Scientist Contributions
Known as the “Father of Modern Chemistry,” this scientist helped establish the law of conservation of mass.
Antoine Lavoisier
A mixture in which the different parts are visible, such as a salad, belongs to this broad category.
Heterogenous
This model describes electrons embedded in a positively charged mass, like raisins in pudding.
Thomson’s plum pudding model
An ice cube melts into liquid water. Identify the type of change.
Physical change
A pure substance made of only one type of atom.
Element
This scientist argued that science should be based on experimental evidence rather than thought alone.
Francis Bacon
Chalk powder is mixed into water. It settles over time and can be removed by filtering. Identify the mixture type.
Suspension
This model introduced a small central nucleus and an atom made mostly of empty space.
Rutherford's model
An iron bicycle develops rust. Identify the type of change.
Chemical Change
The chemical property that describes a substance’s ability to burn in oxygen
Combustible / Combustibility
This scientist recognized that elements could combine to form compounds.
Robert Boyle
A mixture contains fine dispersed particles that scatter light and remain dispersed rather than settling readily. Identify the mixture type.
Colloid
This model places electrons in specific shells with different energy levels.
Bohr’s model
A glass breaks into pieces. Explain briefly why this is a physical change
No new substance forms; the pieces are still glass.
The process of breaking down a compound by passing an electric current through it.
Electrolysis
This scientist proposed an atomic theory stating that compounds form when atoms of different elements combine in definite proportions.
John Dalton
Oil droplets dispersed in vinegar form this type of colloid. An added substance can help keep the droplets dispersed. What type of substance is this
Emulsion / Emulsifying agent
The modern atomic model uses this term for the region where an electron is likely to be found.
Electron cloud
Two clear solutions are mixed. The temperature rises and a solid appears. Identify two signs suggesting a chemical reaction occurred.
Heat is released; a precipitate forms
A student records that a sample is yellow and melts at 80°C. Classify each observation as a qualitative or quantitative physical property.
Yellow: qualitative; melting at 80°C: quantitative
Alchemists failed to turn ordinary metals into gold. What was the new technique of separating matter that was developed during this time
What is distillation
Sample A is clear and does not scatter a flashlight beam. Sample B scatters light but does not settle. Sample C scatters light and settles over time. Classify all three mixtures.
A: solution; B: colloid; C: suspension
A student says, “Once a theory has enough evidence, it becomes a law, and scientists stop changing it.” Identify two errors in this statement.
Theories do not become laws: they explain, while laws describe patterns. Scientific explanations can be revised when new evidence appears.
Water bubbles as it boils. A student says the bubbles prove a chemical reaction occurred. Explain the error.
Bubbles can occur during a physical change. Water vapour is still water, so no new substance forms.
Two solutions react and form a solid. Give the term for the solid, the starting substances, and the substances formed by the reaction.
Precipitate; reactants; products