Physical Science
Study Guide
Learning Target #1
Explain what an element/compound is made of
a) Explain the differences in elements/compounds
b) Determine how many atoms are in a chemical formula
What is an atom?
Atoms are the basic building blocks of ordinary matter.
Atoms can join together to form molecules, which in turn form most of the objects around you
What is an element?
A pure substance that cannot be separated into simpler substances by physical or chemical means.
A pure substance in which there is only on type of particle
A pure chemical substance consisting of only one type of atom
What is an example of an element?
Every particle (atom) in a 5 g nugget of the element gold is like every other particle (atom) of gold
What is a unique characteristic of all elements?
The particles (atoms) of a pure substance are alike no matter where that substance is found.
What factors help scientists tell the difference between different types of elements?
Each element has a UNIQUE set of properties that allows you to identify it.
Each element has its own characteristics
Factors may include:
Physical properties (boiling point, melting point, and density)
Chemical properties (reactivity with acid)
What elements are known as unreactive gases?
Helium
Krypton
Why does a helium-filled balloon float up into the air if it is released?
The density of helium is less than the density of air
Why does a krypton-filled balloon sink to the ground if it is released?
The density of krypton is more than the density of air
How can elements be identified by their physical/chemical properties?
Melting point
Hardness
Density
Texture
Color
Flammable
Reaction with oxygen
Reaction with acid
What 3 categories are elements divided into?
Metals
Nonmetals
Metalloids
What are unique characteristics about metals?
Shiny
Good conductors of electrical currents
Malleable (can be hammered into thin sheets)
Ductile (they can be drawn into thin wires)
What are examples of metals?
Copper
Cobalt
Iron
Nickel
What are unique characteristics about nonmetals?
Not shiny (dull)
Poor conductors of electrical currents
Solids are brittle and nonmalleable
Lead
Tin
What are some examples of nonmetals?
Neon – used in lights
Graphite (carbon) used in pencils
Sulfur
Bromine
What are unique characteristics about metalloids?
Semiconductors (properties of both metal and nonmetal)
Some are shiny, some are dull
Somewhat malleable and ducticle
Some are conductors of electrical currents
What is an example of a metalloid?
Silicon (used to make computer chips)
Antimony
Boron
What is a compound?
A pure substance composed of two or more elements that are chemically combined.
A particle is formed when atoms of two or more elements join together.
A type of matter that forms when two or more elements combine chemically
In order for elements to combine, they must REACT (undergo a chemical change)
It is a new pure substance that is different from the elements that reacted to form it
Compounds are not random combinations of elements – when a compound forms, the elements join in
a specific ratio according to their masses.
What is an example of a ratio of mass in terms of the compound water (hydrogen and oxygen)?
1 g of mass of hydrogen TO 8 g of mass of oxygen
Every sample of water has a 1:8 ratio of hydrogen and oxygen
What are some basic compounds?
H2O = water (hydrogen and oxygen)
H2O2 = hydrogen peroxide (hydrogen and oxygen)
NaCI = table salt (sodium and chlorine)
*sodium is a soft, silvery white metal that reacts violently with water*
*chlorine by itself is a poisonous, greenish, yellow gas*
Baking Soda = sodium, hydrogen, carbon, and oxygen
Sugar = carbon, hydrogen, and oxygen
Carbon Dioxide = carbon and oxygen
What factors help scientists tell the difference between different types of compounds?
Each compound has its own physical properties (boiling point, melting point, density, and color)
Each compound has its own chemical properties (reaction with acid, reaction with light) etc….
How do I determine how many atoms are in a formula?
Chemical Formula
Identify Elements
Number of Atoms
CH4
Carbon
Hydrogen
carbon = 1
hydrogen = 4
C6H12O6
Carbon
Hydrogen
Oxygen
carbon = 6
hydrogen = 12
oxygen = 6
NaCI
Sodium
Chlorine
sodium = 1
chlorine = 1
Chemical formulas contain subscripts. What is the purpose of the subscript?
