BIOLOGY

B I O LO GY /bahy-ol-uh-jee/ noun the study of living organisms, divided into many specialized fields that cover their morphology, physiology, anatomy, behavior, origin, and distribution.

PROJECT BY

V IV I AN LEUNG

AUG 2015

TA B L E O F C O N T E N T S

LAB 01

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Layered Liquids

LAB 02

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The Exploding Lunch Bag

LAB 03

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Blow Up A Balloon With Yeast

ARTICLE

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Food Date Coding Decoded

FIELD TRIP

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The Pacific Science Center

WEB BROWSING

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Obesity

L A B

0 1

L AY E R E D L I Q U I D S This experiment examines the miscibility and density of several liquids.

RUBBING ALCOHOL V E G E TA B L E O I L WAT E R DISH-WASHING LIQUID

HONEY *food coloring was added to water and rubbing alcohol

WHY DO THE LIQUIDS STAY SEPARATED?

STIR UP THE LIQUIDS IN THE GLASS. HAVE ANY OF THE LAYERS MIXED?

Each of the liquids have different masses. The liquid that weighs more or has a higher density, will sink below the liquid that weighs less or has a lower density.

The dish-washing liquid, water, and vegetable oil appeared as if it temporarily mixed with each other.

CAN YOU THINK OF SEVERAL WAYS THAT THE LIQUIDS IN THE GLASS ARE DIFFERENT?

WAIT A FEW MINUTES AND LOOK AGAIN. HAVE ANY OF THE OTHER LIQUIDS SEPARATED?

Each of the liquids are different in their own way.

They differ in color, viscosity (thickness), and density (weight).

The liquids temporarily mixed with each other. However, after awhile, the layers returned to its original position. The layers will always even themselves out because of the different densities.

CAN YOU GUESS WHAT THE RELATIONSHIP IS BETWEEN THE DENSITY OF A LIQUID AND ITS POSITION IN THE GLASS?

RESULTS

The density of a liquid determines its position in the cup. A liquid with the highest density would sink to the very bottom of the cup. Vice versa, a liquid with the lowest density would rise to the top of the cup. The density of honey is 1.42 g/mL, making it the heaviest out of the liquids. Therefore, honey remains at the bottom of the cup.

This experiment serves to examine the miscibility and density of different liquids. The liquids did not mix with each other. Instead, the liquids remained stacked on top of each of one another in separated layers because the liquids are not miscible and vary in density levels.

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L A B

0 2

THE EXPLODING LUNCH BAG This experiment shows the chemical reaction between vinegar and baking soda.

WILL DIFFERENT TEMPERATURE WATER AFFECT HOW FAST THE BAG INFLATES?

By increasing the temperature, the chemical reaction rate will increase.

By decreasing the temperature, the chemical reaction will decrease.

WHAT AMOUNT OF BAKING SODA CREATES THE BEST REACTION?

Using less baking soda would produce less carbon dioxide. In order to create more carbon dioxide, more vinegar and baking soda should be added. Only adding baking soda to the same amount of vinegar will not work at a certain point because there would not be enough vinegar atoms to react with the extra baking soda.

WHICH SIZE BAG CREATES THE FASTEST POP?

The smaller the bag, the faster the pop. By having less space, the carbon dioxide would fill up the bag much quicker.

R ES U LTS

This experiment serves to show the chemical reaction between vinegar and baking soda. Vinegar is an acid and baking soda is a base. When an acid and base are placed together, the chemical reaction forms a gas-in this case, carbon dioxide. Because the carbon dioxide is expanding in a confined sandwich bag, the bag explodes when it can no longer withhold the carbon dioxide.

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0 3

BLOW UP A BALLOON WITH YEAST This experiment shows how yeast produces carbon dioxide.

DOES ROOM TEMPERATURE AFFECT HOW MUCH GAS IS CREATED BY THE YEAST?

Yes, room temperature does affect the amount of gas is created by the yeast. Higher temperatures will cause the yeast to produce more carbon dioxide. However, at some point, the temperature will become too high and destroy yeast cells, causing less carbon dioxide production.

DOES THE SIZE OF THE CONTAINER AFFECT HOW MUCH GAS IS CREATED?

No, the size of the container does not affect how much gas is created.

However, if the container is too big, there may not be enough gas pressure to inflate the balloon.

WHAT WATER/ROOM TEMPERATURE HELPS THE YEAST CREATE THE MOST GAS?

