Black Principle

Energy can not be destroyed nor generated, but it can be transferred from one to other.
Heat is also energy, we can see that it is moving / transferring from a higher temperature to lower temperature.

2 system let say water and ice, if they are mixed together, what will happen?
Water will be colder while ice will be hotter.
They will stay at the same point (temperature), so it means heat loss from the water will be gained by ice, to make them stay balance in one temperature.

In that case we will have equation


Q loss = Q gain


What happen to solid matter when they are mixed to liquid? or solid matter when mixed to gas? and so on.

In this case, you are going to need a heating graph to see how the heat received will move point to point.


To understand the heating (cooling) graph, observe the picture below

As solid (the yellow one) receives heat, the molecule inside will vibrate faster creating space to expand and increasing the temperature. The same thing also happen to the liquid (the light blue and grey one).

During fusion / melting of solid (the green one), we will not find any temperature changes, only state (phase) changing occur, the absorbed heat will be used to overcome the intermolecular bond (which lead to state changing). This also happen during boiling / vaporizing (the blue one)

Once, you have known the step by step imminence of a substance when losing or gaining heat from the heating (cooling graph), it will be easier for you to calculate heat needed or extracted in a system which contain 2 or more state.

Ex : ice at -5C will be mixed with water at 30C, what will happen?

The ice is gaining heat while the water is losing heat, the final temperature of the two system could be below freezing point, at freezing point or above freezing point, depends on the mass of each ice or water. When the final temperature below freezing point( let say, A), it means the ice will gain heat from its heat capacity to a certain temperature (A) while water will lose heat from 30C to 0C (according to its heat capacity) and then water will change state into ice then followed by the changing temperature of the freezing water to a same number as the ice (A).

When the final temperature at freezing point ( 0C ), it means the ice will gain heat from its heat capacity to 0C then followed by the fusion of the ice into liquid while water will lose heat from 30C to 0C (according to its heat capacity).

When the final temperature above freezing point (let say, B), it means the ice will gain heat from its heat capacity to 0C, followed by fusion, turn to water then rising up its temperature to B (of course, at this poinr, it has turned to water) while water will lose heat from 30C to B.

Worked example :

Q 1 kg of alcohol (heat capacity of 3000 J/kgC) at 40C will be mixed with 1 kg of water (heat capacity of 4000 J/kgC) at 75C. What will be the final temperature of the mixture?

A Alcohol will gain heat from water. Take the final temperature as T then we can picture that the heat gained from the water will be 1 kg x 4000 J/kgC x (75-T)C. On the other hand the water will lose heat as 1 kg x 3000 J/kgC x (T-40). The number of heat gained and loss are the same, so we will get equation : 4000 (75 - T) = 3000 (T - 40) then we can find that the final temperature is 60C

Q 1 kg of ice (heat capacity of 2000 J/kgC and latent heat of fusion 300000J/kg) at -4C will be mixed with 1 kg of water (heat capacity of 4000 J/kgC) at 80C. What will the final temperature of the mixture?

A Ice will gain heat from water. Take the final temperature as 0C (stay at water) then ice will gain heat to raise temperature to 0C as 1 kg x 2000 J/kgC x ((0-(-4))C then followed by melting as 1 kg x 300000 J/kg. On the other hand the water will lose heat as 1 kg x 4000 J/kgC x (80-0). The number of heat gained and loss should be the same, however we get equation that 8000 J + 300000 J = 320000 J which is impossible because the heat loss from the water (320000 J) is over the heat gained by ice, so it means after the ice melting, it will raise temperature, let say A. It will make us to recalculate the heat gained by ice as 8000 J + 300000 J + 1 kg x 4000 J/kgC x A C and the heat loss of the water as 1 kg x 4000 J/kgC x (80-A) C. That end the equation as 308000 J + 4000A = 320000 - 4000 A which lead that the final temperature (A) is 1.5C

Q 1 kg of ice (heat capacity of 2000 J/kgC and latent heat of fusion 300000J/kg) at -4C will be mixed with 1 kg of water (heat capacity of 4000 J/kgC) at 10C. What will the final temperature of the mixture?

