Chemistry CT3+4 revision

independant variable

What you change

Dependant variable

What is being measured

Control variable

What stays the same

What do you use a bar chart for?

Discrete data - can only take certain values e.g. shoe size, Categoric data - e.g. type of shoe

What do you use a scatter graph for?

Continues data - can take any value within a range e.g. water temperature

Precision

Measurements have high precision if repeats are close together

Accuracy

Measurements are accurate if they are close to the true value

Instrument precision

An instrument gives more precise readings if the scale graduations are smaller

How can someone improve their accuracy?

• Choice of method

• Measure using larger amounts

• Repeat readings

How can someone improve their precision?

• Identify the control variables and keep them constant

• Use more sensitive measuring instruments

What is the meaning of wavelength?

The distance between one wave peak and the next wave peak along the path of a wave.

What is the meaning of frequency?

The number of wave peaks that pass a point in one second (Number of oscillations per second).

What is the meaning of amplitude?

The maximum displacement of the wave from the rest position.

What is the meaning of time period?

The time taken for a source to produce one wave.

Label this diagram

Labelled diagram

What’s the units of measurement for wavelength?

Metres

What’s the units of measurement for frequency?

Hz

1 kilohertz = 1kHz = 1 000 Hz

1 megahertz = 1MHz = 1 000 000 Hz

1 gigahertz = 1GHz = 1 000 000 000 Hz

1 terahertz = 1THz = 1 000 000 000 000 Hz

What’s the units of measurement for wave speed?

Metres per second (m/s)

What’s the units of measurement for time period?

Seconds (s)

What's the symbol for wave speed

V

What’s the symbol for wavelength

λ

What’s the symbol for frequency

f

equation for wave speed using frequency and wavelength

v = f x λ

equation for frequency using wave speed and wavelength

f = v / λ

equation for wavelength using wave speed and frequency

λ = v / f

equation for time period using frequency

1/f

equation for frequency using time period

1/t

what is a transverse wave

The direction of vibrations at 90 degrees to the direction of energy transfer

what is a longitudinal wave

the vibrations of the particles are parallel to the direction of energy transfer

examples of transverse waves

• ripples on the surface of water

• vibrations in a guitar string

• a Mexican wave in a sports stadium

• the waves on the electromagnetic spectrum

examples of longitudinal waves

• sound waves

• ultrasound waves

What is a wavefront

an imaginary line or surface representing all points on a wave that are in the same phase (e.g., all crests or all troughs) at a specific time

Waves do or don’t transverse energy

Do

Waves do or don’t transverse information

Do

Waves do or don’t transverse matter

Don’t

What does it mean by light is a part of a continuous spectrum

that white light is not just one thing, but a smooth, unbroken blend of all the colours of the rainbow—from red to violet—merged together.

Is light part of a continuous or non continuous spectrum

Continuous

What is the order of the electromagnetic spectrum with the wavelength decreasing and the frequency increasing (including the colours on the visible spectrum)

Radio waves, microwaves, infrared, visible light (red, orange, yellow, green, blue, indigo, violet), ultraviolet, x-rays, gamma rays

What and why are radio waves used for?

Communication: Broadcasting TV, radio, and satellite transmissions, and they are used because of their ability to travel through the air, space and solid materials, meaning they can be used for radiocommunication.

What and why are microwaves used for?

Communication in mobile phones and satellites, and for cooking food. High frequency microwaves have frequencies which are easily absorbed by molecules in food. The internal energy of the molecules increases when they absorb microwaves, which causes heating. Microwaves pass easily through the atmosphere, so they can pass between stations on Earth and satellites in orbit.

What and why is infrared used for?

Night vision equipment, cooking, thermal imaging, and remote controls for TV. it's relatively inexpensive to implement, which contributes to its widespread use in consumer electronics. Furthermore, infrared signals are secure, as they typically require line-of-sight communication, reducing the risk of interception or interference.

What is visible light used for?

Light-sensitive cells in eyes and by photographic film.

What and why is ultraviolet used for?

Fluorescent lighting and security marking for bank notes. Ultraviolet light is used because it causes certain materials to fluoresce (glow), making it useful for fluorescent lighting and for revealing hidden security markings on banknotes to make banknotes hard to fake.

What and why is X-rays used for?

To observe the internal structure of objects in engineering, airport security, and medicine. X-rays are used because they can pass through soft materials but are absorbed by dense materials, allowing images of internal structures to be formed.

What and why are gamma rays used for

To sterilise medical equipment and food, and radiotherapy. Gamma rays are used because they have high energy and can kill cells and microorganisms, making them useful for sterilisation and for treating cancer in radiotherapy.

What are some harmful effects from radio waves

No damage

What are some harmful effects from micro waves

Burns to human tissue

What are some harmful effects from infrared

burned by infrared radiation

What are some harmful effects from visible light

Eye damaged to exposure from very bright lights

What are some harmful effects from ultraviolet

Sunburn, skin cancer, and cataracts

What are some harmful effects from X-rays

Ionising radiation leading to cancer

What are some harmful effects from Gamma rays

Ionising radiation leading to cancer

What are some simple protective risks we can do to protect ourselves from the damage of radio waves

Nothing - no damage

What are some simple protective risks we can do to protect ourselves from the damage of microwaves

microwaves: burns to human tissue
protection: keep a safe distance from microwave sources, do not use damaged microwave ovens, ensure doors are properly sealed, follow safety instructions when using devices that emit microwaves

What are some simple protective risks we can do to protect ourselves from the damage of infrared

infrared: burned by infrared radiation
protection: avoid prolonged exposure to strong heat sources, wear protective clothing, use heat-resistant gloves, keep a safe distance from hot objects

What are some simple protective risks we can do to protect ourselves from the damage of visible light

visible light: damage to eyes (especially very bright light such as lasers)
protection: do not look directly at very bright lights or lasers, wear protective eyewear when needed, reduce exposure to intense light sources

What are some simple protective risks we can do to protect ourselves from the damage of ultraviolet

ultraviolet: damage to surface cells, sunburn, increased risk of skin cancer, eye damage (can lead to blindness)
protection: wear sunscreen, wear protective clothing, use sunglasses, avoid direct sunlight for long periods, stay in the shade

What are some simple protective risks we can do to protect ourselves from the damage of X-rays

x-rays: damage to cells, increased risk of cancer
protection: limit exposure, use shielding such as lead, only use when necessary, wear protective equipment

What are some simple protective risks we can do to protect ourselves from the damage of Gamma rays

Gamma rays: damage to cells, increased risk of cancer
protection: limit exposure, use shielding such as lead, only use when necessary, wear protective equipment

when should you use a curve or a line of best fit in an investigation

If you can see a pattern in the data but it is not linear, then you should draw a curve of best fit.

are all electromagnetic waves transverse or longitudinal

transverse because the vibration direction is perpendicular to the direction of energy transfer.

Do all electromagnetic waves travel at the same speed - and if so what speed

All electromagnetic waves travle at the same speed (3×10^8 m/s) in a vacuum (air).