A water temperature of 105 ° F to 115 ° F and a room temperature between 80 ° F to 90 ° F would activate yeast production, and therefore, create carbon dioxide.

WHAT “YEAST FOOD” HELPS THE YEAST CREATE THE MOST GAS?

Syrup, or any other sugary substance helps yeast produce the most carbon dioxide.

R ES U LTS

This experiment serves to show the chemical reaction between yeast and sugar. When yeast and sugar come together, it releases carbon dioxide. The gas then fills up the container and inflates the balloon.

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A R T I C L E

F O O D D AT E C O D I N G D E C O D E D What are best before dates, and do we really need to depend upon them...?

MON, NOV 7 2011 | BY EMMA EASTON

D

there for the sellers rather than the customer. The “sell by” and “display until” dates are optional and are placed on packed products to indicate to sales staff when food needs to be marked down or taken off the shelf (this is generally a few days before the “use by” date). So, as long as you take note of the other date coding on the packaging, these foods are usually fine to consume after their “sell by” or “display until” date.

ate codes on food products indicate the quality and safety of the food. It seems simple enough... but not always! The most common date codes on food are “best before” and “use by” but there are also “sell by” or “display until” dates, and to complicate matters further some products don’t seem to require date codes at all. So what do all these dates actually mean?

The short answer is that, before these dates, the quality and safety of the food is guaranteed, but eat them after that and it’s up to you to stomach the consequences. But don’t start tearing your hair out yet, because there are some simple tips and tricks to follow to help you decide what you should - or probably shouldn’t - consume.

Here is where things get a little more complicated. The “best before” and “use by” dates provide a lot more information about the potential quality and safety of the food, and so these are the date codes to pay the most attention to. First, “best before” dates are put on food products that have a long shelf life - things like dehydrated foods,

Let’s start with the easy ones, the ones that are

canned foods; in essence, non-perishable foods.

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A R T I C L E

“Best before” indicates that, after this date has passed, the

other forms of poultry, if it gets into a human in a poorly cooked egg or piece of meat, it can make you seriously sick. Food poisoning is never nice and the signs are very

manufacturer says that you are no longer eating a quality product, or that the food may be “nutritionally unstable” and the texture, taste, color and flavor are not what the manufacturer intended. Legally it can still be sold after this date and it is still safe to eat, provided it has been stored correctly and is not damaged – but it may not taste great though! The food is safe to eat because it has been

hard to miss. Unfortunately, pathogenic microorganisms may not make their presence known in an item of food until they are present in very high numbers - tens of millions of microbes - and even then the effect on the food can be very subtle, so you may not realize you’ve even eaten something you shouldn’t - at least until the bugs make their presence felt a few days later...

preserved or made sterile during manufacturing. For instance, canned foods are “retorted” (sealed so air can’t get in and out), and pressure cooked, to prevent MICROBIOLOGICAL SPOILAGE.

But back to date coding - while “best before” indicates quality changes for long-life foods, “use by” is the date to pay attention to, as it is put on food that will readily

Microbiological spoilage is a fancy way of saying that MICROBES (bacteria, viruses and fungi) get in and ruin

spoil at the hands - or should that be FLAGELLAE of contaminating microorganisms. “Use by” dates are employed on products that have a short shelf life and particularly those that need refrigerating. They indicate that food is unsafe to eat after this date and cannot legally be sold. For reasons of safety, manufacturers usually apply a date that’s a day or two before the real “use by” date to protect those people not paying attention or who insist on eating the food anyway. So the general rule is that something that’s a day or two past its “use by” date is probably not harmful, but more than a week over and you’re risking infection by pathogens.

the food. Microbes are everywhere, including inside your body, and some are very beneficial: without yeasts and bacteria, we couldn’t serve up culinary delights like bread, beer and cheese. But not all microbes are good.

Things like MOLDS (forms of fungi) growing on food probably won’t harm you if you eat them, but they can taste vile. But you can spot relatively easily the kinds of changes that these organisms unleash on the food, so it’s easy to avoid them.

But more worryingly, other MICROORGANISMS are much more malignant and can make you ill, sometimes

So now you understand a little more about date coding, but who decides the date code and how it is determined?

Food manufacturers set the date code through a combination of experience, legislation (dependent on the country or region) and shelf-life testing.

fatally so. For example, the bacterial pathogen SALMONELLA is a common cause of serious food poisoning.

