Basic Concepts in Chemistry and Properties of Matter
Key Definitions in Chemistry
Definitions:
Chemistry – A science that deals with the composition, structure, and properties of substances and the changes they undergo.
Matter – Anything that takes up space and can be weighed (i.e., has volume and mass).
Volume – The amount of space occupied by a sample of matter.
Pure Substance – A single kind of matter that cannot be separated into other kinds of matter by any physical means. It always has a definite and constant composition.
Examples: Gold, copper, oxygen, chlorine, diamond.
Mixture – A physical combination of two or more pure substances in which each substance retains its own chemical identity.
Examples: Blood, milk, salt and water, sand and water.
Element – A substance that cannot be broken down by non-nuclear reactions.
Examples: Hydrogen, helium, lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine, and neon.
Compound – A substance consisting of atoms or ions of two or more different elements in definite proportions, joined by chemical bonds into a molecule.
Molecules – The smallest particle of a substance that retains all the properties of the substance and is composed of one or more atoms.
Homogeneous Mixture – A mixture that appears uniform throughout.
Examples: Air, sugar water, rainwater, vinegar, dishwashing detergent, steel, a cup of coffee, mouthwash.
Heterogeneous Mixture – A mixture with visually distinguishable components.
Examples: Oil and water, sand and water, kerosene and water, oil and vinegar, solid earth and liquid water, smog (gas + solid), aerosol (gas + solid), soda (water + CO₂), concrete.
Atoms – Particles of matter that uniquely define a chemical element.
Properties of Matter
Physical Properties
Qualitative vs. Quantitative Properties
Comparison:
Both qualitative and quantitative research are based on a logical and repeatable process. The choice of method is driven by the problem, gap, purpose, and research questions. Both can collect primary and/or secondary data.
Quantitative data is numbers-based, countable, or measurable. Qualitative data is interpretation-based, descriptive, and related to language. Quantitative data tells us how many, how much, or how often in calculations. Qualitative data can help us understand why, how, or what happened behind certain behaviors.
Examples of qualitative data include open-ended survey responses, interview transcripts, and observational notes. Examples of quantitative data include numerical survey responses, test scores, and website traffic data.
Chemical Properties
A chemical property is a characteristic of a substance that may be observed when it participates in a chemical reaction. Examples include flammability, toxicity, chemical stability, and heat of combustion.
Physical vs. Chemical Properties
A physical property is a characteristic of a substance that can be observed or measured without changing the identity of the substance. Physical properties include color, density, hardness, and melting and boiling points.
A chemical property describes the ability of a substance to undergo a specific chemical change.
Calculating Density
Density (D) is calculated using the formula: D = m/v, where ‘m’ is mass and ‘v’ is volume.
