The 2nd Semester test is fast approaching... o yeah! it'll start tomorrow...
29 May: Chemistry
Don't forget to study and do your best
Good luck!
God bless
Ms. Anne :)
Rabu, 28 Mei 2014
CP2: The Transfer of Heat Energy
The
heat source for our planet is the sun. Energy from the sun is transferred
through space and through the earth's atmosphere to the earth's surface. Since
this energy warms the earth's surface and atmosphere, some of it is or becomes
heat energy. There are three ways heat is transferred, into the atmosphere:
- Radiation, conduction, convection
Radiation
If you have stood in front of a fireplace or near a campfire, you have felt the heat transfer known as radiation. The side of you nearest the fire warms, while your other side remains unaffected by the heat. Although you are surrounded by air, the air has nothing to do with this transfer of heat. Heat lamps, that keep food warm, work in the same way. Radiation is the transfer of heat energy by electromagnetic radiation.
Most of the electromagnetic radiation that comes to the earth from the sun is in the form of visible light. Light is made of waves of different frequencies. The frequency is the number of instances that a repeated event occurs, over a set time. In electromagnetic radiation, the frequency is the number of times an electromagnetic wave moves past a point each second.
Our brains interpret these different frequencies into colors, including red, orange, yellow, green, blue, indigo, and violet. When the eye views all these different colors at the same time, it is interpreted as white. Waves from the sun which we cannot see are infrared, which have lower frequencies than red, and ultraviolet, which have higher frequencies than violet light.
Most of the solar radiation is absorbed by the atmosphere and much of what reaches the earth's surface is radiated back into the atmosphere to become heat energy. Dark colored objects such as asphalt absorb more of the radiant energy and warm faster that light colored objects. Dark objects also radiate their energy faster than lighter colored objects.
Conduction
Conduction is the transfer of heat energy from one substance to another or within a substance. Have you ever left a metal spoon in a pot of soup being heated on a stove? After a short time the handle of the spoon will become hot. This is due to transfer of heat energy from molecule to molecule or from atom to atom. Also, when objects are welded together, the metal becomes hot (the orange-red glow) by the transfer of heat from an arc. This is called conduction and is a very effective method of heat transfer in metals. However, air conducts heat poorly.
Convection
Convection is the transfer of heat energy in a fluid. This type of heating is most commonly seen in the kitchen when you see liquid boiling.
Air in the atmosphere acts as a fluid. The sun's radiation strikes the ground, thus warming the rocks. As the rock's temperature rises due to conduction, heat energy is released into the atmosphere, forming a bubble of air which is warmer than the surrounding air. This bubble of air rises into the atmosphere. As it rises, the bubble cools with the heat contained in the bubble moving into the atmosphere.
As the hot air mass rises, the air is replaced by the surrounding cooler, more dense air, what we feel as wind. These movements of air masses can be small in a certain region, such as local cumulus clouds, or large cycles in the troposphere, covering large sections of the earth. Convection currents are responsible for many weather patterns in the troposphere.
If you have stood in front of a fireplace or near a campfire, you have felt the heat transfer known as radiation. The side of you nearest the fire warms, while your other side remains unaffected by the heat. Although you are surrounded by air, the air has nothing to do with this transfer of heat. Heat lamps, that keep food warm, work in the same way. Radiation is the transfer of heat energy by electromagnetic radiation.
Most of the electromagnetic radiation that comes to the earth from the sun is in the form of visible light. Light is made of waves of different frequencies. The frequency is the number of instances that a repeated event occurs, over a set time. In electromagnetic radiation, the frequency is the number of times an electromagnetic wave moves past a point each second.
Our brains interpret these different frequencies into colors, including red, orange, yellow, green, blue, indigo, and violet. When the eye views all these different colors at the same time, it is interpreted as white. Waves from the sun which we cannot see are infrared, which have lower frequencies than red, and ultraviolet, which have higher frequencies than violet light.
Most of the solar radiation is absorbed by the atmosphere and much of what reaches the earth's surface is radiated back into the atmosphere to become heat energy. Dark colored objects such as asphalt absorb more of the radiant energy and warm faster that light colored objects. Dark objects also radiate their energy faster than lighter colored objects.
Conduction
Conduction is the transfer of heat energy from one substance to another or within a substance. Have you ever left a metal spoon in a pot of soup being heated on a stove? After a short time the handle of the spoon will become hot. This is due to transfer of heat energy from molecule to molecule or from atom to atom. Also, when objects are welded together, the metal becomes hot (the orange-red glow) by the transfer of heat from an arc. This is called conduction and is a very effective method of heat transfer in metals. However, air conducts heat poorly.
