1.1: What is Chemistry? Matter is any substance that has mass and takes up space; it is atoms and anything made up atoms. Matter does not include energy such as light, sound, or heat. Chemists often view matter on two characteristic length scales: the macroscopic and the nanoscopic (also called the particle level). 1.2: The Scientific Method Chemists expand their knowledge by making observations, carrying out experiments, and testing hypotheses to develop laws to summarize their results and theories to explain them. In doing so, they are using the scientific method. 1.3: Hypothesis, Theories, and Laws Although all of us have taken science classes throughout the course of our study, many people have incorrect or misleading ideas about some of the most important and basic principles in science. We have all heard of hypotheses, theories, and laws, but what do they really mean? Before you read this section, think about what you have learned about these terms before. What do these terms mean to you? What do you read contradicts what you thought? What do you read supports what you thought? 1.4: Types of Observations Observations are at the heart of the scientific method. Observations can be separated into two general types: qualitative and qualitative. Quantitative observations (also called measurements) must always have a number and a unit. 1.5: Experimental Design Experiments are carefully designed to give researchers an opportunity to make observations to test a hypothesis. Experiments look at the relationship between three types of variables: independent variables, dependent variables, and controlled variables.