It indicates the number of atoms of each element in a chemical formula
How many total atoms are in one molecule of sodium nitrate, NaNO3?
Na = 1
N=1
O=3
Total = 5
Learning Target #2
Explain the properties of matter: Physical Property – Chemical Property
a) Classify substances into groups according to their chemical/reactive
properties
What is matter?
Anything that has mass and takes up space
What are 2 methods used to describe matter?
Physical properties
Chemical properties
What two ways can substances change?
Physical change
Chemical change
What is a physical change?
The substance changes its appearance but not its molecular identity or structure.
A substance changes its appearance but not its identity
What is a physical property?
A characteristic of a substance that can be observed without changing the substance into another
substance.
What are some examples of the differences between a physical change and a physical property?
 Start with an ice cube.
The ice cube melts to water - a physical change.
The ice cube is cold - physical property.
 Start with a piece of paper.
Rip it up. That's a physical change.
Burn the paper - a chemical change.
 Find a glass cup.
Throw it at a wall and shatter it. That's a physical change.
Say the cup weighs about 1 pound. That's a physical property.
What are examples of a physical property?
Color
Hardness
Texture
The temperature at which a solid melts
The ability of a substance to dissolve in water
What are examples of physical change?
 shredding (ripping )a piece of paper
 folding paper into an airplane
 drawing on a piece of paper
 drawing a metal such as copper into a
wire
 pounding a metal such as aluminum
into thin sheets
Shine
Flexibility
The ability of a substance to conduct heat and
electricity




breaking a sheet of glass
ice cube melts into liquid water
filtering a solid from a liquid
a liquid expanding as it is heated
liquid water evaporates into water
vapor
How can a change in state be considered a physical change?
a) When water is boiled and becomes steam, a change of state occurs as it goes from liquid to gas.
However, the water is still water (the water particles are still water particles)
b) When solid gold is melted, it changes state as it becomes a liquid. However, the gold has not
changed its identity, (it is still gold)
What are examples of physical properties of water?
 Boils at 100 degrees C
 Freezes at 0 degrees C

Clear, colorless liquid at room
temperature
What is a physical property of aluminum foil?
Shiny
What is a physical property of a marshmallow?
You can flatten and pull on it but the composition will stay the same
What is a chemical change?
A substance changes its identity
Changes matter from one form to another
New molecules are always formed
When 2 substances react to form a new
material with different properties
What is a molecule?
the simplest unit of a chemical compound that can exist, consisting of two or more atoms held together
by chemical bonds
What is an example of a chemical change?
 silver metal reacting with sulfur to form
sulfur oxide (silver tarnishing, the silver
appears darker)
 burning hydrogen gas in air
 heating a compound until it breaks
down or decomposes
 the oxidation of metals in air



the reaction of an acid and a base
burning gasoline
two solutions are added together and
the new solution becomes hot
What are some common signs that a chemical change has occurred?
 Change in temperature
 The production of a solid
 The substance has changed color
 The production of a gas
What is a chemical property?
A characteristic of a substance that describes its ability to change into other substances.
What is the relationship between chemical properties and chemical changes ?
The chemical properties of a substance (chemical formula) are special characteristics that influence the
chemical reactions of this substance.
What type of evidence can demonstrate chemical properties?
Burning
Tarnishing
Rusting
How do you observe chemical properties of a substance?
You must change it to another substance
How can you tell when a chemical reaction occurs?
Formation of new substances
Changes in energy
What are examples of substances that can change chemically?
 When magnesium burns, it combines with oxygen in the air, forming magnesium oxide – the
flame produced when magnesium burned provides evidence that energy was released
 When iron combines with oxygen it forms Iron oxide (Rust) – The rust produced provides
evidence that energy was released
 When sodium hydroxide combines with hydrochloric acid, we will produce water and sodium
chloride, or table salt.
What are examples of chemical properties of water?
 Made of hydrogen atoms and oxygen
atoms in a 2 to 1 ratio
 Does not burn

Reacts with some metals
What is an example of a chemical property of natural gas?
