Matter and measurement

What defines a pure substance in chemistry?

A pure substance cannot be decomposed into simpler substances and is composed of one kind of atom.

What is a mixture?

A mixture is a combination of two or more substances where each retains its own chemical and physical properties.

How are homogeneous and heterogeneous mixtures different?

A homogeneous mixture is uniform throughout (e.g., a solution), while a heterogeneous mixture consists of physically distinct parts with different properties.

What are intensive properties? Give examples.

Intensive properties do not depend on the amount of the sample (e.g., color, temperature, hardness, density).

What are extensive properties? Give examples.

Extensive properties depend on the amount of the sample (e.g., mass, volume).

What process involves physical changes to separate mixtures?

Separation of mixtures involves physical processes and uses physical properties like boiling point, density, and size.

Describe distillation.

Distillation is a separation method based on different boiling points of substances.

What does chromatography rely on?

Chromatography is based on the ability of substances to adsorb to a surface or their polarity.

What determines temperature on a macroscopic level?

Temperature determines how hot or cold a substance is.

What is the significance of significant figures in measurement?

Significant figures indicate how precisely a quantity is known and reflect the uncertainty of measurement.

What are the rules for determining significant figures?

Non-zero digits are always significant, zeros between non-zero digits are significant, and trailing zeros after a decimal point are significant.

What is the relationship between accuracy and precision?

Accuracy is how closely a measurement agrees with the true value, while precision refers to how closely multiple measurements agree with each other.

How do you convert Celsius to Kelvin?

To convert Celsius to Kelvin, add 273.15 to the Celsius temperature.

What is the role of SI units in describing measurements?

SI units provide a standard for measuring physical quantities and are preferred in scientific communication.

What defines a chemical change?

A chemical change involves a change in the composition of a substance, with bonds being broken and reformed.

Why is chemistry called the central science?

Chemistry is considered the central science because its concepts are foundational to understanding other sciences.