Sunday, 17 August 2014

Mock Test Question

Group Answer

The liquid A (Red) is poured at the same time as the liquid B (Green), which we assumed are at the same temperature.
The spaces between the molecules of the liquid A are larger, thus it is less denser than liquid B , which will cause it to have a lesser weight and float up above liquid B.The spaces between the molecules of liquid B is smaller, thus it is more dense and would cause it to have more weight and therefore sink bloew liquid A.

Group Discussion
http://m.youtube.com/watch?v=F9XTln0B62M

Notes

Observation: After experiment the two liquids mixes up together - shows that the assumption on their same initial temperature isn't really right. The pbservation could have been because of they reaching thermal equilibrium, where the kinetic energy between the molecules of both liquids stops when both of them has the equal average amount of kinetic energy between the molecules.

Think 6

Group Answer
Metal B is a better thermal conductor than metal A. Thus metal B expands faster than metal A since its molecules are able to gain kinetic energy faster and thus it will expand faster. With both metals sticking together, and metal B expanding faster, the whole bimetallic strip bends towards metal A.
When the whole bimetallic strip is cooled (water poured), the molecules of both metals lose kinetic energy. Thus as metal B is a better thermal conductor its molecules loses kinetic energy faster and thus in contracts faster. Since they are stciked together and metal B contracts faster, the whole bimetallic strip bends back to its original straight shape, where both metals have a same length.
Individual Answer
Macro
When the whole metallic strip is heated, as metal B is a better thermal conductor then metal A, metal B would have a greater expansivity than metal A. This causes metal B to gain more thermal energy than metal A and thus metal B can expand more. Having to expand more and also because they are sticking together, the whole bimetallic strip will bend towards the direction of metal A. 
When water is poured on the bimetallic strip, as metal B is a better thermal conductor, it will also contract faster due to the lost of thermal energy and therefore the whole bimetallic strip will bend towards metal B
Micro
Metal B is a better thermal conductor than metal A. Thus the molecules of metal B will gain more kinetic energy and the molecules in metal B has more collisions than the molecules in metal A. This causes the whole bimetallic strip to bend towards metal A, since metal B is expanding at a higher rate and the two metal strips are sticked together.
When the water is poured on the bimetallic strip, molecules of metal B loses kinetic energy faster than the molecules in metal A since metal B is a better thermal conductor. Thus the whole bimetallic strip will quickly shrink back to its original straight position. 

Sunday, 3 August 2014

Think 3, 4 and 5

Think 3

Macro
The tiles are worse thermal conductors than parquet. Thus the right feet will lose thermal energy to the tiles faster than to the than the left feet losing thermal energy to the parquet, therefore the feet on the tiles feels colder than the feet on the parquet.


Think 4
Group Answer
The thermal energy from the hot water will be transferred to the metal surface of the cup, and then transferred to the cold water. Thus the hot water will decrease in temperature, while the temperature of the cold water increases. After that, the temperature in which the two water meet will be room temperature.
Individual Answer
Thermal energy is transferred from a hotter region to a colder region. Therefore since the hot water in the metal cup has a higher temperature of 70 Degree Celsius, the thermal energy of the water in the metal cup will be transferred to the metal cup, and then to the colder water. The water in the metal cup will thus decrease in temperature, while the water outside the metal cup will increase. The thermal energy rate of transfer will decrease as the difference between the two water temperature becomes smaller, therefore the line of the rate of decrease in temperature is a curve. The thermal energy transfer between the water in and outside the metal cup will stop when they reach thermal equilibrium, at 32.5 Degree Celsius. The temperature of the water will not reach at room temperature in the end as the styrofoam cup is a poor thermal conductor, therefore it is able to minimise the effect of the room temperature on the temperature of the water. 

Think 5
We can apply heat to the ring.

The inner diameter of the ring will increase or decrease as the thickness of the ring increase or decreases respectively. 
Explanation: The thermal energy of the heat source will be transferred to the ring, therefore the ring will increase in temperature, and the molecules will gain more kinetic energy and vibrate faster, and the thickness of the ring will increase. This will then cause the inner diameter of the ring to expand in length as well.
With the same concept, when the ring is left for cooling, the temperature of the ring will decrease and the kinetic energy between the molecules will decrease and vibrate lesser. Therefore the thickness of the ring will decrease, and will lead to a decrease in the inner diameter of the ring.