CHEM 1303 Exam 1 - Chapters 2 and 3

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Questions and Answers

What are the metric or SI units used in measurements of volume?

liter (L)

What is the metric unit for length?

meter (m)

What is the metric unit for mass?

kilogram (kg)

What is the metric unit for temperature?

degree Celsius (°C) Signup and view all the answers

What is the metric unit for time?

second (s) Signup and view all the answers

How do you identify a number as measured or exact?

Measured numbers are obtained through measurement and have uncertainty, whereas exact numbers are counted or defined and have no uncertainty. Signup and view all the answers

What are significant figures?

Digits in a number that are meaningful in terms of accuracy or precision. Signup and view all the answers

What is a metric equality?

A statement that expresses the relationship between two different units, such as 1 meter = 100 centimeters. Signup and view all the answers

What is the purpose of writing conversion factors?

To enable the conversion between different units that describe the same quantity. Signup and view all the answers

What is density?

Density is defined as mass per unit volume. Signup and view all the answers

How can matter be classified?

Matter can be classified as pure substances or mixtures, and further into elements or compounds, homogeneous or heterogeneous mixtures. Signup and view all the answers

What are the states of matter?

Solid, liquid, and gas. Signup and view all the answers

What are potential and kinetic energy?

Potential energy is stored energy based on position, while kinetic energy is the energy of an object in motion. Signup and view all the answers

What is specific heat?

The amount of heat required to raise the temperature of a unit mass of a substance by one degree Celsius. Signup and view all the answers

What are the changes of state in matter?

Melting, freezing, sublimation, deposition, vaporization, and condensation. Signup and view all the answers

Study Notes

Units of Measurement

Key metric/SI units include:
- Volume: liter (L)
- Length: meter (m)
- Mass: kilogram (kg)
- Temperature: kelvin (K)
- Time: second (s)

Measured Numbers and Significant Figures

Measured numbers are obtained through measurement; exact numbers result from counting or defined quantities.
Significant figures indicate the precision of a number; rules for counting significant figures include:
- Non-zero digits are always significant.
- Leading zeros are not significant.
- Captive zeros (between non-zero digits) are significant.
- Trailing zeros in a decimal number are significant.

Significant Figures in Calculation

The result of a calculation should reflect the least number of significant figures from the values used.
Rounding rules:
- If the digit after the last significant figure is less than 5, round down.
- If it is 5 or more, round up.

Prefixes and Equalities

Metric prefixes denote multiples or fractions of a unit, allowing conversion in scientific calculations. For example:
- kilo- (k) = 10³
- centi- (c) = 10⁻²

Writing Conversion Factors

Conversion factors facilitate changing between units; examples include:
- 1 inch = 2.54 cm
- 1 liter = 1,000 mL

Problem Solving Using Unit Conversion

Dimensional analysis utilizes conversion factors to change units systematically in calculations. Ensure units cancel appropriately for accurate results.

Density

Density (D) is calculated as mass (m) divided by volume (V): D = m/V.
Knowing the density allows for determination of mass or volume when either is unknown.

Classification of Matter

Matter is categorized as:
- Pure substances: elements (unique types of atoms) and compounds (combinations of elements).
- Mixtures: can be homogeneous (uniform composition) or heterogeneous (distinct, separate components).

States and Properties of Matter

States of matter include solid, liquid, and gas, each exhibiting unique properties.
Chemical properties pertain to the ability of a substance to undergo a chemical change, while physical properties can be observed without changing the substance.

Temperature

Temperature conversions can be done among Celsius, Fahrenheit, and Kelvin. Conversion formulas include:
- °C to °F: F = (C × 9/5) + 32
- °C to K: K = °C + 273.15

Energy

Energy exists in two main forms: potential energy (stored energy) and kinetic energy (energy of motion).
Conversion of energy units may be required, such as joules to calories.

Energy and Nutrition

Nutritional energy is measured in kilocalories (kcal) or kilojoules (kJ); caloric content can be calculated based on food composition.

Specific Heat

Specific heat refers to the amount of heat required to change a unit mass of a substance by one degree Celsius.
Analyze heat loss or gain during processes like heating or cooling using specific heat values.

Changes of State

Changes of state include:
- Melting: solid to liquid
- Freezing: liquid to solid
- Vaporization: liquid to gas
- Condensation: gas to liquid
- Sublimation: solid to gas
- Deposition: gas to solid
Heating and cooling curves illustrate temperature changes during phase transitions without calculations involving heat of fusion or vaporization.

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Description

This quiz covers key concepts from Chapters 2 and 3 of CHEM 1303, focusing on units of measurement, significant figures, and related methodologies in chemistry. Test your understanding of the metric and SI units used in scientific measurements.