Form a Gas

Inflate a balloon without blowing into it, or using a pump! You can do this by making a gas and then getting it to go into a balloon. The gas is called carbon dioxide. It is this gas which forms the bubbles in soda water and fizzy drinks.

Materials:
1. Vinegar
2. Sodium Bicarbonate
3. Balloon
4. Funnel
5. Narrow-Necked Bottle

Procedures:
1. Pour some vinegar into the narrow-necked bottle until it is about a quarter full.
2. Using the funnel, fill the balloon with sodium bicarbonate powder.
3. Stretch the neck of the balloon over the neck of the bottle. Do not let the sodium bicarbonate escape from the balloon.
4. Lift the balloon so that the sodium bicarbonate falls into the bottle. The vinegar begins to fizz and the balloon slowly starts to inflate. The vinegar reacts with the sodium bicarbonate to release bubbles of carbon dioxide gas. As more as gas forms, its pressure increases and the balloon expands.

Exploding drink
Shake a bottle of fizzy drink then unscrew the cap. The drink fizzes up out of the bottle! Carbon dioxide gas is dissolved in the water in the drink. It is kept under pressure in the bottle. When you unscrew the cap, you reduce the pressure and the gas bubbles up out of the water.

Discovery the Gasses in the Air

Put out the candle without blowing on it or touching it. When you do this experiment, you show that air is a mixture of invisible gases. One of these is especially important. It is oxygen which is used when things burn and produce energy.

Materials:
1. Candle
2. Coloured water
3. Glass jar
4. Bowl and Candle holder

Procedures:
1. Put the candle in the holder and place it in the bowl. Then pour in the water.
2. Ask an adult to light the candle. Then place the jar over it. Leave it for a little while.
3. At first, the water level in the jar rises, and then the flame suddenly goes out!

Air and Energy
Like other cars this racing car gets its energy from petrol burning in its engine. Burning fuel provides most of the energy we use for heating and powering machines. This process uses oxygen, which comes from the air around us.

Weight Some Air

When something is very light, people often say “It’s as light as air”. But air is not light at all. Do this simple experiment to show that air is really quite heavy.

Materials:
1. Balloon pump
2. Two balloons
3. Rubber band
4. Two Drawing Pins
5. Long thin piece of wood
6. Ruler
7. Pencil
8. Sticky tape
9. thread

Procedures:
1. Use the ruler to find the centre of the wood. Then mark it.
2. Push a drawing pin into each side at the centre mark.
3. Tie the thread to the middle of the rubber band.
4. Fix the loops of the rubber band around the drawing pins. Lift the wood by the thread. It should balance.
5. Tape one of the balloon to one end of the wood.
6. Tape the second balloon to the other end of the wood. Check that it still balances. Then remove one balloon and blow it up.
7. Tie the neck of the blown-up balloon and attach it to the wood in the same place as before. The balloon make the wood lose its balance.


Drinking with a straw.
When you drink through a straw, the weight of the air helps you. The air above the drinks pushes on the surface of the liquid. As you suck, it forces the liquid up through the straw to your mouth.

Dragon

Dragon by The Tail

Player line up one behind the other grassping the waist of the person in front. The person at the front of the dragon has to try to touch the person at the end of the tail, dragging the dragon as he or she tries to do so. Anyone who lets go is out of the game.
When the person at the front succeeds in touching the person at the end, he or she goes to the end of the line and the next person becomes the head.


Dragon Tiggy
When a person is tagged by ‘he’, the two join hands and so on until all players are joined to form one long dragon.

Dragon Board Game
Make a board game to follow the sequence of a favourite dragon story. Or, make a ‘dragons and ladders’ game. Or make a trail game to find the dragon’s treasure. Or, make up a variation of Battles.

Tailing a Suspect

Sometimes during an investigation, a detective has to tail, or follow, a suspect. The suspect may make contact with other suspects or might lead the detective to more evidence. Try the following activity at school or another safe location to test your ability to tail a person.

Materials

- Notebook
- Pen or pencil
- Watch
- Several helpers


Procedure
1. Gather several helpers together. Inform them that at some point during the next week, you are going to tail one of them as part of an experiment. (Telling them that you are going to tail them makes your task more difficult but will avoid their embarrassment.)
CAUTION: Tail the person at schol or in another safe location, such as a party. Never wander around alone.
2. Choose a day and select one person to follow for one hour. Use your notebook to record notes of his or her activities and any people the person encounters. Record the time for all notes you make.
3. When you have finished tailing the person, review your notes. Are there any activities that surprised you? Could you tell exactly what happened during each encounter with other people? Did the person figure out that you were tailing him or her?

