Many students think of physics as a dry and boring subject. Undoubtedly, for some, it can be. However, learning about the world around you and its physical intricacies is quite interesting and useful.
Students choose their SAT subject tests as per their interests. Physics is a practical choice for students who are curious about how things work. It is a very exciting topic for detail-oriented students.
One of the most interesting topics within the physics SAT syllabus is thermal physics. It is a relatable topic because everything around us is made up of matter.
Let's look at some of the topics within thermal physics that may be important for your SAT physics test. A similar collection of topics is available for your review in the SAT physics syllabus.
Phases of Material
All matter is composed of small particles called atoms. These atoms exist by themselves or join up as molecules. Atoms weigh in nanometers, which represent a billionth of a centimeter. Any tangible object you see around you is made up of billions of atoms.
For instance, solids have a high density due to their tightly packed structure. Atoms in solids are closely bound to each other, with fewer gaps between them. They only move within their fixed position, depending on the temperature.
Liquids are more loosely bound than solids, but they're still held together in a loose arrangement. In the liquid state, particles are not bound to a fixed position. In the case of liquids, the interatomic binding forces are relatively weaker.
On the other hand, gases have the least closely bound atoms, and gas molecules are free to float around without binding.
Density also depends on the material and its viscosity. Some materials in their liquid form can be very tightly packed and viscous, like mercury and molasses.
What is volume? It is the space an object occupies. For simpler shapes, it is a product of all their dimensions.
Using simple formulae, we can calculate the volume of regular shapes like cubes, spheres, cones, and cylinders. For irregular objects, we can use the displacement method to determine volume.
Your SAT prep can become very interesting with subjects that offer practical learning like physics. You can also search for SAT exam preparation to assist you with unique concepts in physics like space physics.
You can understand a physics problem quite easily if you learn through practical experiments and with the help of a competent tutor.
If you heat ice, it will eventually melt and turn into water. Heat it some more, and it will boil up and evaporate in the form of gas.
The melting point is the point where solid transitions into a liquid. The opposite process of melting is freezing when a liquid turns into a solid.
Some solids transition from solid to gas directly, in which case, the transition is known as sublimation.
The boiling point is the point at which a liquid turns into a gas. The converse of this process is called condensation.
Energy And Temperature
Temperature is an estimate of the thermal energy that an object possesses. To give an example, just like density is the amount of matter packed in a specific volume, the temperature is the amount of thermal energy within an object. Both large and small objects have the same amount of thermal energy.
There are two scales of temperature - Kelvins and Celsius. Kelvin is measured in the absolute temperature scale, and hence all calculations with Kelvin are positive. It doesn't go below absolute zero.
There is a clear difference between thermal energy and temperature. Thermal energy is a byproduct of electricity. Meanwhile, the temperature is a measure of the average speed of particles.
Here's a small practical experiment to elucidate the point—boil two different sized pots of water. The larger pot will take longer to heat up due to a higher number of particles. The smaller pot will heat up faster with a greater temperature rise.
It's a good idea to incorporate experiments like these in your physics lessons to make your exam prep fun.
Methods Of Heat Transfer
Let us examine the three ways that transfer heat among different materials.
- Conduction transfers heat through intermolecular collisions between two solids or a solid and a liquid. It may occur in gases and liquids, too but not as efficiently.
- Convection involves molecules moving from one place to another. This is the most common form of heat transfer within fluids, such as liquids and gases.
- Radiation transfers heat through waves. A good example of radiation is the heat we get from the sunlight.
Specific Heat Capacity
The change in a system's temperature depends on its mass, heat capacity (different for each substance), and how much energy you supply.
The specific heat capacity of a material is the thermal energy you need to heat one kg of the material by exactly one degree Celsius.
The more time a material takes to heat, the more time it will take to cool down.
The units for specific heat capacity are joules per kilogram per degree Celsius.
Thermal energy fits into the broader concept of energy.
Specific Latent Heat
To put it simply, this is the thermal energy input a material needs when changing from one state to another.
Every material has two specific latent heats for two boundaries of change. They are known as specific latent heat of:
- Fusion (lf) and
- vaporization (∆Hvap)
As the name suggests, the latent heat of vaporization is the energy you need to change one kilogram of a material from liquid to gas.
While specific latent heat of fusion is the energy needed to change one kilogram of liquid to one kilogram of solid or vice versa, by any specific material.
The latent heats are denoted on a cooling or heating graph. The two phases of melting and boiling points are denoted by two horizontal lines where the temperature remains constant while the state change occurs; the longer the line, the more energy is required to change the material's state.
We can use both equations in certain cases where both the temperature and state will change.
Heat flows from a place of higher temperature to lower temperature. This is a variation of the second law of thermodynamics. When objects at different temperatures interact, heat flows from the hotter object to the cooler one until both temperatures equalize. This is called thermal equilibrium.
Kinetic Theory Of Gases
There are four basic postulates you must keep in mind about gases.
- Gases consist of molecules.
- Molecules are constantly moving and in random motion.
- Newton's Laws determine the motion of molecules
- Collisions are elastic, and no energy is lost.
Learn more about atoms, ions, and atomic structure here.
Pressure And Temperature
The pressure and temperature of a gas are directly proportional to each other. At higher temperatures, particles will move faster and collide with greater intensity, increasing the overall pressure.
Temperature generally stems from the kinetic energy of the particles within a system. The law linking the relationship between pressure and temperature is known as Charles' Law.
Here, the pressure is measured in pascals, and the temperature is measured in Kelvin. This law holds true under constant volume.
Pressure And Volume
Pressure and volume are inversely proportional to each other. With an increase in volume, the gas will spread out more and exert a lower pressure. The force exerted on each molecule will decrease.
The pressure of the gas is measured in pascals, and the volume is measured in cubed meters.
The law relating pressure and volume to each other is known as Boyle's Law, and it holds true under constant temperature.
To increase the pressure, you can either increase the temperature or decrease the volume of the gas.
The gas pressure will increase with a decreased volume due to the particles colliding at a higher frequency in a reduced space.
The temperature of a gas increases with an increase in the internal energy of the gas. Consider a bicycle pump when compressed. It heats up.
Laws Of Thermodynamics
The laws of thermodynamics give us the how and what of heat flow. There are four laws, and they are as follows:
The Zeroth Law
If system A is at thermal equilibrium with system B, which is at thermal equilibrium with system C, system A and system C are also at thermal equilibrium. That's how the zeroth law works.
The First Law
This law states that a system's internal energy increases with the addition of heat or work done. Conversely, the energy decreases if the system gives off heat or does work.
The Second Law
The second law is a bit detailed. It states that heat can flow from a hotter to a colder object but not the opposite. A result of this law is that no engine can work with 100% efficiency. This law also describes entropy, which states that disorder always increases. It shows that order leads to disorder and not vice versa.
The last law states that it is impossible to cool anything to absolute zero.
To prepare for your SAT physics subject exam, we recommend you look at other unique topics like magnetism and electromagnetism.
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