35 Questions
Which of the following best defines a pure substance in chemistry?
A substance with a fixed structure and definite properties
What is the measure of purity used to classify pure substances in chemistry?
Purity rating
Why is it difficult to achieve 100% purity for most pure substances in reality?
Presence of multiple compounds in the substance
Which refining process helps remove impurities from a substance?
Distillation
What is the minimum purity rating required for a substance to be considered pure in chemistry?
99.9%
Which of the following can be classified as a pure substance?
Sugar (C12H22O11)
What process is commonly used to remove impurities from liquids?
Fractionation
Which substance is considered a pure substance because it contains only one type of element?
Water
What is the temperature at which a substance changes from a solid to a liquid called?
Melting point
Which is an example of a homogeneous mixture?
Air
What type of mixtures are generally easier to separate?
Heterogeneous mixtures
What is the ability of a substance to transfer electricity called?
Conductivity
Which method is used to separate components of a liquid mixture with heating and cooling?
Distillation
What is the principle behind the separation of mixtures by chromatography?
Components having different affinities for a stationary phase and mobile phase
What is the main factor used to help identify the components present in a mixture using chromatography?
The retention factor (Rf)
Which method is effective for separating a homogeneous mixture of dissolved solids in a liquid?
Evaporation
What occurs when a supersaturated solution forms into a solid?
Crystallization
What is the main factor that enables distillation to separate components of a liquid mixture?
Differences in vaporization temperature for components
What is the principle of filtration?
Passing the mixture through a filtering agent to separate solids from the liquid
How is dissolving used as a technique for separating mixtures?
Incorporating a solid into a liquid, followed by filtration to remove non-dissolvable components
What is the principle of magnetic separation for mixtures?
Utilizing the magnetic properties of one component to be attracted to and stick to a magnet
What is the role of atomic number in defining an element?
It represents the number of protons in the nucleus of an atom
Which subatomic particle has no charge and is present in the nucleus of an atom?
Neutron
What is the role of a sieve in manual separation?
Sort out mixture components by size using small holes or mesh at the bottom
What is the atomic number of an atom?
The number of protons in the nucleus
What is the mass number of an atom?
The sum of protons and neutrons in the nucleus
How does one determine the number of neutrons in an atom's nucleus?
By subtracting atomic number from mass number
What is the relationship between atomic number and mass number?
They are both fundamental properties of an element
What is meant by isotopes?
Atoms with same atomic numbers but different mass numbers
How can one represent an element using its mass number?
By providing both atomic and mass numbers in a visual representation
What is the atomic number of uranium?
92
What is the atomic number of gold?
79
What does the atomic number of an element represent?
Total protons in the nucleus
What is the difference between mass number and atomic mass?
Mass number considers only protons, while atomic mass considers protons and neutrons
What is an isobar?
Atoms of different elements with the same atomic mass
Test your knowledge on evaporation and filtration methods in chemistry. Learn about the process of evaporating sea salt in France and the principles and procedures of filtration.
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