More Fun Stuff to Do

Detectives seldom follow a suspect by themselves. They usually work in teams to prevent the suspect from getting suspicious. Often a second, third or even a fourth detective will pick up the trail where the previous detective leaves off. Try using a team to trail one of your helpers.

Explanation

It is difficult to tail a person without being noticed. If a suspect sees the same person, especially a stranger, over and over again, the suspect’s brain is alerted that something out of the ordinary has happened. He or she will become more cautious and will try to see whether someone is indeed tailing him or her. This is why the police use teams to follow suspects. One person will follow the suspect for a short time, then a second, third, or eve a fourth detective will pick up the trail. The suspect does not see the same person, so the suspect’s brain is not lerted that something unusual is happening.

Tailin a suspect is a form of surveillance. The term surveillance comes from the French word surveiller, which measn “to watch over.” Police practice surveillance for many reasons. They may watch a suspect’s home or place of work in order to gain information or even to catch the suspect. This is sometimes called a stakeout. They may trail a suspect to get other information, such as a suspect’s habits, daily routine, personal contacts, and place of work, home address, or type of information used.

The detective can be use the information gathered from observing a suspect to form a hypothesis or theory about the suspect, just as a scientist uses information to form a hyphotesis about an experiment. For example, if a suspect meets with the same person ath the same time every day and is seen passing slips of paper to that person, then the detective might make the hypothesis that the suspect is involve in a gambling operation and that the slips ofpaper are betting slips. The detective will then continue to investigate to determine whether that hypothesis is correct, in the same way that a scientist will test a hypothesis through experimentation.

Interviewing Witnesses

During an investigation, much of a detective’s time is spent interviewing witnesses and questioning suspects. If everyone tells the same story, a detective can feel confident that he or she has learned the truth about a crime. But often people lie, or they believe they are telling the truth but are mistaken. Try the following activity to see how good you are at interviewing witnesses.

Materials

- Copy of the picture on crime scene
- Watch or clock
- Pen or pencil
- Notebook
- Several helpers

Procedure

1. Have all of your helpers but one leave the room.
2. Give a copy of the picture on crime scene to the helper.
3. Using the watch or clock, give your helper 1 minute to look at the picture, than take the picture away.
4. Ask your helper what he or she remembers about the picture. Ask questions like “How many people were in the picture?” or ”Was there anything unusual that you noticed?” Record the answers in your notebook.
5. Repeat the procedure with each of the remaining helpers, making sure that the helpers do not hear each other’s answer to your questions.
6. Compare the comments that the helpers made. How many details were mentioned? Did some statements conflict with other statements?

More Fun Stuff to Do

Stage a pretend crime during a party or family gathering, and see wether any of the guests can figure out who did it. You could have someone “steal” some books off a shelf or remove a candlestick. At some point after the crime, choose several guests as witnesses and question each in a separated interview. How did their observations compare? Were their observations good enough for them to figure out who took the books?

Explanation

When interviewing witnesses to a crime, there are several questions that detectives ask to get a description of and information about the suspect. Some typical questions include: What is the sex, race, and approximate age of the suspect? What is his or her height, weight, color of hair and eyes, and complexion? Did you notice any physical scars or marks? Did the suspect wear glasses or have facial hair? What was the voice like? What was the suspect wearing? What did the suspect do?
Interviewers must listen for unexpected information. Often the question will cause the person who is being interviewd to implicate another person, meaning the person will reveal, by accident or on purpose, that someone else was involved in the crime.

Interviewers should remain impartial when they interview witnesses. This means they should not reveal their own opinions or feelings during the interview. Also must be careful not to lead a witness to say something that is not true.

Interviewing witnesses and other methods of crime detection are similar to scientific investigation in general. Scientist brings their own thougts and opinions to their experiments. Often they want an experiment to turn out a particular way, so it is difficult for them to remain impartial. This explains why two scientists, seeing the same information, can come to two opposite conclusions. Each bends the information to support his or her own views. Whether investigating crimes orperforming experiments, scientists must always keep an open mind and be ready for unexpected data.

