# 1: Matter, Measurements, and Calculations

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• 1.1: What Is Chemistry?
Chemistry is the study of matter—what it consists of, what its properties are, and how it changes. Being able to describe the ingredients in a cake and how they change when the cake is baked is called chemistry. Matter is anything that has mass and takes up space—that is, anything that is physically real.
• 1.2: Chemical Change vs. Physical Change
In a chemical reaction, there is a change in the composition of the substances in question; in a physical change there is a difference in the appearance, smell, or simple display of a sample of matter without a change in composition. Although we call them physical "reactions," no reaction is actually occurring.
• 1.3: Indivisible - The Atomic Theory
You learned earlier how all matter in the universe is made out of tiny building blocks called atoms. All modern scientists accept the concept of the atom, but when the concept of the atom was first proposed about 2,500 years ago, ancient philosophers laughed at the idea. It has always been difficult to convince people of the existence of things that are too small to see. We will spend some time considering the evidence (observations) that convince scientists of the existence of atoms.
• 1.4: The Classification of Matter
Matter can be described with both physical properties and chemical properties. Matter can be identified as an element, a compound, or a mixture.
• 1.5: Measurements
Chemists measure the properties of matter and express these measurements as quantities. A quantity is an amount of something and consists of a number and a unit. The number tells us how many (or how much), and the unit tells us what the scale of measurement is. For example, when a distance is reported as “5 kilometers,” we know that the quantity has been expressed in units of kilometers and that the number of kilometers is 5.
• 1.6: The International System of Units
Recognize the SI base units. Combining prefixes with base units creates new units of larger or smaller sizes.
• 1.7: Expressing Numbers - Scientific Notation
Scientific notation is a system for expressing very large or very small numbers in a compact manner. It uses the idea that such numbers can be rewritten as a simple number multiplied by 10 raised to a certain exponent, or power.  Scientific notation expressed numbers using powers of 10.
• 1.8: Expressing Numbers - Significant Figures
Significant figures properly report the number of measured and estimated digits in a measurement. There are rules for applying significant figures in calculations.
• 1.9: Converting Units
The ability to convert from one unit to another is an important skill. A unit can be converted to another unit of the same type with a conversion factor.
• 1.10: Dosage Calculations
Conversion factors are important in calculating dosages.
• 1.11: Percentages
Percentages are used in a variety of ways in healthcare including concentrations of solutions, medication dosages, and reporting changes to measured values for patients over time.

1: Matter, Measurements, and Calculations is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.