Although this bug is carried harmlessly by chickens and

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A R T I C L E

During shelf life testing, the manufacturer takes a sample

of the food (such as a crate of cans or a crate of milk) kept under different conditions and simply watches to see what happens over time. For long life foods, like cans, the room usually has an elevated temperature to speed up the process. Short life foods, like dairy products, are usually kept in a laboratory fridge. At specific time points (daily for short life, weekly or monthly for long life) a portion of the food is taken and tested for quality (taste, texture, flavor, color) and microbe numbers and types. After a certain point, the food will lose quality or contain unsafe numbers of microbes. The date is set at a little bit before this time, to ensure that the food is eaten at a point where it is both safe and still of a high quality.

What about food that doesn’t have a date code? Legally, fruit and vegetables and some deli products don’t need to have a date code. Leftover and takeaway food also doesn’t have a date code. So how long is it safe to store them before tucking in? This comes down to common sense and a little bit of know how. Take-away food is meant to be eaten straight away, but as it’s cooked it will last for a short length of time. If you have any left, put it in the fridge and eat it hot the next day, but don’t leave it any longer.

Deli food and leftover food, provided it is refrigerated, will usually last between 4 and 5 days. This is where common sense kicks in - if it looks or smells funny throw it away!

Fruit and vegetables also come under the common sense rule - if it looks or smells funny, or is growing extra bits

(unless it is a shoot!) then throw it out. If it’s a bit squishy but other than that looks and smells fine, just cut the squishy bit off! As an aside, squishy fruit usually makes the best cakes and desserts...

As a rule, date codes are just a guide and to be meaningful depend on proper storage and food handling. A can with

a “best before” date that has been dented or is bulging is NOT safe. Bulging cans mean that PATHOGENS are in there and multiplying. Throw it away immediately don’t even open it to try it. If you dented the can yourself then you don’t need to throw it away immediately, but you don’t want it in the cupboard for months on end. Try to use it up within the month you dented it. Always follow food storage instructions on the packaging, especially the “refrigerate after opening” instructions. The general rules for unopened, undamaged foods are: if it is on the supermarket shelf it can be stored in the cupboard; if it was in the refrigerator section then it belongs in the fridge and if it’s sold frozen keep it frozen. The mode of storage is determined by the potential of the food to harbor microbes; refrigeration and freezing slow down microbial growth.

So, with a little knowledge, date coding is quite simple.

Pay attention to “use by” dates and keep “best before” in mind. Most importantly, store the food correctly, cook it well, and if it looks or smells bad, avoid eating it.

SOURCE http://www.thenakedscientists.com/HTML/articles/article/date-coding-decoded/

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A R T I C L E

my response to...

F O O D D AT E C O D I N G D E C O D E D

Date codes such as “best before,” “use by,” “sell by,” or “display until” dates are placed on packaging to ensure the quality and safety of food products. Each date code serves a specific purpose, and it is important for people to be aware of the meaning of it when they see it on food packaging.

“Sell by” and “display until” dates are optionally placed to inform employees when to mark down prices or take the product off the shelves. These foods are generally still consumable after their “sell by” or “display until” dates, but before “use by” date.

“Best before” and “use by” dates are marked on nonperishable foods to provide information about the quality and safety of the food. After this date, the product is still safe to eat, but is no longer a quality product. The food is still safe to eat because it has been preserved during manufacturing to prevent microbiological spoilage.

Microbiological spoilage occurs when microbes enter food and spoil it. Some microorganisms are virulent and can make a person sick or even endanger their life. Pathogenic microorganisms are not visible until

they are present in extremely high numbers, such as tens of millions of microbes. However, even then, its presence is not quite evident and will take a few days before the microbes start affecting your body.

“Use by” dates are place on food products with a short shelf life and refrigerated foods. This date code means that the food is not safe to eat after the date and cannot legally be sold. Eating a product with a “use by” date passed more than a week over can infect a person.

A can with a “best before” date that has been dented or is bulging is not safe to eat. A dented or bulging can contains pathogens that are in there and multiplying.

It is important for people to be aware of the meaning of these date codes and how to properly store food.

Food poisoning can potentially put a person’s life at risk. I found this article particularly interesting because it taught me when packaged food is not okay to eat.

Before, I was not aware that different date codes had different meanings. I know now to pay more attention to date codes because it provides information on the safety and quality of the food.

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F I E L D

T R I P

my field trip to...

T H E PA C I F I C S C I E N C E C E N T E R

The PACIFIC SCIENCE CENTER is a science museum located in Seattle, Washington. This award-winning science museum is filled with interactive exhibits and programs to educate people of all ages in science, math, and technology. On this trip, I learned a lot of interesting facts. Here are some of the many new things that learned about.

