Key Concepts in Experimental Science and Chemistry
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38 Terms
Independent variable
The variable that is changed in an experiment.
Dependent variable
The variable that is measured during the experiment.
Control variable
A variable that must be kept the same to ensure a fair test.
Accuracy
How close a result is to the true value.
Precision
How consistent repeated results are.
Hypothesis
A scientific prediction based on knowledge and observation.
Evaluate an experiment
To judge the quality of the method and results, suggesting improvements.
Subatomic particles
Protons, neutrons, and electrons.
Charges of protons, neutrons, and electrons
Proton: +1, Neutron: 0, Electron: -1.
Location of protons and neutrons
In the nucleus.
Location of electrons
In energy levels (shells) around the nucleus.
Atomic number
The number of protons in an atom.
Mass number
The total number of protons and neutrons.
Isotope
Atoms of the same element with different numbers of neutrons.
Groups in the periodic table
Vertical columns that show the number of electrons in the outer shell.
Periods in the periodic table
Horizontal rows that show the number of shells.
Commonality in the same group
Similar chemical properties and the same number of outer electrons.
Noble gases
Group 0 elements; they have full outer shells.
Rate of reaction
How fast a reaction happens.
Factors affecting the rate of reaction
Temperature, concentration, surface area, catalysts, and pressure (for gases).
Effect of temperature on rate
Higher temperature increases particle energy → more frequent and energetic collisions.
Effect of concentration on rate
More particles in the same space → more collisions → faster reaction.
Effect of surface area on rate
More exposed particles → more collisions → faster reaction.
Catalyst
A substance that speeds up a reaction without being used up.
Collision theory
Reactions occur when particles collide with enough energy (activation energy).
Measuring rate
By measuring gas produced, mass lost, or colour change over time.
Who first suggested the idea of atoms?
Democritus - matter is made of tiny, indivisible particles called "atomos".
What was John Dalton's model of the atom?
Atoms are solid spheres; different elements have different atoms.
Who discovered the electron?
J.J. Thomson in 1897.
What was the Plum Pudding Model?
Atoms are spheres of positive charge with electrons scattered throughout.
Who carried out the gold foil experiment?
Geiger and Marsden, under Rutherford's supervision.
What did Rutherford discover from the gold foil experiment?
Most of the atom is empty space with a small, dense, positively charged nucleus.
What was Rutherford's atomic model called?
The Nuclear Model - a central nucleus surrounded by electrons.
How did Bohr improve the atomic model?
He proposed that electrons orbit the nucleus in fixed energy levels (shells).
Why was Bohr's model important?
It explained atomic stability and matched experimental results.
What did James Chadwick discover?
The neutron in 1932, explaining the missing mass in atoms.
What is the modern view of the atom called?
The quantum mechanical model.
What does the quantum mechanical model describe?
Electrons exist in clouds or orbitals, not fixed paths, and it's based on probability.