science blog 2r7
Sunday, May 15, 2011
Sunday, May 8, 2011
1st March 2011
- permanent
- new substances formed
- heat/light energy may be taken in or given out
- for example, cooking, burning of charcoal and steel rusting
Physical change:
- no new substances formed
- reversable
- for example, changes in state and dissolving salt
Chemical reactions:
- changing reactants into products
- provides identies of reactants and products
- provides possible reaction possibilities
- represented using chemical equations
N2+3H2=2NH3
- products are heat and light
- two or more reactants combine chemically to form a new product
- a substance breaks down by the effect of heat(thermal decomposition
Electrolysis;
- digestion
- rusting
- iron comes in contact with oxygen in the air and water
Wednesday, May 4, 2011
1st February 2011
Atom:
protons:
- positively charged(+1)
- electrically neutral
- negatively charged(-1)
- has the mass of 1/2000 unit
- it orbits around the nucleus in electron shells.
The proton/atomic number can be found on the bottom of a chemical symbol in a periodic table while the mass number is the one at the top of the symbol. The chemical symbol is represented by the letters.
The electrons in an atom orbit around the nucleus in regions known as the electron shell. The first electron shell can only hold 2 electrons while the subsequent shells can hold eight electrons each. Arrangement of the electrons is called an atoms electronic configuration or electronic structure. The arrangement of electrons determine the chemical properties of the atom.
- An ion is a changed particle formed from an atom or a group of atoms by the loss or gain of electrons.
- Ions can only be formed through chemical reactions.
- Example 1: a megnesium atom has 12 protons and 12 electrons and its electronic configuration is 2.8.2, so it will lose 2 electrons to become a positively-charged ion. So a magnesium ion has 12 protons and 10 electrons.
- Noble gases are elements like helium, neon, argon, krypton, xenon and radon.
- These atoms often exist as a molecule rather than a single atom.
- For example, hydrogen is held by single bond, oxygen is held by double bond and nitrogen is held by triple bond.
- Hydrogen, oxygen and nitrogen have 2 atoms of the same type, this is known as a diatomic molecules as it contains 2 atoms.
- The number of atoms in each type of molecule does not change.
- A compound can be represented by a compound formula.
Monday, January 24, 2011
24th Jan 2011
-Have no fixed shape
Particulate model of matter is used to explain the differences of three states by their difference in their movement and the arrangement of the particles.
-are arranged in a fixed, regular pattern
-are packed closely together
-are weakly attracted to one another
Monday, October 4, 2010
30th September 2010
Today, we went in depth into DNA. We went through that DNA uses a code to form different types of proteins to make different tissues or organs. The DNA code is the same as words as both make use of letters and when one letter is changed, the whole meaning is different. But this DNA code has a special name called condons. Codons are instructions to make different types of proteins. Alot of codons add up to form DNA. Codons makes use of 4 different letters(A, T, C, G)and only has a combination of 3 letters. The letters A, T, C and G have a special name known as Nitrogenou Bases. A stands for adenine, T stands for thymine, C stands for cytosine and G stands for guanine. For example, a single strand DNA may be like:
TAG CCG CGT TAG ACG TGA
DNA comes in a pair but the other half is complimentary of the original one. So A will always go with T and G will always go with C. So the complimentary strand of the single strand DNA above is like that:
ATC GGC GCA ATC TGC ACT
The double stranded DNA will twist into something like a spiral staircase withn a hollow interior. This is called DNA double helix.
After going through the topic, we were tasked to make a DNA model using stickers and 2 wires. We were given a total of 20 stickers. And on 5 stickers per letter(A, T, C, G), we were required to write a letter on both ends of the sticker. Then we pasted the stickers on the wires following the rule: A goes with T and G goes with C. And this is how my DNA looks like.
Sunday, October 3, 2010
29th September 2010
This is how my DNA looks like:
Monday, September 27, 2010
27th September 2010
Today, we started off the lesson by going through the notes about cells. We went through some examples of different tissues and organs. Afterwards, we went on to do a practical experiment. The experiment was about viewing our cheek cells under the microscope.
2) Spread the specimen on the glass slide.
3) Let it dry for about a minute.