Post on 12-Apr-2020
All About
measuring matters
mass
density
volume
Volume is the amount of space an object takes up.
The base unit of volume in the metric system in the liter and is represented by L or l.
Metric Units
1 liter (L) = 1000 milliliters (mL)
1 milliliter (mL) = 1 cm3 (or cc) = 1 gram*
Which is larger?
A. 1 liter or 1500 milliliters
B. 200 milliliters or 1.2 liters
C. 12 cm3 or 1.2 milliliters*
volume
Measuring Volume
We will be using graduated cylinders to
find the volume of liquids and other
objects.
Read the measurement based on the bottom of
the meniscus or curve. When using a real
cylinder, make sure you are eye-level with the level of the water.
What is the volume of water in the cylinder? _____mL
What causes the meniscus?
A concave meniscus occurs when the molecules of the liquid attract those of the container. The glass attracts the water on the sides.
Measuring Liquid Volume
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Pay attention to the scales for each cylinder.
Measuring Solid Volume
10 cm
9 cm
8 cm
We can measure the volume of
regular object using the formula
length x width x height.
_____ X _____ X _____ = _____
We can measure the volume of
irregular object using water
displacement.
Amount of H2O with object = ______
About of H2O without object = ______
Difference = Volume = ______
10 cm 8 cm 9 cm 720 cm3
200 ml
260 ml
60 ml
Mass refers to the amount of matter in
an object.
The base unit of mass in the metric system in the kilogram and is represented by kg.
Metric Units
1 Kilogram (km) = 1000 Grams (g)
1 Gram (g) = 1000 Milligrams (mg)
Which is larger?
A. 1 kilogram or 1500 grams
B. 1200 milligrams or 1 gram
C. 12 milligrams or 12 kilograms
D. 4 kilograms or 4500 grams
Measuring Mass
We will be using triple-beam balances to find mass.
Once you have balanced the scale, you add up the amounts on each beam to find the total mass.
What would be the mass of the object measured in the picture?
_______ + ______ + _______ = ________ 300g 70g 3.32g 373.32g
PRECISION & ACCURACY
Accuracy
We talk about accuracy when the question we ask is:
How close is the experimentally measured value to the accepted value?
Precision
We talk about precision when the question we ask is: How close is the experimentally measured value to the other experimentally measured values?
Why is this confusing?
• Precise, is often used non-scientifically to
mean exact (which sounds a lot like
accurate!)
Matt John Dan Pete
Assuming the center bull's-eye is our accepted value: Who is the most accurate at throwing darts? Who is the least precise? Describe John’s precision and accuracy to the other dart throwers. example: Pete’s darts are less accurate and less precise than Matt’s, less accurate and more precise than John’s, and more accurate and more precise than Dan’s.
example: Three students weigh a
sample of known weight (4.50 g), four times each
Donovan: 4.56 g, 4.55 g, 4.76 g, 4.58 g » Average = 4.6125 g
» Range 0.21
Mike: 4.55 g, 4.56 g, 4.66 g, 4.53 g » Average = 4.575 g
» Range 0.13
Kevin: 4.77 g, 4.78 g, 4.76 g, 4.79 g » Average = 4.775 g
» Range 0.03
• Who is the most accurate? – Mike is 0.08 g off, Donovan is 0.11 off, and Kevin is off by 0.28 g
– Mike is the most accurate because he is the closest to the true value
• Who is the least precise? – Donovan has the highest standard deviation and the largest range,
therefore he is the least precise.
How Precise are your Measurements?
DENSITY
A distinguishing property
Density is a measure of how
mass and volume are related in an
object.
An object’s density is the amount of
matter it has in a given space.
To find density:
• first measure mass (m)
• and volume (v)
• then use this formula
Density is an important physical property of an object.
1. The density of a substance is always the same (at a given T and p)
mythbusters
sulfer hexofluoride
sulfur hex2
2. The density of one substance is always
different than the density of another substance.
Density math challenge
You went panning for gold and
found a nice nugget.
How do you know if it’s
real or just “fool’s gold”?
mass: 96.6 g
volume: 5.0 cm3
Remember D = m/v
Density of gold 19.32 g/cm3
Density of fools gold (iron pyrite) 5.02 g/cm3
Let’s Try a few Calculations Fun with math in science!
1. A brick of salt with a mass of 433 g measures
10 cm x 10 cm x 2 cm. What is its density?
