Pressured Cooking
thecookingshows.blogspot.com
Quickfire, a cooking program on QTV, showcases how dishes can be prepared in less than 10 minutes. The TV show could have been influenced by the fast-paced lifestyle of the present generation. How about cooking beef stew? It would take hours to have the beef tenderized. Worry no more buddy. We have the pressure cooker to save the day.
A pressure cooker is tightly closed to lock in the gases. As the heat is applied, the pressure keeps on increasing with the rising temperature. The greater the temperature, the faster the heat is transferred to the meat being cooked.
Usually 15 psi (pound-force per square inch) is the pressure applied on food. Normally at this pressure, the food is cooked at 100 degrees Celsius. In a pressure cooker, you will tenderize meat at 125 degrees Celsius.
Pressure is therefore directly proportional to temperature. In fact, after the cooking process, when the pressure cooker is cooled, the pressure within would also drop. Read more on pressure cooker here.
Now, you are under pressure. Take the simple quiz here.
40% or 70% Rubbing Alcohol?
These days, everyone is more aware of the existence of ill-causing microorganisms everywhere. People have become more cautious about taking in food with hands. They want to make sure that their hands are clean, and they do it either by washing with bath soap or sanitizing using rubbing alcohol solutions and gels. Let’s talk about rubbing alcohol as disinfectants. Rubbing alcohol products or brands come in many variants. There are those that have add-on like moisturizers and fragrances. What really matters is the alcohol content. 40% or 70%, which one is better?
Solutions’ concentrations can be expressed in several ways – percent concentration, molarity and molality are the common ones. If you see a label 40% alcohol and the amount is in milliliter (mL), the concentration is in percent concentration by volume. 40% means that for every 100 mL, the product contains 40 mL alcohol. So, for a 70% label, every 100 mL of the product you buy has 70 mL alcohol. If the product is in 250 mL container, a 70% solution would have 175 mL alcohol present. Of course it is the 70% alcohol that is more potent in disinfecting your hands.
Related to %by volume is proof. An 80 proof rum contains 40% alcohol. A 12.4% grape wine is 24.8 proofs. Proof is % times 2.
Test your kemikalidad; take the quiz here.
Pop!
Open that bottle of a 12-ounce cola. Hear the sound? What’s that audible pop you hear?
Carbonated beverages like cola, contain carbon dioxide dissolved in water. For carbon dioxide to be in solution with water, high pressure is required. This pressure is locked in, by placing cap on the bottle’s mouth. For as long as the pressure is confined, carbon dioxide gas is soluble in water. What happens when you remove the cap? Yes, the pressure escapes. This is followed by bubbles of carbon dioxide that seem to escape from the solution. The bubbles indicate that the carbon dioxide becomes less soluble when the pressure is lowered. This is true to gases. Their solubility decreases when the pressure is decreased.
A diver near the bottom of a river or sea is exposed to high concentration of gases. The pressure is greatest at the bottom, so gases are most soluble there. Gases can even get into the bloodstream of the diver and be dissolved in the blood. When ascending, it is wisest that the diver does it slowly. Doing so would allow the gas to escape, before he gets to the surface. Should he do it fast, there would be no sufficient time for the gases to escape out of his body. Once at the surface, the gas would be insoluble and could form bubbles in the blood vessels, blocking the flow of blood. This condition could be fatal. Read more of its effects here.
Flavor of the Road
source: http://hubpages.com/hub/Filipino-Trivia---5
Flavor of the Road is the usual description of the Visayans for the ice cream sold by a “sorbetero”. Sorbetero is a Filipino word for an itinerant ice cream vendor. Ever wonder why does he have to add salt to the crushed ice, (on which the ice cream cylinders/containers are submerged)? One might think that probably, he does this to keep the ice cold. Well, it’s true. Adding salt to the ice will even lower the temperature.
Freezing point is one of the colligative properties of solutions. These properties depend on the amount of solute in a solution. What is the effect of the amount of (table) salt to the freezing point of a solution? As more and more solute particles are added, it would be harder for the molecules of water to bond to freeze into ice. Hence, the temperature has to drop lower, such that water molecules are brought closer to bond.
Pure water freezes at zero degree Celsius. Adding 5.85 g of table salt (NaCl) to 100.0 g of water, will result in a freezing point of – 1.86 deg. C. This is the value of the molal freezing point depression constant (Kf) of water. Molal concentration is expressed as the number of moles of solute divided by the kilogram of the solvent.
