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Unit 1: Introduction to Chemistry › uploads › 2 › 4 › 8 › 9 › ... · Unit 1:...
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Unit 1: Introduction
to Chemistry
I. Observations vs. Inferences
• Observation: information you gather
_________________
***You will NEVER use taste in class!
o Describes ________
Examples
You see the plant is green
You feel the solution is warm
You see it is raining outside
You hear the alarm is beeping
using your five senses
facts
• Inference: a possible _________________or
__________________ based on observations
o __________ be directly observed using the 5 senses.
Examples
The plant is green so it must be healthy
The solution is warm so there must have been a
chemical reaction
The street is wet so it must have rained
The alarm is beeping—there may be a fire
Observations are what you see, feel, hear, taste, or
smell. Inferences are what you think!
explanation
conclusion
cannot
Practice
1. Identify the following as an observation (O) or inference
(I).
____ a. The mineral on the table is clear and smooth.
____ b. The caterpillar did not eat the moth because it is not
a carnivore.
____ c. The container is filled to the 350 mL mark with
water.
____ d. The plant on the left is growing faster because it is
watered more.
O
I
O
I
2. Look at the picture below. Read the
statement and decide if it is an observation (O)
or an inference (I). *Hint: ask yourself, does
this statement describe information gathered
from using the 5 senses?
_____ a. The plant has roots.
_____ b. The plant uses water.
_____ c. The plant has flowers.
_____ d. The plant is in a pot.
_____ e. The plant grew from a seed.
I
I
O
O
I
3. Look at the picture below. Write two observations and two
inferences.
Observation
_________________________________________________________
_________________________________________________________
Inference
_________________________________________________________
_________________________________________________________
II. The Scientific MethodWhat is the Scientific Method?
• The Scientific Method: a __________________ used to help
________________________________________.
o There are ____ steps
1. ________________________________
What do you want to know or explain? Use observations you’ve made to
come up with a topic/problem you want to investigate. This is usually written
in question form
2. ________________________________
Use all available resources to collect data on the topic—i.e. experts,
textbooks, journal articles ,online databases, etc.
3. ________________________________
What do you think will happen? Based on your research, predict the answer
to your question or the outcome of the experiment.
series of stepsanswer a question or solve a problem
State the problem
Background research
Form a hypothesis
6
4. ________________________________
Follow the steps in your procedure to perform your experiments and test your
hypothesis. Record data and observations!
5. ________________________________
Examine all the data collected from the experiment. Tables and graphs are
used to organize the data
6. ________________________________
Based on the analysis of the data, draw a conclusion about your hypothesis.
Does the data support your hypothesis? If the data does not support the
hypothesis, there may be an error in the experiment or the hypothesis is
wrong. You cannot change data—scientists must be unbiased.
o Note: In reality, due to the ever-changing nature of science, there is more
than one correct “scientific method”; scientists do not always follow these
exact steps. These six steps are more like common guidelines that
scientists follow when looking to answer a question or solve a problem.
Run the experiment
Analyze the data
State your conclusion
Parts of an Experiment
• Experiment: an organized ___________________ for
_______________________________
• Main parts of an experiment:
oHypothesis: __________________________
based on observations and previous knowledge.
Typically uses “If…then…” format
Example: If caffeine is added to plant seeds,
then they will grow faster
series of stepstesting a hypothesis
an educated guess or prediction
o Data: ____________________ collected in an experiment
Two types:
1. Quantitative: deals with _________________
oCan be_________________—think __________!
**Quantitative Quantity
Examples:
• Length, Height, Area, Time, Temperature
2. Qualitative: deals with _______________
oCan be ________________ but not measured
**Qualitative Quality
Examples:
• Colors, Smells, Tastes, Appearance
information
numbers
measured amount
descriptions
observed
Practice
Identify the following data as qualitative or quantitative. Circle the
correct answer.
