Dear readers

Dear readers,

It's the end of the year already!! (almost) One school year has passed already, which means... no lessons!! yay! :D
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Though I'll miss having lab lessons.. :|

Anyways. Stay tuned, for I'll most probably be setting up another science blog for next year's science module....... CHEMISTRY!!!!... (I think. Cause I've already had bio and Physics.)
I'll post the link up when the next school year starts.

A BIG THANK YOU to all you readers out there!!!! :D

Entry #11

Thermal transfer

There are three types of thermal heat transfer:

-Conduction

-Convection

-Radiation

All these take place in different substances. 

Conduction

Conduction is the process of thermal energy transfer without any flow of the material medium. 

Conductors and Insulators: Conductors and insulators have different mechanisms to transfer of thermal energy. All solids, gases, and liquids are made up of atoms and molecules. Metals contain free electrons  which move randomly between the atoms and molecules, while non-metals don't. Hence, this proves why metals are better conductors of heat. 

From: http://ed.edim.co/6084142/l1_transfer_of_thermal_energy2.pdf?Expires=1348621281&Signature=KYnjENJ2wCnTrHU~8uwJ9whjkpsroWBwXPYKvDobx-YQ0uqNyQlBaNJFXf9dXEnu7pToK0OcRI5fsmjvfsS6evoLVNbUMR6lu0oZdxILHtj4ESY7z9W65af3Y7rGTjw-BZbGUWAEawx6aWn1LfXaFICMQQuCM7YvCE~Ygs5NpCA_&Key-Pair-Id=APKAI3N2VAFIZ34RBHFA

How it works

When thermal energy is supplied to a substance/object, the molecules of the substance/object that is being heated vibrate vigorously. These particles collide with neighboring particles, making them vibrate as well. Kinetic energy of vibrating particles that are being heated is transferred to neighboring particles (can be linked to the Brownian motion of particles bombarding other particles).

When kinetic energy increases, the temperature increases as well. Hence, conducting thermal energy throughout the substance/object. 

Unique to metals

A faster mechanism of thermal energy transfer takes place at the same time by free electron diffusion. The free electrons gain kinetic energy and move faster. The fast-moving electrons then diffuse into cooler pars of the metal. 

in liquids and gases...

The process of conduction is inefficient. Liquid particles are further apart and collisions of particles are less frequent, even lesser in gas. 

Convection

Convection is the process of thermal energy transfer with the flow of the material medium, specifically by means of currents in a fluid (liquids or gases).  

In liquids, convection is the main process of conduction. 

How it works

When fluids are heated, they expand and become less dense, hence, the less dense fluid will rise (from the heating source, obviously). Cooler fluids being more dense will sink to replace the less dense fluids. This movement in fluid due to a difference in its density sets up a convection current. 

Example: Air-conditioners use this property. They are placed near the ceiling, as warmer air rises towards the ceiling, and hence, the air conditioners can cool this air, making the room cooler as the cooler air is less dense and sinks to our level. Same with the heaters you use in winter/cold country (although it is never cold here.. sigh...) 

Convection currents only occur in fluids (duh). Convection involves the bulk movement of fluids which carry the thermal energy around...? 

You can try the ballon and fire experiment... though, it could get messy! :D

Radiation

Radiation is the continual emission of infrared waves from the surface of all bodies, transmitted without the aid of a medium. This is how the heat of the sun gets to Earth. Space is a vacuum, hence, neither convection nor conduction can take place. (Now you get an idea of how hot the sun is!!)

The sun emits electromagnetic waves. A particular type of wave called infrared waves, makes us feel warm. All objects emit this (including YOU). The hotter the object, the greater the radiation.

In general, a good emitter is also a good absorber. Conversely, poor emitters are also poor absorbers. 

Emission occurs when the surrounding of the emitter is cooler than its surroundings, vice versa. Hence, emission and absorption of thermal energy by radiation depends on the surroundings (link to heat flows from a cooler place to a hotter place).

Factors affecting the rate of radiation

-Colour: Black vs White  (shown in the experiment with thermometers)

-Texture: Dull vs shiny

-Surface temperature

-Surface area

Entry #10

More on Heat!!