2.16 g/cm3
D = m/v m = 433 g v = 10 cm x 10 cm x 2 cm = 200 cm3
D = 433/200 = 2.16 g/cm3
5. An ice cube has a density of 0.917 g/ml and
measures 5.8 cm x 5.8 cm x 5.8 cm. What is its
mass? 178.9 g
D = m/v m = Dv v = 5.8 cm x 5.8 cm x 5.8 cm = 195.11 cm3
m = (0.917 g/ml)(195.11 cm3 = 178.9 g
6. Gasoline will float on water. 450 g of gasoline is
spilled into a puddle of water. If the density of
gasoline is 0.665 g/ml, what volume of gas was
spilled? 676.7 ml
D = m/v v = m/D
v = 450 g ÷ 0.665 g/ml = 676.7 ml
last one…
13. Rocks are sometimes used along coasts to prevent
erosion. If a rock needs to weigh 2,000 kg (about 2
tons) in order not to be shifted by waves, how big
(volume) does it need to be? You are using basalt
which has a typical density of 3200 kg/m3.
0.625 m3
v = m/D
= 2,000 kg
3,200 kg/m3
DENSITY MINI LAB
Floating and Sinking
A study of Density
What Makes something Float or
Sink in water?
Floating and sinking
Using what you know of density and the information that
the density of water is 1 g/ mL (or 1 kg/L) provide an
explanation about how you could predict if an object will
float or sink in water.
What’s the Difference?
A CLOSER LOOK AT MATTER
Atoms, elements, compounds and mixtures
Which of these is matter?
air
water
smoke
light
heat
cold
darkness
jello sound
human
cloud
diamond
What is matter?
• Matter is anything that has mass and
takes up space.
• Matter can be classified by extensive or
intensive properties.
• Extensive properties depend on the
amount of matter in the sample.
• Intensive properties do not depend on the
amount but the type of matter in the
sample.
elements
Pure substances that cannot be broken
down by chemical changes.
Each element has unique properties.
Matter is made up of…
Combine in fixed ratios.
Hydrogen peroxide
Glucose C6H12O6
Property of almost all elements – the ability to
combine with other elements and form
compounds
Matter is made up of…
compounds
elements combine to form larger
particles called compounds.
CLASSIFICATION OF MATTER
mixtures
compounds
Classification model
Pure Substances A pure substance always has the same composition and
the same characteristics/properties (density, color, taste,
smell, boiling point)
compounds
Can be broken down into
simpler substances using
chemical methods
elements
Can’t be broken down any
further. Contain only one
type of atom. Approx. 109
elements
mixtures Made up of two or more substances that are
not combined chemically so do not create a
new substance. They can be separated by
“mechanical” means.
Most things in nature are mixtures
Mixtures
• Mixtures are physical blends of two or
more components.
• Mixtures are classified into two groups:
• Heterogeneous mixtures are not uniform.
Their components are not evenly
distributed.
• Homogeneous mixtures are uniform and
their components are evenly distributed.
What kind of mixture is it?
heterogeneous Homogeneous
heterogeneous
Homogeneous
Heterogeneous
Homogeneous
Classification model
Element, Compound, or
Mixture? Rocks
Element, Compound, or
Mixture? Copper
Element, Compound, or
Mixture? Jelly Beans
Element, Compound, or
Mixture? Table Sugar
Element, Compound, or
Mixture? Diamond
Element, Compound, or
Mixture? Tea
Element, Compound, or
Mixture? Salt
Element, Compound, or
Mixture? Neon Gas
Element, Compound, or
Mixture? Pure Water
Element, Compound, or
Mixture? Aluminum
Element, Compound, or
Mixture? Lemonade
Element, Compound, or
Mixture? Silver
Element, Compound, or
Mixture? Sand
Is a Glow Stick Compound or
Mixture?
Glow sticks give off light when two
solutions are mixed.
The sticks consist of a small, brittle containers within a
flexible outer container. Each container holds a unique
solution.
When the outer container is flexed, the inner container
breaks, allowing the solutions to mix, causing the
necessary chemical reaction. After breaking, the tube is
shaken to thoroughly mix the two compounds.
Separating mixtures Chromatography of inks
Why use chromatography?
remember: chromatography is
used to physically separate
components in a mixture by
passing it in solution across a
medium (the paper) in which the
different components move at
different rates.
chromatography can purify basically any
soluble or volatile substance if the right
adsorbent material, carrier fluid, and
operating conditions are employed.
Calculating Rf (retention factor)
basically it is the
distance traveled by
the compound
divided by the
distance traveled by
the solvent
It's a measurement of how
the compound is interacting
with both the solvent (liquid)
and the solid support (paper).
The Rf value tells you how well the solute dissolves in the solvent. The
higher it rises on the paper, the better it dissolves in the solvent.
Separating a
complex mixture
Another engineering challenge!