Year 9

Forensics

Revision

Sheet

You should be able to recall the correct procedure for managing a crime scene and understand the roles of the First

Attending Officer (FAO) and Scene of the Crime Officer (SOCO) On discovery of, or following a report of a crime,

the crime desk sends out a police officer, the FAO, who makes an assessment of the scene and makes it secure. They

will also identify any hazards at the scene and even decide whether they are Physical, Biological or Chemical. The

FOA then calls for a SOCO who manages the scene because it could easily get damaged - by people curious to see the

scene, by someone involved in the crime tampering with evidence, by someone ‘framing’ a person tampering with

evidence - by damage from animals or weather if the crime scene is outdoors, or by damage by investigators as a

result of inappropriate entry to the scene. Then Photo's will be taken, evidence numbered and identified, descriptions

made and then wherever possible, everything is packaged and labelled.

Fingerprints are unique to each individual person. They can be used to help identify who may have been at the scene of

a crime. Friction ridge skin is found on the palms of the hands and the soles of the feet. These highly varied skin

patterns are formed when a person is still in the womb. No 2 prints or areas of friction ridge skin have ever been

found to be identical in over 100 years of collecting and recording. Fingerprints are individual and do not change over a persons life,

although they do get larger when you grow - the pattern will be the

same. There are lots of ways of collecting latent fingerprints 1. They can be photographed 2. Dusting powder: Carbon, Graphite or

Chalk can be used to show up invisible prints 3. Fluorescent powders

can be used with uv light 4. Superglue and other fuming chemicals

Different types of fibres may show observable differences, they can be used to solve crimes. The discovery of

material fibres on the body of a victim or on the clothes of a suspect can be used to match the clothes worn by the

attacker. The clothes themselves may contain other forms of evidence like bodily fluids or hair. The forensic

scientist using a microscope can make even a single head hair give information about the race, sex and age of its owner,

and while hair does not have the same individual character as a fingerprint, for at least the last 60 years it has been

considered vital.

What is in your blood? Plasma, Red Blood cells, White blood cells and Platelets. The first thing a forensic scientist must do to confirm that a

blood stain or mark is actually blood is a test called the Kastle-Meyer test - if positive then they can confirm that the sample is actually blood - this is called a presumptive test and it leads to other tests which can

establish if the blood is human or not. If it is, then a forensic scientist

will determine the blood group - everyone has a specific blood group. There are4 main Blood types: A, B, AB, & O. Each group can then be

either RhD positive or negative, so your blood group can be one of 8 types.

The genes you inherit from your mother and father determine your blood group. After that forensic scientists will

search for white blood cells from which they can extract DNA. Blood at the scene of a crime can also tell us lots more:

the height of the drop and the angle can affect the blood stain trail. Blood stain trails can point to the point of

impact where the blood is emitted and indicate the force of any blows that might have taken place.

Chromatography is the physical separation of a mixture into its individual components. It can be used to separate the

components of inks and dyes, such as those found in pens, markers, clothing, and even sweets. Chromatography can

also be used to separate the coloured pigments in plants or used to determine the chemical composition of many

substances. The forensic toxicologist is a scientist that may be employed to identify unknown pills that may be

recreational drugs or poisons. These can be identified using chemicals like Marquis reagent.

Painted surfaces are everywhere, so it is not surprising that paint is an important source of trace evidence. The most

common form of paint analysis comes from paint chip analysis in car accidents either from one car to another or, in

the case of a hit-and-run, from the car to the victim. Forensic scientists can use several different techniques to

analyse a paint sample. They could: 1. Analyse using a microscope 2. Match the different layer combinations 3. Use gas

chromatography to find out the chemicals in the paint 4. Use the DVLA registration database to find the car owner

Refraction is the bending of the path of a light wave as it passes across the boundary separating two different media

(materials). Refraction is caused by the change in speed experienced by a wave when it changes medium. We learned

that if a light wave passes from a medium in which it travels fast (like air) into a medium in which it travels slower

(like glass), then the light wave would refract towards the normal (N). If a light wave passes from a medium in which it

travels slow (relatively speaking) into a medium in which it travels fast, then the light wave would refract away from

the normal. Found in the nucleus of nearly all cells, DNA is a protein that

carries a code, the genetic code. This code makes you the type of

organism you are. Each cell in the human body contains 2 sets of

23 chromosomes, the chromosomes are made from DNA.

