Intro to Chemistry Exam 1: Step-by-Step Study Guidance (Chapters 1–4)

Q1. Water, H2O, is an example of a(n) ________.

Background

Topic: Classification of Matter

This question tests your understanding of the basic types of matter: elements, compounds, and mixtures.

Key Terms:

• Element: A pure substance made of only one kind of atom.

• Compound: A substance made from two or more elements chemically bonded together in a fixed ratio.

Step-by-Step Guidance

1. Recall the definition of a compound and compare it to the formula H2O.

2. Consider whether water can be broken down into simpler substances by chemical means.

3. Think about whether water is made of more than one type of element.

Try solving on your own before revealing the answer!

Q2. Which statement about the scientific method is TRUE?

Background

Topic: Scientific Method

This question tests your understanding of the process scientists use to investigate and understand natural phenomena.

Key Terms:

• Observation: Gathering information using the senses or instruments.

• Experimentation: Testing hypotheses under controlled conditions.

• Reason: Logical thinking to interpret observations and results.

Step-by-Step Guidance

1. Review the main steps of the scientific method: observation, hypothesis, experimentation, and conclusion.

2. Identify which answer choices mention observation and experimentation.

3. Eliminate choices that do not align with the scientific method's emphasis on testing and evidence.

Try solving on your own before revealing the answer!

Q3. In the number 12.345, the 1 is in the ________ place.

Background

Topic: Place Value in Numbers

This question tests your understanding of the value of digits in a number based on their position.

Key Terms:

• Tens place: The second digit to the left of the decimal point.

• Ones place: The first digit to the left of the decimal point.

• Tenths, hundredths, thousandths: Digits to the right of the decimal point.

Step-by-Step Guidance

1. Write out the number 12.345 and label each digit's place value.

2. Identify which digit is in the tens, ones, tenths, etc., positions.

3. Locate the digit '1' and determine its place value.

Try solving on your own before revealing the answer!

Q4. A sample of wood with a mass of 3.0 grams was burned in an open dish. The ashes weighed 1.2 grams. What happened to the rest of the wood?

Background

Topic: Conservation of Mass

This question tests your understanding of what happens to matter during a chemical reaction, specifically combustion.

Key Terms:

• Combustion: A chemical reaction with oxygen that produces heat and new substances.

• Conservation of Mass: Mass is neither created nor destroyed in a chemical reaction.

Step-by-Step Guidance

1. Calculate the difference between the initial mass and the mass of the ashes.

2. Consider what products are formed when wood burns (e.g., gases like CO2 and H2O).

3. Decide whether the missing mass was destroyed, converted to energy, or changed form.

Try solving on your own before revealing the answer!

Q5. In reference to Question 4, what percentage of the wood was converted to Ash?

Background

Topic: Percent Composition

This question tests your ability to calculate the percentage of a component in a mixture or reaction.

Key Formula:

$\text{Percent} = \frac{\text{Part}}{\text{Whole}} \times 100\%$

Step-by-Step Guidance

1. Identify the mass of ash (part) and the original mass of wood (whole).

2. Set up the percentage calculation using the formula above.

3. Plug in the values for the mass of ash and the mass of wood.

Try solving on your own before revealing the answer!

Q6. The correct scientific notation for the number 0.00050210 is:

Background

Topic: Scientific Notation

This question tests your ability to express numbers in scientific notation, which is important for handling very large or small values in chemistry.

Key Terms:

• Scientific Notation: A way to write numbers as a product of a coefficient and a power of ten.

Step-by-Step Guidance

1. Count the number of decimal places you move to get a number between 1 and 10.

2. Write the number as $a \times 10^n$, where $a$ is the coefficient and $n$ is the exponent.

3. Make sure to include all significant figures from the original number.

Try solving on your own before revealing the answer!

Q7. The distance between the two hydrogen atoms in a molecule of water is 0.000000000172 m. Express this distance in scientific notation.

Background

Topic: Scientific Notation

This question tests your ability to convert a number from standard notation to scientific notation.

Key Steps:

1. Identify how many places you need to move the decimal to get a number between 1 and 10.

2. Express the number as $a \times 10^n$ with the correct exponent.

Try solving on your own before revealing the answer!

Q8. The correct standard notation of 6.453 × 103 is:

Background

Topic: Scientific Notation to Standard Notation

This question tests your ability to convert a number from scientific notation to standard decimal form.

