Introduction to Chemistry

What is chemistry?

the science of matter and the transformations it can undergo

Why is chemistry important?

it helps us understand our surroundings and plays a central role in medicine, engineering, and many sciences

What are the three domains of chemistry?

macroscopic, microscopic, and symbolic

What is the macroscopic domain?

Objects and events large enough to observe directly.

What is the microscopic domain?

Atoms, molecules, and other particles too small to observe directly

What is the symbolic domain?

Symbols, formulas, equations, and graphs to represent and connect the macroscopic and microscopic domains

What are the steps of the scientific method?

Observation, question, hypothesis, experiment, data analysis, conclusion, and communication

What is an observation?

Identifying and describing a phenomenon

What is a hypothesis?

A tentative, testable explanation or prediction

What is an experiment?

A controlled test used to collect evidence

What is qualitative data?

Descriptive information without numerical information

What is quantitative data?

Numerical measurements or counts

What is matter?

Anything that has mass and occupies space

What is a substance?

Matter with a uniform, constant composition and characteristic properties throughout a sample

What is a compound?

A pure substance composed of two or more elements chemically combined in fixed proportions

What is an element?

A substance that cannot be decomposed into simpler substances by chemical means

What is a physical property?

Can be observed or measured without changing a substance's chemical composition

What are examples of physical properties?

Color, odor, density, melting point, boiling point, solubility, conductivity, and hardness

What is a chemical property?

Describes a substance's ability to undergo a chemical change when it interacts with another substance

What are examples of chemical properties?

Flammability, reactivity with oxygen, reactivity with water, reactivity with acids, corrosiveness, and chemical stability

What is an intensive property?

A physical or chemical trait of matter that doesn’t change, even if you change the size or amount of the substance

What are examples of intensive properties?

Density, boiling point, and color

What is an extensive property?

A physical or chemical measurement that changes depending on the size of the system or the amount of matter in the sample

What are examples of extensive properties?

Mass, volume, and energy

What is a homogeneous mixture?

A combination of two or more substances that have the same uniform composition and appearance throughout

What is a heterogeneous mixture?

A combination of two or more substances where the components are not evenly distributed and remain physically separate

What does kinetic-molecular theory state?

Matter consists of tiny particles in constant motion

What are the properties of a solid?

A definite shape, a fixed volume, and particles that are tightly packed together in fixed positions

What are the properties of a liquid?

A definite volume but take the shape of their container, flowing freely because their particles are close together yet able to move past one another

What are the properties of a gas?

No fixed shape or volume, and they expand to fill any container they occupy

How can compounds be decomposed?

Through chemical processes that break their chemical bonds

What is the difference between an element and a compound?

elements cannot be chemically decomposed into simpler substances, while compounds contain two or more elements chemically combined in fixed proportions.

What is a measurement?

Pairs a number with a unit

Why are units important?

They provide a standard for comparison and give meaning to numerical measurements

What system of units does chemistry use?

The International System of Units, or SI

What is the SI base unit for mass?

Kilogram (kg)

What is the SI base unit for length?

Meter (m)

What is the SI base unit for time?

Second (s)

What is the SI base unit for temperature?

Kelvin (K)

What is the SI base unit for amount of substance?

Mole (mol)

What is the SI base unit for electric current?

Ampere (A)

What is the SI base unit for luminous intensity?

Candela (cd)

What does the prefix kilo mean?

10³

What does the prefix centi mean?

10⁻²

What does the prefix milli mean?

10⁻³

What does the prefix micro mean?

10⁻⁶

What does the prefix nano mean?

10⁻⁹

What does the prefix pico mean?

10⁻¹²

What does the prefix mega mean?

10⁶

What does the prefix giga mean?

10⁹

What does the prefix tera mean?

10¹²

What does the prefix femto mean?

10⁻¹⁵

What is dimensional analysis?

A method used to change units using conversion factors

What is a conversion factor?

A ratio based on an equality between two units

What is the main rule of dimensional analysis?

Set up conversion factors so that unwanted units cancel

How many centimeters are in 1 inch?

2.54 cm

How many centimeters are in 1 meter?

100 cm

How many grams are approximately in 1 pound?

453.59 g.

How many milliliters are in 1 liter?

1000 mL.

How many cubic centimeters are in 1 milliliter?

1 cm³.

How many seconds are in 1 minute?

60 s.

How many minutes are in 1 hour?

60 min.

What is volume?

Volume is the amount of three-dimensional space occupied by matter.

What units can be used for volume?

Cubic units such as cm³ and m³, or metric units such as L and mL.

Is volume an SI base quantity?

No. Volume is a derived quantity based on length.

What is area?

Area is the measure of a two-dimensional surface enclosed by a boundary.

What units are used for area?

Squared units such as cm² or m².

What is density?

Density is a physical property that relates mass to volume.

What is the formula for density?

Density = mass ÷ volume, or D = m/V.

What is the formula for mass using density and volume?

Mass = density × volume, or m = D × V.

What is the formula for volume using density and mass?

Volume = mass ÷ density, or V = m/D.

What is a common unit for density?

g/mL.

What is the density of water approximately?

1.00 g/mL near room temperature.

What are significant figures?

Significant figures are the digits in a measurement that communicate its precision.

Which digits are always significant?

All nonzero digits.

Are captive zeros significant?

Yes. Zeros between nonzero digits are significant.

Are trailing zeros significant when a decimal point is written?

Yes.

Are leading zeros significant?

No.

Are placeholder trailing zeros in a whole number without a written decimal point significant?

No.

How should a liquid level be read in a graduated cylinder?

Read the liquid level at the bottom of the meniscus.

What is the estimated digit in a measurement?

The final digit recorded in a measurement is the estimated digit.

Are estimated digits significant?

Yes. Every digit, including the final estimated digit, is significant.

What do significant figures communicate?

They communicate measurement precision.

What is the significant-figure rule for addition and subtraction?

Round the answer to the least number of decimal places.

What is the significant-figure rule for multiplication and division?

Round the answer to the fewest number of significant figures.

What happens when the first dropped digit is below 5?

Keep the retained digit unchanged.

What happens when the first dropped digit is above 5?

Increase the retained digit by 1.

How is an exact 5 followed only by zeros rounded?

Round so the retained digit is even.

What is the SI unit for thermodynamic temperature?

Kelvin (K).

What is the Celsius-to-Kelvin conversion?

T(K) = T(°C) + 273.15.

What is absolute zero?

0 K.

At what temperature does water freeze on the Celsius scale?

0°C at 1 atm.

At what temperature does water boil on the Celsius scale?

100°C at 1 atm.

What is temperature?

how hot or cold an object is.

What is heat?

Heat is energy transferred because of a temperature difference.

What is kinetic energy?

the energy an object or particle has because of its motion

What is the formula for kinetic energy?

KE = ½mv².

What is potential energy?

Energy associated with position or composition.

What is thermal energy?

Energy associated with the random motion of particles in matter.

What does temperature reflect?

The average kinetic energy of particles.