One Problem, One Answer
Often, whenever your class is solving a math-related problem, you and your classmates would have different answers. Some would have 2 digits, others would have 3 and so on. In a chemistry class for instance, you have this problem. The graduated cylinder contains 14.35 mL water. When a chunk of metal is added, the volume reads 17.0 mL. What is the volume of the metal? Would it be 2.65 mL, 2.7 mL or 2.650 mL? You have one problem, you should have one answer.
How do make sure that you’ll have all the same answer? The answer – give only the significant figures. This depends on what mathematical operation is involved. See what is done in addition (also true in subtraction). We look at and count the number of digits after the decimal in each of the given. Look for the given term that has the smallest number of decimal places. Round off the answer to the same number of places. In the problem about the volume of the chunk of metal (in the first paragraph), the least number of digits after the decimal in the given is one (in 17.0, there is 1 digit, which is 0 after the decimal). Therefore the answer should be 2.7 mL, which contains one digit (7) after the decimal. Review on rounding off numbers. Take a look at the figure. It demonstrates how the answer is expressed.
In multiplication and division, we count the number of digits of each given. The answer will have the same number of digits as the given with the least number of digits. For example, the dimensions of a block of wood are 2.1 cm, 3.023 cm and 4.11245 cm. The product is 26.107066335 cm3. Counting the digits at the given, 2.1 cm has the least number of digits; there are 2. The answer will therefore have 2 digits; it should be 26 cm3. Look at the figure. It shows how the answer is expressed when multiplying. This is also done when dividing.
Want to know more about significant figures? Click here.
I hope that after reading this blog and taking its quiz below, you will have the same answers in all math-related problem solving endeavors.
Love Kalamansi Juice
I have been coughing for a while already. I really need some dose of vitamin C. Good thing there’s a lot of kalamansi fruit in the kitchen. Using a steel knife, which is a mixture of iron and carbon (Fe + C), I sliced some 6 fruits of kalamansi and squeezed the mixture (Vitamin C, water and other compounds) of its juice. I added pure substance distilled water (H2O), and another pure substance table sugar, C12H22O11.
Pure substances and mixtures can be mixed to form a mixture like kalamansi juice. Matter can be either in forms of pure substances or mixtures.
Pure substances like distilled water (H2O) and table sugar (C12H22O11) are particularly called compounds. They are made up of two or more elements chemically combined in definite proportions. Table salt (NaCl), Caustic soda (NaOH), iron rust (Fe3O2. H2O), fructose (Honey sugar, C6H12O6), pure ethyl alcohol (C2H5OH) are examples of compounds. The knife I used is made up of elements iron and carbon. Iron (Fe) alone is an element. So is carbon (C). Elements are also pure substances because they only contain one kind of atom. Aluminum (Al) is purely made up of Al atoms. Copper (Cu), gold (Au) and mercury (Hg) are other common elements. Elements and compounds are pure substances.
Mixtures can be prepared in whatever proportions. In preparing a fruit juice drink, you can add 2 tbsp of sugar or just 1; either way, you form the same mixture. Steel can be fabricated in varied proportions of iron and carbon. Carbon in steel can be 0.2% or 1.5%. Either concentration can form steel. Mixtures are combinations of elements or blends of compounds or of elements and compounds. The air is a mixture of nitrogen, oxygen, carbon dioxide and other gases. Solutions like 70% ethyl alcohol, fruit juices, mineral water and seawater are all mixtures. Colloids like milk, mayonnaise, and gelatin are also mixtures.
Let’s group them here.
Hmmmnn! Just finished one glass of kalamansi juice. Love it. It’s time to test your skill in identifying pure substances and mixtures. Click here to take the quiz.
Measuring All Day
Why do we have to keep on measuring just every day? 1 cup of rice, a pinch of salt, a dash of ground pepper, 500.0 ml mineral water, 1 liter of water, 2 km distance to travel, the slow speed of 7 m/s of the vehicle to school, the 10-minute walk from home to school, a hefty 3 kg backpack … And then in chemistry class, here comes again this measuring thing! How can you just get rid of these? Well I tell you kid, you can’t get away from measuring because you practically do and observe it every day, even all day. When your vehicle drops by a gasoline station, you can’t help but notice the number of liters of fuel shown on the gas pump/dispenser. When you buy food items, you have to specify the number of grams of your orders.
click image to see larger view
We use measuring device to get the quantity of the unknown. The quantity could be mass or volume. Matter has mass and occupies space called volume. A platform balance has its standard masses, which we use to identify the unknown mass of an object. The figure on the left shows the parts of a platform balance. The pointer rests at zero when both the mass of the object and the standard are the equal. We COMPARE the unknown quantity with a standard when we measure. When both quantities are equal, then the mass of the unknown is the same as the standard. In a platform balance, we place the object at the left pan; the standard weights at the right plate. We use the riders, which are also standards, by moving them to and fro the arms of the device to attain balance. The mass of the riders and the set of weights, when the platform beam is balanced, are equal to the mass of the object. If in the small rider, the mass is 2.35 g, 40 g in the big rider and a total of 125 g in the set of weights, then the mass of the object is 167.35 g.