Convection
Convection is the transfer of heat energy in a fluid. This type of heating is most commonly seen in the kitchen when you see liquid boiling.
Air in the atmosphere acts as a fluid. The sun's radiation strikes the ground, thus warming the rocks. As the rock's temperature rises due to conduction, heat energy is released into the atmosphere, forming a bubble of air which is warmer than the surrounding air. This bubble of air rises into the atmosphere. As it rises, the bubble cools with the heat contained in the bubble moving into the atmosphere.
As the hot air mass rises, the air is replaced by the surrounding cooler, more dense air, what we feel as wind. These movements of air masses can be small in a certain region, such as local cumulus clouds, or large cycles in the troposphere, covering large sections of the earth. Convection currents are responsible for many weather patterns in the troposphere.
CP2: Preparing Salts
There are methods that can be used in
preparation of salt. Reaction of acids is one of the methods.
Acids + Metals à salt + hydrogen
gas
Acids +
Carbonates à salt + carbon dioxide + water
Acids + bases à salt + water
The
uses of salts are fertilizers (ammonium nitrate, potassium nitrate), food
(flavorings) and Industrial (modifying properties of paint formulation).
Solubility Table
|
Nitrates
|
All Soluble
|
|
Sulfates
|
All soluble
except calcium, lead and barium
|
|
Chlorides
|
All soluble
except silver, mercury, lead
|
|
Carbonates
|
All insoluble
except sodium, potassium, ammonium
|
|
Hydroxides
|
All insoluble
except sodium, potassium, ammonium, barium and calcium
|
Precipitation
is a method by simply mixing two (2) aqueous solutions together to form an
insoluble salt.
Ba(NO3)2(aq)
+ Na2SO4(aq) à BaSO4(s)
+ NaNO3(aq)
Titration
is a method by simply mixing two (2) aqueous solutions together to form a
soluble salt. It is usually between an acid and a base. It uses a universal
indicator and neutralization takes part. Salt formed can then be crystallized
out in pure form.
Proper Attitudes that should be developed in Chemistry
Curiosity
Wants to explore and find out
Wants to seek solution for a given problem.
Example: Louis Pasteur’s experiment (Pasteurization)
Open-mindedness
Willingness to accept new ideas but at the same time not believing that all you read or find out is true or correct.
Proper experimentation should be followed
Humility (Humble)
Not being too proud of what you have discovered; a willingness to say “I am wrong” and to change your ideas when new evidences is presented
Example: Harold Urey’s experiment about Moon’s surface
Creativity (Creative)
Looking new ways to solve problems.
Using new techniques in presenting results.
Example: Using Bar graphs/making models
Objective
Being fair and not letting opinions or beliefs affect your work. It must be based on facts and experiments.
Example: John Dalton’s theory of matter
Honesty (Truthful)
Being honest and not changing the results of experiments.
“Honesty is the best policy”
Example: record every data because every data counts
Perseverance (Persevering)
Working on a problem until a solution is found.
Being obedient and diligent is the key.
Example: scientist worked so hard until they find solutions in their experiment.
Responsibility (Responsible)
Showing care and concern for living things and the environment.
Example: stop animal testing and global warming by using earth friendly products.
Teamwork
Sharing scientific information with other scientists.
Share facts not gossip or opinions.
Example: cooperation is a must to have a good team.
Electromagnets in our daily life
CP2 Physics :Appliances with electromagnets
What Home Appliances Use Electromagnets?
Household Appliances That Contain Magnets
- While the futuristic-sounding term "electromagnet" might conjure up images of extremely advanced, sophisticated technology that you would never expect to find lying around the house, manufacturers actually use electromagnets in a number of common home appliances. Unlike permanent magnets, electromagnets only display magnetic properties when electrical currents pass through them. Learn more about electromagnets and how different appliances utilize them.
- If it were not for an electromagnet, each time you went to push down the tab or handle on your toaster, the bread would disappointingly pop right back up untoasted. As Drexel University's Geometric and Intelligent Computing Laboratory notes, when you push down a toaster tab on a functioning toaster, a piece of material wedges itself in between two electrical prongs, thereby completing a circuit. The resulting electrical current, in addition to producing heat, activates a small electromagnet. This electromagnet attracts a metallic section on the back of the tab, holding it, and the wire bread-clamps that hold the bread, in place. Once the toaster heats the bread for the time you set it for, it will disrupt the electrical current and deactivate the electromagnet, allowing the tab and clamps to pop back up.