1.The baby weighs 20 pounds Qualitative Quantitative
2.Ms. Marble is annoyed Qualitative Quantitative
3.The solution is purple Qualitative Quantitative
4.Ms. Marble has $1,000,000 Qualitative Quantitative
5.There are ten boys in the class Qualitative Quantitative
o Experimental Group: the group that
_______________________ - the test group
The variable that is being tested is ________________
in this group
• Independent Variable – the factor that is
____________________ in the experiment. “The
variable “I” change”.
• Dependent Variable – the variable that “depends”
on the independent variable. This is the ______
collected.
• Constants – factors that
________________________throughout the entire
experiment. Only test one variable at a time!
*the independent variable is the cause, the dependent
variable is the effect*
receives the treatment
manipulated/changed
changed
data
remain the same
o Control Group: the group that
___________________________________
The standard of comparison – important in order
to compare results of the variable being tested
Exposed to the _______ conditions as the
experimental group _________ for the variable
being tested
doesn’t receive the treatment
same
except
Practice1. SpongeBob noticed that his favorite pants were not as clean as
they used to be. His friend Sandy told him that he should try using
Clean-O detergent, a new brand of laundry soap she found at Sail-
Mart. SpongeBob made sure to wash one pair of pants in plain water
and another pair in water with the Clean-O detergent. After washing
both pairs of pants a total of three times, the pants washed in the
Clean-O detergent did not appear to be any cleaner than the pants
washed in plain water.
a. What was the problem SpongeBob wanted to investigate?
b. What is the independent variable?
c. What is the dependent variable?
d. What should Sponge Bob’s conclusion be?
Does using clean-o detergent clean his pants better than plain
water?
Laundry soap
How clean his pants get
Using clean-o does not make his pants more clean
2. We want to test if fertilizer helps plants. One plant is given
fertilizer, while the other plant is not. Both plants are the same
type, given the same size planter, the same amount of light, and
the same amount of water. After letting both plants grow for one
week, we observe that the plant given the fertilizer has grown
taller. Identify the following:
Experimental Group:
Independent Variable:
Dependent Variable:
Control Group:
Constants:
Plant given fertilizer
Plant without fertilizer
Plant growth
Fertilizer
plant type, size of planter, amount of
light/water, length of experiment
III. Data Representation - Graphs
• Graphing is used by scientists to display the data that is
collected during a controlled experiment.
In science, a ______ graph is most commonly used.
• The graph should contain 4 major parts: the title, the
independent variable, the dependent variable, and the scales
for each variable.
1. ___________: this shows what the graph is about. A basic
title follows the following format: “the effect of (the
independent variable) on (the dependent variable)”
2. _____________Variable: this is the factor that is
controlled or manipulated by the experimenter. This
variable should be placed on the horizontal or x-axis and
should be labeled with a name and units
line
title
independent
3. _____________Variable: this is the variable that changes in
response to the independent variable. It is the result of what
happens because of the independent variable. This variable is
placed on the y or vertical axis and should be labeled with a name
and units
4. The Scales for each Variable: the scales are the numbers on the
axes that guide where you plot your points. Scales must be
evenly spaced, consistent, and carefully selected so that the data
fills up the whole graph. It is very common for students to guess
the scale but there is a better way!
Last step: Always round up to a number that is convenient. For
example, if you get 18.7 as your value for each square on the
x-axis, that rounds up to 19 but 20 is much easier to work
with.
Highest X Value = value for each square on x-axis
Number of lines
Highest Y Value = value for each square on y-axis
Number of lines
dependent
• When completing a graph, remember STALK!
S --
T --
A --
L --
K --
Scale
Title
Axis
Labels
Key
Example
pH of
water
Number
of
tadpoles
8.0 45
7.5 69
7.0 78
6.5 88
6.0 43
5.5 23
*Hint – in a data table, the variable that goes on the x
axis (the independent variable) is typically on the
__________; the variable that goes on the y-axis (the
dependent variable) is typically on the __________.
Just think of it as alphabetical order!