Reproductive cells only have one set. These combine to make a new

person with different genetic material to both parents. Each

person's DNA is unique except for identical twins. It is inherited so

there will be similarities in the DNA of family members. It can

provide crucial evidence in a criminal investigation – it is present in blood (in the white blood cells) or in other body

fluids, it may even be extracted from cells found at the base of hair fibres. Genetic profiling involves comparing crime

scene DNA with that from a suspect or with a profile stored in a database.

A forensic entomologist’s job may include: Identification of insects at various stages of their life cycle, such as eggs, larva, and adults. Collection and preservation of insects as

evidence. Determining an estimate for the postmortem interval or PMI (the time between

death and the discovery of the body) using factors such as insect evidence, weather

conditions, location and condition of the body, etc. Testifying in court to explain insect-

related evidence found at a crime scene. Forensic entomologists use their knowledge of

insects and their life cycles and behaviors to give them clues about a crime. For example,

Blow flies are attracted to dead bodies and often arrive within minutes of the death of

an animal whereas many beetle species tend to be found when the body is decomposing

Pollen can be used to link a suspect to the scene of a crime. If Pollen is found on clothing it can be another piece of

evidence to link a suspect with the scene of a crime. If there is no Pollen then a suspect's defense could argue that

he/she wasn’t there! This is called Forensic Palynology

Many different chemical compounds are used as Poisons. Many Non Metals like Arsenic are poisonous. Organic

compounds such as pesticides and plant & animal toxins are poisonous - Hemlock, Lily of the Valley. Certain Metals and

Metal Ions are poisonous including Lead Mercury and Thallium. Testing for Metal Ions involves a process called flame

testing, different metals produce different colour bunsen flames. Asecond test is to use precipitation which is

something that can happen when an insoluble solid is formed from two solutions that are mixed.

Alcohol alters behaviour, excessive use of alcohol can damage the liver and developing foetus. Alcohol is often a factor

in many criminal cases. If the Police think that a driver might be over the limit they may ask them to carry out a

breathalyser test. They have to blow hard into a breathalyser device. An air sample from deep inside the lungs is

tested for the concentration of alcohol.

At a crime scene, the unique imperfections on the surface of a tool or the sole of a shoe may be transferred to softer surfaces. This can help to identify the tool used. The nature of tool marks is

determined by the type of tool used, the hardness of the surface, the force applied, and the motion of one surface over another.

Investigators analyse the impression evidence to find unique characteristics to link shoes, tires, tools, and other objects found in a suspect’s possession to evidence at a crime scene.

Forensic Anthropologists analyse skeletal remains to determine the

identity of a victim as well as his/her life history, cause of death,

or other clues about a crime. DNA samples can be collected from

bone, teeth, and hair to provide clues to a person’s identity.

Scientists may also be able to gain clues as to a person’s past,

recent injuries, or the cause of death based on bone fractures and

other signs of trauma.

Y9 Space Summary Sheet

The solar system

The universe contains over 100 billion galaxies. A galaxy is a group of billions of stars. Our own galaxy is called

the Milky Way, and it contains about 300 billion stars (300,000,000,000) and one of these is our Sun.

Planets and other objects go round the Sun, and these make up the solar system, with the Sun at the centre.

The solar system contains different types of objects including:

a star - the Sun

planets, which go around the Sun

satellites, which go around planets

smaller objects such as asteroids and comets

Mercury to Neptune

There are eight planets in the solar system. Starting with Mercury, which is the closest to the Sun, the plan-

ets are:

Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune

If you can't remember the correct order, try this sentence, or make one up of your own:

My Very Easy Method Just Speeds Up Naming

Pluto and the dwarf planets

Scientists have discovered other objects orbiting the Sun. These include comets, asteroids and dwarf plan-

ets, like Pluto and Eris. Pluto used to be considered the ninth planet in our solar system. But in 2006 scientists

renamed it as a dwarf planet. So now we have 8 planets in the solar system.

Heliocentric model

People used to think that the Earth was at the centre of the universe, with everything going around it. We

now know that this is not correct. Scientific observations and space exploration show that the Sun is at the

centre of our solar system. The Earth and other planets go around it. We say that the planets are in orbit

around the Sun.

This model is called the heliocentric model. (Helios is the ancient Greek word for Sun.)

The Solar System and beyond

We live on a planet called the Earth. The Earth gets heat and light from the Sun. The Earth spins on its axis

once every 24 hours. The side of the Earth facing the Sun has daylight, and it is night on the side facing away

from the Sun.

