Chem10171 day1

CHEM 10171-04

Dr. Nicole Brinkmannnbrinkma@nd.edu

415 Jordan Hall of Science1-1302

CHEM 13171

Who should take it?Anyone who…• Feels anxious about

heavy first-year load as science or EG major

• Feels anxious about college chemistry

• Wants to develop good college-level study skills

Who should wait till organic?

Anyone who…• Had a 5 on AP

Chemistry test

Why study chemistry?

Combustible materials contain phlogistonSome more (charcoal), some less (metal)

Burn charcoal in closed container

Fire goes out

Why does phlogistonneed air?

Air gets saturatedwith phlogiston

Some things burn more than othersObservation

Why?Ask Questions

Pose an explanation

Burn metalTry SomethingTry Something

Observation Forms calx whichweighs more than metal

Observation

Ask QuestionsHow can the

loss of phlogistonincrease the mass?

Ask Questions

Phlogiston hasnegative mass

Pose an ExplanationPose an Explanation

Observation

Ask questions

Pose an explanation

Try something

If new observation

Ask more questions

Pose additional explanations

Heated Hg calx and got Hg and gasTotal mass of Hg & gas = mass Hg calx

Heated Hg with gas and got Hg calxMass Hg calx = total mass of Hg & gass

Observation

Why?Ask Questions

Heating Hg with gas caused the two tocombine into the calx; heating the calxcaused it to break into Hg and the gas

Pose an explanation

Burn Hg in closedcontainer then lightcandle in container

Try Something

Candle goes out

Observation

Ask Questions

Is this consistent with previousobservations & explanations?

Yes

Propose a theory

No

Revise

Observation

(Ask questions)

Hypothesis

Experiment

Observation

Ask more questions

Propose a theory

Revisehypothesisas needed

Further experiments

Revise theoryas needed

MODERN SCIENTIFIC METHOD

What is chemistry?

• The study of matter and its properties, the changes that matter undergoes, and the energy associated with those changes. (MSS, p. 4)

• The study of matter and its properties, the changes that matter undergoes, and the energy associated with those changes. (MSS, p. 4)

• Matter – anything that has mass & volume

Properties & Changes

If you combine A&Band get C, is this achemical change orphysical change?

Chemical changebecause the Substanceshave changedcomposition.

Properties & Changes

If you combine A&Band get D, is this achemical change orphysical change?

Chemical changebecause the Substanceshave changedcomposition.

Properties & Changes

If you change theconditions C andget D, is this achemical change orphysical change?

Physical changebecause the Substanceshave changedcomposition.

Properties & Changes

If you change theconditions C andget D, does D havedifferent propertiesthan C?

Same chemicalproperties b/c it’sthe same substance.Different physicalproperties b/c it’s ina different form.

Properties & Changes

Are there chemical or physical changesbetween A and B?

CC: 3Y2 + 3R -> RY2 (new composition)CC: 3R + 3B -> 3RB (new composition)PC: 3B(s) -> 3B(g)

Properties & Changes

• Aluminum foil is cut in half• Clay is molded into a pot• Milk goes sour• Water in an ice cube tray freezes• Food scraps are composted• Rubbing alcohol evaporates in your

hand• Hydrogen peroxide bubbles in a cut

PPCPCPC

Properties & Changes

• Can we make some generalizations about chemical and physical properties and changes?

Energy

(b)

Two states of the samesystem are shown as (a)and (b).

Where does eachstate belong in the PEdiagram?

Where does the PE gowhen it is lost from the state with higher PE?

Energy

Measuring

What is the length of the metal strip?(a) 7.5 cm (b) 7.25 cm (c) 7.4 cm (d) 7.45 cm

In science, we use significant figures – all the digits you canread plus the first digit that you can estimate.

Density

DW = 1.0 g/mL, DC = 0.88 g/mL, DA = 1.4 g/mLWhich is a possible density for B? (a) 0.79 g/mL (b) 0.86 g/mL (c) 0.94 g/mL (d)1.2 g/mL

DW = 1.0 g/mL, DC = 0.88 g/mL, DA = 1.4 g/mLWhich is a possible density for B? (a) 0.79 g/mL (b) 0.86 g/mL (c) 0.94 g/mL (d)1.2 g/mL

Density = M/V units: g/mL

DC < DBDB < DWDW < DA

You have 3 pieces of metal each having the same mass.You drop each into one of three graduated cylinders eachof which started with 25.0 mL of water.Which metal is the most dense?

V = 3.2 mL V = 2.9 mL V = 3.5 mL

D = M/V division by the smallest V will give the biggest D

If the mass of B is 25.0 g, what is the density of B?(a) 8.6 g/mL (b) 8.62 g/mL (c) 8.621 g/mL (d) 8.6207 g/mL

A 25.0 g sample ofwater was measuredfour times by fourdifferent students.Which student(s) was(were)precise in his/hermeasurements?Which was (were) accurate?

A B

DC

The volume of abox is length xwidth x height:V=LWHWhat is the volume of this box?(f)10000(g)100000(h)1

1m

100cm

100cm

The volume of abox is length xwidth x height:V=LWHWhat is the volume of this box?•10000•100000 cm3

•1 m3

1m

100cm

100cm

-Apples/oranges-Canceling units-Converting units

p. 18-21

Re-cap

• Modern scientific method• Definition of chemistry• Understanding of some basic concepts:

physical chemical properties/changes, energy, density, measurements – significant figures, accuracy/precision, units