The Scene of the Crime

It’s no exaggregation to say that following proper procedures during the first investigation of the crime scene can make the difference between a solved crime and an unsolved one. Try the following activity to learn some of the procedures performed at the scene of a crime.

Materials

- Your bedroom or another room of your house
- Several sheets ofwhite paper
- Marking pen
- Masking tape
- Pen and/or pencil
- Notebook
- Camera (optional)
- Tape measure
- Several plastic bags

Procedure

1. Pretend a crime has been commited in the room you’ve selected. Suppose something has been stolen from the room.
2. Secure the scene of the crime. With a sheet ofpaper and themarking pen, make a sign that reads, POLICE INVESTIGATION, DO NOT ENTER.Use the masking tape to tape the sign across the entrance to the room.
3. Begin to record your observations of the room in your notebokk. Remember, when investigating a crime scene, you cannot knowwaht is important and what isn’t. You need to record everything you find. If you have a camera, take severalpicture of the room.
4. Use another sheet of paper and the pencil to make a sketch of the room. Measure the dimensions of the room using the tape measure, and record the measurements in the sketch. Draw in window and door locations and the placement eny funiture.
5. Examine the roomcarefully. Record your observations in your notebook. Add to your room diagram the location ofany important items you find.
6. Begin to look for physical evidence may include hair and fibers, a glass or other object that could contain fingerprints, a diary or notebook, or anything else you think might be important. Examine the wastebasket. What do its contents tell you?
7. Save each piece of physical evidence in a plastic bag to examine later using the procedurs you’ll learn.

Explanation

The first duty at the crime scene is to secure the scene of the crime. This is usually done by the first police officer to arrive. If a person is badly injured at the scene, the officer will give assistance and call for medical aid.

Many crimes are investigated by the police officer on duty, but in more serious crimes, such as those that involve serious injury or the loss of expensive objects, a detective is often assigned to the case. A detective has usually received additional training, beyond that given to a police officer, in how to investigate a crime. When the detective arrives, he or she begins to record the scene of the crime by taking photographs, making sketches of the site, and taking notes.

The detective or members of a special forensic scinece team collect physical evidence. Physical evidence cololected from the scene of the crime is stored in labeled bags or containers, and then sent to the forensic science laboratory for later investigation.

The investigators at the crime scene must be very careful to collect and preserve allphysical evidence and to record all of their observatios. These data will be used later to solve the crime.

Detective Science in Action

You never know when something unusual found at the scene of a crime will be important to an investigation. In 1994 Dr. Gail Anderson, a forensic entomologist (a scientist who studies insects), was asked to aid wildlife enforcements officials who were trying yo put a stop to poaching (the killing of wildlife either without a license or out of season). In British Columbia, Canada, poachers often kill black bears and take their gallbladers, small internal organs that are valuable in certain cultures.

Investigators found insects on several black bears that had been killed by poachers. Dr.Anderson knew that insects have specific stages of development, from egg to adult. By examining the stage of the insect’s development and working backward, she was able to approximate the actual date the bears were killed. Wildlife officials could then focus their investigation on individuals who were in the area on that day. The insects found on the bear’s eventually led to the arrest of the poachers.

Mystery Box

Good observation skills involve all the scenes (the ability of the brain and nerves to react the world around us through sight, hearing, smell, touch, and taste). Sight is just one of the senses. What a forensic scientists, detective, or witness hears, smells, feels, or tastes may also be important clues. Try the following investigation to sharpen your nonvisual observationn skills.

Materials

- empty shoe box or similar box with lid
- various objects made from different materials-such as a rubber ball, a roll of toilet paper, a metal jar lid, a bar of soap, a plastic toy, a piece of fruit such as an apple, banana, or orange, etc—gathered by your helper with out your knowledge
- helper

Procedure

1. Leave the room.
2. Have your helper put several of objects in the shoe box and put the lid in place.
3. Return to the room and, without opening the box, try to guess how many objects are in the box and what the objects are made of. If possible, guess what the objects are. You can tilt, gently shake, and smell the box to help you.
4. After you have made your predictions, open the box and see how well you did. What objects were the easiest to determine? What objects were the hardest to determine?
5. Repeat the activity with other objects. Give your helper a turn at guessing.

