Chemistry - Science 10

REVIEW

Classification of MatterMATTER

MIXTURES PURE SUBSTANCES

SUSPENSIONSParticles of one of the substances remain partly clumped together Ex/Orange Juice

MECHANICAL Particles of the different substances remain clumped together. Ex/ cereal,nuts,bolts,pepper

SOLUTIONS Particles of thedifferent substancesare completely mixedtogether.Ex/ Coffee with sugar

ELEMENTS Contain only asingle type of atomEx/ Gold-Au or Calcium-Ca

COMPOUNDS Contain 2 or moretypes of atoms, joinedtogether.Ex/ Ethanol CH3CH2OH

Two Types of Mixtures

Heterogeneous- Different from place to place Not evenly mixed Included suspensions and mechanical mixtures Chocolate chip cookie, gravel, soil

Homogeneous- The same throughout Evenly mixed solutions Kool-aid, sea water, air

Pure Substance

Elements- Simplest kind of matter Can’t be broken down further All one kind of atom About 120 kinds of elements Each has a 1 or 2 letter symbol Each behaves differently Everything else is made up of them

Pure Substances

Compounds- Made of two or more elements chemically combined Atoms combine together to make molecules All molecules of a compound are the same

They mix in the same ratio Compounds behave completely differently

from the elements that make them Ex. Water H2O–liquid puts out fire: hydrogen

burns, oxygen supports combustion

Physical vs. Chemical Changes Physical Changes: No new substance has been

formed.(ex/ ice cube melting, or crumpling a piece of paper.

All the molecules stay the same Might look a little different Keeps original properties Changing phases Making a mixture Cutting Grinding Dissolving

Chemical Changes: If one or more substances have been produced, substances with properties different from the starting materials, then a chemical change has taken place.

Products are not at all like the reactants Makes new odor, color, etc. Completely new properties

Clues to tell you a “Chemical Change” has taken place:

A new colour may appear. Heat or light may be given off. Bubbles of gas may be formed. Solid material may form in a liquid. The change may be difficult to reverse.

Chemical Reactions

Chemical Reaction is another term for chemical change. (ex. Fast- fireworks, or slow- rust)

Starting materials are called reactants. (Found on the left of the arrow in a chemical equation)

Any substance produced in the reaction is a product. (on the right of the arrow).

Word Equations

Word equations tell us the names of the reactants and products in a reaction. Reactants on the left,(of the arrow) products on the right.

Note: It does not tell us the amounts of the atoms/elements required to make the reaction go!

Ex/ SodiumChlorine-----Sodium Chloride

Mass and Chemical Change

The Law of Conservation of Mass: In a chemical reaction, the total mass of

the reactants is always equal to the total mass of the products

Chemical Formulas

Tell the element and number of atoms in a molecule

Symbols identifies the element Subscripts tell the number of atoms Don’t write one as a subscript

Chemical Formulas

H2O

2 Hydrogen atoms 1 Oxygen atom

subscript

Chemical Formulas

C12H22O11

12 Carbon atoms

22 Hydrogen atoms

11 Oxygen atoms

Chemical Properties

Used to describe how substance reacts How it changes

By combining with other substances Or breaking apart

Reactivity how a substance combines with other substances

Things like flammability, rusting, etc.

Physical Properties

Can be observed or measured without changing the composition

Melting point , boiling point, hardness, odor, ability to conduct electricity and heat

Density – how heavy something is for its size Ratio of mass to volume If the density of substance is less than its

surroundings, it floats

Density

Found by dividing the mass by volume D = m

V Units of g/mL or g/cm3

Water has a density of 1 g/mL

Law of Conservation of Energy

In all chemical changes, energy cannot be created or destroyed

All the energy you put in, you get out It might be hard to count

KINETIC MOLECULAR THEORY

•All matter is made up of extremely small particles that are always moving (atoms and molecules) with spaces between them

•The particles are close together and slowest moving in solids, and farthest apart and fastest in gases

•Heat makes the particles move faster

Changes of State of Matter

sublimation

GAS

LIQUID

SOLID

solidification melting

sublimation

condensation evaporation