click image to see larger view
Matter also occupies space. The amount of space occupied is the volume. Often we deal with liquids and so we find graduated cylinder as a helpful tool in getting the volume of a liquid. In most cases, we get the volume of water. Water, when inside the cylinder, would form a curved line on the surface. This is the meniscus, and we take the volume reading from it. Take a look at the figure on the right. The volume reading is really based on the lower meniscus. There are 10 lines between 10 ml and 20 ml. Hence, each line is equal to 1 ml.
Take the quiz now. Click here.
First Day High
The first week of school would have brought us many experiences. New classmates, teachers, subjects and new environment are among the common encounters one can have in the “first day high”. Perhaps, one thrilling instance would have been the time when your advisers call out your names after the opening ceremony. “What section do I belong to?” “I wish my friends are still my classmates this time.” “Yes, my crush belongs to our class!”
Now that you are third year, expect for a “something new, something different” life. Fourth year students would always look back at their lives as juniors. This could be brought by the many memories they made when they were in third year. Many of my third year students before were part of this site. Here, we shared our thoughts and discuss some life’s experiences with Chemistry. They too took the simple online quizzes, to test their “Kemikalidad“, their abilidad in chemistry.
For a start, let me know about your thoughts in this site. Kindly read some blog entries (two or more). Just click on any topic in “KEMIKAPOST, RECENT” found at the upper right side of this home page. After your readings, click the link below to answer some questions.
Link: KEMIKAINTERVIEW
It’s Game Time!
Exchange Fruits in the Basket
When I was in elementary, one of our teachers had our class played a game, “exchange fruits in the basket”. Two students hold hands and form a “basket”. There could be 10 or more baskets depending on the number of participants. At the start of the game, each of the baskets, which are arranged into one big circle is filled with one fruit/student. There’s a contestant placed at the middle of the circle of baskets. Such a student calls “exchange fruits in the basket!” Everyone is required to look for another basket, including that one at the middle. The one who would not have any basket shall be placed at the middle and shall call again “exchange fruits…”
One time in my chemistry class, a student of mine noticed that writing formulas is just like a game called “exchange fruits”. She’s correct. See what happens when writing a formula of a compound.
Let’s analyze these item by item.
1. Fe or Iron has a charge of 2+. This charge is like the “fruit” in the basket of Fe. The Nitrogen, N has a charge/fruit of 3-. When the compound of these two ions are formed, they simply just have to “exchange their fruits”. Look what happens to the fruits when they are at another basket/ion. Yes, they are written as subscripts, after the exchange. So we have Fe3N2.
2. The sodium, Na has a charge of 1+. There’s no need to write 1 as subscript for PO3 or phosphite.
3. The ion SO4 with a charge of 2- is enclosed in parenthesis at the resulting formula because it is made up of two atoms.
4. When the charges are the same for two ions, the resulting formula will have the a subscript of 1, which shall not be written anymore.
5. NH4 is also enclosed having more than 1 atom.
It’s Quiz Time! Click here.
There’s Something in the Name
Ever looked at food item labels? You must be most familiar with sodium chloride, monosodium glutamate (MSG) and even the ions dissolved in a mineral water. So how have these names and that of other chemicals like those in the picture below, been made?
You see, there are compounds that have only two kinds of atoms. You would know, that it is a binary compound when its ending is “ide”. Just like sodium chloride, for NaCl, or potassium chloride (KCl). Try these below.
KBr Potassium bromide
ZnO Zinc oxide
BaS Barium sulfide
Al2O3 Aluminum oxide
Aluminum oxide, in its formula, shows subscripts 2 and 3 respectively. Click here to know more.
If a compound has more than two kinds of atoms, it is a tertiary compound. They end with “ate” (with more oxygen) or “ite” (with less oxygen). The food label above shows calcium phosphate or Ca3(PO4)2, ferrus sulfate or FeSO4, copper sulfate or CuSO4 and calcium iodate or Ca(IO3)2. Take a look at these ones.
Li3PO4 Lithium phosphate
Li3PO3 Lithium phosphite
NaFO4 Sodium perfluorate
NaFO3 Sodium fluorate
NaFO2 Sodium fluorite
NaFO Sodium hypofluorite