- Many computer printers rely on electromagnets to power their motors, which in turn power the printer's moving parts. As Solarbotics notes, these motors are known as stepper motors, and many other commonelectronics, such as fax machines and hard disk drives, also make use of them. A single stepper motor contains several stationary electromagnets known collectively as the stator, which surrounds a rotating, permanent magnet, known as the rotor. According to Images Scientific Instruments, to generate power, the motor conducts an electrical current into only one electromagnet at a time. As each electromagnet activates, it pulls the rotor towards it.
- Unlike the above types of home appliances, microwave ovens do not utilize small electromagnets for momentarily attracting sections of metal. Instead, the entire microwave oven unit itself acts like a giant electromagnet to create a controlled zone of electromagnetism inside of its cooking chamber. As the University of Colorado Department of Physics notes, microwave ovens generate electromagnetic waves known as microwaves, which cause water molecules to move or vibrate. As the moving water molecules rub up against other molecules in the food or drink you are heating, they produce friction. This friction in turn generates heat and warms your items.
Household Appliances That Contain Magnets
- A kitchen would be difficult to run without the use of magnets.
A large number of household appliances use magnets. Electromagnets are magnets that can be activated and deactivated through the application of electricity. This is useful in a number of common household items. People use them in their everyday lives, such as the magnets installed into shower curtains in order to easily stick them to the wall. A similar function is used in refrigerators.
- Your refrigerator uses a magnetic strip in its door. All refrigerators must seal to lock out the warm air and keep cool air inside. A magnet is what allows these seals to be so effective. The magnetic strip runs the length and width of the refrigerator and freezer door.
- A solenoid is an electromagnetic coil. This is a piece of metal with a wire around it. When electricity is applied to the wire, the metal becomes magnetic. Many dishwashers have a timer activated magnetic solenoid underneath them. When the time is up, according to Repair Clinic.com, the solenoid opens a drain valve that drains the dishwasher.
- All cathode ray tube, or CRT, televisions have magnets inside them. According to the How Magnets Work website, the image on any CRT TV is produced as a stream of electrons from an electron ray gun in the back of your TV. This stream is directed down a tube, called the cathode ray tube. The electrons travel straight until they are affected by electromagnets, along the sides of the tube. The electromagnets direct the stream toward the corners, sides and middle of your TV screen, allowing you to see it as it appears.
Computers use magnets in several ways. First, CRT computerscreens are produced like television screens. The electromagnets bend the stream of electrons making it visible on a large screen. According to How Magnets Work, computer disks are coated with metal that stores and transmits electromagnetic signals in patterns. This is how the information is stored on a computer disk.
LCD and plasma screens for both televisions and computers have static liquid crystals or gas chambers and do not operate the same way. These new technologies are not affected by magnets in household objects the way that a CRT screen would be.
- You can tell how many magnets a doorbell contains simply by listening to the number of tones it produces. According to the Knox News website, doorbells also contain solenoids like dishwashers. The solenoid in a doorbell causes a spring-loaded piston to strike a bell. It happens twice, because as you release the button the magnet passes beneath the piston again causing it to strike. This is where the "ding dong" sound comes from. Doorbells that have more than one tone have more than one chime, piston and magnet.
- A kitchen would be difficult to run without the use of magnets.
Laboratory Rules
-Do not run into or out of the laboratory
-Make sure that school bags are stored safely
-Put stools under the bench when not in use
-Leave the bench-top clean and dry
-Do not run in the laboratory
-Do not run in the laboratory
- Do not eat or drink in the laboratory
- Work quietly
- Work quietly
- Tie back longhair and if lab coats are available wear them, buttoned up
- Wear safety spectacles when anything is to be heated or if any hazardous chemicals are tobe used.
- Never point a test-tube containing chemicals at anyone, and do not examine the contents by looking down the tube.
- Tell the teacher about any breakage or spillage at once.
- Only carry out investigations approved by your teacher, and use the gas, water and electricity supplies sensibly.
- Do Not Pipette By Mouth - Ever
- Read the Chemical Safety Information
- Dress Appropriately (for chemistry lab, not fashion or the weather)
- Identify the Safety Equipment
- Don't Taste or Sniff Chemicals
- Don't Casually Dispose of Chemicals Down the Drain
- Don't Eat or Drink in Lab
- Don't Play Mad Scientist
- Take Data During Lab
Kamis, 22 Mei 2014
Langganan:
Postingan (Atom)