Lecture 1-Elements,compounds & mixtures Flashcards
What is a molecule?
A group of 2/+ atoms that are joined together
How can elements exist?
As atoms/molecules
What are compounds made of?
Molecules
How do chemical reactions change the identity of compounds?
Rearranging the atoms to change the ratios of chemical combinations
What is combing power/valency?
The ability of an atom of one element to combine with other atoms based on the n.o of e- an atom will give/take to form a chemical bond
What determines the atom’s chemical + electrical properties?
E- in the outermost orbitals
What is the RAM equation?
Mass of 1 atom of element
——————————————–
1/12 mass of 1 atom of carbon-12
What is the RMM equation?
Mass of 1 molecule of substance
————————————————
1/12 mass of 1 atom of carbon-12
What are the qualities of intensive properties?
- Doesn’t depend on the amount of matter
- Identify substances
Examples of intensive properties?
Density, Colour, Boiling point
Examples of extensive properties?
Mass, Volume, Weight
What do physical properties examine and why?
A sample of pure substance
-because of molecular structure + strength of intermolecular forces
How are chemical properties observed and why?
During a chemical reaction
-because of the distribution of e- (around the atom’s nucleus)
A physical change is a change in …..?
energy
A chemical change is a change in……..?
identity
How do you separate mixtures?
By using differences in physical properties
Basic separation techniques?
Filtration Crystallization Extraction Distillation Magnetisation Chromatography
What is density?
Mass to volume ratio
Can pure substances be separated by physical means?
NO
What is an element?
The simplest from of matter that has a unique set of properties
What is a compound?
A substance that contains 2/+ elements chemically combined in a fixed proportion
What is a heterogeneous mixture and give an example?
MULTIPLE PHASE
- Various properties
- non-uniform appearance
e. g. emulsion / colloid
Describe a distinctive property of pure substances?
Can only change in identity + properties chemically