The Earth orbits around the Sun. It takes one year to go around once. A year is actually 365.25 days long, so

every four years we have a leap year, when an extra day is added. The Moon is a satellite of the Earth. It orbits the Earth once every 28 days. This is called a lunar month. We can see the Moon because it reflects light from the Sun. The Moon seems to change shape during the

month. The different shapes are called phases of the Moon. The phases happen because we cannot always

see all of the part that is lit by the Sun. Sometimes the Moon blocks the light from the Sun. When this

happens we get a solar eclipse. If the Moon goes into the shadow of the Earth we get a lunar eclipse.

Moon

The Earth’s axis is tilted. When the northern hemisphere is tilted towards the Sun it is summer in the UK.

Days are longer than nights, and the Sun is higher in the sky. The Sun’s rays are more concentrated, so it

feels hotter.

Planets do not make their own light. We can sometimes see the planets because they reflect light from the

Sun. The Sun is a star. It is a ball of gas that gives out large amounts of heat and light energy. The Sun is like

the stars you can see in the sky at night. The stars do not look very bright because they are a lot further

away than the Sun. People often group stars into patterns called constellations. The Sun is one of millions of stars in our galaxy, which is called the Milky Way. There are millions of galaxies

in the Universe. The stars are a very long way from Earth. Scientists measure distances to the stars using light years. A light

year is the distance that light can travel in one year.

Gravitational forces

All objects are attracted towards each other by a force called gravity. Gravity only becomes noticeable when

there is a really massive object like a star, planet or moon. You can find out more about gravity in the Revision

Bite called Forces.

Gravity and the solar system

Gravitational forces between the Sun and planets keep the planets in orbit around the Sun. Without these

forces, the planets would fly off into deep space.

Their orbits are slightly squashed circles called ellipses. Diagrams often show the orbits as very squashed,

but this is just to get a sense of perspective and to fit the diagrams onto the page.

The planets furthest out are also the coldest because they receive the least heat energy from the Sun.

Orbit times and speeds

Planets that are further from the Sun:

move more slowly

take more time to complete an orbit

For example, Mercury, the closest planet to the Sun, takes just 88 Earth days to complete an orbit. But Nep-

tune, the furthest out, takes 164 Earth years to complete an orbit.

Y9 Food Science Summary

Sheet

We can do tests to find out which substances are in foods. For example, starch makes iodine solution go a

blue–black colour.

Nutrition information labels on foods tell us what the food contains. The labels also tell us how much chemical

energy is stored in the food. The amount of energy is measured in kilojoules (kJ).

Eating too much of some foods can cause problems. Too much fat may cause heart disease.

Vitamins Vitamins are needed in very small amounts for growth and health. The main vitamins are vitamin A, the B

complex of vitamins, vitamin C and vitamin D.

Microbes & Food Bacteria and yeast are important in making foods and drinks. Yeast is used to make bread dough rise. It

uses oxygen, from the air found in pockets in the dough, for aerobic respiration.

This process produces carbon dioxide which makes the bread rise.

Yeast are also used to make beer and wine. In this case there is no air and so they use anaerobic

respiration. When yeast use anaerobic respiration it is called fermentation.

The ethanol is a waste product of this reaction.

Feeding relationships Food chains and food webs show the feeding relationships between different organisms in a habitat.

The numbers of organisms at each level in a food chain can be shown as a pyramid of numbers. The size of

the bars shows the number of organisms. Usually there are fewer organisms as you go along a food chain

because energy is lost at each level, for example, for movement. sometimes the pyramid has an unusual

shape if the organisms are very different in size.

e.g. grass → caterpillar → robin → sparrowhawk

rose bush → aphids → ladybirds

Farming methods

Intensive farming practices include growing high-yield crops, using fertilisers and pesticides and

keeping animals indoors. Food production is increased but there are unwelcome side effects.

Organic farming bans chemical inputs and has a less harmful effect on the environment but of-

ten produces less, more expensive food.

Y9 Rockshow Summary

Sheet What are waves?

Amplitude

As waves travel, they set up patterns of disturbance. The amplitude of a wave is its maximum

disturbance from its undisturbed position. Take care, the amplitude is not the distance

between the top and bottom of a wave.

Amplitude and wavelength

Wavelength

The wavelength of a wave is the distance between a point on one wave and the same point on

the next wave. It is often easiest to measure this from the crest of one wave to the crest of

the next wave, but it doesn't matter where as long as it is the same point in each wave.

Frequency

The frequency of a wave is the number of waves produced by a source each second. It is also

the number of waves that pass a certain point each second. The unit of frequency is the hertz

(Hz). It is common for kilohertz (kHz), megahertz (MHz) and gigahertz (GHz) to be used when

waves have very high frequencies. For example, most people cannot hear a high-pitched sound

above 20kHz, radio stations broadcast radio waves with frequencies of about 100MHz, while

most wireless computer networks operate at 2.4GHz.

