CHEMICAL BONDS

Basic concept on chemical bonds

1. Ionic bond: The bond formed when one atom looses electrons and the other accepts  

      them. It is formed when a metal bonds to a non-metal, example: NaCl

Original electronic configuration : Na  2:8:1                      Cl    2:8:7

Sodium loses one electron from its outermost shell (valence shell)  to become   Na+ 2:8                   and  chlorine gains this electron to become Cl^-   2:8:8   

 Hence  Na⁺Cl^{-    ----------->} NaCl

2. Covalent bond: This is the bond formed through the sharing of electrons. It is formed

    when non-metal bond to each other. Examples: H₂, Cl₂, HCl

Illustration of covalent bonding

Water is neither purely ionic nor purely covalent because the electrons are not shared equally. The more electronegative element, oxygen, tends to pull the shared electrons from the less electronegative (electropositive), hydrogen atom. One end, or pole, of the molecule has a partial positive charge (+), and the other end has a partial negative charge (-).Water is best described as a polar compound.

As a rule, when the difference between the electronegativities of two elements is less than 1.2, we assume that the bond between atoms of these elements is covalent. When the difference is larger than 1.8, the bond is assumed to be ionic. Compounds for which the electronegativity difference is between about 1.2 and 1.8 are best described as polar, or polar covalent.

Hydrogen bonding: When hydrogen atoms are joined in a polar covalent bond with a small atom of high electronegativity such as O, F or N, the partial positive charge on the hydrogen is highly concentrated because of its small size. If the hydrogen is close to another oxygen, fluorine or nitrogen in another molecule, then there is a force of attraction termed a dipole-dipole interaction. This attraction is known as hydrogen bonding.

Hydrogen bonding has a very important effect on the properties of water and ice. Hydrogen bonding is also very important in proteins and nucleic acids and therefore in life processes. 

THE REFLEX ARC

When a person steps on a sharp object, the response is immediate. It does not initially involve the brain. This involves the reflex arc which occurs in the spinal cord. The reflex arc consists of the sensory neuron (also called the afferent neuron), which transmits the stimuli of pain to the spinal cord. Within the spinal cord, it relays with the interneuron which decodes the message and sends the response to the muscles of the limbs via the motor neuron (also called efferent neuron) to bring about an action.

Diagram showing the reflex arc.

BASICS OF ELECTRICITY

There are two types of electrical circuit arrangements.
1. Parallel circuits: There is an alternate path to the flow of the current if other paths are blocked.

Note on diagram below: The symbol "R" represents any form of resistance such as bulb resistors, etc. The symbol "E" represents a cell such as battery, a current generator.

2. Series circuit: There is only one path for the current to flow. When this path is blocked, there will be no flow of current.
 
 Animation in a series circuit.

UNITS OF ELECTRICAL QUANTITIES

Variable	Symbol	Unit	Symbol
Voltage	V	Volts	V
Current	I	Ampere	A
Resistance Power	R P	Ohm Watt	Ω W

Formulas you should know:

1. Voltage = Current x Resistance

2. Power = Voltage x Current

You should be able to use these formulas in calculations.

MAGNETISM AND ELECTROMAGNETS

Magnetism

There is a magnetic field around a magnet. This is a mathematical representation of the interaction between the magnetic material and electrical current. It is represented by magnetic field lines which moves out of the north pole into the south pole.

Diagram of magnetic field lines.

It is very important to note the direction of the arrows on the field lines.

Interaction between two magnets
1. North and South poles attract (opposite pole attract). Diagram of attractive forces.
2. North and north poles will repel; south and south poles will repel (Like poles repel).

Diagram of repulsive forces for north to north poles.

Diagram of repulsive forces for south to south poles.

Electromagnetism is the study that involves the use of electricity to create magnet and vice versa (that is, using a magnet to generate electricity).

What is a solenoid?

The solenoid is a long coil containing a large number of close turns of insulated copper wire. A magnetic field  is produced by the current carrying solenoid. The strength of magnetic field produced by a current carrying solenoid is directly proportional to the number of turns and the strength in the solenoid. It is also dependent on the nature of "core material" used in making the solenoid. When soft iron rods are used as cores, they produce the strongest magnetism. Solenoids are used for making electromagnets. 