Key Steps:

1. Multiply the coefficient by 10 raised to the given exponent.

2. Move the decimal point to the right for positive exponents.

Try solving on your own before revealing the answer!

Q9. In the number 48.93, which digit is estimated?

Background

Topic: Significant Figures

This question tests your understanding of which digits in a measurement are certain and which are estimated.

Key Terms:

• Significant Figures: All the digits in a measurement, including the estimated digit.

• Estimated Digit: The last digit in a measurement, which is uncertain.

Step-by-Step Guidance

1. Identify the last digit in the number, which is always the estimated digit.

2. Review the rules for significant figures in measurements.

Try solving on your own before revealing the answer!

Q10. Determine the answer to the following equation with correct number of significant figures: 106 ÷ 9.02 × 1.9

Background

Topic: Significant Figures in Calculations

This question tests your ability to apply the rules for significant figures in multiplication and division.

Key Rules:

• For multiplication and division, the result should have the same number of significant figures as the measurement with the fewest significant figures.

Step-by-Step Guidance

1. Count the significant figures in each number: 106, 9.02, and 1.9.

2. Perform the calculation as written: $\frac{106}{9.02} \times 1.9$.

3. Round your answer to the correct number of significant figures based on the number with the fewest significant figures.

Try solving on your own before revealing the answer!

Q11. Determine the answer to the following equation with correct number of significant figures: 2.02 + 8.102 - 0.0297

Background

Topic: Significant Figures in Addition and Subtraction

This question tests your ability to apply the rules for significant figures in addition and subtraction.

Key Rules:

• For addition and subtraction, the result should have the same number of decimal places as the measurement with the fewest decimal places.

Step-by-Step Guidance

1. Line up the numbers by their decimal points and perform the calculation.

2. Determine which number has the fewest decimal places.

3. Round your answer to match that number of decimal places.

Try solving on your own before revealing the answer!

Q12. A U.S. nickel five cent coin has a mass of approximately 5 grams. Five grams is equivalent to which term?

Background

Topic: Metric Conversions

This question tests your ability to convert between different metric units of mass.

Key Conversion Factors:

• 1 gram (g) = 1000 milligrams (mg)

• 1 gram (g) = 100 centigrams (cg)

• 1 gram (g) = 1,000,000 micrograms (μg)

Step-by-Step Guidance

1. Multiply 5 grams by the appropriate conversion factor to get milligrams, centigrams, or micrograms.

2. Compare your result to the answer choices.

Try solving on your own before revealing the answer!

Q13. How many liters are in 333 mL?

Background

Topic: Volume Conversions

This question tests your ability to convert between milliliters and liters.

Key Conversion:

$1 \text{ L} = 1000 \text{ mL}$

Step-by-Step Guidance

1. Set up the conversion: $333 \text{ mL} \times \frac{1 \text{ L}}{1000 \text{ mL}}$

2. Simplify the expression to find the number of liters.

Try solving on your own before revealing the answer!

Q14. A plastic block has dimensions of 2.2 cm × 3.0 cm × 1.5 cm and a mass of 12.4 grams. Will the block float in water and why?

Background

Topic: Density and Buoyancy

This question tests your ability to calculate density and compare it to the density of water to predict floating or sinking.

Key Formula:

$\text{Density} = \frac{\text{mass}}{\text{volume}}$

Step-by-Step Guidance

1. Calculate the volume of the block: $2.2 \text{ cm} \times 3.0 \text{ cm} \times 1.5 \text{ cm}$

2. Calculate the density using the mass and the volume you just found.

3. Compare the block's density to the density of water (1.0 g/mL).

4. Decide if the block will float (density less than water) or sink (density greater than water).

Try solving on your own before revealing the answer!

Q15. When gold is melted and formed in a mold to make a piece of jewelry, what type of change is taking place?

Background

Topic: Physical vs. Chemical Changes

This question tests your understanding of the difference between physical and chemical changes.

Key Terms:

• Physical Change: A change in state or appearance without changing the chemical composition.

• Chemical Change: A change that produces new substances.

Step-by-Step Guidance

1. Consider whether melting gold changes its chemical identity.

2. Decide if the process is reversible and if new substances are formed.

Try solving on your own before revealing the answer!