A Ice will gain heat from water. Take the final temperature as 0C (stay at water) then ice will gain heat to raise temperature to 0C as 1 kg x 2000 J/kgC x ((0-(-4))C then followed by melting as 1 kg x 300000 J/kg. On the other hand the water will lose heat as 1 kg x 4000 J/kgC x (10-0). The number of heat gained and loss should be the same, however we get equation that 8000 J + 300000 J = 40000 J (which is impossible), from the number we can see that heat needed for ice to become water (308000 J) is higher than the given heat from the water (40000 J) , so we can predict that not all ice become water (only port of ice, let say m) it means the equation will become 8000 J + 300000m = 40000 J, and this equation is possible. In this case the final temperature is 0C

Latent Heat

Do water boil at a certain point?
Every matter will boil or melt at certain point.
When matter boil / melt at certain point, so how can heat quoted at that point?
In that case you need a term to explain heat needed when there's no temperature changes.
This will lead to LATENT HEAT.
Latent heat can be used to describe amount of heat needed to change state / phase or in the area where there's no temperature changes / constant temperature.
The amount of heat needed will be quote as :
Q = m L
where Q as quantity of heat needed to boil / melt, m as mass of the melting / boiling matter, and L as the latent heat of 1 kg of matter to boil / melt

Do you know that if you boil water in a highland, you will get point below 100C?
And so do impurities also influence boiling and melting point of water.
Study how long does it take to boil water and water with salt in it, ok :)

Heat Capacity

What can you conclude from the animation?
They are having an increase in temperature when heat is given, aren't they?
The term we used to describe that matter will increase in temperature when heat is given is said HEAT CAPACITY.
At the same heat given but difference in mass, will also give a difference in temperature raise.
Now observe below animation


What can you observe from the experiment?
Both metals is increasing in temperature, however, copper will increase higher compare than aluminum, why is that?
The heat capacity of copper can be said is lower than aluminum when the same heat is given but the raise of temperature of copper is higher than aluminum.
Now, can you figure out which matter will have higher amount of heat capacity? That's right, the one with higher amount of heat capacity, mostly are isolators.

We can say that heat given will be transferred by matters to increase their former temperature.
Amount of the temperature raise depends on :

• Mass of matter (from the first animation, it shows that higher mass will have lower temperature raise and so on)


• Kind of matter (from the second animation, it shows that different matter has different heat capacity)

In short, we will get this equation

Water Anomalyous

Observe a glass of iced water, what did you see?

Does the ice float or sink?

Ice always floats in water, isn't it?

Since ice floats in water, it means ice has lower density than water.

Lower density can be caused by:

1. Increase the volume

2. Decrease the mass

How about ice? What happen to ice to make it lower in density? Did you decrease the mass of water to be made into ice?

Of course not, generally all things will remain in mass, but change in volume (because of thermal expansion, it could expand or contract actually)

When we make ice from water, there's no changing in mass, the one which changing is state (phase, from liquid to solid).

Normally, during cooling, all matters will contract, so the volume will decrease.

However, that's not happening to water when they are changing into ice, water will expand (when we put in freezer, to make ice), that will lead to the increase of volume.

If you notice, everytime you make ice cube in a container, you will see that ice will fill the container more than you put before (when remain as water), so it is clear that ice has higher volume than water.

Since ice has higher volume than water, it means when ice melt to water, the ice will decrease in volume, to become water, normally.

But then will water remain normal? Or will it expand under hot condition and contract under cold condition?

Of course.

This will occur at 4 C and above.

That's why we say there is a strange property of water when become ice or ice when become water (anomalyous of water).

This phenomenon only occurs at 0 - 4 C.

Observe the graph below to see how volume of water interact to temperature.

You can see that at 4 C the water will reach its minimum volume, so it means the density will be the highest and then the density will increase comparable to the temperature and so on.

Heat Transfer

Heat is energy, internal energy which commonly used to describe the heat of body.
Internal energy is similar to mechanical energy. So, heat can be generated as kinetics energy and potential energy. To differentiate kinetics and potential energy of heat, we can define the principle of potential and kinetics energy itself. Kinetics energy is related to the movement, for heat, the kinetics energy is described by the movement of the particle inside during heating and cooling.
Potential energy is related to the condition, thus potential energy is described by the state changing of a particle.
Energy can not be generated and destroyed, means heat can not be generated nor destroyed. It only moves from one particle to anothe.
There are several ways of heat transfer :

1. Conduction
Conduction is commonly used for all solid matter.
As one matter to other has different amount to absorb heat, we can not assume that the heat transfer for one matter to other will show the same performance.
This will lead to the understanding of conductor and isolator.
Conductor means good in heat transferring, i.e. metal.
Isolator means bad in heat transferring, i.e. wood, plastics.