At freezing point, Length = 16cm

At boiling point, Length = 48

Difference in Length = 32cm

1ºC = 0.32cm

32u à 100 ºC

1ºC = 32÷100u

For 1ºC, no. of cm.

can also be calculated as 1cm, how many ºC.  

Thermometers are calibrated by first, using pure melting ice to determine the zero point (ice point) and then using boiling water to determine the boiling point (100 ºC)

From here, we can divide the scale into 100 equal parts.

Alternatively, we can also use this formula:

Source: http://www.one-school.net/Malaysia/UniversityandCollege/SPM/revisioncard/physics/heat/thermometer.html 

A Question....

Is water a suitable material to be used in a liquid glass thermometer??

No. Water has a very small range of temperature of 0ºC too 100ºC, which is the ice and steam point of water respectively. Also, water is less sensitive to heat, or in other words, water needs a lot of energy to expand than mercury for a change to be noticeable. (That's why in cold countries, only the surface of lakes are frozen, as water gains and loses heat slowly. This can also be attributed to the bottom of the lake maintaining a constant temperature.... that, I'm not too sure either. :p)

Entry #9

Temperature

The temperature is based on the idea of thermal equilibrium to quantify "hotness". 

Process to thermal equilibrium:

When 2 objects of different temperatures are placed in contact with each other, heat will flow from the hotter object to the cooler object unit they have the same temperature. This is NOT necessarily the mid-temperature. When they are in this state, they are in thermal equilibrium.

The temperature of a substance increases when the average velocity of the particles increase. The heat causes an increase of vibrations of particles in the substance.

Temperature Scales

Fahrenheit (ºF)

Celsius/Centigrade (ºC)

Kelvins (K)

All these scales have 2 things in common: A zero point and a scale. 

Celsius/Centigrade: Has 2 fixed points: Melting point of ice (Ice point) and Boiling point of water                        (Steam point)

Fahrenheit: Ice point is 32ºF, Steam point is 212ºF

Kelvin: Same scale as Centigrade scale, change of temperature of 1ºC = change of temperature of 1K. The Kelvin scale only has 1 fixed point, which is the absolute zero, or the point where particles stop moving and cease to have temperature. (0K)

IMPORTANT CONVERSION!!

0K = -237.15ºC

100K = -173.15ºC

Difference = 237.15

ºC = K-273.15

K = ºC-273.15

Thermometers

A thermometer is any device that has a physical property that changes with temperature. 

The range of temperature is the Highest - Lowest temperature reading on the scale. 

Some physical properties

1. Volume of liquid

2. Electrical resistance of metal

3. Pressure of gases in constant vol container

4. Conductivity of a semi-conductor device

Properties of a thermometer

-Sensitivity (How small a change it can register)

-Responsiveness (How fast it registers)

-Range (How wide the range of temperature it can measure)

Okay.... so that's all for now. (Hope everything came out right... my handwriting is nearly unreadable. Xp Was in a rush.)

Entry #8

Heat

Four things that I need to learn for this unit:

1. Kinetic model of matter (Or kinetic theory)

2. Temperature and heat (Thermal energy)

3. Thermometer properties (Reading scales)

4. Thermal energy transfer (The process and rates)

Kinetic Theory

First off, we shall talk about the 3 states of matter. By now, the three states of matter should be very familiar. As I had mentioned in the sound post, the particles of the three states of matter are different, hence, their different qualities. 

Solids

Has fixed shape and volume

Has High density

Normally hard and rigid

Incompressible

The molecules in solids are tightly packed together and have very strong molecular bonds, hence giving them a high density.

Liquids

Has fixed volume

Has no fixed shape

Incompressible

Relatively high density

The molecules of liquids are loosely packed together and can slide over each other, with weaker molecular bonds than solids, hence, they have no fixed shape.

Gas

Has no fixed shape or volume

Compressible

Low density

The molecules of gas have very weak molecular bonds, hence the molecules can move about freely to expand or to be compressed. 

Now, that aside, let's continue to the Brownian motion.

Brownian motion

Particles are constantly moving in random motions. Their movements are unpredictable. Air molecules move around and bombard dust particles, thus we can see dust flying around in front of the projector/bright light because the dust particles are being bombarded by the air molecules. 

Einstein explained that it is not the dust particles (or any other particles) that possess the energy to move, but that it is the air molecules that possess the kinetic energy.

