Science Chapter 2 test review

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What does a physical change affect?
one or more physical properties of a substance without changing the identity of the substance
What do physical changes NOT change?
a substance's identity
What happens to energy during a physical change?
it is absorbed or released
What happens after a physical change?
a substance may look different, but the arrangement of atoms that make up the substance is not changed
When does a chemical change happen?
one or more substances are changed into entirely new substances that have different properties
Where do chemical changes happen?
EVERYWHERE
What are two examples of chemical changes?
When a battery dies, when a fruit ripens
What do chemical changes form?
new substances
interaction
the action or influence between things
What happens when a chemical change is taken place?
clues often suggest that a chemical change has happened- odor, color, etc
What do chemical changes cause?
color changes
fizzing
foaming
the production of sound
heat
light
odor
Why can't chemical changes be reversed by physical changes?
Because new substances are formed in a chemical change, a chemical change cannot be reversed by physical changes
_______ can be separated by physical changes
Mixtures
________ must be broken down by chemical changes
compounds
Why can mixtures be separated?
Because mixtures are not chemically combined, each part of the mixture has the same chemical makeup that it had before the mixture was formed
What if components of a mixture have different boiling points?
you can heat the mixture in a distillation device
What happens first when components are boiled and evaporated?
they separate from the mixture
What is another technique for separating mixtures?
to use a centrifuge which spins a mixture rapidly until the components separate
What can compounds be broken down?
elements
element
a substance that cannot be broken down into simpler substances by chemical means
atom
The smallest unit of an element that keeps the element's chemical properties
molecule
the smallest unit of a substance that behaves like the substance
compound
a substance made up of atoms of different elements
pure substance
matter that has a fixed composition and definite properties
mixture
a combination of substances that are not chemically combined
melting point
the temperature at which a substance changes from a solid to a liquid
boiling point
the temperature at which a liquid changes to a gas
density
a measurement of how much matter is contained in a certain volume of a substance
reactivity
the capacity of a substance to combine with another substance
physical change
a change of matter from one form to another without a change in chemical properties
chemical change
a change that occurs when one or more substances change into entirely new substances with different properties
matter
anything that takes up space
Three examples of matter
air, light, sound
What has matter but doesn't have mass or volume?
light and sound
chemistry
the study of matter and its changes (explore the makeup of properties, changes, and interactions of matter)
How can matter be classified?
what makes up the matter is an example
Matter can be classified as three things what are they?
an element, a compound, or a mixture
Elements are represented by _______.
symbols
Where are elements used?
worldwide
The symbol is always a _______ _______, and can be followed by a _______ _____
capital letter; lower case
examples of element
WHOLE PERIODIC TABLE
Atoms that make up a molecule act as a ____
unit
Why do atoms join together?
to make a million of molecules
What happens when elements combine to make a compound?
they always combine in the same proportions
What does every compound differ from?
the element that it contains
What do chemical formulas represent?
compounds
What do chemical formulas show?
how many atoms are in each element
How do you know how many atoms are in each element?
written as a subscript after the element symbol
What if there is only one atom in an element?
no subscript # is used
Why might there be a #(s) placed in the front of a chemical formula?
to show the # of molecules
How are mixtures classified?
by how the substance is mixed
What is water? Why?
pure substance; because it has a fixed composition and definite properties
heterogeneous mixture
not evenly distributed
homogeneous mixture
the components are evenly distributed
When something is miscible, it is __________.
able to be mixed
When something is immiscible, it _______.
will settle out.
What can mix with liquids?
gasses
What are carbonated drinks?
homogeneous mixture
What can physical properties help identify? What should you use to identify this (2)?
substances; observations or measurements
What can your senses observe is a PP? (4)
shape, color, odor, and texture
state
the physical form of a liquid
How can the melting and boiling point stay constant?
if the pressure remains the same
What are physical properties that can be measured? (5)
strength
hardness
magnetism
the ability to conduct electricity
heat
How is density different from weight?
A sub. that has a low density is light in comparison with something else of the same volume
What does a chemical property describe?
how a substance changes into a new substance, either by combining with other elements or by breaking apart into new substances
flammability
the ability to burn
Describe matter, and explain why light is not classified as matter.
Matter is anything that has mass and takes up space. Light isn't made of atoms.
State the relationship between atoms and elements. Are atoms and elements matter?
Each element is made of one kind of atom. They both take up space.
Define molecule, and give examples of molecules formed by one element and molecules formed by two elements.
A molecule is the smallest unit of a substance that acts as the substance. Hydrogen, oxygen, and chlorine are formed by one element and molecules formed by two elements.
List the two types of pure substances.
Elements and compounds
State the chemical formula for water.
List two physical properties and two chemical properties.
Two physical properties are color and texture. Two chemical properties are flammability and reactivity.
Define physical change and chemical change, and give examples of each type of change.
physical change- a change of matter from one form to another without a change in chemical properties
ex: breaking chalk
chemical change- a change that occurs when one or more substances change into entirely new substances with different properties
ex: burning of compounds
Explain why changes of state are physical changes.
A physical change affects one or more physical properties of a substance without changing the identity of the substance.
Explain why physical changes can easily be reversed but why chemical changes cannot.
Because new substances are formed in a chemical change, a chemical change cannot be reversed by physical changes.
Identify two ways to break down a compound into simpler substances.
When you open a bottle of soda, compounds in the soda break down into carbon dioxide and water.
If a current is passed through melted table salt, the elements sodium and chlorine are produced.
List two clues that indicate a chemical change.
A change in odor or color is a good clue that a substance is changing chemically.