24th Jan 2011

Particulate model of matter

Today, we went through some worksheets on the topic particulate model of matter. I did not type the post for the topic the other time so I will use this post to explain the topic. Since we did some holiday assignment based on this topic, so we had some basic knowledge on this chapter. We also learned some parts of this chapter in Primary School.

Diffusion

The process whereby particles of matter move from one region of higher concentration to a region of lower concentration. e.g. spreading of smells like cooking or perfumes.

The rate if diffusion is based on the temperature. The relative moleculiar mass also affects the diffusion rate.

Kinetic particle theory

Matter is made up of tiny particles that are always in constant motion. The kinetic energy of a particle changes with temperature.

particulate model of matter

Solids:

-Have fixed shapes

-Have fixed volumes

-Cannot be compressed

Liquids:
-Have no fixed shape

-Take the shape of containers

-Have fixed volumes

-Cannot be compressed

Gases:

-Have no fixed shape

-Take the shape of containers

-Have no fixed volume

-Fill up the space of containers

-Can be compressed
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.

Particulate model of solids

The particles in a solid:

-are strongly attracted to one another

-are packed closely together
-are arranged in a fixed, regular pattern

-can only vibrate about their fixed positions

Particulate model of liquids

The particles in a liquid:

-are attracted to one another
-are packed closely together

-not arranged in a fixed, regular pattern

-can move over short distances

Particulate model of gases

The particles in a gas:
-are weakly attracted to one another

-are far apart from one another

-can move freely in any direction

Changes in state of matter

Melting:

When a solid is strongly heated, the particles gain energy and vibrate more vigorously in their fixed positions.When the particles gain enough energy, they break free from each other and move about randomly. Although the particles are no longer held in their fixed positions, they are still close together.

Freezing:

When a liquid is cooled, the particles lose energy and move about more slowly. As the temperature falls, the particles move more slowly until the force of attraction allow them to return to their fixed positions. The substance has changed from a liquid to solid.

Boiling:

When a liquid is heated, the particles gain more energy and move about more vigorously. When the particles have enough energy,they break free from one another. The particles become randomly arranged, spaced far apart and moving at high speeds.

Condensation:

When a gas is cooled, the particles lose energy and they move about less vigorously and at lower speeds. As the temperature falls,the particles lose more energy until they are close enough to be attracted to one another. The substance has changed from a gas to a liquid.

Heating curves(solid-liquid)

-Ice starts to melt at its melting point.

-Temperature remains constant over a period of time.*

-A mixture of solid and liquid exist during the process.

-Temperature will continue to rise once all the ice has changed to water.

Heating curves(liquid-gas)

-Water starts to boil at 100 degrees.

-temperature remains constant.*

-A mixture of liquid and gas exist during the process.

-Temperature will continue to rise as the heating continues.

Cooling curves(liquid-solid)

-The liquid is cooled.

-Temperature drops until the substance reaches its freezing point.

-The liquid freezes into solid state.

-Temperature remains constant**

-A mixture of liquid and solid exist in the process.

*Heat is used to overcome the forces of attraction holding the particles together.

**Heat energy is released as strong attractions are formed between particles to hold them together in a crystal lattice

30th September 2010

Making our own DNA

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.

29th September 2010

Viewing DNA of a fruit

The lesson before this one, Mdm Riza told each of us to bring a either a banana or a strawberry as we needed to conduct a practical which was extracting DNA. On that day itself, although Mdm Riza emphasized to only bring bananas or strawberries, Alot of us bought different variety of fruits. These included apples, guavas, watermelons and others. Before conducting the practical, we were introduced to the topic DNA. We also got to listen to the DNA song.

Here are some things we went through:

- What does DNA stand for?

DNA stands for Deoxyribonucleic acid

-What is the function of DNA?

It contains genetic materials that are used to make protein

Where is DNA found?

Inside the nucleus of every cell.

- What are proteins for?

To make different organs and tissues.

Here are the steps for viewing the DNA of the fruit:

1) Use about 1/4 of the fruit.

2) Place the fruit inside a ziplock bag.

3) Mash it up until there are no big pieces left. (to break down the cell membrane)

4) Add in 1/2 a teaspoon of salt and 2 teaspoon of detergent. (to break down the nucleus wall)

5) Continue mashing it.