The exact distribution of energy for each particle may not be constant, but the average distribution of energy stays constant.

Before moving on, some processes to take note of...

(I hope you can read my handwriting.... ^^'')

You may ask "What is the difference between evaporation and vaporization?" Now, vaporization takes place at a fixed temperature. Evaporation on the other hand, takes place all the time, any time (any time the substance feels like, anyways. XD..............Just kidding. ) <--- LAME

Okay, back to work.

Particles in constant motion

Molecules are attracted and repelled by mutual forces of attraction and repulsion respectively. When molecules heat up, their kinetic energy increases and when they cool down, their kinetic energy decreases. 

Now, linking back to the three states of matter: 

Solids: Molecules vibrate about fixed positions only. They are held together by very strong intermolecular bonds. Molecules are also closely packed together in a regular pattern, resulting in high density.

Liquids: Molecules are randomly arranged with the particles slightly further apart as compared to solids, resulting in relatively high densities. They are free to move about but are confined within a vessel. 

Gas: The molecules re very far apart. They are randomly arranged and will occupy any available space. This results in low densities. There is very little attraction between molecules and they will move about randomly at very high speeds.

Another Experiment!

This experiment is on the rate of temperature change.

Materials

-Hot water

-1 Silver metallic cups

-1 black metallic cup

-Covers

-Plastic beaker

-2 thermometers

-Laptop!! :)

In the first experiment, we are trying to find out how the color of the container affects the rate of temperature change.

Step 1: Using the plastic beaker, collect 100cm3 of hot water and pour it into the silver metallic cup. Do the same for the black cup.

Step 2: Place the covers on the cups and stick the thermometers into the hot water through the hole in the cover (remember to use a retort stand so that the thermometer is suspended!). 

Step 3: Record the temperature at the start of the experiment, and record the temperature for every minute.

And so the wait begins.....

....Finally!!

Yay. so now, you have the results....

From the data collected, we can see that the color DOES affect the rate of temperature change. The water in the silver cup loses heat faster than the water in the black cup. Hence, we can conclude that black is a better radiator of heat. :D

You can use the laptop to tabulate/make a graph with the data collected so that it is easier to compare.

Self-directed learning Day1!!

Okay, since my physics teacher is away for today and tomorrow, she will (obviously) not be in class = free block!!!!!! Just kidding. She set us a task to learn on the next topic which is.............. Heat and Temperature!!!!! :D (yay much?? :p) 

So, here's what I've learnt so far:

Heat does not equal to temperature. Temperature is what we use to measure the average kinetic energy of the particles in a substance, either in ºC (celsius/centigrade)  or ºF (fahrenheit). 

Th higher the temperature, the more average kinetic heat the particles have.

The average kinetic energy depends on the temperature and mass of the molecules. 

(To understand it more, here's a link to a website that has interactive simulators for you to try out: http://mw.concord.org/modeler/ )

Heat is (again) a type of energy. It refers to the transfer of energy from a region of high temperature to a region of low temperature. This transfer of temperature is known as heat. (Whaaaaat?? Isn't heat supposed to be a form of energy?? o.0)

This transfer of energy only stops when it achieves equilibrium (as usual), which means both regions will be of the same temperature in the end. 

Entry #7

Physics Journal 7

Light

What is light?

Light is a form of energy (obviously).

Light radiates from its point source in an outward fashion. This process is called dissemination of energy from a source. This is also a form of Electromagnetic radiation. This electromagnetic radiation is capable of inducing visual sensation. This explains why we are able to see when there is light. 

Good to Know!

There are 6 major theories:

-Tactile theory

-Emission theory

-Corpuscular theory (Newton)

-Wave theory (Huygens)

-Electromagnetic theory (Maxwell)

-Quantum theory (Einstein) 

(I'm not going to explain the theories as they will make this post kinda long. Plus, I'm also not very sure about their details. :\ ) 

Moving on...

Luminous and non-luminous objects

Luminous objects are objects that can produce their own light, while non-luminous object cannot produce light of its own. 

Here is a diagram of how we can see luminous and non-luminous objects:

(I hope you can read my handwriting. :| )

And here is a diagram of what can happen to light :

Light is either: 

Absorbed

Reflected or

Transmitted 

or ART for short. XD

Colourful Light

Light has three primary colours:

Red, Blue and Green. If all of them are of the same intensity, they will form white light.

