Chapter 2
Section 1
Measuring Mass & Volume
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.
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?
96.2g / 6 = 16.033333g
with SF = 16.0g
*Matter
is anything that has mass and takes up
space.
*All matter has mass.
*Steel, plastic, rubber, and glass are different kinds
of matter.
* One
gram
( g ) is one-thousandth of a
kilogram.
* One large paperclip has a mass of about
one gram (1,000 large paperclips = about 1
kilogram).
* Grams are also convenient for analyzing
food.
*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.
* 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.
Mass and weight are different!
*Volume is the amount of space an object takes up.
The fundamental unit of volume in SI is the
cubic meter (m
3
).
*More convenient smaller units are cubic
centimeters (cc or cm
3
), liters (L) and
milliliters ( mL )
*Measuring the volume of liquids is easy.
*Pour the liquid into a graduated cylinderand read the meniscus at eye level.
*You will notice that the surface of the liquid forms a curve rather than a straight line.
*This curve is called the meniscus. Read the volume at the center of the meniscus.
*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.
*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.
Classwork
*Section Review 2.1 pg 35
*#1 - 6
Homework
*Read 2.2
Physical Science
Chapter 2
Section 2
Density
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.
*Density
describes how much mass is in a
given volume of a material.
* Solids, liquids and gases are matter, so
they all have density.
*The density of water is about one gram per
cubic centimeter.
* The units used for density depend on
whether the substance is solid or liquid.
*For liquids use units of grams per milliliter
(g/mL).
* Density is a property of material
independent of quantity or shape.
10.0
*Density changes for different substances because:
*Atoms have different masses.*Atoms may be “packed” tightly or loosely.
*Mass
is measured
with a balance or
scale.
*Use the
displacement
method or calculate
the
volume
.
* To find the density of a material, you need
to know the mass and volume of a sample of
the material.
* Water is an exception to this rule.
* Liquids tend to be less dense than solids
of the same material.
*Ex. solder
Practice Problem: You measure the volume of
a screw to be 2.5ml and the mass to be 19.5g.
What is the density of the screw? What
material is the screw made of?
Classwork
*2.2 Section review all questions
Homework
*Read 2.3
*Density worksheet 2.2
Physical Science
Chapter 2
Section 3
Graphing
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.
* A
graph
is a visual way to organize data.
*A
scatterplot
or XY
graph
is used to see
if two variables are
related.
* A
pie graph
shows the amount each part
makes of up of the whole (100%).
* A “connect-the-dots”
line graph
is often
used to show trends in data over time.
*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.
*Pressure and diving depth as an example;
* 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?
Making an XY graph
* Choose x and y-axis
*Depth is the independent variable = x axis
*Pressure is the dependent variable = y axis
* Make a scale
*Most graphs use ones, twos, fives or tens
OR calculate the value per box
*When scientists create scatterplots, they are usually working with large amounts of data.
*Here is a scatterplot of data for the Old Faithful geyser in Yellowstone National Park, Wyoming.
*The graph shows there are generally two types of eruptions: short-wait-short-duration, and long-waitlong-duration.
*This discovery about the geyser activity would be hard to make without the visual aid of the scatterplot!
Plotting your data
* In a
direct relationship
, when one variable
increases, so does the other.
The speed and distance variables show a direct relationship.
*When there is no relationship the graph looks
like a collection of dots.
No pattern appears
In an inverse relationship
, when one
variable increases, the other decreases.
*What is the speed of the car at 50 cm? *Find the known value on the x axis
*Position = 50 cm
*Draw a line vertically upward from 50 cm until it hits the curve.
*Draw a line across horizontally to the y-axis from the same place on the curve.
*Read the speed using the y axis scale.
*Speed = 76 cm/s
Reading a graph
Classwork
*2.3 Section review all problems
Homework
*Read 2.4
Next Class Day
Physical Science
Chapter 2
Section 4
Solving Problems
Learning Goals
*Apply a four-step technique to solve
problems.
*Use the design cycle to solve problems.
2.0cm
2.0cm
2.5cm
This block is made
out of Platinum.
What is it's mass?
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…
Classwork
*2.4 Section Review #1 - 6
Homework