More Fun Stuff to Do

To develop your sense of touch, have a helper first blind fold you and then put several objects in front of you. Touch the objects, but do not pick them up. Can you identify them? Without removing the blindfold, pick upthose that you could not identify. Can you tell what they are now? Remove the blindfold and see how well you did. Repeat the activity with other materials, but this time have your helper wear the blindfold.

Explanation

Forensic scientists and detective must use all five of their sense when investigating a crime. They often use the sense of sight to observe the scene of the crime and record what they see. But often the other four senses--hearing, smell, touch, and taste--will give a forensic scisntist information that may or may not be important evidence or clues. For example, that faint smell or bitter almond in a dringking glass might mean cyanide poisoning. Three loud bangs heard by witnesses could be gunfire or just a car misfiring.

Here is an exercisethat you can use to improve your other senses. Sit on a park bench on a warm spring day. Close your eyes and observe what is happening around you. Can you identify five sounds that you hear? Can you identify three smells?

You Are The Detective

Your mother picks you up from school one afternoon. Before returning home, she has to stop at the bank to make a deposit. The two of you stand in line at the bank, waiting for your mother to be helped. Suddenly, one of the tellers screams, “We hav been robbed!” What did you see while you were standin in line that might help with the investigation of the crime? Use your powers of observation to see what you remember.

Materials

- Picture on the stage
- Timer
- Pen or pencil
- Paper

Procedure

1. Observe picture on the stage for exactly 30 seconds. Look at everything that you thing might be important.
2. After 30 seconds, cover the picture and answer the question below. Write the answers on the sheet of paper.
3. How observant were you? Compare your answer to the picture.

Questions

1. What time was it on the clock?
2. What was the date?
3. Describe the person at the front of the line. Was it a man or a woman? Was he or she wearing a hat? What kind of clotes was the person wearing? Could you tell how tall the person was? Did he or she have any distinguishing features?
4. Did you notice anything unusual in the picture?

More Fun Stuff to Do

Repeat the activity, but this time put the picture away overnight and try answer the questions the next day. How good is your memory of the picture after 24 hours?

Explanation

When you observe, you create in your mind images of what you see. But what you see also has to be transmitted to your brain and stored in order for you to remember it later. As you found out in this activity, there is a lot of room for error in this process. When you first observed the picture, maybe you didn’t notice certain details. Or may be you saw details but didn’t think they were important to make a point of remembering them.

If you did More Fun Stuuf to Do activity, you also know that time affects memory. Much of what we observe is stored in our short-term memory, and we remember it only for a few hours, or may be only a few minutes.

If we store observations in our long-term memory, however we may remember them for years. Repeating something over and over help us remember it. Another helpful way to remember something is to associate it in our minds with something else. For example, most people would not be able to draw a map of Poland from memory. But if asked to draw a map of Italy, many people would be able to draw a fairly good sketch. Why? Because the shape of Italy resembles a boot. The shape of Italy sticks in our mind because we associate it with a common shape.

You can improve your powers of observation by doing the following exercise. Look at a department store display window for 30 seconds, then turn away and write down everything that you saw. Compare your notes with the real thing and write down the items that you left out. If you keep practicing this, your powers of observation will greatly improve.

Counterfeiting

We all know what dollar bill looks like, but how many of us have really examined one carefully? Trythe following activity to investigate how fake bills, called counterfeit bills, are detected.

Materials

- picture of counterfeit bill
- $1 bill
- pencil
- paper

Procedure

1. There are at least twelve things wrong with the $1 bill on the sample. Examine the picture and see how many errors you can find. Write down your answers.
2. After you have found as many errors as you can, compare the picture to the real $1 bill. Write down any additional errors you notice.
3. Compare your answers with the list on the next page. Did you find the more errors listed?

Explanation

To counterfeit means to make a copy of something with the intent to trick or deceive. It used to be very difficult to counterfeit paper muney. The counterfeiter had to make special plates, or replicas, of each side of the bill being counterfeited. There were many places where mistakes could be made. The wrong hair on the president or an error in the serial number could ruin moth of work.

With the rise of color copiers, however, counterfeiting money is now easier. New high-speed, high-quality laser copiers are a quick and simple way to duplicate money. To combat counterfeiting on this new generation of copiers, the U.S government is now printing money on special paper that can’t be purchased by anyone but the government. Counterfeit money will not only look different, but feel different, too. The Canadian government has begun using a high-tech solution to stop counterfeiting. They’ve started placing holograms on their money, similar to the ones on credit cards.

