Week 1: Matter. Atoms and Elements Flashcards
Define a molecule?
Atoms bonded together
What kind of bond holds water molecules together?
Hydrogen bonds
Do the majority of substances exist as atoms or molecules? Why?
Molecules, due to bonding with either with the same or other elements.
Define a compound
Two or more different elements chemically bonded together.
What does a molecular formulae involve?
Atomic symbols and subscript numbers.
(e.g. C2H6)
What can matter be divided into?
Mixtures and pure substances
What does a pure substance involve?
Only one kind of substance.
(Can be chemically bonded substances)
What does a mixture involve?
Two or more substances that are in physical contact but not chemical contact.
Can be separated without breaking bonds.
How can mixtures be separated into pure compounds?
By physical processes such as:
- distillation
- chromatography
What are the two types of pure substances?
Elements - Cannot be broken down into simpler substances in chemistry.
Compounds - Contain more than one element, chemically combined together in a single pure substance.
Name the physical properties of substances?
- Freezing/melting temperature
- Boiling/condensing temperature
- Density
- Colour
- Refractive index
- Solubility
- Spectroscopic properties
What is the refractive index?
“Measure of the bending of a ray of light when passing from one medium into another.”
What are spectroscopic properties?
“In simple words, it is a method to measure how much light is absorbed by a chemical substance and at what intensity of light passes through it.”
Define chemical properties
- Reactivities with other elements/compounds which changes a substance into another substance.
What are the three chemical properties?
- Burning
- Oxidation
- Hydrolysis