What is an electromagnet? Diagram

When an electric current flows through a soft iron rod placed inside a solenoid, a temporary magnet is created. It acts as a magnet only so long as the current is flowing in the solenoid. This combination of a solenoid and a soft iron core is called an electromagnet. An electromagnet, therefore, consists of a long coil of insulated copper wire wound on a soft iron core.

Here are some uses of electromagnets:

1. Used in cranes to lift heavy metal.

2.  Used in electric bells

3. Used in radio speakers

4. Used in microphones

5.  Used in dynamos

STRUCTURE OF THE HUMAN BRAIN

The brain is very complex but we will discuss the basic concepts needed for the exam.

1. Cerebrum: This forms the bulk of the brain and it is responsible for the intellectual functions such as thinking, learning, motor skills, sensory functions, personality, etc.
2. Cerebellum: This is the center that helps with balancing of the body during various movements.
3. Medulla oblongata: This is the cardio-respiratory center. It controls the rate of the heart and also the rate of respiration. It is closely related to first cervical bone which has the protrusion called the dens. When the dens fractures during a whiplash injury, it can compress on the medulla and then the heart and respiratory system will fail to function.
4. Thalamus: This relays motor and sensory signals to the cerebral cortex. It regulates consciousness, sleep, and alertness. 
5. Hypothalamus: The hypothalamus is responsible for certain metabolic processes such as the synthesis and secretion of certain neurohormones (often called releasing hormones or hypothalamic hormones). It also plays a role in autonomic nervous system by controling body temperature, hunger, important aspects of parenting and attachment behaviors, thirst, fatigue, sleep, and circadian rhythms.
6. Pons: This acts as a relay station between the cerebrum and the cerebellum. It is also plays a role in sleep and dreaming.

THE STRUCTURE OF THE EAR

Click here to look at the Diagram of the human ear

There are three parts of the human ear. We will not deal with the fine details here. Just know the basic things.
1. Outer ear: This extends from the pinna (ear lobe) to the tympanic membrane/tympanum (ear drum). It has the auditory canal or meatus. This conducts sound to the middle ear.
2. Middle ear: The middle ear house the three bony structure called incus (anvil), malleus (hammer), and stapes (stirrup). They vibrate to transmit the sound waves to the inner ear.
3. Inner ear: The houses the cochlear, semi-circular canals, and the vestibule. There are three semi-circular canals arranged at right angles to each other (superior, lateral, and posterior semi-circular canals)

Important to note: The cochlear is the organ for hearing. The semi-circular canals are the organ for balancing.

Think about what will happen when the cochlear or semi-circular canal is damage.

THE STRUCTURE OF THE EYE

Today, we will discuss the basic structure of the human eye.

•          Lens: For focusing of objects onto the retina.

•          Iris: Controls the amount of light entering the eye by changing the size of the pupil.

•          Pupil: This is the aperture (hole) bounded by the iris.

•          Retina: The back of the eye where the image is formed. Contains the light sensitive structures rods and cones.

•          Rods: Needed for night vision since they are very sensitive to light. Helps to distinguish between black and white objects.

•          Cones: Needed for day time vision and for distinguishing between colors.

•          Optic nerve: Transmits the image from the retina to the brain.

•  The lens divides the eye into anterior and posterior chambers. The anterior chamber contains the fluid called aqueous humor and the posterior chamber contains the gel-like substance called the vitreous body.
• The ciliary muscles control the thickness of the lens. That is, it stretches the lens.
• The Canals of Schlemm drain the aqueous humor.

QUESTIONS FOR THE DAY

Label the numbered parts and state their functions.



Answers to the numbered parts

THE ENDOCRINE SYSTEM

An endocrine gland is a gland without ducts. The secretions are released directly into the blood. The endocrine glands secrete hormones that regulate various metabolic activities in the body.
Here is a good diagram of the endocrine system. Click here. You can be given a diagram like this and you could be asked to identify the various glands.

Hypothalamus: The hypothalamus produces eight (8) hormones. Some of the hormones stimulate the pituitary gland to produce other hormones.