There are many document besides paper money that can be counterfeited. With the aid of copiers, payroll and other checks are commonly forged. But even nonpare items, such as credit cards, can be copied. As with money, holograms have been added to credit cards to make them harder to forged. And special dyes that can only be seen under ultraviolet light are used to add pictures and words to the front of the credit card.

Slant Analysis

The slant of a signature is another way to compare handwriting. Perform your own slant analysis to master the technique.

Materials

- pen or sharp pencil
- sheet of white paper
- sheet of tracing paper
- ruler

Procedure

1. Write your name two times on the sheet of white paper.
2. Place the tracing paper over your signature.
3. Use the ruler to make a slash through each letter in each signature so that each slash has the same slant as the letter.
4. Compare the two series of slanted lines. Are they similar?

More Fun Stuff to Do

Write your name on another sheet of paper. Have a helper forge your signature below your real signature. Make a slant analysis. How do the two signatures compare? Could this methode of handwriting analysis prove that your helper’s signature was forged?

Explanation

All four methode of handwriting analysis--top-of-letter, bottom-of-letter, spacing, and slant—help forensic scientists examine and compare handwritten documents. Often forensic scientists perform several forms of analysis on the same handwriting to confirm that it is a forgery. These methodes can be done more accurately by using computers. A sample signature can be scanned and placed in the computer’s memory for later comparison.

Detective Science in Action

One of the most famous kidnapping cases in the United States happened in 1932 when the baby son of Colonel and Mrs. Charles Lindbergh was kidnapped. Colonel Lindbergh was the first person to make a solo airplane flight across the Atlantic and was widely considered a hero. The conviction of Bruno Richard Hauptman, arrested for kidnapping the Lindbergh baby, was based in part on the testimony of handwriting experts. They compared the writing on the ransom note with handwriting samples that the police obtained from Hauptman after his arrest.

Spacing Analysis

Experts also compare the spacing between words and letters to analyze and identfying handwriting. Try a spacing analysis to see how this technique is done.

Materials

- pen or sharp pencil
- sheet of white paper
- sheet of tracing paper
- ruler

Procedure

1. Write your name two times on the sheet of white paper.
2. Place the tracing paper over your signature.
3. Make a small mark on the tracing paper at all of the low points of the beginning and ending of each letter in each signature.
4. Use the ruler to join the righmost mark of each letter to the leftmost mark of the next letter for each signature, creating a series of short lines between the letters.
5. Compare the two sets of lines. Are they similar?

More Fun Stuuf to Do

Write your name on another sheet of paper. Have a helper forge your signature below your real signature. Make a spacing analysis. How do the two signatures compare? Could this methode of handwriting analysis prove that your helper’s signature was forged?

Bottom-of-Letter Handwriting Analysis

Another way to analyze handwriting is to analyze the bottom of the letters.

Materials

- pen or sharp pencil
- sheet of white paper
- sheet of tracing paper
- ruler

Procedure

1. Write your name two times on the sheet of white paper.
2. Place the tracing paper over your signature.
3. Make a small mark on the tracing paper at all of the low points of each letter in each signature.
4. Use the ruler to join each mark to the one next to it, creating a zigzag line across the bottom of each signature.
5. Compare the two zigzag lines. Are they similar?

More Fun Stuff to Do

Write your name on another sheet of paper. Have a helper forge your signature below your real signature. Make a bottom-of-letter analysis. How do the two signatures compare? Could this method of handwriting analysis prove that your helper’s signature was forged?

Top-of-Letter Handwriting Analysis

Each person’s style of handwriting is unique and can be identified, often even if a person is trying to disguise his or her handwriting. Try the following activity to see one way handwriting is analyzed.

Materials

- pen or sharp pencil
- sheet or white paper
- sheet of tracing paper
- ruler

Procedure
1. Write your name two times on the sheet of white paper.
2. Place the tracing paper over your signature.
3. Make a small mark on the tracing paper at all of the high points of each letter in each signature.
4. Use the ruler to join each mark to the one next to it, creating a zigzag line across the top of each signature.
5. Make a top-of-letter analysis by comparing the two zigzag lines. Are they similar?

