The Scientific Method & the Study of Matter

Flashcards reviewing the scientific method, scientific laws and theories, states of matter, physical and chemical properties/changes, and classification of matter.

What is the definition of chemistry as presented in the lecture?

Chemistry is the study of matter and its interconversions.

How is matter defined in chemistry?

Matter is anything that has mass and takes up space.

What is the main difference between qualitative and quantitative observations?

Qualitative observations focus on qualities and characteristics such as sound, color, touch, and taste, whereas quantitative observations focus on numbers with a specific number and unit.

What criteria make a hypothesis good according to the scientific method?

A good hypothesis is a tentative explanation of observations that is falsifiable, meaning its predictions can be confirmed or rejected with additional observations, and it is easy to test with chemical procedures.

What is the scientific definition of a theory?

A theory is an explanation for why nature behaves the way it does, which evolves from a hypothesis that survives many experimental tests.

According to John Dalton's Atomic Theory, what happens to atoms during a chemical reaction?

Atoms of one element cannot change into atoms of another element; instead, atoms simply rearrange to form new compounds.

What is a scientific law?

A scientific law is a brief statement that summarizes past observations and predicts future ones.

What is the Law of Conservation of Mass?

The Law of Conservation of Mass states that in a chemical reaction, matter cannot be created or destroyed.

Who formulated the Law of Definite Proportions and in what year?

Joseph Proust formulated the Law of Definite Proportions in $1797$.

What does the Law of Definite Proportions state?

It states that all samples of a given compound, regardless of their source or how they were prepared, have the same proportions of their constituent elements.

What is the Law of Multiple Proportions?

The Law of Multiple Proportions states that when two elements ($A$ and $B$) form two different compounds, the masses of $B$ that combine with $1.00\,g$ of $A$ can be expressed as a ratio of whole numbers.

According to the Law of Multiple Proportions example, what is the ratio of oxygen masses that combine with $1.00\,g$ of carbon in carbon dioxide versus carbon monoxide?

Carbon dioxide has $2.67\,g$ of oxygen per $1.00\,g$ of carbon, while carbon monoxide has $1.33\,g$ of oxygen per $1.00\,g$ of carbon, giving a ratio of $\frac{2.67\,g}{1.33\,g} = 2$.

What is the main distinction between a law and a theory in science?

A law summarizes a series of related observations, whereas a theory gives the underlying reasons for them.

How are particles arranged in a solid state of matter?

In a solid, particles are in fixed positions and adjacent to each other, giving the solid a fixed shape.

How do particles behave in liquid and gas states of matter?

In a liquid, particles are adjacent to each other but not in fixed positions (taking the shape of their container), whereas in a gas, particles are far apart and moving (having no fixed shape or volume).

What are physical properties of matter, and what are some examples?

Physical properties are characteristics of matter that do not depend on chemical composition, such as density, color, melting point, and boiling point.

What defines a physical change in matter?

A physical change is a change matter undergoes without changing its chemical composition, such as dissolving, mixing, or phase changes.

Based on the phase change diagram, what terms describe the direct transitions between solid and gas phases?

The direct transition from solid to gas is called sublimation, and the direct transition from gas to solid is called deposition.

What is a chemical property of matter, and what are some examples?

A chemical property is a characteristic of matter displayed only when changing chemical composition, such as flammability, toxicity, acidity, and reactivity.

What is a chemical change, and what examples are provided in the lecture?

A chemical change is a change matter undergoes by changing chemical composition; examples include rusting, combustion (burning), and decomposition.

What is the difference between intensive properties and extensive properties?

Intensive properties are independent of the amount of substance (such as boiling point, color, and temperature), whereas extensive properties depend on the amount of substance (such as volume, mass, size, weight, and length).

Why are all chemical properties classified as intensive properties?

All chemical properties are intensive properties because they are independent of the amount of substance.

What defines a pure substance in chemistry?

A pure substance is made up of only one component, and its composition does not vary from one sample to another.

What is an element?

An element is a pure substance that cannot be broken down into simpler substances by chemical changes, consisting of a group of atoms that have the same or similar properties.

What is a compound?

A compound is a pure substance made up of two or more elements in fixed proportions.

What is the mass percent composition of hydrogen and oxygen in water ($H_2O$)?

Water ($H_2O$) is composed of $11.11\%$ hydrogen and $88.89\%$ oxygen by mass.

What is the mass percent composition of hydrogen and oxygen in hydrogen peroxide ($H_2O_2$)?

Hydrogen peroxide ($H_2O_2$) is composed of $5.93\%$ hydrogen and $94.07\%$ oxygen by mass.

How is a mixture defined in chemistry?

A mixture is composed of two or more substances that can be separated by physical changes.

What is the distinction between a heterogeneous mixture and a homogeneous mixture?

A heterogeneous mixture has variable composition, whereas a homogeneous mixture has uniform or consistent composition.

According to the classification of matter flowchart, how is matter organized into subcategories?

Matter is divided into Pure Substances (which split into Elements and Compounds) and Mixtures (which split into Heterogeneous and Homogeneous mixtures).