science mid year year 9 exam

A comprehensive set of vocabulary flashcards covering atomic structure, chemical reactions, radioactivity, scientific variables, energy types, wave physics, and basic electricity based on the provided lecture transcript.

Atomic Number

The number of protons in an element, which determines the element's identity and position on the periodic table.

Nucleus

The center of an atom where neutrons and protons live.

Compound

A substance identified in a chemical formula by the presence of more than one capital letter.

Neutral Atom

An atom with no overall charge because the number of protons and electrons are equal.

Isotopes

Atoms with the same number of protons but a different number of neutrons, which affects the mass number.

Anion

A negatively charged ion formed when an atom gains electrons in its valence shell.

Cation

A positively charged ion formed when an atom loses electrons from its valence shell.

Electron Configuration (First 20 Elements)

The arrangement of electrons following the array $2.8.8.2$.

Groups

The $18$ columns in the periodic table.

Periods

The $7$ rows in the periodic table.

Flame Test

A procedure where electrons gain energy and jump to a higher shell; when they fall back down, they release energy as light of specific colors and wavelengths.

Exothermic Reaction

A reaction where energy is released and the surrounding area gains heat; reactants have more heat than the products.

Endothermic Reaction

A reaction where heat is absorbed and the surrounding area loses heat; products have more energy than the reactants.

Half-life

The specific time it takes for the amount of a radioactive material to be reduced by half.

Independent Variable

The variable in a scientific experiment that is changed by the researcher.

Dependent Variable

The variable in a scientific experiment that is being measured.

Controlled Variable

Factors in an experiment that must remain constant to ensure a fair test.

Accuracy

How close a calculated or measured value is to its true, accepted value.

Precision

How close together the data points are to each other.

Energy

The ability to do work or cause a change.

Kinetic Energy

The energy of moving objects in motion.

Potential Energy

Energy that is stored in a substance or object.

Energy Transfer

When energy is moved from one object to another without changing its form.

Energy Transformation

When energy is changed from one form into another form, such as electrical energy turning into light.

Sankey Diagrams

Diagrams that show how energy is transferred or transformed, measured in Joules ($J$), using arrow thickness to represent the amount of energy.

Albedo

The amount of radiation of wavelengths that a surface reflects, ranging from $0$ to $1$.

Convection

Heat transfer that travels as warm air becomes less dense and rises.

Conduction

The movement of heat through the physical touch of objects.

Radiation

The movement of heat through electromagnetic waves.

Transverse Waves

Disturbances that move the medium at right angles to the direction in which the wave travels.

Longitudinal Waves

Disturbances that move the medium back and forth, parallel to the direction in which the wave travels.

Mechanical Waves

Waves that require a medium to pass through, such as sound waves.

Non-mechanical Waves

Waves that do not need a medium to pass through, such as light waves.

Wavelength

The distance between one point on a wave to that same point on the next consecutive wave.

Frequency

The number of waves that pass through a fixed point per second, measured in hertz ($Hz$).

Amplitude

The size of the maximum part of the wave from the rest position to the crest; it determines the loudness of a sound.

Compressions

Areas on a longitudinal wave where particles are packed closely together, creating high pressure.

Rarefactions

Areas on a longitudinal wave where particles are spread apart, creating low pressure.

Wave Speed Formula

Speed is calculated as $\text{frequency} \times \text{wavelength}$; wavelength is $\frac{\text{speed}}{\text{frequency}}$; and frequency is $\frac{\text{speed}}{\text{wavelength}}$.

Electromagnetic Radiation

Waves generated by the continuous interaction of changing electric and magnetic fields traveling at right angles to one another.

Geostationary Satellites

Satellites located $35,800,km$ above Earth that stay fixed in their points and take $24$ hours to orbit.

LEO Satellites

Low Earth Orbit satellites located $160-2000,km$ above Earth that orbit every $90-120$ minutes and are used for two-way communication.

Open Circuit

A pathway where the continuous flow of electrical charges is broken by a gap.

Closed Circuit

A continuous pathway with no gaps, allowing electrical charges to flow.

Current

The rate at which electric charge flows past a point in a circuit, measured in amperes ($A$).

Voltage

The pressure that pushes electrons through a circuit, measured in volts ($V$).

Resistance

The natural opposition to the flow of electric current, measured in ohms (\text{\Omega}).

Alternating Current (AC)

An electric current where electrons constantly change direction; efficient for buildings and houses.

Direct Current (DC)

An electric current where electrons move smoothly in one direction from the negative to the positive terminal.

Why are radio waves useful for long-distance communication.

Radio waves have the longest wavelengths on the electromagnetic spectrum. Their range is between a piece of paper and larger than the planet, which makes them good for long distance communication. They can bend around objects with diffraction, and they can travel at the speed of light. 

How are digital signals sent around the world using satellites

Digital signals start at a phone, which is connected to a satellite dish, which sends the message/ communication to a satellite. The satellite then moves, and sends the information down to a ground station where the message needs to be received. The ground stations are connected to a cable network, which then sends the message to the receiver. 

How is information sent quickly around the globe using fibre-optic cables and compare fibre internet and satellite internet.

Information is sent through fibre optic cables by infrared light, reflecting off the inner surfaces of the optic cables. The information is coded with morse code like pulses, which is more efficient as there is less chance of misinterpretation. Both fibre optic cables and satellite internet travel at extremely fast speeds but fibre optic cables aren’t affected by extreme weather and are reliable. Satellite signals are widely available with limited equipment needed and can be used for communication after a natural disaster. Optic cables are limited in rural areas and are expensive/ need good infrastructure. Satellite signals can be affected by the weather and are a risk to creating more space junk. 

What are the various applications of radio-wave spectrum including microwaves and radio waves

The radiowave spectrum is the ‘low frequency’ part of the electromagnetic spectrum. Microwaves have long wavelengths and a low frequency, but not as low as radiowaves. Their wavelength scale is around the size of  dice. Radiowaves have the longest wavelengths, around the size of a football field. 

What are the various features of the electromagnetic spectrum. 

On the electromagnetic spectrum, we can only see the visible spectrum, which is a very small part of the spectrum. On the spectrum, the lowest frequency (highest wavelength) is shown to be radio waves, which then follows up the spectrum like a number line in the order microwaves, infrared waves, visible spectrum, ultraviolet waves, x-rays and gamma rays

Explain the relationship between amplitude and loudness, frequency and pitch of sound

Amplitude measures the energy of the wave, and the more amplitude the louder the sound. Amplitude determines the loudness (like how an amplifier increases sound). Loudness is measured in decibels (db). Frequency is measured in hertz (Hz), and measures how many waves pass through a fixed point per second. The pitch depends on the frequency, as the more vibrations (frequencies) there are per second, the higher the pitch. If the sound has a low frequency, the pitch will be low. 

the signs of a chemical reaction

The signs of a chemical change are a change in temperature (when heat isn’t added), change in colour, formation of a new gas, creation of a solid, release of sound/ light and disappearance of a solid.