Chemistry Journal Entry 7

This week, we saw diffusion happening in front of our own eyes!

Basically what is diffusion?

Diffusion is the movement of substances from a region of higher concentration to a region of lower concentration 

The higher the temperature, the faster the rate of diffusion.

In the experiment, Mr Foo demonstrated diffusion by showing the spread of iodine vapor throughout the gas jar.

At the start of the experiment, the iodine vapor was at the bottom of the gas jar. There was a violet colouration at the bottom of the jar and over time, it faded. The purple colored vapor rose and spread throughout the jar.

We could then conclude that gaseous particles are in constant and random motion.

Relating it to matter...

Matter is made up of small particles which are in constant motion and random direction.

WHY DOES DIFFUSION ONLY HAPPEN IN LIQUIDS AND GASES?

The water and gas molecules are able to move freely and hence, diffusion is able to take place. In solids however, molecules are packed so tightly that a negligible amount of movement occurs and inhibits diffusion.


KINETIC PARTICLE THEORY

A solid

• cannot be compressed 
• fixed volume
• fixed shape 
• high density 

A liquid is

• cannot be easily compressed 
• no fixed shape 
• fixed volume 
• high density, but usually lower than solids

A gas 

•  can be easily compressed 
• no fixed volume
• no fixed shape - take the shape of the whole container
• low density

Solid particles vibrate about fixed positions, held together by strong intermolecular bonds between them -> fixed shape and volume 

Liquid particles are free to move about between clusters but confines within vessel containing it due to strong  attractive forces between them -> fixed volume but take the shape of container holding it 

Gas particles are always in high speed, independent motion in random manner with negligible attractive forces between them -> no fixed volume and shape, but highly compressible

BROWNIAN MOTION

We actually learnt this in physics. Pollen grains were ovine because the smaller and faster moving water particles were constantly colliding with them. 

- Random motion of visible particles (pollen grains) caused by small, invisible ones 

- Random motion of the smoke particles is caused by the bombardment of air molecules 

- When temperature increases, smoke particles gets more agitated and change direction more often. 

Boiling 

- Liquid to gas

- Gain energy

- Move faster 

- Further apart

- Completely overcome hydrogen bonding

- Far apart and away from each other

At boiling point, water molecules lose heat energy so as to bond with the molecules. 

Thank you!

 

Chemistry Blog Entry 6

SEPARATION TECHNIQUES


There were mainly 3 techniques we actually learnt about.

1. Crystallization ( most interesting!!!)
2. Simple Distillation
3. Chromatography ( 2nd interesting) 

There are actually many separation methods but those above were mainly the ones that were highly emphasized on.

CRYSTALLIZATION

To separate a dissolved solute from a solution 

Commonly used to separate the heat labile solutes from their solutions

Keywords: ** Heat-labile : substances which are easily decomposed

Experiment : Forming crystals 

We used copper sulfate which is actually a blue powdery substance to create crystals. 

My partner and I did the experiment that did not involve rapid cooling. Thus, we did not really put it into the beaker filled with ice. 

The scariest part of the experiment was the part which you had to check for the formation of crystals using the glass tube. I was really afraid to mix the bottom part ( in case somehow we actually get burnt) so we ended up saturating the mixture a LITTLE bit. Hence we had to add more water , boil it again and get the crystals. 

Before all of this, we had to use a method called FILTRATION. Basically, we had to filter all the copper sulfate chunks so that there will be no impurities. 

Filtration -> Separation of insoluble substances from liquid 

Insoluble substance- Residue

Usage of filter paper

Keywords:** Saturated solution: A solution that contains the maximum amount of solute dissolved in a given volume of a solvent at a particular temperature

DIFFERENCES BETWEEN RAPID COOLING AND SLOW EVAPORATION 

Rapid cooling of saturated solution - small and ill-shaped crystals

Slow evaporation of a cold saturated solution - Large and well defined crystals obtained

SIMPLE DISTILLATION 

Purpose: To separate the solvent from a solution of solute

Purifies liquid 

- Always use a round bottom flask 

Purpose of boiling stones: To allow the surface of the liquid to be in equilibrium with a gas 

It prevents water from being heated beyond its boiling point.