It can burn
What is a chemical change of a marshmallow?
The sugars will burn or cook, producing a crust made of new substances
What evidence is there in a green leaf that chemical reactions in the leaf produce chlorophyll?
The leaf turns a darker shade of green
What other evidence is shown of a chemical reaction with a green leaf?
Formation of water (type of condensation) – production of gas (oxygen) bubbles on the leaf
What happens to the atoms after a reaction has taken place?
 The atoms of the reactants have not changed.
 The atoms have combined in new ways to form different products with different molecules.
If the atoms after a reaction have not changed but the molecular identity of a substance has changed.
What can we infer?
It shows that chemical changes cause changes in matter
Learning Target #3
Explain how mixtures can be separated using physical properties
a) identify and explain different types of mixtures
What is a mixture?
 It is made up of two or more substances – elements, compounds, or both, that are together in
the same place but are not chemically combined
 Each substance has the same chemical makeup it had before the mixture was formed.
 No chemical changes
What is an example of a mixture?
 Cheese and Tomato Sauce do not react with each other when used to make a pizza
 Granite is made up of a mixture of three minerals: quartz, pink feldspar, and black mica:
different ratios of different mixtures give granite its various colors
 Salt water is a mixture of salt and water
 Air is a mixture of nitrogen, oxygen, carbon dioxide, and water vapor
How can a mixture be separated?
 Distillation: Separate salt from salt water by heating the mixture: Separate crude oil into
gasoline and kerosene
 Magnet: Separate a mixture of the elements iron and aluminum: iron is attracted to the
magnet, but aluminum is not
 Centrifuge: machine that separates components of the blood according to density
 Pick the pieces out
 Separation may require more than one step
How does a mixture differ from compounds?
Each substance in a mixture keeps its individual properties
What are different types of mixtures?
Solution
Suspension
What is the difference between mixtures and compounds?
Mixture




Components are
elements, compounds, or both
Components keep their original
properties
Separated by physical means
Formed using any ratio of components
Colloid
Compound
Components are elements
Components lose their original
properties
Separated by chemical means
Formed using a set mass ratio of
components
What is a solution?
A solution is a mixture that appears to be a single substance, but is composed of particles of two or more
substances that are distributed evenly amongst each other
 Often described as homogeneous mixtures (because they have the same appearance and properties
throughout the mixture
 Example: salt water --- salt is the solute and water is the solvent
Solutions, continued
Examples of Solutions…
Solutions may also be solids, such as steel.
http://my.hrw.com/sh2/sh07_10/student/flash/visual_concepts/75243.htm
Alloys (ancient India’s metallurgy) are solid
solutions of metals or nonmetals dissolved
in metals.
What are examples of solutions in different states?
 Gas in gas----- dry air
 Gas in liquid----- soft drinks, tap water, gasoline, and many cleaning supplies
 Liquid in liquid ---- antifreeze
 Solid in liquid-----salt water
 Solid in solid ---- brass, steel
What is an alloy?
Solid solutions of metals or nonmetals dissolved in metals.
What does dissolving mean?
The process in which particles of substances separate and spread evenly throughout a mixture is known
as dissolving.
What is a solute?
The substance that is dissolved
What is a solvent?
The substance in which the solute is dissolved
 When two liquids or two gases form a solution, the substance with the greater volume is the
solvent.
Why do the particles in a solution never settle out?
The particles in solutions are so small
They cannot be removed by filtering
They don’t even scatter light ( you can’t see the path of light through it )
What is concentration?
A measure of the amount of solute dissolved in a solvent
 Can be expressed in grams of solute per milliliter of solvent
How can a solution be described?
Concentrated
Dilute
What does solubility mean?
The ability of a solute to dissolve in a solvent at a certain temperature
 Can be expressed in grams of solute per 100mL of solvent
How do gases become less soluble (decrease) in liquids?
The temperature is raised
What happens to the solubility of gases in liquids?
