Natural Sciences: Chemistry, Particle Model of Matter, Electricity, and Visible Light

Comprehensive practice flashcards covering the Periodic Table, atomic structure, chemical reactions, the particle model of matter, static and current electricity, and visible light optics.

What is an element?

A pure substance made up of only one type of atom that cannot be split into simpler substances or changed into another element by chemical reactions.

What are the three subatomic particles that make up an atom and their electric charges?

Protons have mass and carry a positive charge ($+$), neutrons have mass and carry no charge (neutral), and electrons have very little mass, a large amount of energy, and carry a negative charge ($-$).

Why is an atom considered electrically neutral?

Because the number of negatively charged electrons ($-$) spinning in orbits is equal to the number of positively charged protons ($+$) in the nucleus.

How many electrons can the first and second electron orbits hold?

The 1st orbit can hold a maximum of $2$ electrons, and the 2nd orbit can hold a maximum of $8$ electrons.

What are the key properties of Group 1 elements (Alkali Metals)?

They are soft and can be cut with a knife, explode in water, and are very reactive.

What are the key properties of Group 17 elements (Halogens)?

They are reactive non-metals that form salts and are toxic and dangerous.

What is a diatomic molecule, and which seven elements form them?

A molecule consisting of two of the same kind of atoms chemically bonded together: Hydrogen ($H_2$), Nitrogen ($N_2$), Oxygen ($O_2$), Fluorine ($F_2$), Chlorine ($Cl_2$), Bromine ($Br_2$), and Iodine ($I_2$).

From left to right, what classification of matter does each beaker represent in this diagram?

Atoms, Molecules, Compound, and Mixture.

What is the difference between a molecule and a compound?

A molecule is formed when two or more atoms join together chemically (whether of the same or different elements), whereas a compound specifically consists of two or more different elements chemically bonded together.

In the electrolysis of copper chloride ($CuCl_2$), which electrode is connected to the positive terminal and which to the negative terminal?

The anode is connected to the positive terminal ($+$) of the battery/cell, and the cathode is connected to the negative terminal ($-$).

What is thermal decomposition?

A decomposition reaction in which heat energy is used to split up a compound into the elements it is made of.

How do particle arrangement, movement, and compressibility compare between solids and gases?

In a solid, particles are closely packed in a regular arrangement, vibrate in fixed positions, have low kinetic energy, and are virtually incompressible. In a gas, particles have no regular arrangement, large spaces between them, move randomly and quickly with high kinetic energy, and are easily compressed.

According to this change of state diagram, what are the names of the phase transitions between a solid and a gas?

The transition from a solid directly to a gas is sublimation, and the transition from a gas directly to a solid is deposition.

What is diffusion, and why does it occur rapidly in gases?

Diffusion is the process by which particles spread throughout a liquid or gas resulting in an even distribution (equilibrium); it occurs quickly in gases because there are very large spaces between the particles.

What occurs at the particle level during thermal expansion and contraction?

When heated, particles gain kinetic energy and move further apart (expansion); when cooled, particles lose kinetic energy and move closer together (contraction). The size and number of individual particles do not change.

What are the three ways to increase gas pressure inside a container?

1. Add gas (more particles cause more wall collisions). 2. Increase temperature (particles move faster and collide harder). 3. Compress the gas (decreasing volume gives particles less space, increasing collision frequency).

Why do only electrons move during static charging while protons stay in place?

Electrons orbit the nucleus on the outside of the atom and can transfer from one atom to another, whereas protons are held tightly inside the nucleus.

What causes an object to acquire a static positive or negative charge?

A positive charge is caused by a shortage of electrons (losing electrons), while a negative charge is caused by an excess of electrons (gaining electrons).

What is electrical polarisation?

When a charged object is brought near a neutral object, repelling like charges to the far side and leaving the near side with an opposite relative charge, causing the two objects to attract.

How many electrons are equivalent to one Coulomb ($1\,\text{C}$) of charge?

$1\,\text{C} = 6.25 \times 10^{18}$ electrons.

What three things are required for an electric current to flow?

1. A source of electrical energy (cell or battery). 2. A closed circuit (complete path). 3. Conductors (connecting wires).

What three methods can be used to strengthen an electromagnet?

1. Add more cells in series. 2. Place an iron nail inside the coil. 3. Add more turns of wire around the nail.

What happens to total resistance, total current, and bulb brightness when more light bulbs are added in parallel?

The total resistance decreases, the total current increases, and the bulbs continue to glow with the same brightness as a single bulb.

What is the difference between a luminous object and an illuminated object?

A luminous object emits its own light (e.g., the Sun, candles, fireflies), whereas an illuminated object does not emit light but reflects light from an external source (e.g., the Moon).

What is the wavelength range of the visible light spectrum detected by the human eye?

$400\,\text{nm}$ to $700\,\text{nm}$.

What are the three rules of light reflection off a plane mirror?

1. The incident ray and normal line always lie in the same plane. 2. The angle of incidence equals the angle of reflection ($i = r$). 3. The reflected ray and incident ray are always on opposite sides of the normal.

How does a light ray behave when it passes from a less optically dense medium to a more dense medium?

The light slows down and bends towards the normal line.

What causes white light to disperse into rainbow colours when passing through a triangular prism?

Each wavelength of light travels at a different speed and bends at a different angle: red light has the longest wavelength and is bent the least, while violet light has the shortest wavelength and is bent the most.

What are the roles of the cornea, pupil, iris, and retina in the human eye?

The cornea is a transparent protective front layer; the iris is a colored muscle controlling how wide the pupil opens; the pupil lets light in; and the retina is the sensory layer at the back containing rods and cones where an inverted image forms.

Why does a banana appear yellow under white light?

The banana absorbs all other visible wavelengths ($R, O, G, B, I, V$) and reflects only the yellow wavelength into the eye.

How do additive light colour mixing and subtractive pigment colour mixing differ in their primary colours and end results?

Additive mixing uses primary light colours (Red, Green, Blue) which combine to form White light, whereas subtractive mixing uses primary pigment colours (Cyan, Magenta, Yellow) which combine to absorb all light and form Black.