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Questions and Answers
What happens to the melting point of a substance when it is impure?
What happens to the melting point of a substance when it is impure?
- It has no effect on the boiling point.
- It increases significantly.
- It lowers and can have a range of temperatures. (correct)
- It remains the same as the pure substance.
Which of the following best defines a pure substance?
Which of the following best defines a pure substance?
- A mix of two or more elements.
- A single element or compound with no impurities. (correct)
- A compound that can be easily separated.
- Any liquid at room temperature.
What color flame is produced by the presence of sodium cations?
What color flame is produced by the presence of sodium cations?
- Blue-Green
- Lilac
- Yellow (correct)
- Crimson
Which substance would exhibit a lilac flame color when heated?
Which substance would exhibit a lilac flame color when heated?
Which of the following statements about compounds is true?
Which of the following statements about compounds is true?
Flashcards
Compound
Compound
A substance formed when two or more elements combine chemically.
Pure Substance
Pure Substance
A substance with a specific melting point composed of only one element or compound.
Melting Point
Melting Point
The temperature at which a solid turns into a liquid.
Impure Substance Melting Point
Impure Substance Melting Point
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Flame Color and Cation
Flame Color and Cation
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Study Notes
Compounds and Elements
- A compound is a substance formed when two or more elements are chemically combined.
- An element is a substance that consists of one or more atoms and cannot be broken down into simpler substances by chemical means.
- A pure substance is a single element or compound that is not mixed with any other substance.
Melting and Boiling Points
- Melting point is the temperature at which a solid changes to a liquid.
- Boiling point is the temperature at which a liquid changes to a gas.
- A pure substance has a sharp melting point.
- An impure substance has a melting point that has a range of values.
Colour of Flame and Cations
- Different metal ions produce characteristic colours when heated in a flame.
- Crimson flame is associated with Lithium (Li+).
- Yellow flame is associated with Sodium (Na+).
- Lilac flame is associated with Potassium (K+).
- Brick Red flame is associated with Calcium (Ca2+).
- Blue-Green flame is associated with Copper (Cu2+).
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