Questions
1.What is the independent variable?
2.What is the dependent variable?
3.What is one conclusion you can make from this data?
left right
pH of water
Number of tadpoles
The # of tadpoles is greatest around a pH of 6.5-7
• Sometimes, a graph may contain two sets of data. If that is
the case, you will need to make a key to label which line is
which.
Example
Day Plant
height
without
fertilizer
(cm)
Plant
height
with
fertilizer
(cm)
1 3 13
2 7 17
3 8 19
4 10 23
Questions
1.Which is the control group? How do you know?
2.Which is the experimental group? How do you
know?
3.What is one conclusion you can make from this
data?
Plants without fertilizer – didn’t receive the
treatment
Plants with fertilizer – did receive the treatment
Plants that received fertilizer grew taller than the
plants that didn’t
IV. Measurement
1. Distance (length, width, height)
Unit Abbreviations
mm = ___________________ cm =______________________
km = ____________________ m = _______________________
How much does each one equal?
1 m = ________mm 1 m = ________cm 1 km= _________m
What do you
want to
measure?
Definition Tool Basic Metric
Unit and
Abbreviation
Distance Amount of
space between
2 points
Ruler, meter
stick,
measuring tape
Meter
(m)
millimeter centimeter
kilometer meter
1000 100 1000
2. Volume
Unit Abbreviations
mL = ______________________ cL = _______________________
kL = _______________________ L = ________________________
How much does each one equal?
1 L = __________mL 1 L = _________cL 1 kL= __________L
What do you notice about these units and the units for distance?
What do you
want to
measure?
Definition Tool Basic Metric Unit
and Abbreviation
Volume Amount of space
a substance
takes up
Liquids –
graduated
cylinder
Solids - ruler
Liquids – milliliter
(mL)
Solids – cubic
centimeters (cm3)
milliliter centiliter
kiloliter liter
1000 100 1000
The prefixes and relationships between prefixes are the same. Only the
base unit changes
Finding Volume: There are three ways to find the volume of
different objects:
1)Calculate the volume of solid cubes or rectangular objects
using a formula
2)Measure the volume of liquids using a graduated cylinder
3)Develop a procedure to calculate the volume of oddly shaped
objects
Hint!!!! Volume is a 3 DIMENSIONAL measurement. Your
units will be mL for liquids and oddly shaped objects and a
length measurement cubed (cm3, m3, mm3) for cubic solids.
1mL = 1 cm3
1) Calculate Volume: Cubes and Rectangular Prisms
In order to calculate the volume of a cube or rectangular prism, you will
use the following formula. Find the volume of this box by using the
length, width, and height measured for you:
Example: A textbook has the following dimensions…
Length = 28cm
Height= 3cm
Width= 22cm
What is its volume?
H = 3cm
L = 6cm
W =1cm
6cm 1cm 3cm
18cm3
1848cm3
In order to measure liquids, it is necessary to use a graduated cylinder,
beaker or flask. Practice measuring liquids by looking at the pictures:
a. Find the _____________ (the upside down bubble). Draw an arrow
to the bottom of the meniscus in each drawing.
b. Read the line closest to the bottom of the meniscus. Record your
answer in mL.
_____ _____ ______
2) Measure Volume: Liquids
meniscus
43 mL 35 mL 52.8 mL
How can you find the volume of strangely shaped objects? After
watching the demonstration, write a procedure explaining how you will
find the volume of oddly shaped objects using only a graduated cylinder:
This procedure for finding the volume of oddly shaped objects is called
______________________________.
3) Develop a Procedure of Volume: Oddly Shaped Objects
1. Gather material: graduated cylinder (or something that measures
volume), water, and object
2.
3.
4.
water displacement
Measure out a few mL of water in graduated cylinder.
Record initial volume
Place object in graduated cylinder and see how much
the water level rises. Record final volume
Subtract the initial volume from the final volume—the
difference is the object’s volume
3. Mass
Unit Abbreviations
mg = ______________________ cg = _______________________
kg = _______________________ g = ________________________
How much does each one equal?