Sound waves are longitudinal waves that must pass through a medium. Echoes are reflections of

sounds.

Light and other forms of electromagnetic radiation travel as transverse waves. These waves

can travel through a vacuum, and they all travel at the same speed in a vacuum.

Vibrations

When an object or substance vibrates, it produces sound:

the greater the amplitude, the louder the sound the greater the frequency, the higher the pitch.

These diagrams show snapshots from oscilloscope traces of three sounds.

Sounds 1 and 2:

the sound waves have the same frequency, so the sounds have the same pitch sound 2 has a greater amplitude than sound 1, so sound 2 is louder.

Sounds 2 and 3:

the sound waves have the same amplitude, so the sounds have the same loudness sound 3 has a greater frequency than sound 2, so sound 3 is higher pitched.

Light Objects which create light are luminous sources. Light travels in straight lines. Light waves travel through

transparent objects but not through opaque objects. Shadows are made because light cannot travel

through opaque objects. Translucent objects show a glow of light through them.

Reflection

Light rays are scattered by rough surfaces, and a reflection cannot be seen. A plane mirror is a flat mirror. Light is reflected evenly by a plane mirror.

The angle of incidence is equal to the angle of reflection. When light shines on to an object viewed in a mirror, the

rays are reflected into the eye. They seem to come from a

position behind the mirror. The image is the same size as

the object and the same distance from the mirror. In the

image left is right and right becomes left.

Refraction

When light hits something transparent it changes direction. This is called refraction. Refraction takes

place at the interface between two substances. When light is transmitted through glass it slows down and

bends towards the normal. When it travels back out it speeds up again and bends away from the normal.

Colour White light is a mixture of colours. White light can be split up using a prism to give a spectrum of seven

colours (red, orange, yellow, green, blue, indigo, violet). The splitting of colour into a spectrum is called

dispersion.

A rainbow is produced when water droplets in the air refract sunlight. Different colours can be made by

mixing light of the three primary colours (red, green and blue). Coloured light can be made using a filter. A

red filter lets red light through, but absorbs all the other colours.

We are able to see colours because objects do not reflect all the colours in light:

White objects reflect all the colours. A red object only reflects red and all other colours are absorbed.

This idea applies to all colours except black. Black objects absorb all colours.

Resistors Resistors restrict or limit the flow of current in a circuit. The ability of a material or component to

resist current flow is measured in ohms. There are three main types of resistor:

fixed resistors

variable resistors

special resistors, such as thermistors and light-dependent resistors (LDRs)

How does a Loudspeaker Work?

The loudspeaker uses a coil which can slide backwards and forwards over the central pole of

a circular permanent magnet. The coil is joined by the brown bars to a paper cone, shown below.

The wire from the amplifier carries an alternating current which makes the coil (and the paper

cone) move backwards and forwards at the same frequency as the changing current. The paper

cone then moves the air backwards and forwards which creates the sound.

Pressure

You may get told off if you swing around on one leg of a chair instead of sitting properly. Apart from

the risk that you will damage the chair or hurt yourself, the chair leg can damage the floor. This is

because it puts too much pressure on the floor.

Working out pressure

To work out pressure, we need to know two things:

1. the force or weight applied

2. the area over which the force or weight works.

This is the equation for working out pressure:

pressure = force ÷ area

Pressure can be transmitted through liquids. In hydraulic machines, exerting a small force over a small

cross-sectional area can lead to pressure being transmitted, creating a large force over a large cross-

sectional area. This ability to multiply the size of forces allows hydraulics to be used in many

applications such as car-braking systems.

Worked example

Study the diagram of the hydraulic jack. Calculate the force on piston B.

Step 1: Calculate the pressure of the liquid inside piston A

Force in piston A = 30 N

Cross-sectional area in piston A = 0.2 m2

Pressure = force ÷ cross-sectional area

Pressure = 30 ÷ 2 = 150 Pa

Step 2: Change the subject of the equation to find the force in piston B

Remember that the pressure within this closed system is transmitted equally in all directions.

Therefore the pressure in piston B is also 150 Pa.

Cross-sectional area in piston B = 1.0 m2

force= pressure × cross-sectional area

force = 150 × 1.0 = 150 N

In this example, the hydraulic jack can lift load forces five times greater than the effort force put in.

Applications of hydraulics

It takes a large force to slow down or to stop a car that is travelling at speed.Hydraulics are used in

the braking system of a car. They cause a relatively small force from the driver’s foot to be multi-

plied to produce a greater force, which acts equally on all four brake pads.