1. Thyrotropin-releasing hormone - This acts on the pituitary to release thyroid stimulating hormone (TSH)
2. Growth hormone-releasing hormone-This acts on the pituitary to release growth hormone (GH)
3. Gonadotropin-releasing hormone -This acts on the pituitary to release gonadotropins, namely, Follicle stimulating hormone (FSH) and Luteinizing hormone (LH).
4. Corticotropin-releasing hormone -This acts on the pituitary to release adrenocorticotropic hormone.
5. Oxytocin -This causes uterine contractions and also helps with secretion of the breast milk during lactation.
6. Dopamine - It is a neuroendocrine transmitter. Acts as a neuro-transmitter and also stimulates the release of othe hormones.
7. Vasopressin (Antidiuretic hormone -ADH) - Acts on the kidneys to prevent the lost of water via the urine.
8. Somatostatin - It inhibits the release of growth hormone.

Pituitary gland: Has an anterior (hormone-producing glandular) portion and a posterior (neural) portion which is an extension of the hypothalamus.  Two hormones ( Oxytocin and ADH) produced by the hypothalamus are stored in the posterior pituitary later release.

Four of the six pituitary hormones are tropic hormones. They regulate the function of other endocrine glands.Here are the hormones produced by the anterior portion:

1.  Growth hormone (GH): It stimulates growth of all body tissues but especially skeletal muscle and bone. GH mobilizes fats, stimulates protein synthesis, and inhibits glucose uptake and metabolism. Over production can lead to gigantism while underproduction can lead to dwarfism.

2. Thyroid-stimulating hormone (TSH): This promotes normal development and activity of the thyroid gland. 

3. Adrenocorticotropic hormone (ACTH): This stimulates the adrenal cortex to release  corticosteroids. 

4. The gonadotropins (follicle-stimulating hormone (FSH) and luteinizing hormone (LH)): These regulate the functions of the gonads in both sexes. 

     (a) FSH stimulates sex cell production.  

     (b) LH stimulates gonadal hormone production. 

5. Prolactin (PRL): This promotes milk production in humans females. 

The posterior portion stores and releases two hypothalamic hormones:

1. Oxytocin: This stimulates powerful uterine contractions during labor and delivery of babies. It also causes milk ejection in nursing women. 

2. Antidiuretic hormone (ADH): This stimulates the kidney tubules to reabsorb and conserve water. This results in the production of small volumes of highly concentrated urine and decreased plasma osmolality. Underproduction leads to a condition called diabetes insipidus, where the affected person passes a lot of diluted urine.

Thyroid gland

It produces the thyroid hormone (TH), which includes thyroxine (T4) and triiodothyronine (T3). It increases the rate of cellular metabolism. 

Calcitonin, is produced by the parafollicular cells of the thyroid gland. It decreases the blood calcium levels.

Parathyroid glands

It secretes parathyroid hormone (PTH), which causes an increase in blood calcium levels.

Pancreas

The pancreas is both an exocrine and an endocrine gland. Exocrine means that it has ducts. The endocrine portion (islets of langerhans) releases insulin and glucagon. It also releases smaller amounts of other hormones to the blood.

Glucagon, released by alpha (α) cells - It increases the glucose level in the blood.

Insulin is released by beta (β) cells - It reduces the glucose level in the blood. It increases the rate of glucose uptake and metabolism by most body cells. 

Gonads

The ovaries of the female release two main hormones - estrogens and progesterone. Estrogens stimulate maturation of the female reproductive system and development of the secondary sexual characteristics. Progesterone works with estrogens in establishing the menstrual cycle.

The testes of the male produce testosterone. It promotes maturation of the male reproductive organs, development of secondary sex characteristics, and production of sperm by the testes.

Pineal gland

The pineal gland produces the hormone  melatonin, which influences daily rhythms such as sleep and wake patterns.

Thymus 
It is an important organ of the immune system during the developmental stages of life. It vanished by the time of birth. The T-cells mature here.