1 g = _________mg 1 g = ________cg 1 kg= _________g
Again, notice the prefixes and relationships are the same as distance
and volume! Only the base unit changed!
Finding Mass: When finding the mass of an object using a balance, make
sure the balance is ________________ and in the correct _________!
What do you
want to
measure?
Definition Tool Basic Metric Unit
and Abbreviation
Mass Amount of matter
(atoms and
molecules) in an
object
Scale or
balanceGrams (g)
milligram centigram
kilogram gram
1000 100 1000
zeroed units
4. Temperature
There are three units of temperature: Fahrenheit (°F), Celsius (°C),
and Kelvin (K). Although we are used to using ______________,
in science we typically use ________________ and
__________.
What do you
want to
measure?
Definition Tool Basic Metric Unit
and Abbreviation
Temperature
• Hotness/coldn
ess of a
sample
• The
____________
____________
of molecules in
a substance
thermometer
average kinetic
energy
Celsius (°C)
Celsius Kelvin
Fahrenheit
Match the correct label with the diagram below:
Body Temperature
Freezing Point of Water
Boiling Point of Water
Room Temperature
As mentioned before, in science temperature is measured in
Celsius or Kelvin. Often times, it is necessary to convert
between the two. Looking at the picture above, what do you
predict the equation is to convert Celsius to Kelvin?
K =
Using algebra, this equation can also be written to convert
the other way, from Kelvin to Celsius:
°C + 273
°C = K - 273
Practice
Record the following temperatures and convert them to Kelvin.
Note, the thermometers are in degrees Celsius.
Temperature in °C = Temperature in °C =
Temperature in K = Temperature in K =
17
290
63
336
Metric Conversions
In the metric system, we can make smaller or larger units by
adding a prefix. To convert from a larger unit to a smaller unit
or vice versa, all you have to do is move the
_____________________!
• Unit (or base unit) can be grams, liters, meters, etc. It is
whatever you are measuring without a prefix
decimal point
Practice
1. Convert 18mL to liters
2. Convert 300km to meters
3. Convert 450mg to grams
4. Convert 20km to cm
0.018 L
300,000 m
0.45 g
2,000,000 cm
V. Percent Error
T
Examples:
1.Michael Scott measured the piece of paper to be 24 cm long. It was actually
20 cm long. What is the percent error?
2.The mass of a rock was measured by a student and determined to be 325
grams. The actual mass of the rock was 330 grams. Calculate the percent
error in the student's measurement of the rock's mass.
3.In an experiment, the density of copper is determined to be 9.45 g/mL. The
accepted value for the density of copper is 8.960 g/mL. Find the percent error.
VI. DensityDensity: How much matter (atoms and molecules) is packed in
an object or in other words, how much mass is located in a
specific volume of space. The units for density are _____ or
______
**Remember 1 mL = 1 cm3
Equation – see Table ___:T
g/mLg/cm3
Practice1. Find the density of a liquid with a mass of 10 grams and a
volume of 10cm3
2. If you have a lead ball with a mass of 450 g and a density of 45
g/cm3, what is the volume?
3. Helium has a density of 0.1786 g/L. If you have 1000 L of
helium, what would its mass be?
4. A rock has a mass of 120.5g. It is put into 103.35 mL of
water and the water rises to 118.42 mL. Find the density of
this rock.
5. What is the density of an unknown block having a mass of
972.3g and dimensions of 4.57cm by 15.32 cm by 11.28cm?
• The density of a specific substance does not change at a
given temperature. For example, the density of pure water is
always _______.
o Because of this fact, density can be used to identify
substances.
Example:
A person brings in what he thinks to be a gold ring to a
jewelry store. The ring has a mass of 4.5 g and a volume of
0.233 cm3. He knows the density of gold is 19.3 g/cm3. Is
this a gold ring? How do you know?
1 g/mL