Chemistry - Test 1

Accuracy

How close numbers are to a target.

Precision

How close values are to each other.

How do you read a graduated cylinder?

Read at eye level and read the meniscus.

Certain Digits

What you can read

Uncertain Digits

The last digit, an estimate.

What is this measurement?

6.235 cm (5 is the estimate/uncertainty)

What are sig figs?

All certain digits + one uncertain digit.

What are the sig fig rules?

1. Any non-zero number is significant

2. Sandwiched zeros are significant.

3. Zeroes to the left of the first significant number are not significant.

4. Zeroes at the end are only significant after a zero and a decimal.

Give sig figs for each number:

13476

1087

0.78

.00657

43.0

67.00

1900

6000

0150.0

1500.0

5

4

2

3

3

4

2

1

4

5

What rules do you following when adding and subtracting decimal numbers?

Add them all up then round to the least amount of decimals based on the added/subtracted numbers.

Add these numbers:

32.567 + 135.0 + 1.4567

169.0237 → 169.0

What is the rule for multiplying and dividing decimals?

Go off of the lowest number of sig figs

Multiply these:

23.7 × 3.8

43.678 × 64.1

90.06 → 90.

2799.7598 → 2.80 × 10³

What is scientific notation?

A shorthand to express large or small numbers.

What is the scientific notation format?

This

Write these in scientific notation:

142.63

1,500,000

0.00336

1.4263 × 10²

1.5 × 10⁶

3.36 × 10^-3

What are the base units for length, mass, and volume?

Meter, grams, liter.

What is a difference between metric and english units?

Metric units are power 10 based. English units are definition based.

When changing units using the metric system, which should have the one and which should have the power?

The prefix should have one and the base should have the power.

Change 2.6 mg to g

2.6 × 10^-3 g

Convert 7.00 in to cm

17.78 = 17.8 cm

What type of property is density?

A physical property of matter and an intensive property.

What is density?

The amount of mass in a specific volume

Density equation with units?

D = M/V

Mass: Kg, g

Volume: cm³ , mL, L

1 mL = ?

1 cm³

What happens to the most dense?

Rank the liquids from most to least dense

Rank the cubs from most to least dense

It will sink.

L2 > H2O > L1

S3 > S2 > S1

H2O = S2

What is an intensive property?

It does not depend on the amount of material

Why is the volume displacement method used?

To measure density/volume of irregularly shaped objects.

What two things must be followed to make sure volume displacement method works?

The object cannot float and it cannot dissolve in water.

How do you convert C to F?

F = (9/5)C + 32

How do you convert F to C?

C = 5/9(F-32)

How to convert C to K?

K = C +273

How to convert K to C?

C = K - 273

A bracelet has a mass of 50.901 g. When the bracelet is placed in a graduated cylinder containing water, the water level rose from 15.5 mL to 20.3 mL. What is the density of the bracelet? Is it silver or platinum? (d of silver = 10.5 g/mL) (d of plat = 21.45 g/mL)

10.6 or 11 g/mL. Silver.

What is chemistry?

The study of matter and its interactions

What is matter?

Anything with mass and volume (density).

Matter has density. It must have both.

What is a substance?

A type of matter with specific composition and properties.

Ex) Water, air, carbon dioxide.

What is mass?

How much matter an object has. It is constant.

What is weight?

Attraction for a body. It varies.

Gravity. Greater pull = greater weight

What does definite mean?

Does not change

Is shape definite or indefinite for solids, liquids, and gases?

Solids: Definite

Liquid: Indefinite

Gas: Indefinite

Is volume definite or indefinite for solids, liquids, and gases?

Solids: Definite

Liquids: Definite

Gases: Indefinite (They can be compressed)

Rank the states of matter from lowest to highest energy

Lowest: Solid

Higher: Liquid

Highest: Gas

Rank the density of the states of matter from highest to lowest

Highest - Solid

Lower - Liquid

Lowest - Gas

Rank the speed of particles of each state of matter from lowest to highest

Lowest (only vibrates) : Solids

Faster : Liquids

Fastest : Gases

What are the solid → liquid and liquid → solid changes called?

Solid → liquid: Melting

Liquid→ Solid: Freezing

What are liquid → gas and gas → liquid called?

liquid → gas: Evaporating

Gas → liquid: Condensing

What are solid → gas and gas → solid called?

