SCIENCE SKILLS
Chapter Two: Science Skills
2.1 Mass and Volume
2.2 Density
2.3 Graphing
2.4 Solving Problems
Section 2.1 Learning Goals
Explain the meaning of mass and
describe the units for measuring mass.
Distinguish between mass and weight.
Define volume and explain how the
volume of matter is measured.
Investigation 2A
Measuring Mass and Volume
Key Question:
How do you measure mass and volume?
2.1 Measuring mass
Mass describes the amount
of matter in an object.
The SI unit for mass is the
kilogram (kg).
The kilogram is too large a
unit to be convenient for
small masses.
One gram (g) is one-thousandth of a kilogram.
What is the estimated mass of ONE zinc nut?
2.1 Matter
Matter is anything
that has mass and
takes up space.
All matter has mass.
Steel, plastic, rubber,
and glass are
different kinds of
matter.
A car has a lot more of each
kind of matter than a bike.
2.1 Mass and weight are different
 We tend to use the terms mass and
weight interchangeably, but they are
not the same thing.
 Mass is the amount of matter in an
object.
 Weight is a measure of the pulling
force of gravity on an object.
2.1 Mass and weight are different
 A 2.3 kg bag of
flour has a mass of
2.3 kilograms no
matter where it is
in the universe.
 The weight of the
bag of flour is less
on the moon.
The 5 lb bag of flour
on Earth weighs only
.8 lbs on the moon!
2.1 Volume
Volume is the amount of space an object
takes up.
The fundamental unit of volume in SI
is the cubic meter (m3).
More convenient smaller units are
cubic centimeters (cc or cm3), liters
(L) and milliliters (mL).
2.1 Volume
Measuring the
volume of liquids
is easy.
Pour the liquid
into a graduated
cylinder and read
the meniscus at
eye level.
2.1 Displacement
You can find the
volume of an irregular
shape using a
technique called
displacement.
Put the irregularly
shaped object in water
and measuring the
amount of water
displaced.
2.1 Comparing
mass and volume
Mass and volume are two
different properties of
matter.
Size does not always
indicate an object’s mass!
How the matter is packed
into space is more
important.
Chapter Two: Science Skills
2.1 Mass and Volume
2.2 Density
2.3 Graphing
2.4 Solving Problems
Section 2.2 Learning Goals
Define density in terms of mass and
volume.
Identify units used to express the
density of materials.
Apply the density formula to solve
problems.
Investigation 2B
Density
Key Question:
How is an object’s density
related to its volume,
mass, and tendency to
sink or float?
2.2 Density
Density describes how much mass is
in a given volume of a material.
2.2 Density
Solids, liquids and
gases are matter, so
they all have density.
The density of water
is about one gram per
cubic centimeter.
2.2 Density
The units used
for density
depend on
whether the
substance is
solid or liquid.
 For liquids use
units of grams
per milliliter
(g/mL)
 For solids use
density in units
of g/cm3 or
kg/m3.
2.2 Density of common materials
Density is a property of material
independent of quantity or shape.
2.2 Density of common materials
Liquids tend to be
less dense than
solids of the same
material.
 Ex. solder (“sodder)
2.2 Density of common materials
Water is an exception to this rule.
The density of solid water (ice) is less
than the density of liquid water.
2.2 Determining Density
 To find the density of a
material, you need to
know the mass and
volume of a solid sample
of the material.
1. Mass is measured with a
balance or scale.
2. Use the displacement
method or calculate the
volume.
2.2 Density
Density changes for different substances
because:
1. Atoms have different masses.
2. Atoms may be “packed” tightly or loosely.
Solving Problems
Calculating Density
1. Looking for:
 …the density of the candle
2. Given:
 …mass = 1500 g; volume = 1700 mL
3. Relationship:
 D = m/V
4. Solution:
 1,500 g ÷ 1,700 mL = 0.8823529 g/mL
# Sig. fig = .88 g/mL
Chapter Two: Science Skills
2.1 Mass and Volume
2.2 Density
2.3 Graphing
2.4 Solving Problems
Section 2.3 Learning Goals
Use graphs to create a visual
representation of data.
Analyze trends on a graph.
Explain the difference between a direct
relationship and an inverse relationship.
Investigation 2C
Thickness of Aluminum Foil
Key Question:
What is the thickness of
aluminum foil?
2.3 Graphing
 A graph is a visual way to organize
data.
 A scatterplot
or XY graph is
used to see if
two variables
are related.
2.3 Graphing
 A bar graph
compares data
grouped by a
name or
category.
2.3 Graphing
 A pie graph
shows the
amount each
part makes of
up of the whole
(100%).
2.3 Graphing
 A “connect-the-dots” line graph is
often used to show trends in data
over time.
2.3 How to make an XY graph
Scatterplots show how a change in one
variable influences another variable.
The independent variable is the variable
you believe might influence another
variable.
The dependent variable is the variable that
you hope will change as a result of the
experiment.
2.3 How to make an XY graph
Pressure is critical to safe diving.
How does an increase in depth affect
the pressure?
What sort of graph would best show
the relationship between pressure
and depth?
2.3 How to make an XY graph
1. Choose x and y-axis
 Depth is the independent variable = x axis
 Pressure is the dependent variable = y axis
2. Make a scale
 Most graphs use ones, twos, fives or tens
 OR calculate the value per box
3. Plot your data
4. Create a title
* Exception- when time is a variable
2.3 Identifying graph relationships
In a direct
relationship,
when one
variable
increases,
so does the
other.
The speed and distance variables show
a direct relationship.
2.3 Identifying graph relationships
When there is
no relationship
the graph
looks like a
collection of
dots.
No pattern appears.
2.3 Identifying graph relationships
In an
inverse
relationship,
when one
variable
increases,
the other
decreases.
2.3 Reading a graph
What is the speed of the car at 50 cm?
1. Find the known value on the x axis
 Position = 50 cm
2. Draw a line vertically upward from 50 cm
until it hits the curve.
3. Draw a line across horizontally to the yaxis from the same place on the curve.
4. Read the speed using the y axis scale.
 Speed = 76 cm/s
Chapter Two: Science Skills
2.1 Mass and Volume
2.2 Density
2.3 Graphing
2.4 Solving Problems
Section 2.4 Learning Goals
Apply a four-step technique to solve
problems.
Use the design cycle to solve problems.
2.4 Solving Problems
Solving Problems
Calculate marble’s volume & density
1. Looking for:
 volume, then density
2. Givens:
 mass = 6 g , water displaced 30 to 32 mL
3. Relationships:
 water displaced = marble volume, D = m/V
4. Solution:
 32 mL – 30 mL = 2 mL
 D = 6 g / 2 mL
= 3 g/mL
2.4 How to solve design problems
Use what you know to design a
solution that solves the problem.
Unlike “formula problems,” design
problems have many correct solutions.
The solutions are only limited by your
creativity, ingenuity, skill, and
patience.
2.4 How to solve design problems
What does your
design need to
accomplish?
What constraints
do you have?
Think of an idea.
Follow the design
cycle…
Density and Ocean Currents
Did you know that there are underwater
waterfalls in the ocean?
While it may seem strange for water to fall
through water, it really happens due to
density differences in ocean water coming
from different sources.