Transcript Observations

Scientific Method
Use the worksheet
The Scientific Method
• What is the scientific method?
– It is a process that is used to find answers to
questions about the world around us.
Is there only one “scientific method”?
– No, there are several versions of the scientific
method. Some versions have more steps, while
others may have only a few. However, they all
begin with the identification of a problem or a
question to be answered based on observations of
the world around us and provide an organized
method for conducting and analyzing an
experiment.
What is a hypothesis?
• It is an educated guess based on observations
and your knowledge of the topic.
What is data?
• It is information gathered during an
experiment.
Sequence
•
•
•
•
•
Identify the Problem
Form a Hypothesis
Create an Experiment
Perform the Experiment
Analyze the Data
– Modify the Experiment
• Communicate the Results
Chemistry
• the science of matter;
• a branch of the natural sciences;
• deals with:
– the composition of matter
– properties of matter
– reactions
WHAT’S THE MATTER?!?!
If someone asks you, "What's
the matter?" You will reply
"Matter is anything that has
mass and volume..."
Matter
• anything that has mass and
occupies space
• Matter can be broken down into a
substance or a mixture.
Substances
• any material with a definite chemical
composition
– either ELEMENTS or COMPOUNDS
H – hydrogen; O - oxygen or H2O
Element
• A chemical substance that cannot be broken
down or transformed
• There are about 120 known elements
– Hydrogen
– Carbon
– Oxygen
– Lithium
– Sodium
– Chlorine
H
C
O
Li
Na
Cl
The Periodic Table can
be found on page 28-29
of your text book and
on the inside back cover
Categories of Matter
Compound
• Two or more elements combined into one
substance
– Salt NaCl
– Carbon Dioxide CO2
– Hydrogen Peroxide H202
– Sugar C6H1206
Mixture
• a combination of two or more materials
• Categorized as homogenous or
heterogeneous.
• combined physically; just mix.
• no new substances formed.
Homogeneous
• A homogeneous mixture has the same
uniform appearance and composition
throughout.
– Vinegar
– Shampoo
– Pepsi
Heterogeneous
• A heterogeneous mixture consists of visibly
different phases
– Sand in water
– soup
– granite
– salad
Observations
• The act of noting and recording something
with instruments.
• An observation is a description of an event.
Use your senses
• Observations help us decide how a certain
variable might affect the problem
An observation DOES NOT…
• Interpret the result (this happened because
we stirred the solution)
• Assume the conclusion (it is rust versus it
looks like rust)
Qualitative Observation
• A descriptive observation
– Color
– Shape
– Texture
– Hot/cold
Quantitative Observation
• A numerical observation
– Temperature
– Mass
– Volume
Qualitative
Quantitative
Heavy
2 tons
Far from earth
300 light years away
Microscopic
Smaller that 1
micrometer
Burns quickly
Burns at a rate of 1
centimeter per minute
Hot
350°C
2 ways that matter can be
changed:
1. Physical change
2. Chemical change
Physical Properties of Matter
• can be experienced using one of the five senses or
detected through any measuring device without
changing the substance
• How it Looks (Shiny, Dull, Color, etc.)
• How it Feels (Hard, Soft, Rough, Smooth, etc.)
• How it Smells (Sweet, Sharp, Terrible, No Smell, etc.)
• How it Sounds (Loud, Soft, Echo, No Sound, etc.)
• What it Does (Bounce, Stretch, Tear, Break, Magnetism,
etc.)
• Measurements (mass, volume, density, temperature,
length, etc.)
Physical Change
• a change that does not change the chemical
nature of the substance
• Change of state (Solid, Liquid, Gas)
Examples:
• boiling water
• dissolving sugar in water
• cutting apples
Chemical Property
• Indicates how a substance reacts with
something else
• Observed by reacting the substance to test its
property
– Flammability
– Reacts with water
– Reacts with acids
– Doesn’t react with air
Chemical Change
• Occurs when chemical bonds are broken and
new bonds are formed
Signs of a chemical Change
– Formation of a new substance
• solid precipitate
– Color change
– Gas is produced
– Energy change (gets hot/cold)
– Light is produced
Physical Vs. Chemical Change
•
•
•
•
Burning Gasoline?
Boiling Water?
Breaking glass?
Compression of a spring?
Dino Measurement Lab
• Perimeter – distance
around the outside of
an object
• Area – amount of space
an object takes up in
two dimensions
• Mass – use the same
balance each day
Volume
• Must use proper measuring techniques
Volume:
Read
- on a flat surface
- at eye level
- from the bottom of the meniscus
Volume by displacement
Record initial volume Vi = 4.8 mL
Record final volume Vf = 5.6 mL
Volume of the dinosaur =
Vf - Vi = 5.6 – 4.8 = 0.8 mL
Density
Mass ÷ Volume
Density
• Density is a physical property.
– It may be used to identify a substance.
• Density is the amount of mass contained in a
unit of volume.
• The states of matter differ in density:
– Solids are more dense than liquids, which are
more dense than gases, which are more dense
than plasma.
THE EQUATION
D
=M
Density = Mass
V Volume
Examples
• What is the density of a piece of metal with a
volume of 245 cm3 and a mass of 612 g?
D=M
V
= 612 g
245 cm3
= 2.50 g/cm3
What is the volume of a liquid with a density of
0.45 g/mL and a mass of 34. 24 g?
D=M
V
V=M
D
= 34.24 g
0.45 g/mL
= 76 mL
THE TRICK
Review
• Chemistry is the study of matter.
• Matter is anything that has mass and volume.
• Matter can be classified. Make the flow chart.
• Mixtures can be separated physically.
• Substances come from the periodic table.
Scientist describe matter using:
•
•
•
•
Qualitative observations
Quantitative observations
Physical properties and changes
Chemical properties and changes
Create your own examples:
Example
Qualitative Observation
Quantitative Observation
Physical property
Physical change
Chemical property
Chemical change
Energy
• The capacity to do work
– Moving an object (like an electron)
Exothermic
• Release energy
• Energy is a product in the form of heat and/or
light
• Reaction feels warm
Endothermic
•
•
•
•
Absorb energy
Energy is a reactant
Feels cold
Ex: photosynthesis – plants absorb light
energy from the sun to produce sugars and
oxygen.