This competency includes about 17 multiple-choice questions which make up about 14% of the entire exam.
These questions test your knowledge of the matter, its characteristics, and how it behaves.
Let’s talk about some concepts that you will more than likely see on the test.
Components of an Atom
A common topic tested in the matter section is atoms. Atoms are the basis of chemistry because they are the foundation of life. All matter is made up of atoms. Atoms are the smallest units that make you, me, and everything else you see (and don’t see) in the world.
Three Basic Parts:
Although they are tiny building blocks, atoms are a combo of three different parts that you can remember as PEN. Just as an author crafts a story with a pen, matter is created using an atom’s pen: proton, electron, and neutron.
Although they are at opposite ends of the word ‘pen’, the protons and neutrons actually work together inside an atom’s center (the nucleus).
Although they are wrapped up together, the protons and neutrons are not the same. The proton is positively charged (p = positive), while the neutron carries no charge at all (n = neutral).
Circling the protons and neutrons like clouds of negativity, the negatively charged electrons are not found inside the nucleus. Electrons are much smaller than the other two parts of an atom but are attracted to the nucleus by the protons’ positive vibes.
Why is the ‘PEN’ So Important?
The role of a proton, electron, and neutron does not change in different types of matter. However, it is the number of each of these parts found inside a particular atom that makes a thing a thing. See the example below:
Gold and argon are both elements found on the Periodic Table. Elements are substances that cannot be broken down into other substances. There are 92 naturally occurring elements.
Gold has an atomic mass of 196.967 atomic mass units. It contains the following:
Argon has an atomic mass of 39.948 atomic mass units. It contains the following:
The masses of both of these elements are very different. The protons, electrons, and neutrons contained in their individual atoms vary, as well. But do you see a pattern here? Although it isn’t true every time, the number of protons inside an atom usually equals the number of electrons. Wanting to find an element’s atomic number? Look at how many electrons and protons it has.
On the periodic table, you will find gold in spot 79 and Argon in the 13th block.
A gas is one of the four fundamental states of matter, along with solids, liquids, and plasma.
In the 18th century, scientists began to experiment with different gases and realized that there is a connection between the following: pressure, temperature, and volume.
Through experiments, these early science gurus realized that because the molecules of all gases are spaced far apart, they act in a very predictable way. This led to the creation of three different gas laws:
- Boyle’s Law
- Charles’ Law
- Avogadro’s Law
Boyle’s Law in Scientific Terms: If a certain amount of ideal gas is kept at a set temperature, then the pressure and volume of the gas are inversely proportional.
In symbols, the law is represented as PV=k.
What This Really Means: Boyle’s Law describes how when the pressure of a gas increases (doubles), the volume of the gas will decrease by half.
Real World Example of Boyle’s Law: The Balloon Experiment
Trap a small amount of air in a balloon and then tie the end with a string. Place the balloon inside of a 50 ml syringe.
Now place the bulb inside the syringe without squeezing the piston. The results: the balloon remains the same as the air escapes from the front (atmospheric pressure stays the same).
Next, close the outlet of the syringe and squeeze the piston. What do you think will happen then? The balloon becomes smaller as the pressure increases.
Charles’ Law in Scientific Terms: When temperature increases, the volume of a gas increases, as well and at the same rate.
What This Really Means: Even though you can’t see oxygen, helium, or any other gas, they are still matter and contain atoms. As a gas begins to heat up, its atoms start moving around more quickly. This causes its volume, or the space it takes up, to grow, as well. As it cools, the atoms will slow down and the volume will go back down.
Real World Example of Charles’ Law: The Shrinking Balloon
Maggie, an event planner, was filling up helium balloons for a birthday party. The supply room where the helium tank was kept was very hot. After filling the balloons fully, Maggie tied each one with string and took them into the room where the party would take place. After hanging up some decorations, she turned on the air conditioner. When Maggie returned with the cake a few hours later, she was shocked to find that the balloons looked like they had lost some of their air.
Maggie took the shriveled balloons back into the storeroom so that she could refill them. To her surprise, the balloons appeared to be full of helium again! Were her eyes playing tricks on her? No, Charles’ Law was at play.
Avogadro’s Law in Scientific Terms: When at the same temperature, equal volumes of gases and pressure contain equal numbers of molecules.
What This Really Means: This gas law explains that the number of molecules a gas has doesn’t depend on itself (what gas it is) but instead, three other forces: temperature, volume, and pressure.
Real World Example of Avogadro’s Law:
Think of four gases that you know: nitrogen, oxygen, carbon, dioxide, helium, etc. Now imagine yourself placing equal amounts (volume) of each of these gases in separate pressurized containers and leaving them in the same room. Avogadro’s Law holds that because they are under the exact same conditions where temperature, volume, and pressure are concerned, they will have the exact number of molecules when measured.