ANSWERS TO QUESTIONS FOR THE DAY

1. A car is traveling at the speed of 20 mph. How far will it travel in 5 hrs?
A. 4 mi
B. 100 mi  (distance = speed x time; 20 mph x 5 hrs= 100)
C. 20 mi
D. 25 mi

2. A car is traveling at the speed of 20 mph. How far will it travel in 30 minutes?
A. 600 mi
B. 50 mi
C. 10 mi (distance = speed x time; change 30 minutes to hours first, then 20 mph x 0.5 hrs= 100)
D. 15 mi

3. What is the distance traveled in 5 seconds by the car whose graph is shown below?

A. 10 m
B. 50 m (The distance is the area under the graph from 0-5 s, this is a triangle so Area=1/2 x 5 x 20 = 50)
C. 100 m
D. 20 m

Use the graph below to answer the following questions.



4. During which time interval is the object decelerating?
A. 12-16 s
B. 4-10 s
C. 0-2 s
D. 10-12 s

5. During which time interval is the object accelerating?
A. 12-16 s
B. 4-10 s
C. 0-2 s
D. 10-12 s

6. During which time interval is the object moving with a constant speed?
A. 2-10 s
B. 4-10 s
C. 0-2 s
D. 10-12 s

7. During which time interval did the object travel the greatest distance?
A. 2-10 s (The distance is the area under the graph. You can estimate this using the number of boxes)
B. 4-10 s
C. 0-2 s
D. 10-12 s

7. During which time interval did the object travel the shortest distance?
A. 2-10 s
B. 12-16 s
C. 0-2 s The distance is the area under the graph. You can estimate this using the number of boxes)
D. 10-12 s

8. An object travels a distance of 15 meters when an force of 4 N  act on it. What is the work done?
A. 30 J
B. 19 J
C. 60 J (Work = force x distance)

D. 11 J

QUESTIONS FOR THE DAY

1. A car is traveling at the speed of 20 mph. How far will it travel in 5 hrs?
A. 4 mi
B. 100 mi
C. 20 mi
D. 25 mi

2. A car is traveling at the speed of 20 mph. How far will it travel in 30 minutes?
A. 600 mi
B. 50 mi
C. 10 mi
D. 15 mi

3. What is the distance traveled in 5 seconds by the car whose graph is shown below?

A. 10 m
B. 50 m
C. 100 m
D. 20 m

Use the graph below to answer the following questions.



4. During which time interval is the object decelerating?
A. 12-16 s
B. 4-10 s
C. 0-2 s
D. 10-12 s

5. During which time interval is the object accelerating?
A. 12-16 s
B. 4-10 s
C. 0-2 s
D. 10-12 s

6. During which time interval is the object moving with a constant speed?
A. 2-10 s
B. 4-10 s
C. 0-2 s
D. 10-12 s

7. During which time interval did the object travel the greatest distance?
A. 2-10 s
B. 4-10 s
C. 0-2 s
D. 10-12 s

7. During which time interval did the object travel the shortest distance?
A. 2-10 s
B. 12-16 s
C. 0-2 s
D. 10-12 s

8. An object travels a distance of 15 meters when an force of 4 N  act on it. What is the work done?
A. 30 J
B. 19 J
C. 60 J
D. 11 J

IMPORTANT MOTION FORMULAS

There are some few motion formulas that you should know for the test.

1. Distance = speed x time 

2. Work = Force x distance

3. acceleration = change in velocity  =  Final velocity - Initial velocity  

                            change in time              Final time - Initial time

                            

Positive slope means the car is accelerating, that is the velocity is increasing with time. Zero slope means the velocity is constant (that is, not changing with time), and negative slope means the car is slowing down (that is, the velocity is decreasing with time)

Also, you must know the standard international (SI) units of the following:

1. Work -------------Joules (J)

2. Force ------------- Newtons (N)

3. Velocity ---------- meters per second (m/s)

4. Time ------------ seconds

MOVEMENT ACROSS THE CELL MEMBRANE

Today, we will discuss the various types of movements across the cell membrane. This is a very important topic that you should know very well for the test. Don't just memorize the definitions but know different applications of the concepts. It is important to know some of the examples of hand!

