CHEM 201 EXAM 1(contains contents of all of chapter one and half of chapter 2)

What is matter?

Anything that has mass and takes up space.

What are atoms?

The building blocks of matter.

What is an element?

A substance made of only one kind of atom.

What is a compound?

A substance made of two or more different elements chemically bonded together.

What are the two major categories of pure substances?

Elements and compounds.

What is a mixture?

A combination of substances in which the components retain their identities.

What are the two types of mixtures?

Homogeneous and heterogeneous mixtures.

What is a homogeneous mixture?

A mixture with a uniform composition throughout.

What is a heterogeneous mixture?

A mixture with a nonuniform composition.

How can mixtures be separated?

By physical methods.

What is the major difference between a compound and a mixture?

A compound has elements chemically bonded in a fixed composition; a mixture contains substances physically combined in variable proportions.

What law says a pure compound always has the same elemental composition by mass?

The Law of Constant Composition, also called the Law of Definite Proportions.

What is the composition of pure H₂O by mass according to your notes?

About 11% hydrogen and 89% oxygen.

What is a physical property?

A property that can be observed or measured without changing the substance's identity.

Give examples of physical properties.

Density, color, odor, melting point, and hardness.

What is a chemical property?

A property that describes a substance's ability to undergo a chemical change.

What is a physical change?

A change that does not change the identity of the substance.

Give examples of physical changes.

Melting, freezing, sublimation, and cutting.

What is a chemical change?

A change that produces one or more new substances.

Give examples of chemical changes.

Combustion, oxidation, decomposition, and burning.

What is an intensive property?

A property that does not depend on the amount of substance present.

Give examples of intensive properties.

Density, color, and boiling point.

What is an extensive property?

A property that depends on the amount of substance present.

Give examples of extensive properties.

Mass, volume, and energy.

What is filtration used for?

Separating a solid from a liquid.

What property does distillation use to separate substances?

Differences in boiling points.

What does chromatography separate substances based on?

Differences in solubility and interactions with the materials involved.

What is the SI unit for mass?

Kilogram (kg).

What is the SI unit for length?

Meter (m).

What is the SI unit for temperature?

Kelvin (K).

What is the SI unit for volume?

Cubic meter (m³).

What does the metric prefix kilo- mean?

10³ or 1,000.

What does milli- mean?

10⁻³ or 0.001.

What does pico- mean?

10⁻¹²

What is the formula for converting Celsius to Kelvin?

K = °C + 273.15.

What is the formula for converting Celsius to Fahrenheit?

°F = (9/5)°C + 32.

At what temperature does water freeze?

0°C or 32°F.

At what temperature does water boil?

100°C or 212°F.

How many milliliters are in 1 liter?

1,000 mL.

What is the relationship between mL and cm³?

1 mL = 1 cm³.

What is the formula for density?

d = m/V.

What is the formula for mass using density?

m = dV.

What is the formula for volume using density?

V = m/d

What are common units for density?

g/mL and g/cm³.

A substance has a mass of 20 g and a volume of 5 mL. What is its density?

4 g/mL.

If density = 2 g/mL and volume = 10 mL, what is the mass?

20 g.

If mass = 30 g and density = 5 g/mL, what is the volume?

6 mL.

What is accuracy?

How close a measurement is to the true value.

What is precision?

How close repeated measurements are to one another.

What are significant figures?

The digits in a measurement that convey meaningful precision.

Are all nonzero digits significant?

Yes.

Are captive zeros significant?

Yes. Zeros between nonzero digits are significant.

Are leading zeros significant?

No.

Are trailing zeros after a decimal point significant?

Yes.

How can you make the number of significant figures clear when trailing zeros are ambiguous?

Use scientific notation.

When adding or subtracting, how do you determine the number of significant figures?

Use the fewest decimal places.

When multiplying or dividing, how do you determine the number of significant figures?

Use the fewest significant figures.

How many significant figures are in 0.00450?

3.

How many significant figures are in 4.50?

3.

How many significant figures are in 100.0?

4.

What is dimensional analysis?

A method of converting between units using conversion factors.

What should happen to unwanted units during dimensional analysis?

They should cancel.

What unit should remain at the end of a dimensional-analysis problem?

The desired unit.

Why are conversion factors useful?

They allow you to change units without changing the actual quantity.

Who developed the atomic theory in the early 1800s?

John Dalton.

When did Dalton develop his atomic theory?

Around 1803–1807.

What is a scientific law?

A statement or summary describing how matter behaves.

What is a scientific theory?

An explanation that attempts to explain why matter behaves as it does.

What did Dalton's atomic theory help explain?

Experimentally derived chemical laws.

What is the Law of Constant Composition?

A pure substance always has the same elemental composition.

What is the Law of Conservation of Mass?

Mass is neither created nor destroyed during a chemical reaction.

In a chemical reaction, how does the total mass of reactants compare with the total mass of products?

They are equal.

In 2H₂ + O₂ → 2H₂O, if the reactants have a total mass of 36.0 g, what is the mass of the products?

36.0 g.

What are the three main subatomic particles?

Protons, neutrons, and electrons.

What charge does a proton have?

Positive (+1).

What charge does a neutron have?

No charge (0).

What charge does an electron have?

Negative (−1).

Where are protons located?

Negative (−1)

Where are protons located?

In the nucleus.

Where are neutrons located?

In the nucleus.

Where are electrons located?

Outside the nucleus.

Which two particles have approximately the same mass?

Protons and neutrons.

Which subatomic particle has a very small mass compared with protons and neutrons?

The electron.

What happens when like charges interact?

They repel.

What happens when opposite charges interact?

They attract.

Who discovered the electron?

J.J. Thomson.

What experiment/equipment did Thomson use to study electrons?

Cathode-ray tubes.

What are cathode rays?

Streams of negatively charged particles called electrons.

From which electrode do cathode rays originate?

The negative electrode, called the cathode.

Why did Thomson conclude cathode rays were negatively charged?

The rays bent toward a positively charged plate.

What else could cathode rays do that supported the idea they were charged particles?

They could be bent by magnets and could impart negative charge to objects they struck.

What did Thomson's experiments show about electrons?

Electrons are negatively charged particles with mass.

What was Thomson's model of the atom called?

The plum pudding model.

What did the plum pudding model propose?

That negative electrons were embedded in a positively charged sphere of matter.

What was Thomson's charge-to-mass ratio for the electron?

1.76 × 10⁸ C/g.

Who determined the charge of the electron?

Robert Millikan

What experiment did Millikan perform?

The oil-drop experiment

What did Millikan determine from his oil-drop experiment?

The magnitude of the electron's charge.

What is the magnitude of the electron's charge?

1.602 × 10⁻¹⁹ C.

What is the charge of an electron including its sign?

−1.602 × 10⁻¹⁹ C.