2. Convection
Convection is commonly used for liquid and gas.
One characteristics of convection is the heat flow.

3. Radiation
Radiation used for gas and or vacuumed condition

Bimetallic Strips

Bimetallic strips is a 2 joined metal that mesh closely to become an union.
Bimetallic strips will expand also under hot condition and contract under cold condition, however since bimetallic strips contain 2 metals, which will not expand / contract as same amount one another, they will bend according to its linear coefficient of thermal expansion.
This characteristics is very useful for electric used (mostly Mini Circuit Breaker), because they can react if there is an overheating. (Try to figure out where the bimetallic strip is).

Thermal Expansion

Generally, all thing will expand under hot condition and contract / compress under cold condition.
The amount of increment during expanding or contracting for each matter will be different, based on their characteristics.
Generally, the expansion and contraction of gas is the biggest amongst other, and the expansion and contraction of liquid is bigger than solid.

To know the increment, people conducted an experiment to find the difference at certain temperature and found the number as linear coefficient of thermal expansion (for an increment in length) and volumetric coefficient of thermal expansion (for an increment in volume).

By knowing those data, you can assume which matter will give you higher length / volume under hot condition and contrary lower length / volume under cold condition.

For example if you want to create a liquid thermometer, you should find material with high expandibility for its liquid hence a low expandibility for the liquid' container (it's explained why thermometer are covered with glass, which is less to expand compare to the liquid / alcohol / mercury).

You can see also that the increment depends on the temperature changes.

What else might influence the increment?

How about the initial length or volume?

I run an experiment as follow to find their relationship.

First, I gave a matter (which has linear coefficient of thermal expansion 12 10^-6 /C and volumetric coeffiicient of thermal expansion 36 10^-6 / C) a number of temperature changes and find the increment at two point of view that is length and volume.

I got data as follow :

Second, I gave the same matters (with various length / volume) a same temperature change, then observe their final length and volume.
I got data as follow :

Can you find the relation ship of the initial, final, coefficient of thermal expansion and temperature changes?

You are right, the final length / volume will increase as the initial length / volume increase also they can be increased by getting higher temperature changes.

We can say that :

Thermometer

Thermometers are widely used for measuring temperature (hot or cold one).
There are 3 kind of thermometers, that is :
1. Liquid (normally mercury or alcohol) thermometer (commonly used)
Liquid thermometer contains liquid (not solid ar gas) inside it.
This liquid could be anything as long it has characteristics as follow :

• Expand at hot condition and contract at cold condition.
• Good expandibility, mean amongst other liquid it will expand or contract more.
• Remain as liquid at working area of the thermometer, for example if we want to create a thermometer which will be used for measuring 0 - 100C, it means we must find liquid which has melting point below 0C and has boiling point over 100C

2. Thermocouple (for higher temperature, mostly used by industry)

3. Infra Red thermometer (must be placed at certain distance to keep its accurateness)


Everyone has different sense is saying hot or cold, for example if you stay in the air conditioned room, you will say outside the room is hotter, however for the person who live in a desert, he will say the same outside room (that you say hot) is colder than his place (at the desert).
To standarized the hot or cold feeling, people create scales that is:

• Celcius scale

Celcius used water for scaling, he marked the temperature when water freezes at 0C and the temperature when water boils at 100C

• Reamur scale

The same principle as Celcius however the temperature when water boil at 80C

• Fahreinheit scale

Fahreinheit used brine and water for scaling, the temperature when brine freezes is marked at 0F and the temperature when water boils is market at 212F

• Kelvin scale

Kelvin used water' absolute zero (mean there is no action at all of the molecule at that temperature) and continue to boil at 100K

• etc

Generally we can say that the relation between Celcius scale, Reamur Scale and Fahreinhet scale can be compared as 5 : 4 : 9
And the relationship between Celcius Scale and Kelvin Scale is Celcius scale is 273 less then Kelvin scale
Why don't you try to figure their relationship by information above...
Good luck...

Can We Feel Sea Breeze in The Night?

Each object has a different characteristics to absorb heat.
In this case, let say, land and water are 2 different things, each has their own ability to absorb heat.
During daytime the land is hotter than the water.
Since the hotter air (from the land) always rises up, it means the cool air (from the water) will move to replace the rising air.
It means we will feel the sea breeze during the daytime.
In the night, the water is warmer than the land, so the hot air (from the water) will rise and be replaced by the cool air from the land.
That's why land breeze occurs in the night.
If there was much heat at night, will sea breeze occur?