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 H– Carbon C– Oxygen O– Lithium Li– Sodium Na– Chlorine Cl

Categories of Matter

The Periodic Table can be found on page 28-29 of your text book and on the inside back cover

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 change2. 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 Lab

Objective: The package claims the dinosaur grows over 600% when

placed in water. Is this claim true?

Measurements

• Length – Head to tail• Height – head to foot• Thickness – width under belly

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 techniquesVolume:Read- on a flat surface- at eye level- from the bottom of the meniscus

Volume by displacementRecord 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 VDensity = Mass Volume

Examples• What is the density of a piece of metal with a

volume of 245 cm3 and a mass of 612 g?

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

= 612 g

245 cm3= 2.50 g/cm3

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• Reactants Products + Energy

Endothermic

• Absorb energy• Energy is a reactant• Feels cold• Reactants + Energy Products