Science Midyear Review 2015 - Ms. Jadah's Virtual...

Science Midyear Review 2015

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Grade 10 Science Midyear ExamReview

Chapter One: Atoms and Elements

1. The Atom

History of the Atom• Dalton's Atomic Model: Atoms are solid, indivisible balls of

different masses

• Thomson's Atomic Model: Saw the atom as a blueberry muffin (muffin dough is positively charged while blueberries are embedded in them that are negatively charged electrons)

• Rutherford's Atomic Model: A small, dense, nucleus contains the entire positive charge of the atom, while electrons are scattered randomly in a large space around the nucleus.

• The RutherfordBohr Atomic Model: Consists of a very small nucleus surrounded by electrons moving in a series of orbits.


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, nonmetals to the right and metalloids along the staircase.

Group 1: Alkali MetalsGroup 2: Alkaline Earth MetalsGroup 7: HalogensGroup 8: Noble Gases



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Representing Atoms

Lewis Dot Notation: (Only look at valence electrons)

Oxygen: Boron:

O B RutherfordBohr Model:Oxygen:

8+

Simplified Atomic ModelCarbon:

6 p+2 e 4 e

Chapter One: Atoms and ElementsIonsAn 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

As an Atom:

Chapter Two: Molecules and Solutions

1. How did Beryllium become Be+2? a) It gained 2 electronsb) It gained 2 protonsc) It lost 2 electrons d) It lost 2 protons

2. What has happened to a posive ion? a) It has lost electrons b) It has gained electrons c) It has lost protons d) It has gained protons

3. How many protons and electrons does N‐3 have?

IonsChapter Two: Molecules and Solutions Solutions and Concentration

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

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

? ppm = ? g 1000L

ml L

- 1000

x 1000

? mg1 L? ppm = OR



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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?

Electrolytes

An electrolyte is a substance that allows an electric current to flow through the soluon (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. Ex: NaCl and AgNO


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 ____ times more acidic than a solution with a pH of 4.

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


Energy

a. The Law of Conservaon 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 energyAmount of energy consumed x 100

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

Chapter Three: Different Forms of Energy


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Chapter Three: Different Forms of Energy

Thermal Energy: Thermal energy is energy from fire, the sun or a heang element.

It comes from the random movement of all the microscopic parcles in a substance. As the temperature increases, there are more parcles and increased thermal energy.

Heat: The transfer of thermal energy between two environments with different temperatures. Heat always pases from the warmer to the cooler environment.

Temperature: The measure of the degree of agitaon of the parcles of substance.

Chemical ChangesThe Law of Conservaon of Mass (Maer)

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 g

C OOH

O

H

H

O

H

O OC

H H

H

HO O

Example: Find the mass of H2 in the chemical reaction below.

2 Na + 2 H2O > 2 NaOH + H2

46 g + 36 g > 72 g + ?

Chapter Four: Changes in Matter

Types of Chemical ChangeChapter Four: Changes in Matter

Acid‐Base Neutralizaon : a chemical change involving the reacon of an acid with a base, producing a salt and water

Oxidaon : a chemical change involving oxygen (or with properes similar to oxygen)

Combuson : a form of oxidaon that releases a large amount of energy


Types of Chemical Change


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Cellular‐Respiraon : a chemical change where glucose and oxygen are used to generate energy, the reacon also produces carbon dioxide and water

Sugar + Oxygen > Energy + Carbon Dioxide + Water

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

Solar energy + Carbon Dioxide + Water > Sugar + Oxygen

Types of Chemical Change


Signs a chemical change has occured: ‐ release of gas‐ emission or absorpon of heat‐ emission of light ‐ a change in colour ‐ the formaon of a precipitate

Ex: baking bread, burning wood

Does not alter the nature or the characteriscs of maer. The atoms and molecules of the substance do not change.

Ex: chopping wood


Balancing Chemical Equations

1. _____ H2 + _____ O2 _____ H2O _____ H3PO4 _____ H4P2O7 + _____ H2O


Negavely Charged Bodies: have more electrons then protons

Posively Charged Bodies: have less electrons then protons

Remember that the number of protons never changes! Substances can only lose or gain electrons.

Conductors allow the free flow of electrical charges

Insulators hinder the free flow of electrical charges

Chapter Five: Electricity and Magnetism


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

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

Opposite charges aract Like charges repel

A B B C

A B B C C D

Chapter Five: Electricity and MagnetismStatic ElectricityMost objects and substances are neutrally charged (same number of protons and electrons)

Objects can become posively (+) charged by losing electrons

Objects can become negavely (‐) 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?

Plastic Wool

What about wool and glass? Wool Glass


Static ElectricityChapter Five: Electricity and Magnetism

Three methods to charge an object:

• Friction: Starts with two neutral objects, and the friction pulls electrons away from one of the objects and transfers them to the other. Afterwards there are two objects with opposite charges.

• Conduction: Starts with one charged object and one neutral object. The charge of one object is shared between two objects when they come into contact. Afterwards there are two objects with like charges.

• Induction: Starts with one charged object and one neutral object. The closeness of the charged object causes the charges in the neutral object to separate. Afterwards you have one charged object and one object carrying a partial positive charge on one side and a partial negative charge on the other side.

+

++ + +

+ +++

+

Ohm's Law

V = IR

where V is potential difference (in )

I is Current Intensity (in )

R is Resistance (in )


Ex: Find the resistance of a circuit that draws 0.06 amps with 12 volts applied.

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