Science Midyear

ExamReview

Science Midyear Exam ReviewTerm One

1. The Atom

Science Midyear Exam ReviewTerm One

2. History of the Atom

Not on Midyear

Science Midyear Exam ReviewTerm One

3. Periodic Table

3. Periodic Table - A row (period) tells us how many shells an element has.

- A colum (group) tells us how many valence electrons an element has.

Metals are to the left of the staircase, non-metals to the right and metalloids along the staircase. Group 1: Alkali Metals

Group 2: Alkaline Earth MetalsGroup 7: HalogensGroup 8: Noble Gases

Science Midyear Exam Review4. Representing Atoms

- Lewis Dot Notation: (Only look at valence electrons)

Oxygen: Boron:

O B- Rutherford-Bohr Model:

Oxygen:

8+

- Simplified Atomic ModelCarbon:

6 p+2 e- 4 e-

Science Midyear Exam Review5. Ions

An ION is an atom that has become electrically charged by losing or gaining one or more electrons.

How do we know whether an atom will gain or lose electrons?They want to become like the noble gases, they want to become stable and have full valence electron shells.

P. 42 - 43

Lithium:

3 p+

2 e- 1 e-

Ion form:

3 p+2 e-

Oxygen:

8 p+

2 e- 6 e-

8 p+

2 e- 6 e-

Charge= +1

Charge= -2

Science Midyear Exam Review

5. Ions

Oxygen:

8 p+

2 e- 6 e-

8 p+

2 e- 6 e-

What has happened to a positive ion?

a) It has lost electrons

b) It has gained electrons

c) It has lost protons

d) It has gained protons

Science Midyear Exam Review6. Solutions and Concentration

An aqueous solution is a solution with water. (Ex; Water and Salt)

1% = 1 (g or ml)100 (ml or g)

1 ppm = 1 g 1000L

mlL

- 1000

x 1000

1 mg1 L1 ppm = OR

6. Solutions and Concentration

3. Analysis of a 25 L sample of well water shows that it contains 6 mg of dissolved arsenic.What is the concentration in ppm of dissolved arsenic?

1% = 1 (g or ml)100 (ml or g)1 ppm = 1 g

1000L

1 mg1 L1 ppm = OR

ml

L

- 1000

x 1000

1. Calculate the concentration (g/L) if 30 g are dissolved in 250 ml of solution.

2. What is the PPM concentration if 0.06 g are dissolved in 3000 ml of solution?

120 g/L

20 PPM

0.24 PPM

Science Midyear Exam Review7. ElectrolytesAn electrolyte is a substance that allows an electric current to flow through the solution (when it's dissolved in water).

Acids: Releases H+ ions. Starts with HEx: HCl and H2SO4

Bases: Releases OH- ions. Ends in OHEx: NaOH and Mg(OH)2

Salts: Produced by the chemical bonding of a metal and non-metal. Doesn't start with H, doesn't end in OH

Ex: NaCl and AgNO

Science Midyear Exam Review7. Electrolytes: PHPH Scale ranges from 0 to 14If the PH level is less than 7, the solution is acidicIf the PH level is 7, the solution is neutral. If the PH level is greater than 7, the solution is basic.

or Basic

The difference of one unit between two substances actually indicates that one of the substances is 10 times more acidic than the other.

For example, a solution with a pH of 3 is _10__ times more acidic than a solution with a pH of 4.

A solution with a pH of 9 is _100_ times less basic than a solution with a pH of 11.

Science Midyear Exam Review8. EnergyEnergya. The Law of Conservation of Energy: Energy cannot be created nor destroyed; it can only be transferred or transformed. b. Energy efficiency: the percent of energy consumed by a machine or system that was transformed into useful energy.

Energy efficiency = Amount of useful energy

Amount of energy consumedx 100

Example: A fluorescent light bulb uses 100 joules of electrical energy. 25 Joules is light energy, how energy efficient is this light bulb?

25 %

Science Midyear Exam Review9. Chemical Changes

The Law of Conservation of Mass (Matter)The total mass of reactants is always equal to the total mass of products.

p.110

Before the reaction After the reactionDuring

CH4 + 2 O2

CO2 + 2H2O

16 g + 64 g 44 g + 36 gC OO

H

O

H

H

O

H

O OC

H H

H

HO O

Example: Which of the following examples below can be used to verify the Law of Conservation of Mass?

a) 5 g + 11 g ---> 12 g + 4 g

b) 12 g + 8 g ---> 6 g + 15 g

c) 24 g --> 11 g + 13 g

Science Midyear Exam Review9. Chemical Changes p.110

Example: Which of the following examples below can be used to verify the Law of Conservation of Mass?

a) 5 g + 11 g ---> 12 g + 4 g

b) 12 g + 8 g ---> 6 g + 15 g

c) 24 g --> 11 g + 13 g

Science Midyear Exam Review10. Types of Chemical ChangeAcid-Base Neutralization: a chemical change involving the reaction of an acid with a base, producing a salt and waterOxidation: a chemical change involving oxygen (or with properties similar to oxygen)Combustion : a form of oxidation that releases a large amount of energyCellular-Respiration: a chemical change where glucose and oxygen are used to generate energy, the reaction also produces carbon dioxide and water

Photosynthesis: a chemical change that produces glucose and oxygen from solar energy, carbon dioxide and water

Photosynthesis

Solar energy + Carbon Dioxide + Water -> Sugar + Oxygen

Sugar + Oxygen -> Energy + Carbon Dioxide + Water

Balancing Chemical Equations

1. _2___ H2 + _____ O2 _2__ H2O

__2__ H3PO4 _____ H4P2O7 + _____ H2O

Science Midyear Exam Review11. ElectricityNegatively Charged Bodies: have more electrons then protonsPositively Charged Bodies: have less electrons then protonsRemember that the number of protons never changes! Substances can only lose or gain electrons.

Conductors allow the free flow of electrical chargesInsulators hinder the free flow of electrical charges

Science Midyear Exam Review11. Electricity

+ - + +If A is negatively charged, what charge does C have?

If A is positively charged, what charge does D have?

Opposite charges attract Like charges repel

A B B C

A B B C C D

Science Midyear Exam Review12. Static ElectricityMost objects and substances are neutrally charged (same number of protons and electrons)Objects can become positively (+) charged by losing electronsObjects can become negatively (-) charged by gaining electrons

Tendency to gain electrons(acquire a

negative charge)

Tendency to lose electrons

(acquire a positive charge)

Plastic

Nickel

Paper

Silk

Wool

Glass

What charge will each substance acquire when plastic and wool are rubbed together?

PlasticWool

What about wool and glass? Wool

Glass

Science Midyear Exam Review13. Ohm's Law V = IR

1.Find the current through a 12-ohm resistive circuit when 24 volts is applied.

2.Find the resistance of a circuit that draws 0.06 amperes with 12 volts applied.

3.Find the applied voltage of a circuit that draws 0.2 amperes through a 4800-ohm resistance.

2 A

200 Ohms

960 V

How should you prepare for your midyear science exam?1. Study!Read through your notes and worksheets, ask yourself questions about what you are reading, explain it to someone else because teaching is a great way to learn.

2. Visit facilelearningLook through the topics we have covered, answer the questions. Take your time!

3. Get a good night's sleepTeenagers should be sleeping 8.5 to 9 hours a night. Go to bed early, keep yourself energized.

4. Eat wellHave a big and healthy breakfast before your exams. Bring healthy snacks to school.