Gr 9 Science Exam - Chem

The particle theory of matter

Discovered by John Dalton

Matter is anything that has mass

1. All matter is made up of tiny particles that have empty spaces between them

2. Different substances are made up of different particles

3. Particles are in constant motion

4. Particles move faster with heat increase

5. The degree that particles are attracted to each other is different in different substances

States of Matter

Solids are rigid and have definite shapes

Their atoms are usually: closely packed together, regularly arranged, little movement, do not expand with heat, and extremely hard to compress

Liquids flow and take the shape of a container

Molecules in liquids are randomly oriented, expand slightly with heat, compress slightly under pressure

Gas less dense than liquids and solids, occupy all parts of a container, can expand infinitely, and is easily compressed

Distinguishing between a Compound and an Element

Element: can be found on the periodic table

Compound: made with 2+ elements

Chemical and Physical Properties of Matter

Physical:
Gives us information about what a substance is like

They are characteristics of a substance that can be determined without changing the composition of that substance

Make observations using our 5 senses

Chemical:

A property of a substance that describes its ability to undergo changes to its composition to produce one or more new substances

Include how a substance interacts with other substances such as water oxygen or acids

Can only be observed when a chemical change occurs

Qualitative and Quantitative Properties

Qualitative observation: not measured and does not have a numerical value

E.g. colour, odour, texture

Quantitative: measured and has a numerical value

E.g temperature, height, mass

Characteristic physical properties

A physical property that is unique to a substance and that can be used to identify it.

It can be determined without changing the composition of the sample

Density: ratio of mass to volume, usually in g/㎤ and g/mL

D = m/V m = DV V = m/D

Melting point: solid to liquid

Freezing point: liquid to a solid

Boiling point: liquid to gas

Electric conductivity

Physical and chemical change

Physical Change can usually be reversed

Is a change in which the composition of the substance remains unaltered and no new substances are produced

E.g. when ice melts into liquid or when paper is folded into an airplane

Chemical change always results in the formation of one or more new substances

The original substance does not disappear

The components of the original substance are simply rearranged in the process of forming a new substance

Evidence of a Chemical Change

A change in colour: has formed a different colour than the original substance

A change in odour: formed a new detectable odour

Production of gas: new substance is produced in the form of gas

Bubbles are visible, not caused by heating

Change in temperature or light: energy is released (exothermic) or absorbed (endothermic) during a chemical change

E.g. photosynthesis vs cellular respiration

Formation of a precipitate: does not dissolve in the mixture and shows up as a solid called precipitate

Mixtures

Made up of 2+ different kinds of particles

Solutions (Homogeneous Mixture): uniform mixtures, particles combine to make a pure substance appearance

Mechanical Mixture (Heterogeneous Mixtures): can distinguish (visible) between the two particles

Alloys

A metal by itself is a pure substance because it is only one type of particle

But when metals are mixed together they are called alloys, which are solid solutions (Homogeneous) of 2+ metals

Made by melting down pure metals and physical mixing them to make a solution

The Periodic Table Locations

They have similar physical and chemical properties

Metals: located on the left central side of the staircase

Solid, Luster/shiny, good electrical conductors, easy to shape (malleable)

Nonmetals: on the right upper portion of the periodic table

Mostly gas, dull powdery solids, or bromine as the only liquid, poor conductors of electricity, hard to shape and brittle

Metalloids: along the zigzag line dividing metals and nonmetals

Properties of both metals and nonmetals

Democritus

all matter can be divided into smaller and smaller pieces until a single indivisible particle was reached

Aristotle

everything is made up of earth air water and fire

John Dalton

each atom is a simple sphere with nothing else internally

J.J. Tomson

Atoms as a whole are neutral but negative electrons are scattered throughout it

There must be something positive in the atom for it to be neutral

Ernest Rutherford

Most of the atom is empty space where negative electrons move in

There is a small dense ball in the center, called the nucleus

The nucleus is positively charged, containing protons

James Chadwick

uncharged/neutral particles in the nucleus called neutrons

Niels Bohr

each electron have specific amounts of energy (electron shells)

Periods and groups on the periodic table

Periods are rows that go horizontally

A group/family are columns that go vertically

Groups on the periodic table

Group 1 under hydrogen: Alkali metals

Soft, high luster, highly reactive with other elements usually halogens

Group 2: Alkaline earth metals

Reacts often with oxygen, bright when burning

Group 3 to 12: Transition metals

All similar to each other

Group 17: Halogens

Highly reactive usually with alkali metals, solid liquid or gas at room temp,

Group 18: Noble gases

All gas, no reactions, colourless, odourless, tasteless

Hydrogen

Doesn’t fit into any of the other categories, similar to alkali metals but isn't a gas

Isotopes

Atoms of the same element have the same number of protons but varying # of neutrons

Ions

gained or lost electrons

Cations: lost electrons, usually metals (+1)

Anions: gain electrons, usually non-metals (-1)

Oxygen gas test

glowing splint (not lit) above a test tube relights with oxygen

Carbon dioxide gas test

extinguishes lit/burning splint with a squeaky pop OR bubble it through lime water → turns milky

Hydrogen gas test

extinguishes lit/burning splint with a squeaky pop, it’s flammable therefore → combustion

difference between an ionic bond and a molecular bond

Ionic Bond: when a metal comes into contact with a non-metal, they create an ionic bond (attraction between cations and anions), resulting in an ionic compound

Molecular Bond: 2 non-metals come together and share an electron, making covalent bonds which can turn into molecular compounds or molecular elements

difference between molecular elements and molecular compounds

Molecular elements: 2 atoms of 1 element

7 of these elements (diatomic): BrINClHOF

Bromine, Iodine, Nitrogen, Chlorine, Hydrogen, Oxygen, Fluorine

Molecular compounds: 2+ different elements

Chemical formulas show what elements are present

E.g. h2o, the 2 shows there are 2 hydrogen atoms

How Atoms Combine

Metals and metals

Alloys: created by melting two or more metals and mixing them together while still in liquid form, only homogeneous mixtures that aren’t transparent

Metals and non-metals

Name the metal first and the non-metal second

Keep the root of the non-metal and add an “-ide” at the end

Non-metals and nonmetals

They share an electron, the positive charge of both nucleus attract the electron

Covalent bond

Naming Molecular Compounds

mon(o) - only applies for the second element

di - 2

tri - 3

tetra - 4

penta - 5

…hexa…hepta

Names and Formulas of Ionic Compounds

Zero-sum rule: the sum in all charges must equal zero

Univalent metal: creates only 1 type of charge

Multivalent metal: can form more than 1 type of ion; e.g. copper can be 1+ or 2+

They will always include a roman numeral to indicate which type it is

E.g. copper(l) and copper(ll)

Standard Atomic Notation

Element symbol is located in the middle

Atomic number is on the bottom left (# of protons or # on the periodic table)

Mass number is on the top left (protons + neutrons)

Charge is on the top right (positive, negative, neutral)

Atomic structure

The number of protons in the nucleus determines what the element number is (atomic number) of the element

Atom: p+ = e–

Ion: p+ ≠ e–

Mass #: p+ + n0