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