More Fun Stuff to Do

Write your name on another sheet of paper. Have a helper forge (copy with the intent to deceive) your signature 1 to 2 inches (2.5 to 5 cm) below your real signature. Make a top-of-the-letter analysis of the two signatures. How do they compare? Could this method of handwriting analysis prove that your helper’s signature was forged?

Explanation

An individual’s handwriting depends on several things, such as the brain, the eye, and the hand of the individual. It is affected by a person’s physical and emotional well-being, the position in which he or she is writing, and circumstances that might influence speed. Normally, a person’s handwriting will be slightly different from signature to signature. So, is a series of signatures on checks are exactly the same, it may indicate that someone forged the signatures by copying or tracing them. If the signatures are very different, however, this can also indicate that the signatures are fakes.

A signature in often all that is needed to withdraw money from a bank account, to write a check, or to make a purchase with a credit card. These are most common situations in which forgery, the act of falsifying documents, occurs. Every year, millions of dollars are lost to forgeries. Forgeries are found by comparing the signature in question with a known example of a person’s handwriting. For example, banks and credit card companies keep a file of copies of their customer’s signatures, and if they think that a check or credit slip might be a forgery, they will compare the signature in question with the signature in their files. If the signatures are different, they will call the police for a complete investigation. Forensic scientists will then do an even more thorough analysis of the signatures.

Typewriting Analysis

If a crime communicates using a typewriter or a computer printer, it may be possible to identify which machine was used. A typed letter demanding blackmail money or instructing someone where to find a kidnapping victim could be traced back to a suspect’s typewriter or compuer printer. Try the following activity to investigate how detectives analyze typewriting to solve crimes.

Materials

- pencil
- paper with typing on it from several sources, such as papers your friends and family members have typed using different typewriters and computers
- scissors
- glue
- 3-by-5-inch (7.5-by-12.5-cm) index cards
- magnifying lens

Procedure

1. Use the pencil to number all of the typed pages yopu’ve collected.
2. Use the scissors to cut several words out of each page. Glue the words on the index cards, using a separate card for words taken from each page.
3. Record the number of the page the words came from on each card.
4. Use the magnifying lens to obeserve the words on each card. What do you notice about each? Compare the same letter, such as e or a, on each card. How are the letters different?

More Fun Stuff to Do

Have a helper cut a word from one of the pages while you look away. Try to determine which page the word came from by comparing it to your sample cards.

Explanation

Few people write letters on typewriters today. Word processors, computers, and printers have made writing letters much easier. Even so, there are differences between how a letter is made by each machine. By looking carefully at those differences, detectives can determine which machine wrote a certain letter.

Detective Science in Action

In a famous spy case in 1950, Alger Hiss was brought to trial for passing secret documents to the Soviet Union. Hiss was convicted of perjury (lying while under oath), largely because of the evidence that involved his typwewriter. Typed documents taken from a Soviet spy contained valuable information from the U.S. Styate Department. The typing on these documents matched Hiss’s typewriter, which had rather unusual print. The prosecution claimed that Hiss had used the typewriter to copy State Department documents that were later given to secret agents from the Soviet Union.

Indented Paper

If another piece of paper is directly under the piece that is written on, the paper underneath will pick up an impression of the writing. This can be valuable evidence for a detective who is looking for clues in a missing-person case or trying to match the origin of a ransom note in a kidnapping case. Try the following activity to see how this technique is done.

Materials

- several sheets of white paper
- ballpoint pen
- lamp or other light source
- pencil

Procedure

1. Stack the paper. Use the ballpoint pen to write an address or a phone number on the top sheet of paper.
2. Remove the top sheet, then hold the second sheet of paper up to the lamp. Can you see anything?
3. Lay the second sheet flat. Use the edge of the pencil lead to lightly shade over the place where the writing was made. Can you read the address or phone number on the second sheet?

More Fun Stuff to Do

Repeat the experiment, using different types and amounts of paper, and exerting either more or less pressure while writing. Do these changes affect your ability to read the writing on the second sheet of paper?

Explanation

How well the impression can be read will depend on a number of factors, such as the thickness of the paper, whether the sheets were on a hard or a soft surface, and the amount of pressure exerted by the writer.

If an indented sheet is found as evidence at a crime scene, this technique can be used to match it to a threating letter or a ransom note. If a diary or a business ledger with pages torn out is found, this technique can also be used to determine what was written on the missing pages.