Here's a diagram (taken from: http://www.diycalculator.com/imgs/console-09.gif) for reference:

Also, light follows the law of reflection, where the angle of incidence is the same as the angle of reflection. 

An Experiment!!

Light Experiment: On the law of Reflection.

Materials: 

-Pins

-L-shaped mirror

-Soft board

-Plain paper

-ruler

-Protractor

-Pencil

Step 1: Draw a line AB with the point C in the middle.

Like this:

       

A-----------------.--------------------B

                        ^

                        C

(Oookay, that isn't quite right but... yea...)

Step 2: Draw the normal in a dotted line. (The normal is the dotted line down the middle)

Step 3: Draw 3 angles (measured from the normal), 20º, 40º and 60º. These lines will be the rays of incidence, or incident rays.

Step 4: Place the mirror on line AB. The normal should be in the middle of the mirror. (Mark out where the mirror stands. This is very helpful and will minimize error. :))

Step 5: Place Pin A and B about 5cm apart on the line of the 20º angle, such that Pin B is blocking the reflection of Pin A.

Step 6: on the blank side of the normal, pin Pin C in line with the reflection of Pins A and B (i.e., blocking the reflection)

<-- Like that.

Step 7: Pin Pin D in line with Pin C.

Step 8: Mark out the points where the pins have pierced the paper and draw a line that goes through point C. This acts as the reflecting ray.

Repeat with 40º and 60º.

In the end, you'll have something like this:

Measure the angles between the reflecting rays and the normal. This should be equal to the angle of incidence (angle between the incident ray and the normal), as light follows the law of reflection where the angle of incidence is equal to the angle of reflection. 

It's okay if the results are slightly off though. :) mine were one or two degrees off. But if they are really far apart... I guess something went wrong.

Meanwhile....

Fooling around!! :D

A miniature teepee!! XD lols.. I was bored. 

<-------Forever alone... 

Okies, that's all for now.

Entry #6

Physics journal 6

Sound part 2

First-- even more terms to remember! (Wait, i think i wrote these down already, but never mind.)

Amplitude: Biggest displacement of particle (From equilibrium position. I.e., its fixed position in the column --> refer to part 1)

Frequency: No. of back and forth vibrations that the particle has. (how many cycles in 1s) 

How to read a sound graph:

On the graph sketched (not very well. ^^'''), is a sample of a wavelength. This kind of curve is called a sine curve. 

As can be seen, the highest point of the sine curve is called the crest, while the lowest point is called the trough. 

How does :

(i) The amplitude affect the loudness?

(ii) The frequency affect the pitch?

Well, 

(i) The lower the amplitude, the softer the sound. (has bigger waveforms)

     The higher the amplitude, the louder the sound. (has smaller waveforms)

(ii) The lower the frequency, the lower the pitch. (has longer waveforms)

      The higher the frequency, the higher the pitch. (has shorter waveforms)

An oscilloscope is used to display waveforms.

Echo

Echo is a reflection of sound. Sound obeys the laws of reflection (i=r)

Sound waves can be reflected by surfaces. Ideal surfaces are smooth, large, upright, and far away. 

A distinct echo can only be heard if the reflecting surface is far enough from the source. If the reflected sound follows very closely, we hear a prolonged sound called reverberation.

To determine the speed of sound, 

Let V be speed, d be distance and t be time.

V=d/t

Period = 1/freq. or freq. = 1/period.

Note: the presence of wind will affect the time taken for sound to travel through air and cause inaccuracies.

Determine the speed of sound by echoes: V=2d/t

Entry #5

Physics Journal 5

Moving on to.....

Sound part 1

Sound is...

∆  a form of energy

∆  a longitudinal wave of disturbances in a medium (usually air)

The source of sound: Vibrations

Types of medium:

∆  Gas

∆  Liquid

∆  Solids

When an object vibrates, it creates a series of compressions and rarefactions of air.

Some terms:

Compression: Region of high pressure/layers of air that are close together

Rarefaction: Region of low pressure/layers of air that are further apart

This travels through air(medium) as a longitudinal wave. The air particles vibrate back and forth about its original position. 

To see:

Picture still air as columns of particles.