Purpose of Condenser: To cool the water vapor and condense it to form water droplets

FINAL PRODUCT: DISTILLATE

( Shown to use with the coke) 

Leftover product: Water and sugar in separate apparatus

CHROMATOGRAPHY 

To separate a mixture of solutes with different solubility and degree of absorption 

Chromatography paper 

RETENTION FACTOR: 

Rf value = Distance moved by substance 

              Distance moved by solvent 

Uses: 

Separate and identify compounds 

** A compound is a two or more elements chemically combined. 

** Locating agent: Chemical substance that will produce colored products on reaction with the colorless compounds 

**** Solvent front 

DECANTING 

Separating insoluble solids from liquids 

That's all!

Thank you!

                                     

Chemistry Journal Entry 5

Atomic Structure

Guess what? There are even smaller things in atoms. Mainly there are three different parts in an atom. 

1. PROTONS

2. NEUTRONS 

3.ELECTRONS 

Protons carries one positive electric charge, a relative mass of 1, and with a  symbol P. Neutrons carries no electric charge, has a relative mass of 1 and symbol is N. Electrons carries one negative electric charge, has a relative mass of 1/1840 which is negligible but important. ( Symbol : e)

Masses of particles are determined by Atomic Mass Unit. ( amu) 

1 amu is 1.67 x 10 to the power of 27 kg 

WHICH IS REALLY REALLY SMALL. 

A cell is already so small, an atom is even smaller, it is really astounding.

Then we have the PROTON NUMBER and the NUCLEON NUMBER. 

Proton Number is basically the atomic number. It is usually found on the left below corner of a chemical symbol. 

The nucleon number is the total number of neutrons and protons in an atom. It is usually found on the left top corner of the chemical symbol. 

That's all! ;)

Chemistry Journal Entry 4

We actually started on a new topic, " Elements, Compounds, and Mixtures ". We learnt the differences between a metal and a non-metal and a metalloid.  

Differences between metal and nonmetal

1. A metal is shiny and lustrous while a non-metal is dull. 
2. A metal is a solid while a non-metal is usually a gas or a liquid. 
3. A metal is malleable, sonorous and ductile while non-metals are brittle( if it is a solid). 
4. Metals usually have a high melting and boiling points while non-metals usually have low melting and boiling points.
5. Metals are good conductors of heat and electricity while non-metals are the opposite. 

Metalloids usually exhibit both properties of a metal and a non-metal and therefore,they are called METALLOIDS. 

What you see here is a a Periodic Table of Elements. Guess what? There's one element named einsteinium which is named after Albert Einstein. So interesting! The Periodic Table is arranged according to increasing proton numbers from left to right. 

Chemistry Journal Entry 3

Today was a 2hr chemistry lab lesson. Hehe, I remembered to wear my safety goggles!!!! Basically, we played around with the bunsen burner. We had to close the air hole , attached the gas tube to the gas tap, and then used the lighter and light it. When you light it, it will be yellowish flame. Then, if you open the air hole, it will become a blue flame. My lab partner and I used the copper wires and tried to "barbecue" it and it turned like reddish-yellowish. The tip of the inner blue flame was the HOTTEST. I can't help, but be curious at how high the temperature is in that teeny weeny flame from a bunsen burner. Will you be able to supposedly cook things with it? I am not exactly sure, but its just a question that came out of nowhere. Is a bunsen burner's heat equivalent to a stove's ? Maybe, I guess. ;)

I adopted an element: Cadmium. My reason: It sounded very very cadbury-like, unfortunately, its cancer causing. 

Chemistry Journal Entry 2

So today, we actually got this worksheet where we had to classify different types of circles. We had dotted black and white circles. I think we were basically trying to mirror how the periodic table is constructed right? Instead of the colors, sizes, the periodic table shows from left to right the increasing number of protons, correct me if I am wrong;)

Then THE INTERESTING PART! We were supposed to guess other people's classification. It was relatively easy,  but some groups' classification was confusing. We weren't able to get what they were really trying to say. 

Chemistry Journal Entry 1

Laboratory Safety 

I personally think while we are in the chemistry labs, we really have to be careful on what we are handling. Every thing in the world actually poses a certain form of danger, especially in science labs when we could actually do experiments that sometimes , could even change history. Some rules are especially important. As seen in the video ( the funny one;D ), if you don't tie your hair up properly , you might actually burn your hair. If that happens, then we need run to get the fire blanket and wrap it around the person's head. Then , we have another important rule: to wear the safety goggles at  ALL TIMES. I am a real scaredy-cat when it comes to handling things like chemicals, and fire. You don't really worry about me, I will dutifully wear my safety goggles at all times. ;D