CHM-100 Final Exam Review: Step-by-Step Study Guidance

Q1. What units are used for measurement of what properties in each system?

Background

Topic: Units of Measurement in Chemistry

This question tests your understanding of the different units used to measure physical properties (such as mass, length, volume, temperature) in the metric (SI) and US customary systems.

Key Terms and Concepts:

• SI (International System of Units): The standard system used in science.

• US Customary System: Commonly used in the United States for everyday measurements.

• Properties: Mass, length, volume, temperature, etc.

Step-by-Step Guidance

1. List the main physical properties commonly measured in chemistry (e.g., mass, length, volume, temperature).

2. For each property, identify the SI unit (e.g., kilogram for mass, meter for length).

3. For each property, identify the US customary unit (e.g., pound for mass, inch/foot for length).

4. Consider any common prefixes used in the metric system (e.g., milli-, centi-, kilo-).

Try solving on your own before revealing the answer!

Final Answer:

Mass: SI unit is kilogram (kg); US customary unit is pound (lb).

Length: SI unit is meter (m); US customary unit is inch (in), foot (ft).

Volume: SI unit is liter (L); US customary unit is quart (qt), gallon (gal).

Temperature: SI unit is kelvin (K) or degree Celsius (°C); US customary unit is degree Fahrenheit (°F).

In chemistry, SI units are preferred for consistency and ease of conversion.

Q2. What are the steps of the scientific method, in order?

Background

Topic: Scientific Method

This question tests your knowledge of the logical process scientists use to investigate phenomena and solve problems.

Key Terms:

• Observation

• Hypothesis

• Experiment

• Conclusion

• Theory

Step-by-Step Guidance

1. Start by identifying the initial step, which involves noticing something or asking a question.

2. Next, determine what step involves proposing a possible explanation or answer.

3. Consider what comes after forming a hypothesis—how do scientists test their ideas?

4. Think about how results are analyzed and what is done with the findings.

5. Finally, consider how repeated experiments and consistent results can lead to broader scientific theories.

Try solving on your own before revealing the answer!

Final Answer:

1. Observation/question

2. Hypothesis

3. Experiment

4. Analysis of data

5. Conclusion

6. (If supported, may develop into a theory after repeated validation)

Q3. How do you write numbers in scientific notation and identify place values?

Background

Topic: Scientific Notation and Place Value

This question tests your ability to express numbers in scientific notation and understand the value of each digit in a number.

Key Terms and Formulas:

• Scientific Notation: A way to express very large or very small numbers as a product of a number between 1 and 10 and a power of 10.

• General form: $a \times 10^n$

Step-by-Step Guidance

1. Identify the first nonzero digit in the number; this will be the digit to the left of the decimal in scientific notation.

2. Count how many places you move the decimal point to get a number between 1 and 10; this determines the exponent.

3. If you move the decimal to the left, the exponent is positive; if to the right, it is negative.

4. Write the number as $a \times 10^n$ where $a$ is the new number and $n$ is the exponent.

Try solving on your own before revealing the answer!

Final Answer:

Example: 45,000 = $4.5 \times 10^4$; 0.0062 = $6.2 \times 10^{-3}$.

Place value refers to the value of each digit depending on its position (ones, tens, hundreds, tenths, hundredths, etc.).

Q4. How do you determine significant figures, round to the correct number of significant figures, and apply sig fig rules in calculations (multiplication/division or addition/subtraction)?

Background

Topic: Significant Figures (Sig Figs)

This question tests your understanding of how to identify significant digits in a measurement, round appropriately, and apply rules for sig figs in calculations.

Key Terms and Rules:

• Significant Figures: Digits in a number that carry meaning about its precision.

• Multiplication/Division: The result should have as many sig figs as the measurement with the fewest sig figs.

• Addition/Subtraction: The result should have as many decimal places as the measurement with the fewest decimal places.

Step-by-Step Guidance

1. Identify all nonzero digits as significant; zeros between nonzero digits are also significant.

2. Leading zeros are not significant; trailing zeros are significant only if there is a decimal point.

3. For multiplication/division, count the sig figs in each number and use the smallest count for your answer.

4. For addition/subtraction, line up decimal points and use the least number of decimal places in your answer.

Try solving on your own before revealing the answer!

Final Answer:

Example: 0.00450 has 3 sig figs; 2.35 × 1.2 = 2.8 (rounded to 2 sig figs).

For 12.11 + 18.0 = 30.1 (rounded to 1 decimal place).

Q5. How do you convert between temperature units?

Background

Topic: Temperature Conversions

This question tests your ability to convert between Celsius, Fahrenheit, and Kelvin temperature scales.

Key Formulas:

• $\text{K} = \text{°C} + 273.15$

• $\text{°C} = (\text{°F} - 32) \times \frac{5}{9}$

• $\text{°F} = (\text{°C} \times \frac{9}{5}) + 32$

Step-by-Step Guidance

1. Identify the starting and target temperature units.

2. Choose the appropriate formula based on the conversion needed.

3. Plug in the given value and perform the calculation up to the last step.

Try solving on your own before revealing the answer!

Final Answer:

To convert 25°C to K: $25 + 273.15 = 298.15$ K.

To convert 68°F to °C: $(68 - 32) \times \frac{5}{9} = 20$°C.