When there is a disturbance, the particles are pushed and hence they vibrate on their original spot. (Ok, not very scientific, but works for me.) 

The direction of vibration is parallel to the direction of travel of waves. 

Some more terms: 

Transverse waves: up-down direction

Longitudinal waves: left-right direction

Water waves: up-down-left-right direction (??) [like ripples]

Compressions and rarefactions travel along the waves. 

The wavelength is defined by one centre to another centre of a subsequent compression or rarefaction.

SPEED OF SOUND: 340m/s in air

                                    1500m/s in water

                                   5000m/s in solid (steel)

<-- Here's why.

Entry #4

Physics journal 4

Density

Density is the Amount of substance g/vol. 

Equation: mass/vol.

Unit: Kg/m3 or g/cm3 
e.g. Density of water: 1g/cm3


The Density of a substance is the same, no matter how much of the substance there is.

Floating or sinking

If...

Density of substance > Density of surrounding fluid, Substance will sink.

If...

Density of substance < Density of surrounding fluid, Substance will float. 

Take a look at my density ladder...

Oookay, this density ladder is made up of honey, glycerine, blue food coloring and oil, but the glycerine has been stained by the blue food coloring.

Most dense --> Least dense:

Honey, glycerine, blue food coloring, oil.

From here we can see the difference in density of these four liquids. 

Entry #3

Physics Journal 3

Measurement
Significant Figures

When recording measurements......

1 Take note of the precision of a measuring instrument.
e.g. with a vernier caliper, the fixed scale of the vernier caliper may either have the units of 1mm, or 1cm. BE CAREFUL WHEN READING!!!!! (Happened to me once. :p)

2 Read to the smallest 1/2 division of the smallest scale.
e.g. when the smallest scale on your ruler is 1mm, the smallest value you should read to is 1/2mm.

Now for length measurements.
There are 3 kinds of apparatus (to the smallest scale)
Meter rule (0.1cm), Micrometer screw gauge (0.001cm) and Vernier caliper (0.01cm).

Intro to the micrometer screw gauge 

*Take the reading at the point where a line on the vernier scale is aligned with the fixed scale
*Don't take 1/2 division for the smallest division
*If thimble is right on the datum, round it down to the nearest whole.

Zero error also applies for the micrometer screw gauge (msg)
Here's the example for the Vernier caliper:

Significant figures


Rules for Significant figures:

-All non-zero digits are Sig. Figs.
-All final zeros after the decimal point are significant
-Zeroes between non-zero digits are always significant
-Zeros used before the first non-zero digit are not significant
-All the zeroes that come after a sig fig may or may not be significant if there is no decimal point

Thoughts: I find the topic on significant figures rather confusing at first as to when and how to use them. :|

Entry #2

Physics Journal 2

Prefixes
Scientific Notation

Prefixes
What is a prefix?
Say, the base quantity is meter.
A common prefix for this unit is centi.
Put them together and you get centimeter.
In other words, centi is the prefix for the base quantity meter.


Table of common prefixes 

Scientific notation


The standard form of Scientific notation: Nx10e (Ten to the power of e, cause idk how to make the e small ><) 
N Being a number between 1 and 10
e Being the Index/exponent that can vary.


e.g.
Express 4660.0 in scientific notation.
To make it a number between 1 and 10, we move the decimal place (d.p.) to the left.
Therefore 4660.0 becomes 4.66. Since the d.p. has been moved by 3 places, 4660.0's index notation should be written this way: 4.66 X 103 (10 to the power of 3. )


Thoughts: I find this rather straight forward but without regular revision, it is easy to forget the rules on how to get the Scientific notation. :)

Entry #1

Physics Journal #1

What I have learnt: 

                               Types of Quantities

                               How to calculate Formulae

Physical Quantities             Base Quantities              Derived Quantities

Temperature                       Length                            Area

Time                                  Time                                Volume

Distance                             Mass                               Speed

Weight                               Temperature                   Acceleration

                                           Electric Current              Density

                                          Amt of Substance

                                          Luminous Intensity

Table of Values and how to get Derived Quantities

How I feel: I feel rather happy that I am managing physics quite well, and I get a feeling of accomplishment when I manage to get the calculations correct. ^^

Other comments: I feel that I should be more careful as I can still make careless mistakes in the calculations.  ^^’||