Question

Classify each of the following as an observation or a law. a. When water boils, small bubbles form in the liquid and rise rapidly to the surface. b. Two grams of hydrogen combine with sixteen grams of oxygen to form eighteen grams of water. c. Chlorine and sodium readily combine in a chemical reaction that emits much heat and light. d. The properties of elements vary periodically with the mass of their atoms.

Short answer

a. Observation, b. Law, c. Observation, d. Law

Step-by-step solution

- Define Observation and Law

To solve this exercise, understand the difference. An observation is a statement that describes a straightforward fact or occurrence that one can witness directly. A law, on the other hand, is a broad statement that describes natural phenomena that have been tested repeatedly and are universally accepted as true.

- Classify Item a

This is an observation because it describes what happens when water boils, which is a fact that can be directly witnessed without offering an explanation for why it occurs.

- Classify Item b

This is a law, specifically the Law of Conservation of Mass, because it describes a universal principle that matter is not created or destroyed in a chemical reaction.

- Classify Item c

This is an observation because it is a description of what happens when chlorine and sodium react, without describing a universal principle.

- Classify Item d

This is a law, known as the Periodic Law, because it describes a fundamental and universally accepted relationship about how the properties of elements are related to their atomic masses.

Key concepts

Law of Conservation of Mass

Understanding the Law of Conservation of Mass is essential when studying chemical reactions in chemistry. It is a fundamental principle stating that mass is neither created nor destroyed during a chemical reaction. In simpler terms, if you start with certain amounts of reactants, the mass of these reactants will equal the mass of the products formed after the reaction.

For example, when hydrogen and oxygen combine to form water, as seen in our exercise, 2 grams of hydrogen and 16 grams of oxygen give rise to 18 grams of water. Here, the total mass before and after the reaction remains constant, illustrating this law perfectly. It is a crucial concept that helps students balance chemical equations and understand the stoichiometry of reactions.

Periodic Law

The Periodic Law is a cornerstone of modern chemistry and provides a systematic framework for understanding the properties and behaviors of the elements. This law states that the properties of elements are periodic functions of their atomic numbers; meaning that when the elements are arranged in order of increasing atomic number, elements with similar properties recur at regular intervals or 'periods.'

For instance, if you look at the periodic table, you'll notice that all noble gases are lined up in one column, sharing characteristics such as high stability and low reactivity. Being familiar with the Periodic Law aids students in predicting the behavior of elements in chemical reactions and understanding the trends across different groups and periods of the periodic table.

Scientific Observation

Scientific Observation is a fundamental tool that scientists use to gather data about the world. It involves using one or more of the senses to gather information and take note of phenomena occurring in natural settings. Observations can also be enhanced by tools like microscopes or thermometers to detect details not perceivable by the naked eye.

As illustrated in our exercise, observing water boiling and the formation of bubbles is a direct observation. It focuses on describing a specific event (the boiling of water) without providing a reason or broader principle governing this behavior. Observations are the building blocks for developing scientific hypotheses and theories. They prompt questions, pose problems, and lead to further investigations and experiments.

Chemical Reaction

A Chemical Reaction is a process where substances, called reactants, transform into different substances, known as products. During a chemical reaction, atoms are rearranged through the breaking and forming of chemical bonds, resulting in new substances with different properties from the reactants.

For example, the combination of chlorine and sodium to produce salt and release energy, as mentioned in our exercise, is a type of chemical reaction known as an exothermic reaction because it emits heat and light. Understanding chemical reactions is vital for students as it forms the basis of explaining how different materials interact in our world, from biological processes to industrial applications. By studying reactions, students gain insight into reaction rates, energy changes, and the variety of factors that affect the transformation of substances.