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
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
 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
Put the irregularly
shaped object in water
and measuring the
amount of water
2.1 Comparing
mass and volume
Mass and volume are two
different properties of
Size does not always
indicate an object’s mass!
How the matter is packed
into space is more
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
Identify units used to express the
density of materials.
Apply the density formula to solve
Investigation 2B
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
 For solids use
density in units
of g/cm3 or
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
 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
2.2 Density
Density changes for different substances
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
 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
2.3 Graphing
 A pie graph
shows the
amount each
part makes of
up of the whole
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
The dependent variable is the variable that
you hope will change as a result of the
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
when one
so does the
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
No pattern appears.
2.3 Identifying graph relationships
In an
when one
the other
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
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
2.4 How to solve design problems
What does your
design need to
What constraints
do you have?
Think of an idea.
Follow the design
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.