Transcript Let’s talk Chemistry!

Let’s talk Chemistry!
A common way of defining matter is - anything that
has mass and occupies volume (takes up space).
Substances that cannot be broken down in to simpler
substances are
Elements
The chemical formula for water is H2O, this means
that each water molecule contains
Two hydrogen atoms and one oxygen atom
You put 1 gram of salt into on liter of water, the result
is an example of a
Homogeneous mixture – the mixture is the same
throughout
The science of what matter is made of and how it
changes is
Chemistry
The smallest unit of a substance that behaves like the
substance is a
Molecule
The chemical formula for sulfuric acid is H2SO4. How
many atoms are in one molecule of sulfuric acid?
7
The chemical formula for table sugar is C12H22O11.
How many oxygen atoms are in each sugar
molecule?
11
A material that can be represented by a chemical
formula is a
Pure substance
What is an example of a gas-liquid mixture?
A carbonated drink
The resistance of a fluid to flow is referred to as
Viscosity
Matter assumes several forms. What state of matter
holds its shape without a container?
Solid
The kinetic theory states that the higher the temp the
faster the particles that make up a substance move
The change of a solid directly into a gas is
Sublimation
The ability to change or to move matter is referred to
as
Energy
All changes of the state of matter require
Energy
Evaporation refers to the change of state from a
Liquid to a gas
The law of conservation of mass states that mass
Cannot be created or destroyed
During a chemical or physical change, energy may be
Converted into another form
A liquid changes rapidly into a gas at the liquid’s
Boiling point
Knowing the chemical properties of a substance will
tell you how the substance
Reacts with other substances
Physical properties are
Properties that can be observed or measured without
changing the composition of matter: appearance,
texture, color, odor, melting point, boiling point,
density, solubility, polarity, freezing point, etc.
Give an example of a physical change.
Ice melting, salt dissolving, water boiling, etc.
Volume = mass divided by density. Lead has a density
of 11.3g/cm cubed. What is the volume of a block
of lead with a mass of 282.5g?
25 cm cubed
What is a chemical change?
When one or more substances react, they become a
third unique substance often with new physical and
chemical properties.
Ice floats in water because
Ice is less dense than water
Digesting food is an example of what kind of change?
Chemical
The tendency of a less dense substance to float in a
more dense liquid is called
Buoyancy
What makes up the atomic nucleus? What is its
charge?
Protons and neutrons; +
What is the charge of an electron?
-1
Atoms have no electric charge because
Equal number of protons and electrons
Bohr’s model show electrons behaving like
Planets orbiting the sun
Modern atomic theory indicates that it is nearly
impossible to determine an electron’s exact
Position
Atoms of elements that are in the same group have
the same number of
Valence electrons
Valence electrons determine an atom’s
Chemical properties
Ionization refers to the process of
Losing or gaining electrons
Oxygen has atomic number 8. This means oxygen has
8 protons and 8 electrons
An atom’s mass number equals the number of
Protons + neutrons
0
Where on the periodic table are the alkali metals
found?
Left most column of the periodic table
List 3 alkali metals
Na, K, Li
Most halogens (group 17) form compounds by
Gaining an electron to form a negative ion
ep+ n
Cl
He
Group 18 noble gases are inert because
Their outermost energy level is full
Carbon and other nonmetals are found in which area
of the periodic table?
On the right side
A mole is an SI base unit that describes the
Amount of a substance
Avogadro’s constant is defined as the number of 23
particles in
One mole of a pure substance
Molar mass is defined as
The mass in grams of 1 mole of a substance
C
6.02 x 10
The forces that hold different atoms or ions together
are
Chemical bonds
A mixture is different from a compound because each
substance in a mixture
Retains its own properties
Each molecule of hydrochloric acid, HCl, contains one
atom of hydrogen and
One atom of chlorine
An ionic compound is made of _____. Give an
example of a common ionic compound.
Ions; NaCl (table salt)
In what form of matter do the molecules have the
greatest attractions to one another?
