Table of contents

1. Matter and Measurements4h 31m
2. Atoms and the Periodic Table5h 23m
3. Ionic Compounds2h 18m
4. Molecular Compounds2h 18m
5. Classification & Balancing of Chemical Reactions3h 17m
6. Chemical Reactions & Quantities2h 27m
7. Energy, Rate and Equilibrium3h 46m
8. Gases, Liquids and Solids3h 25m
9. Solutions4h 10m
10. Acids and Bases3h 29m
11. Nuclear Chemistry56m
BONUS: Lab Techniques and Procedures1h 38m
BONUS: Mathematical Operations and Functions47m
12. Introduction to Organic Chemistry1h 34m
13. Alkenes, Alkynes, and Aromatic Compounds2h 12m
14. Compounds with Oxygen or Sulfur1h 6m
15. Aldehydes and Ketones1h 1m
16. Carboxylic Acids and Their Derivatives1h 11m
17. Amines39m
18. Amino Acids and Proteins1h 51m
19. Enzymes1h 37m
20. Carbohydrates1h 41m
21. The Generation of Biochemical Energy2h 8m
22. Carbohydrate Metabolism2h 22m
23. Lipids2h 26m
24. Lipid Metabolism1h 45m
25. Protein and Amino Acid Metabolism1h 37m
26. Nucleic Acids and Protein Synthesis2h 54m

1. Matter and Measurements

Significant Figures (Simplified)

GOB Chemistry

1. Matter and Measurements

Significant Figures (Simplified)

Previous problemNext problem

1:17 minutes

Problem 20a

Textbook Question

Identify the exact number(s), if any, in each of the following pairs of numbers:
a. 5 pizzas and 50.0 g of cheese

Verified step by step guidance

Step 1: Understand the concept of exact numbers. Exact numbers are values that are counted or defined, not measured. They have no uncertainty and are considered to have an infinite number of significant figures.

Step 2: Analyze the first number in the pair, '5 pizzas.' Since this is a counted quantity (you can count the number of pizzas), it is an exact number.

Step 3: Analyze the second number in the pair, '50.0 g of cheese.' This is a measured quantity because it involves a unit (grams) and is determined using a measuring device. Measured quantities are not exact and have a limited number of significant figures.

Step 4: Conclude that in this pair, '5 pizzas' is the exact number, while '50.0 g of cheese' is a measured number.

Step 5: Remember that exact numbers are often integers from counting or defined values (e.g., 1 dozen = 12), while measured numbers involve units and are subject to uncertainty.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Quantitative Comparison

Quantitative comparison involves evaluating the numerical values of different items to determine their relationships. In this case, it requires assessing the quantities of pizzas and cheese to identify any exact numerical relationships or conversions between them.

Units of Measurement

Units of measurement are standard quantities used to express physical quantities. Understanding the units involved, such as 'pizzas' and 'grams,' is crucial for making accurate comparisons and conversions, as they represent different types of items and quantities.

Conversion Factors

Conversion factors are ratios used to convert one unit of measurement into another. In this scenario, if a specific relationship or conversion between pizzas and grams of cheese exists (e.g., how much cheese is needed per pizza), applying the correct conversion factor is essential for determining the exact numbers.