Decomposition

Decomposition is the natural pprocess of decay. Often the decompositon of materials surrounding a body can give a forensic scientist valuable information. Not all materials decompose at the same rate. Organic material, which is material from plants or animals, decomposes differently from inorganic, or man-made, material. Forensic scientists can study the state of decomposition of these materials to approximate time of death. Try this activity to learn materials can decompose at different rates and how that information can help solve crimes.

Materials

- clear plastic 2-qurt (2-liter) soda bottle
- scissors
- cheesecloth
- rubber band
- tape
- 2 cup (500 ml) sand
- 2 quarts (2 liters) garden soil (from an outdoor location)
- organic material, such as leaves, twigs, grass, shredded newspaper, and needles
- inorganic materials, such as Styrofoam, plastic, and scraps of fabric or leather
- pen or pencil
- notebook
- rubber gloves
- several sheets of newspaper
- stick
- worms (optional)
- tap water
- adult helper

Procedure

NOTE: This activity requires adult help.

1. Remove the label as best you can from the plastic soda bottle.
2. Have your adult helper cut the bottle into two sections, making the cut approximately one-third of the way from the bottom.
3. Cover the mouth of the bottle with cheesecloth and secure it with the rubber band.
4. Turn the drop section of thebottle upside down and place it in the bottom section as shown. Tape the two sections together.
5. Put the sand in the upside-down container. Place a 1-cup (250 ml) layer of the garden soil on top of the sand.
6. Look at the organic and inorganic materials. Which items do you think will decompose quickly? Why? Whicj items do you think will take longer to decompose? Why? Record your predictions in your notebook.
7. Add a small amount of each organic and inorganic materialto the container, then add another layer of soil. Continue to layer organic and inorganic materials and soil until they reach the top of the container. Add more materials on top of the last layer of soil.
8. Add worms to the container, if you like.
9. Pour water into the container until it starts to drip through the cheesecloth.
10. Set the container where it will not be disturbed for a month. Water the container twice a week.
11. Observe the container every other day. Record your observations.
12. After a month, put on the rubber gloves and pour the contents of the container onto the newspaper. Use the stuck to move the soil arround. Observe the condition of the organic and inorganic materials. Were your prediction correct?

CAUTION: Always wear rubber gloves when examining the experiment materials. Return worms to the earth and throw out the rest of the project when you are finished. Be sure to wash your hands thoroughly when you are done.

Explanation

Decomposition is nature’s way to recycle organic, or living, material. Organic material is broken down into nutrients that can be reused by plants as they grow. Some inorganic, or nonliving, material is broken down as well, but usually at a slower rate. Bacteria, fungi, worms, and microorganisms all help to break down these materials.

Worm in particular help to speed up the process of decomposition. They make extensive networks of tunnels that help air and water reach the roots of plants. The tunnels also provide air and water for other soil-dwelling insects and small organisms that help with the process of decomposition. Worms also turn the soil by moving deep soil up to the surface and by dragging plant materials underground. One cup (250 ml) of soil may contain more than 5 billion living creatures!

Forensic scientists use their knowledge of the decomposition rates of various substances to help solve crimes in several ways. For example, the state of decomposition of a letter found behind a house could link a suspect to the time of robbery, while a rotting apple core could be an important clue for police looking for a lost camper.

Heat Loss

There are many timesthat the temperature of an object plays an important role in solving a crime. Heat from the engine of an automobile may indicate that it has just been driven. A warm cup of coffee on a kitchen table may mean that a suspect has just left. The temperature of a body can indicate to detectives when a death has occurred. Try the following activity to see how temperature can be used by forensic scientists.

Materials

- 2 cup (500 ml) of hot coffee
- coffee cup
- thermometer (measures up to 212oF [100oC])
- stopwatch or watch with second hand
- pen or pencil
- notebook
- adult helper

Procedure

NOTE: This activity requires adult help. Have your adult helper keep the hot coffee at the same temperature throughout the experiment by placing it on a stove or hot plate.

1. Have your adult helper pour 1 cup (250 ml) of hot coffee into the coffee cup.
2. Put the thermometer in the coffee, start your stopwatch, and record the temperature of the coffee in your notebook.
3. Continue to record the temperature of the coffee at 1-minute intervals until the temperature no longer changes. Empty the cup of coffee.
4. Leave the room. Have the adult helper pour another cup of hot coffee into the coffee cup and note the time that he or she pours the coffee.
5. Have the adult helper wait several minutes before inviting you back into the room.
6. Take the temperature of the coffee. Compare the temperature to your records. How many minutes has it been since your helper poured the coffee into the cup?

