Test Review for 3rd Period

• You must end up with the same amount you started with.

• Mass cannot be created or destroyed

Conservation of Mass

Conservation of Mass

• Matter is not created or destroyed

A change in matter that results in one or more new substances. You change what it is.

Chemical in the original substance combines with another chemical to create a new substance

Chemical Changes

Goal- Have the same number of atoms on both sides of the equation.

Rules◦ Coefficients (numbers in front) multiply

◦ You can not change subscripts (numbers behind)

◦ If there is no subscript after an atom, then you know there is only 1 atom present

Balancing Equations

Balancing Equations

1. Write equation

2. Count Atoms H O

H O

2 2 2 1

Balancing Equations

3. Use coefficients to balance the equation

H O H O

2 2 2 1

2

24

H O

2 2

H O

4 24

• H2 + O2 H2O • H2 + Cl2 HCl

• SO2 + O2 SO3

• Mg + O2 MgO

Balancing Equations Practice

2 2

2

2 2

2 2

How do we make the reaction go faster?

• There are four things that we can change to make the reaction go faster.• They are • Temperature• Surface area•Concentration•Using a catalyst

1. Temperature

•When we increase the temperature we give the particles energy•This makes them move faster •This means they collide with other particles more often•So the reaction goes faster.

2. Surface area

• If we make the pieces of the reactants smaller we increase the number of particles on the surface which can react.• This makes the reaction faster.

The particles on the surface can react

When cut into smaller pieces the particles on the inside can react

3. Concentration• If we make one reactant

more concentrated, there are more particles

in the same volume to react• So the reaction goes

faster.

There are less red particles in the same volume so there is less chance of a collision

There are more red particles in the same volume so there is more chance of a collision so the reaction goes faster

http://www.youtube.com/watch?feature=player_embedded&v=kjKyEdrVXJA

4. Using a catalyst

•A catalyst is a chemical which is added to a reaction.• It makes the reaction go faster.• The catalyst does not get used up in the reaction.• It gives the reaction the energy to get started

Enzyme catalyst

http://www.youtube.com/watch?v=XX9Xo6zm_kM&feature=player_detailpage

Atoms

• Modern Atom Model• Nucleus-Protons and Neutrons• Electrons around nucleus, never know the true location

Protons

• Positively charged particle• In nucleus• Mass 1 amu

Neutrons

• Neutral (no) charge particle• In nucleus• Mass 1 amu

Electrons

• Negatively charged particle• In electron cloud (orbitals) around the nucleus• Mass 0 amu

Elements

• Made of atoms of one kind

• The type of element depends on the atomic number, or the number of protons it has• Most elements occur naturally, but some have to be created in a lab

Periodic Table• Elements are organized on the Periodic Table

according to atomic number and properties of the element

Open textbook to pages L14 – L15

Symbol

• The abbreviation letters used for each element

Atomic Number

• Number of protons (each element has a different # of protons)

• Number of electrons (same as # of protons so the element is electrically neutral)

Atomic Mass

• Mass of the Atom or # of the protons plus neutrons• Each proton equals 1 amu and each neutron equals 1

amu (atomic mass unit)

How do you find the average number of neutrons in an atom?

atomic mass ( rounded) – atomic number

Groups• Groups: or Family = columns• Share similar properties

• Numbers on top indicate what group it is• Noble gases-Group 18 (or 8A)• Halogens-Group 17 (or 7A)• Alkali metals-Group 1

Periods

• Periods = rows• Atomic mass increases from left to right• Number of protons increases from left to right• Number of electrons in the outer shell of the atom increases from left

to right• Only hydrogen and helium are in the 1st period

Look at L14 –15 or L186 – L187

Evidence of Chemical Reactions or Change

https://www.youtube.com/watch?v=cZMkqagL8Ps (2:52) Evidence of a Chemical Reactions

Evidence of Chemical Change

•New ________appears

•Bubbbles or ________

•Precipitate forms (____ material)

•_____ is produced

•______ is produced

•______ is given off

•Difficult or impossible to __________

color

fizzing

solid

reverse

Heat

Light

Sound