REVIEW FOR 8TH GRADE
QUARTERLY
DR. GERARD MAKIN
CLARENCE MIDDLE SCHOOL
CHEMICAL CHANGES
• A chemical change has occurred when:
1. There is a color change (rust)
2. A gas is released (baking soda and vinegar)
3. When a precipitate is formed. (vinegar in milk
forms curds that fall out of solution)
PHYSICAL CHANGE
• A PHYSICAL CHANGE IS WHEN A SUBSTANCE
CHANGES SHAPE OR STATE WITHOUT CHANGING ITS
CHEMCAI PROPERTIES.
1. CUTTING WOOD
2. FREEZING OR BOILING WATER
3. CUTTING HAIR
MEASUREMENT
• The measurement of a liquid or the amount of space
and object takes up is volume measured in liters,
milliliters(cc,cm3).
• The distance between objects or places is measured in
meters or kilometers.
• Density is how much matter occupies a specific volume
in g/cm3 (how tightly packed the particles are)
• The mass of an object is the quantity of matter in an
object measured in grams and kilograms(same all over
the universe not based on gravity)
DENSITY OF LIQUIDS
• Liquids of different density will form layers when
occupying the same container.
DENSITY OF SOLIDS
• All objects densities are compared to water which
is 1.0 g/cm3
• If an object is less dense than water it will float at
some level within that water depending on how
close to or far from 1.0 g.cm3 it is.
• Objects whose density is greater than 1.0g/cm3 will
sink in water.
DENSITY OF AN IRREGULAR OBJECT
WHICH WILL FLOAT OR SINK
PHASE CHANGES
• When a phase change is occurring the
temperature remains constant.
WATER CYCLE
• Water evaporates to a gas theN condenses to a
cloud and as the air gets colder it further condenses
into rain or precipitation.
LESSON 4.1
INTERPRETING GRAPHS
Practice : For the following line graph, answer the questions given.
1) Barry’s pulse rate is taken every 6 hours over 3 days. The graph shows his
pulse rate in beats per minute.
(a)
Write down the first pulse rate shown on the graph.
(b)
Write down Barry’s highest pulse rate shown during the three days.
(c)
Work out the difference between his highest and lowest pulse rates shown on 3rd May.
• What is the real-world
meaning of the graph at
right, which shows the
relationship between the
number of customers getting
haircuts each week and the
price charged for each
haircut?
 The number of customers
depends on the price of the
haircut.
 So the price in dollars is the
independent variable and the
number of customers is the
dependent variable.
 As the price increases, the
number of customers decreases
linearly. As you would expect,
fewer people are willing to pay a
high price; a lower price attracts
more customers.
 The slope indicates the number of
customers lost for each dollar
increase.
 The x-intercept represents the
haircut price that is too high for
anyone.
 The y-intercept indicates the
number of customers when
haircuts are free.
EXAMPLE
 Students at
Central High
School are
complaining that
the juice vending
machine is
frequently empty.
Several student
council members
decide to study
this problem. They
record the
number of cans in
the machine at
various times
during a typical
school day and
make a graph.
EXAMPLE
 a. Based on the
graph, at what
times is juice
consumed most
rapidly?
 b. When is the
machine refilled?
How can you tell?
 c. When is the
machine empty?
How can you tell?
 d. What do you
think the student
council will
recommend to
solve the
problem?
SOLUTIONS
• Although the student council members in the
example are interested in solving a problem related
to juice consumption, they could also use the graph
to answer many other questions about Central High
School:
•
•
•
•
When do students arrive at school?
What time do classes begin?
When is lunch?
When do classes let out for the day?
PART 2
• This graph tells a story. It could be a story about a
lake, a bathtub, or whatever you imagine. Spend
some time with your group discussing the
information contained in the graph. Write a story
that conveys all of this information, including when
and how the rates of change increase or decrease.
IDENTIFYING
VARIABLES
3 KINDS OF VARIABLES
• Manipulated Variable – something
that is changed by the scientist
• What is tested
• What is manipulated
3 KINDS OF VARIABLES
• Responding Variable – something
that might be affected by the
change in the manipulated variable
• What is observed
• What is measured
• The data collected during the
investigation
3 KINDS OF VARIABLES
• Controlled Variable – a variable
that is not changed
• Also called constants
• Allow for a “fair test”
Students of different ages were
given the same jigsaw puzzle to
put together. They were timed to
see how long it took to finish the
puzzle.
Identify the
variables in this
investigation.
WHAT WAS THE MANIPULATED
VARIABLE?
•Ages of the students
• Different ages were tested by
the scientist
WHAT WAS THE RESPONDING
VARIABLE?
•The time it took to put the
puzzle together
• The time was observed and
measured by the scientist
WHAT WAS A CONTROLLED VARIABLE?
•Same puzzle
• All of the participants were
tested with the same puzzle.
• It would not have been a fair
test if some had an easy 30
piece puzzle and some had a
harder 500 piece puzzle.
ANOTHER EXAMPLE:
AN INVESTIGATION WAS DONE WITH AN
ELECTROMAGNETIC SYSTEM MADE FROM A BATTERY
AND WIRE WRAPPED AROUND A NAIL. DIFFERENT
SIZES OF NAILS WERE USED. THE NUMBER OF PAPER
CLIPS THE ELECTROMAGNET COULD PICK UP WAS
MEASURED.
What are the
variables in this
investigation?
MANIPULATED VARIABLE:
•Sizes of nails
• These were changed by the
scientist
RESPONDING VARIABLE:
•Number of paper clips
picked up
• The number of paper clips
observed and counted
(measured)
CONTROLLED VARIABLES:
•Battery, wire, type of nail
• None of these items were changed
ONE MORE:
THE HIGHER THE
TEMPERATURE OF WATER,
THE FASTER AN EGG WILL
BOIL.
What are the
variables in this
investigation?
The variables
• Manipulated variable –
temperature of water
• Responding variable – time to
cook an egg
• Controlled variable – type of egg
LAST ONE:
THE TEMPERATURE OF
WATER WAS MEASURED AT
DIFFERENT DEPTHS OF A
POND.
What are the
variables in this
investigation?
The variables
• Manipulated variable – depth of
the water
• Responding variable –
temperature
• Controlled variable –
thermometer