Solids
Often atoms join so that each atom will have
A full outer energy level (gaining or losing electrons)
When two hydrogen atoms bond, the positive nucleus
of one atom attracts the
Negative electron of the other atom
An ionic bond is a bond that forms between
Ions with opposite charges
Solid ionic compounds have high melting points
Because they contain charged ions and are locked
tightly together
In which type of bond do atoms share electrons?
Covalent bonds
The name dinitrogen tetroxide tells you that this
compound contains
Two nitrogen atoms and 4 oxygen atoms
Formaldehyde, CH2O, and acetic acid, C2H4O2, have
the same empirical formula but different
Molecular formulas
A carbon atom can bond to four other atoms because
it has
4 valence electrons
Polymers are large organic molecules that are made
of
Repeating units (DNA, proteins, starch, plastics, etc.)
A protein is a polymer made of
Amino acids
The “rungs” of the DNA “ladder” are made of
Nitrogenous bases
A change in color, such as rusting of metal, is a sign
that
A chemical change has occurred or is taking place
A substance that undergoes this change is a
Reactant
C6H12O6 + 6O2 -> 6H2O + 6CO2
A–T
C-G
In an exothermic reaction, energy is transferred from
The reactants to the surroundings
The energy source in photosynthesis is
The sun
A synthesis reaction is a reaction between at least two
compounds in which
A + B -> AB
A new, more complex compound is formed
The product of the synthesis reaction between
sodium and chlorine gas is
Sodium chloride
When water is broken down by electrolysis
The products are O2 and H2 gases
A chemical equation is balanced by changing or
adding
C6H12O6 + _O2 -> _H2O + _CO2
Coefficients
A balanced chemical equation shows the proportions
of reactants and products necessary for
Mass to be conserved
In the reaction 2Mg + O2 -> 2MgO, the law of definite
proportions states that for every 2 moles of Mg you
will need how any moles of O2?
1
In a balanced equation, the total mass of products
Always equals the total mass of reactants
A balanced chemical equation indicates both the
number of particles of reactants and products and
the number of
Moles
What factors can speed up a chemical reaction?
High pressure, larger surface area, higher
temperature, presence of a catalyst
Large, bulky molecules react more slowly than small
ones because they have less opportunity to
Collide with other molecules
An enzyme is a catalyst that
Can speed up specific biological reactions
When a chemical reaction and its reverse are
occurring at the same time and at the same rate,
the reaction has achieved
Equilibrium
What is the relationship between chemical
equilibrium and the rates of forward and the
reverse reaction?
The forward and reverse reactions must be equal
A heterogeneous mixture is one that is not
Uniform throughout
A homogeneous mixture is
Uniform throughout
A mixture that separates into different layers when
you stop stirring it is
A suspension
You can usually filter out solid
particles in a suspension by
Using a paper filter to catch the particles
You can skim the fat off the top of a kettle of cold
soup because fat is
Less dense than water and rises to the top
Distillation can be used to separate
solutions of miscible liquids because
Different liquids have different boiling points
Solubility refers to the
Grams of solute per 100g of solvent
Loose sugar dissolves much faster than a sugar cube
because loose sugar has
A greater surface area
You can make a solute dissolve more quickly
In a solvent by
Heating the solvent
Water can dissolve charged particles because
Its atoms have partial charges
Water is the universal solvent because
An unsaturated solution is one that
Can dissolve more solute at the current conditions
What happens when a supersaturated solution cools
down?
The solute will precipitate out of the solution
What are some characteristics of bases?
Turn litmus paper blue, have a pH over 7, are slippery,
contain hydroxide ions
Acids are substances that
Turn litmus paper red, have a pH under 7, taste bitter
A solution that is mildly acidic would have a pH of
Approximately 6
`
The label on a bottle indicates that the substance
inside has a pH of 13. This tells you that the
substance is
Strongly basic
Examples of bases include:
Baking soda, oven cleaner, drain cleaner
Fusion occurs when nuclei
Combine
The opposite reaction to fusion is
Fission
In the equation E = mc (c is squared)…the c stands for
The speed of light (E – energy, m – mass)