Explanation

When the object is removed from a source of heat, its temperature begins to drop. It cools rather rapidly until it reaches the temperature of the surrounding air, at which point its temperature stabilizes. The heat loss of the same size of object at the same initial temperature occurs at the same rate each time. This allows one to determine, with some degree of accuracy, the time that the object was removed from the heat source. In this activity, as long as the same amount of coffee at the same initial temperature was poured the second time, and as long as the room temperature did not change, you should have been able to estimate the time the coffee was poured.

At death, a body stops generating heat and its temperature drops gradually. At first the cooling is relatively rapid –approximately 1.5oF (0.8oC) per hour—but this rate slows after a few hours. In addition to size, initial temperature, and the temperature of the surroundings, body type will also affect the cooling rate. A thin body will cool more rapidly than a heavier one. By taking a body’s temp[erature, a forensic scientist can estimate the time of death.

Microorganism

Very small plants and animals called microorganisms are found on land and in the water. Like microbes, seeds, and spores, microorganisms can be important in an investigation. Try the following activity to investigate microorganisms that are found in water.

Materials

- large glass jar with lid
- water from a pond or lake
- magnifying lens
- microscope (optional)

Procedure

NOTE: This is an outdoor activity

1. Use the jar to collect some water from a pond or lake, then put the lid on the jar.
2. At home, use the magnifying lens or microscope to examine the water for microorganisms. How many different microorganisms can you find?
NOTE: Many of the microorganisms are clear or light-colored and are very small, so you will have to look carefully. They may appear to be small that move!

Explanation

Small plants and animals live in the water are the foundation of all life. These microorganisms are eaten by larger organisms, which in turn are eaten by still larger organisms. This food chain allows many different organisms to live on earth.

Microorganisms found in the water can give valuable information to a detective. Microorganisms called diatoms (microscopic algae that contain a sandlike substance called silica in their cell walls) are very important. The presence or absence of diatoms in a dead body found in water can tell forensic scientists whether the victim drowned or died before entering the water. When death is caused by drowning in natural water, such as lakes and rivers, the water in the body, aspecially that in the lungs but even water in the bloodstream, will contain diatoms. If the victim was already dead when the body entered the water, no diatoms will be found.

In investigations in which a body is found in a different location from where it drowned, forensic scientists study diatoms to determine with considerable accuracy the area of origin. This is because there are over 15,000 species of diatoms, and any combination of them found in a sample is like to be unique.

Dust and Dirt

Dust, dirt, and soil can be important evidence in an investigation. Try the following activity to see how dirt can be used to solve a crime.

Materials

- dirt from three location
- plastic bags
- marking pen
- 3 sheet of white paper
- magnifying lens

Procedure

NOTE: This is an outdoor activity.

1. Collect dirt from three locations. Place it in the plastic bags and mark the location on each bag.
2. At home, place a dirt sample from each bag on separate sheets of white paper. Examine the samples with the magnifying lens.
3. How are the dirt samples different? Is the soil light or dark? What does the soil look like? What size are the gains in the soil? Do you see any stones? Is there any decaying plant material in the soil? What characteristics could you use identify the dirt from a particular place?

Explanation

Soil is one-half air and water, both of which are necessary for plants and animals to live. The rest of soil consists of recycling organisms-such as fungi, molds, bacteria, and earthworms- pieces of rock, and humus (decaying plant and animal matter). The size of the soil particles determines whether soil is sand, silt, or clay. Sands has the largest soil particles and clay has the smallest.

All this information can be used to study soil samples found at a crime scene. Dust and dirt are common as trace evidence because they are easily carried from the scene of a crime in the soles of shoes, on clothing, or on the tires of a vehicle. Forensic scientists compare the dust and dirt found at a crime scene with selected samples to determine where they came from.

Detective Science in Action

In 1977, Janie Sheperd had been missing for four days. Her car, discovered on a London street, had been driven roughly 75 miles (120 km) from her home. By analyzing thick deposits of mud found undermeath the vehicle, investigators determined that the car had been driven in one of four surrounding counties, which greatly narrowed the search area.