Movement of substances across the cell membrane

1. Diffusion or passive transport: It is the movement of materials from a region of higher to a region of lower substance concentration.                                                                                                                                                                                                                                         Examples: When a bottle of perfume is opened, the scent spreads throughout the room. A drop of ink placed in a cup of water spreads throughout the water by diffusion.                                                
2. Active transport: It is the movement of molecules from a region of lower concentration to a region of higher concentration in which energy is needed in the form of ATP. The movement of the substance is against a concentration gradient.                                                                                                                                                                                                                                                          Examples: Sodium is pumped out of the cell by active diffusion. Potassium is pumped into the cell by active diffusion.                                                                                                                                       
3. Osmosis: It is the flow of water molecules from a less concentrated solution (hypotonic solution) to a higher concentrated solution (hypertonic solution) through a semi-permeable membrane.                                                                                                                                                                Example: When a red blood cell is placed into water, the water flows across the cell membrane into the cell because of the dissolved salts in the cytoplasm.                                                              Water flows from the soil into the roots of plants by osmosis.                                                                   
4. Facilitated diffusion: As certain substances move into the cell by simple or passive diffusion, they create the opportunity for other substances to go into the cell freely.                                                                                                                                                                                              Example: Glucose follows sodium as it enters the cell by facilitated diffusion.                                               
5. Endocytosis: This is the process by which the cell engulfs or captures substances into the cytoplasm. It consist of pinocytosis (Cell-drinking) and phagocytosis (Cell-eating)                                                            
6. Exocytosis: This the process by which the cell extrudes or gets rid of substances  from within the cell to the outside.                                                                                                                                              

PHYSICS - LAWS OF MOTION

We will study some physics today. Horray! You need to know some basic physics for the test. We will consider some of the laws of motion and their applications.

NEWTOW'S LAWS OF MOTION

1. A body at rest will remain at rest or if it is in motion, it will continue to move unless an opposing force acts on it. This law explains why if you leave a book on a table, it will be there forever unless somebody moves it. It also explains why somebody is thrown out of a moving car or bus live a projectile when the vehicle comes to a sudden stop. You move at the same speed of the vehicle you continue to move with this speed until the windshield stops you (opposing force)

2. The force on an object is directly proportional to its acceleration and the mass. The acceleration is inversely proportional to the mass. In others words, as the acceleration and the mass increase, the force increases. As the mass increases, the acceleration decreases and vice versa.

Force = Mass x Acceleration 

3. Action and reaction forces are equal but in opposite directions. What does this mean? If you push a wall, you exert an act force on it. The wall pushes you back with the same force (reaction force) which is in the opposite direction. The same thing happens with you standing on the ground.

QUANTITIES

There are two types of quantities used in science.

1. Scalar quantity: This quantity has only magnitude. Example: mass, time, density, volume, distance, speed, etc. Only the magnitude or size matters! For example, traveling 2 miles is distance or traveling at the speed of 2 mph or 2 km/hr.

2. Vector quantity: This quantity has both magnitude and direction. For example, displacement, velocity, weight, force, etc. The direction has to be specified.  For example, traveling 2 miles north is displacement or traveling at the velocity of 2 mph or 2 km/hr west.

ATOMIC STRUCTURE

STRUCTURE OF THE ATOM AND ELECTRON CONFIGURATION 

MATH PRACTICE QUESTIONS

PRACTICE 1
1	When taking a patient’s pulse, one counts 23 beats in 15 seconds. How many times will the patient’s heart beat in 1 minute
2	76.2  x 1.04
3	Divide 3.45 by 0.15
4	Write 5/7 as a decimal
5	A recipe requires 2½ cups of nonfat milk. A person already has ¾ cup. How much more is needed?
6	Of the children coming into a clinic, 7.5% have a certain condition, For every 150 children that visit the clinic, how many are expected to have this condition?
7	A woman’s diet contains 75% of the recommended amount of iron. If the recommended amount is 18 mg, how much more iron does she need to meet this requirement?
8	The 6% sales tax on textbooks was $3.54. How much did the textbooks themselves cost?
9	If 30% of a certain number is 120, what is the number?
10	Solve the following system of equations 3x + 2y = 16 4x + 2y = 24
11	A 3-oz serving of corned beef hash supplies 153 calories. How many calories will be supplied in 5-oz serving?
12	You spent 1/5 of your salary for taxes, ¼ for rent, and 1/10 for movies. What fraction of your salary is left for other expenses and savings?
13	If 65% of a student body of 2000 students passed a mathematics examination, how many students did not pass?