Solid → gas: Sublimation

Gas → Solid: Deposition

When is deposition used?

Coat a metal with a metal. Typically in lab settings.

What are physical properties?

Describe the characteristics of a substance.

Ex) Boiling pt, color, shape, size, shape

What are chemical properties?

Describe change in properties or resistance to change.

Ex) Reactivity, oxidation, pH

Answer these: (Physical or chemical)

Physical

Chemical

Chemical

Physical

Chemical (corrosion)

Physical

Chemical

Chemical

Physical

Physical changes of matter?

Do not alter the properties or identity

Ex) Ice → water

Chemical changes of matter?

Affect the identity.

Ex) Water hydrolyzed (decompose)

-Get something new

-Usually chemical reactions

What are pure substances?

One type of substance

Have fixed composition

Cannot be separated by physical processes.

What are elements?

Elements are pure substances

They cannot be separated into simpler substances by chemical means

One type of atom

Ex) copper, aluminum

What are compounds?

A type of pure substance

They can be separated into simpler substances by chemical means

Combined atoms

Ex) Salt (NaCl) and Water (H2O)

What are mixtures?

Two or more types of substances

Variable compositions

Can be separated by physical processes

What are homogenous mixtures?

Have a uniform composition

They look the same, you only see one thing

Ex) Salt water (NaCl, H2O), brass (Cu , Zn)

What are heterogenous mixtures?

Nonuniform composition

See what is what

Ex) Pizza, water and sand

What are all compounds by definition?

Homogenous

Do this

Heterogenous mixture

Homogenous mixture

Homogenous mixture

Heterogenous mixture

Heterogenous mixture

Pure element

Heterogenous mixture

Pure element

Compound

Homogenous

Pure element

What did Democritus do?

The atom is indivisible called “atomos”

What did Dalton come up with? What are the four statements?

Atomic theory

1. Matter is composed of particles called atoms

2. Atoms of the same element have the same properties

3. Combining atoms makes a compound with different properties

4. Atoms cannot be created or destroyed (No longer valid because of nuclear)

What did J.J. Thompson do?

Cathode ray tube, discovered electrons.

Used a cathode ray where a negative electron beam was attracted to a positive plate

Came up with the plum model

What did Rutherford do?

Gold foil experiment

1. Go through → atom is mostly empty space

2. Bounce back → Dense center

3. Deflected → Positive center

Discovered nucleus/positive particle (proton).

What are the particle charges of protons, neutrons, and electrons.

Proton (+)

Neutron (o)

Electron (-)

What is the relative mass of the three particles?

Proton (1 amu)

Neutron (1 amu)

Electron (0 amu)

What is the location of the three particles?

Proton: Nucleus

Neutron: Nucleus

Electron: Outside

How do you calculate protons?

The atomic number

How do you calculate neutrons?

Mass number - protons = neutrons

How do you calculate electrons?

Electrons = protons in neutral atoms

What is important about atomic number?

It is unique to each atom and gives the identity

What is the mass number ?

Protons + neutrons.

Average rounded

Nuclear charge is

how many protons are in nucleus

Do this

Top left: Atomic mass

Below top left: Atomic number

Below that: Electron cofiguration

Top right: Oxidation states

Bottom right: Symbol

Do this

Cl-35: 17 18 17 17 35 +17 35.456

Si-30: 14 16 14 14 30 +14 28.085

C-14: 6 8 6 6 14 +6 12.011

What are ions?

Atoms with electron charge

What is a neutral atom?

When protons = electrons. It has no charge. Na, Cl, C

What is a negative atom?

Anion. number of electrons > number of protons

Ex) Cl^- and O^-2

What is a positive atom?

Cations

Number of electrons < number of protons

Ex) Na^+ and Mg^+2

For Cl^- how many protons, neutrons, and electrons?

Protons: 17

Electrons: 18

Neutrons: 18

For Mg^+2 how many protons, neutrons, and electrons?

Protons: 12

Electrons: 10

Neutrons: 12

What are isotopes?

Atoms of the same element with different numbers of neutrons. (Diff mass numbers)

What are the two representations of isotopes?

Mass number on top

Atomic number on bottom

What is weighted atomic mass?

Average mass of isotopes that compose that element weighted based on natural abundance.

What is the weighted atomic mass formula?

Average atomic mass = (fractional abundance) x (isotopic mass)

This

55.9 amu