal Work Samples

Although I did not participate in any science sabbaticals, but I read magazines like National Geographic and also I have many encyclopedias to read. The National Geographic is for updating me on current science issues and new discoveries, and the encyclopedias are for increasing my knowledge. Here are some photos! Enjoy!

Growth in Science

In my primary school, I was taught a lot on theory but never actually had the opportunity to try out all those experiments. Now, I am taught a lot more and i can also do practical instead of just learning about the experiment in theory. I feel that I learn things better when I actually work on them, as I can remember things more when I experience them instead of memorizing theories. This helps a lot when it comes to memorizing things for me. Also, secondary school science has shown me science in a new light. I used to think science was boring, but, after doing practical, they became a lot more interesting to me.

Termly Performance

For my Term 1 test, I scored 68 marks.
For my Term 2 test, I scored 60 marks.
For my Term 3 test, I scored 65 marks.

I will aim for an A in the EOY exams.

Cells, Tissues, Organs and Systems

Cells are the basic unit of our body. Cells group together to form tissues. Many tissues in turn form organs. Each system consists of organs. So, our body is built on this basis. Cells > Tissues > Organs > Systems.

In this chapter we learnt about the different type of cells, tissues and organs.


The cell is the functional basic unit of life. It was discovered by Robert Hooke and is the functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. Some organisms, such as most bacteria, are unicellular (consist of a single cell). Other organisms, such as humans, are multicellular. Humans have about 100 trillion or 10¹⁴ cells; a typical cell size is 10 µm and a typical cell mass is 1 nanogram. The longest human cells are about 135 µm in the anterior horn in the spinal cord while granule cells in the cerebellum, the smallest, can be some 4 µm and the longest cell can reach from the toe to the lower brain stem . The largest known cells are unfertilised ostrich egg cells, which weigh 3.3 pounds.

In 1835, before the final cell theory was developed, Jan Evangelista Purkyně observed small "granules" while looking at the plant tissue through a microscope. The cell theory, first developed in 1839 by Matthias Jakob Schleiden and Theodor Schwann, states that all organisms are composed of one or more cells, that all cells come from preexisting cells, that vital functions of an organism occur within cells, and that all cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells.

The word cell comes from the Latin cellula, meaning "a small room". The descriptive term for the smallest living biological structure was coined by Robert Hooke in a book he published in 1665 when he compared the cork cells he saw through his microscope to the small rooms monks lived in.

There are different cell parts with different functions. The cell parts below are those found in 

animal cells.

Nucleus: Contains genetic material. Directs activities of the cell. Controls cell division and 
growth.

Cytoplasm: Fills the cell and contains substances needed for reactions in the cell.

Mitochondrion: Cellular respiration.

Cell membrane: It is selectively pemeable to control movement of substances into and out of the 


cell.

Vacuole: Storage compartment for water, sugars and pigments.
Ribosome: Produces protein from a set of genetic instructions.
Cell wall: Provides support for plant cell.
However, animal cells do not have chloroplasts nor do they have cell walls.

The two types of cells are animal cells and plant cells. Animal cells are different from plant cells in their 


structure. 

The picture above is what an animal cell looks like.

This is what a plant cell looks like. 

See the difference? 

Yes, a plant cell has cell wall and chloroplasts while the animal cell doesn't. Also, the plant cell's vacuole is 

much larger than an animal cell's and there is only one vacuole in a plant cell.

Now, tissues.

Tissues are really cells grouped together. There are a few kinds of tissues which perform different functions.


Plants and animals' tissues are different too. Plants have Epidermal, Xylem, Phloem, Photosynthetic and palisade tissues.


Animal tissues include epithelial, muscle, connective, nerve and glandular tissues.
All these tissues form organs.
Examples of plant organs are roots, stems, leaves. While examples of animal organs are the stomach, liver and   
small intestines.


These form systems such as respiratory system & digestive system.

Elements, Mixtures and Compounds

This topic covers elements, mixtures and compounds.

Elements: Elements are substances which cannot be split into simpler substances by any known chemical methods. They are all given a name and a chemical symbol. Altogether there are 109 known elements, and are all listed in the periodic table with their atomic mass, chemical symbol and atomic number.

The table below is the periodic table.

Mixtures: Mixtures are elements mixed together and they can be separated by physical methods such as distillation, filtration, using a magnet and evaporation. Mixtures also have properties similar to its constituent elements. Mixtures such as air are combinations of nitrogen, carbon dioxide, oxygen, etc.etc.

Compounds: Compounds are elements( 2 or more) chemically combined. They can only be separated by chemical methods such as burning, electrolysis etc.etc. Compounds have properties different from its constituent elements. Examples of such compounds are water, magnesium oxide and sodium chloride. However, compounds can only form if the elements are joined in the correct proportion. Eg. Water only forms when 1 part hydrogen mixes with 1 part oxygen.