It decreases as the temperature is raised
What happens when water is boiled?
Bubbles of gas appear in hot water long before the water begins to boil
The gases that are dissolved in the water cannot remain dissolved as the temperature increases because
the solubility of the gases is lower at higher temperatures
What happens to the solubility of most solids as the temperature gets higher?
More solute can dissolve at higher temperatures.
What are three ways to make a solute dissolve faster?
 Mixing the solution (stirring or shaking)
 Heating the solution causes particles to move more quickly
 Crushing the solute into smaller particles increases the amount of contact between solute and
the solvent
What is a suspension?
A suspension is a mixture in which particles of a material are dispersed throughout a liquid or a gas but
are large enough that they settle out.
 The particles in a suspension are large enough to scatter or block light
 A suspension can be separated by passing it through a filter (the liquid or gases pass through
easily, but the solid particles stay behind)
 Known as heterogeneous mixtures because the different components are easily seen
 Examples:
Shaking a snow globe to watch it snow, but then the snow settles on the bottom
Blood (red blood cells, white blood cells, and platelets are suspended in a solution called plasma
Muddy water
Italian salad dressing
Medicine
What is a colloid?
A colloid is a mixture in which the particles are dispersed throughout but are not heavy enough to settle
out.
 Particles in a colloid are large enough to scatter light.
 A colloid cannot be separated by passing it through a filter.
Learning Target #4
Explain/utilize the principle of conservation of matter
a) Balance chemical reactions/simple version--total mass of reactant = total
mass of product
What is matter?
 The stuff that makes up everything in
the world

All objects are composed of matter.
What are examples of matter?
Things you can easily see
Plants
Animals
Rocks
Soil
Things you can't see
Oxygen
Air
Water
What is law of conservation of matter?
 The total amount of matter of the reactants (mass of the reactants) must equal the total
amount of matter of the products (mass of the products) in a chemical reaction.
 Atoms cannot be created or lost in a chemical reaction.
 Atoms cannot be created or lost in a closed system, but can change form
 When substances undergo physical or chemical changes, matter is not created nor destroyed
 The number of atoms is not changed by a chemical reaction
What is unique about matter?
Matter cannot be created or lost, but it can change forms.
Give an example of matter that has undergone a chemical change
For example,
If you burned charcoal, the charcoal would undergo a combustion reaction. If you added the masses of
all the products of the reaction (ashes, soot, gases), however, you would find that this mass would be
equal to the original mass of the charcoal. Mass was not created or lost, it just changed forms (from
charcoal to ashes, soot, and gases).
How is matter affected in a chemical reaction?
 During a chemical reaction, matter is not created or destroyed
 This means that even though an object may have undergone a physical or chemical change, the
amount of matter (i.e. the mass) must always remain the same.
How are atoms affected in a chemical reaction?
All atoms present at the start of the reaction are present at the end
What is a basic example of conservation of matter (mass)?
A class is made up of a group of students and a teacher together in a room
When the bell rings, people from the class move from room to room, ending up in different classes
The number of people in the school has not changed ---- only the arrangement has. To describe a
reaction accurately based on the law of conservation of matter, what must happen?
A chemical equation must show the same number of each type of atom on both sides of the equation
Reactant + Reactant
Product
In a chemical reaction, the total mass of the reactants is 10.0 grams. What is the total mass of the
product?
Exactly 10.0 grams
In a chemical reaction, the total mass of the reactants is 15.0 milliliters. What is the total mass of the
product?
Exactly 15.0 milliliters
What does the phrase “matter is conserved” mean?
The amount of matter will stay the same
How much matter is in the following equations?
1st example
Magnesium metal (Mg) reacts with oxygen gas (O2) forming Magnesium oxide (MgO)
Magnesium + Oxygen
Magnesium Oxide
Reactants
.5g
.2g
Product
.7g
2nd example
Hydrogen (H2)reacts with oxygen (O2) to form a product of water (H2O)
Hydrogen + Oxygen
Water
Reactants
Product
1.2g
.6g
1.8