6) Let it settle for a while.

7) Pour a bit of it into a cylinder. Make sure no big pieces flow out.

8) Tilt the cylinder to 45 degrees and slowly pour in 10ml of alcohol.

This is how my DNA looks like:

27th September 2010

Viewing our cheek cells under the microscope!
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.

Here are the steps:

1) Using a toothpick, gently scrape the inside of your cheek
2) Spread the specimen on the glass slide.
3) Let it dry for about a minute.

4) Put a drop of iodine over the specimen.

5) Carefully place a piece of cover slip over the specimen.

6) Place the slide on the stage of the microscope

7) Adjust the coarse focus knob and objective lens to make the specimen clear for viewing.

1) Scrape cheek gently

2) Spread over slide

3) add a drop of iodine

4) cover specimen with cover slip

5) Place specimen under microscope

6)What you will expect to see:

21st September 2010

Making a cell using inedible materials



Today, we conducted a practical experiment on creating a cell using inedible materials we we were told to bring the lesson before by Mdm Riza. My groupmates were Ming Ze, Alec, Yi Heng and myself. I brought some strings to represent the ribosome and Golgi apparatus . Ming Ze brought a piece of brown paper that was crumpled into a ball and taped to represent the nucleus. Alec brought an eraser that was coloured green to represent the mitochondrion. And Yi Heng brought a piece of plastic to represent the endoplasmic reticulum. We took some beads and beans to represent the vacuole and other unidentified parts. We took a photo after placing each material into the agar which is the cytoplasm.

19th August 2010

3) (i) Today I learnt that factories make use of the fractionating column to separate crude oil into its simpler hydrocarbons. In order for separation to occur, the substances must have different boiling points.

Process:

- The crude oil is first burned in the furnace.

- The substances that have the lowest melting point and is the lightest will travel to the top of the column.

- The substances with the highest melting point pand is the heaviest will travel to the bottom of the column.

- The substances at the top are in gaseous state while the ones in the centre are in liquid state and the ones in the bottom are in solid-liquid state.

- more complex substances are found at the bottom while

less complex substances are found at the top.

(ii) Today we also went through of how the distillation set-up works.

process:

- The mixture is first heated in a beaker.

- The water evaporates into vapour.

- The vapour condenses in the condenser

- The water droplets flows down the condenser and into the conical flask

-If the temperature on the thermometer increases, it means that you are no longer collecting water.

(iii) Today we also compared some of the differences between fractional distillation and distillation

Some of the points are:

- Fractional distillation separates more than one substances while distillation separates two substances.

- Fractional distillation makes use of a fractionating column while distillation makes use of a Liebig condenser.

- Fractional distillation is used in factories while distillation is used in labs

2) (i) What other substances besides crude oil can be separated using fractional distillation?

(ii) How does the substances in the fractionating column stay in their corresponding segments?

1) I can apply what I learnt today when I need to separate a mixture of two iquids using distillation.

16th August 2010

3) (i) After todays practical experiment, I know how to separate solutions using the method distillation. Mdm Riza showed us experiment on distillation.
The apparatus needed were:
-bunsen burner
-tripod stand
-beaker
-solution of syrup amd water
-conical flask
-condenser
-thermometer
steps:
- The water first boils from the mixture in the beaker and then then turns into a gaseous state after being heated.
- The water vapour then condenses in the condenser.
- It flows down the condenser and then into the conical flask.
(ii) Chromatography is used to separate coloured substances like ink or dye. We conducted an experiment on chromatography by ourselves today.
The apparatus needed were:
- chromatography paper
- test tube holder
- test tube
- solvent
- ink
- cork
-pencil
steps:
- Draw a horizontal line across the breadth of the chromatography paper about 3 cm from the bottom.
- Fill the test tube with a height of 2 cm of solvent
- Place the chromatography paper into the tast tube
- Cover the test tube with the cork
- Place the test tube on the test tube holder and wait for the colour of the ink to change.
(iii) During todays experiment, we used the learning method of predicting, observing and explaining. I think this is a good learning technique as it can let us think of what the topic is before going deeper in depth.
2) (i) Is the syrup left in the beaker after it boils?
(ii) Can we use other types of paper besides chromatography paper to carry out the experiment?
1) Distillation can be used when we don,t have water with us besides sea water to obtain pure water.