“

From apple trees to honey bees, we’re more alike than you think. We all take in energy. We all take in supplies and get rid of waste. We all react to the world around us. We all defend ourselves. We all reproduce and pass on genetic information to our offspring. Inside you, organs work together to keep your body balanced.

”

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F I E L D

T R I P

Model of HIV

Our digestive tract is really long!

THE DIGESTIVE SYSTEM The human digestive system is truly diverse. The digestive tract is more than 20 feet long. Our stomach makes 2 liters of liquid a day including hydrochloric acid.

When bacteria breaks down undigested material in our colon, it can produce up to 700 milliliters of gas!

HIV The human immunodeficiency virus, or HIV, attacks certain kinds of white blood cells.

Model of T4 virus

learn more at www.seafodwatch.org!

EAT SMART Many seafood species are harvested or farmed using methods that harm ocean wildlife and environment. Sometimes, these methods make our seafood unhealthy to eat. Did you know farm-raised salmon are injected with a pink dye to recreate the same pink flesh tone when it was still alive? Instead of farm-raised salmon, it is recommended to eat wild caught salmon from Alaska.

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T4 T4 is a bacteria-attacking virus.

T4 can not move by itself. It must bump into the right bacterium to take it over and make copies of itself. It kind of looks like a robot, doesn’t it?

W E B

B R O W S I N G

OBESITY What is obesity?

What are its risks and how can it be prevented?

Obesity is a condition where an individual has an abnormal or excessive amount of body fat. Obesity occurs over time when calories accumulate faster than it is burned through exercise or normal daily activities.

Obesity is very common in the United States. More than one-third of U.S. adults are obese. Obesity is higher among middle-aged adults than among younger adults and the elderly. According to the Center for Disease Control and Prevention, approximately 17% of children and teens aged 2-19 years old are obese.

Body mass index, or BMI is a method of measuring body fat by dividing a person’s weight by the square of his or her height. A person with a BMI of

30 or more is considered obese.

Being obese can potentially put a person at risk for diabetes, cardiovascular disease, stroke, arthritis, or cancer. However, obesity can be prevented. If you are obese, losing even 5 to 10 percent of your weight can delay or prevent any other risks to health. Dietary changes, more exercise, and behavior changes can help you lose weight. Weight gain is inevitable if more calories are taken in than burned. Therefore, it is important to live a healthy lifestyle by making better food choices and being more active. Slow and steady weight loss is recommend as the safest way to lose weight permanently. Also, try to always keep moving. Simply parking further from store entrances, gardening, or doing more household chores can go a long way.

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B R O W S I N G

O B E S I T Y:

SOURCES

“A crude population measure of obesity is the body mass index (BMI), a person’s weight (in kilograms) divided by the square of his or her height (in metres). A person with a BMI of 30 or more is generally considered obese.”

- HTTP://WWW.WHO.INT/TOPICS/OBESITY/EN/

“More than one-third (34.9% or 78.6 million) of U.S. adults are obese.” “Obesity is higher among middle age adults, 40-59 years old (39.5%) than among younger adults, age 20-39 (30.3%) or adults over 60 or above (35.4%) adults.”

- HTTP://WWW.CDC.GOV/OBESITY/DATA/ADULT.HTML

“Approximately 17% (or 12.7 million) of children and adolescents aged 2—19 years are obese.”

- HTTP://WWW.CDC.GOV/OBESITY/DATA/CHILDHOOD.HTML

“Being obese increases your risk of diabetes, heart disease, stroke, arthritis, and some cancers. If you are obese, losing

even 5 to 10 percent of your weight can delay or prevent some of these diseases. For example, that means losing 10 to 20 pounds if you weigh 200 pounds.”

- HTTPS://WWW.NLM.NIH.GOV/MEDLINEPLUS/OBESITY.HTML#SUMMARY

“Dietary changes, increased physical activity and behavior changes can help you lose weight.”

- HTTP://WWW.MAYOCLINIC.ORG/DISEASES-CONDITIONS/OBESITY/BASICS/DEFINITION/CON-20014834

“Reducing calories and practicing healthier eating habits are vital to overcoming obesity. Although you may lose weight quickly at first, slow and steady weight loss over the long term is considered the safest way to lose weight and the best way to keep it off permanently.”

- HTTP://WWW.MAYOCLINIC.ORG/DISEASES-CONDITIONS/OBESITY/BASICS/TREATMENT/CON-20014834

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