C2 Elements, compounds and mixtures Flashcards
What is relative atomic mass?
The mean mass of an atom of an element compared to 1/12 the mass of a carbon-12 atom
What does a chemical formula tell you?
How many atoms of each element there are in a unit of a substance
How many atoms are there in one unit of methane (CH4)?
5 atoms-one carbon and 4 hydrogen
What is an empirical formula?
An empirical formula shows the simplest whole-number ratio of the atoms of each element in a compound
What is the empirical formula of C6H12O6?
CH2O
What is relative formula mass?
The mean mass of a unit of substance compares to 1/12 the mass of a carbon-12 atom (the mass of the atoms in the nucleus)
What does pure mean in science?
In science, pure means that there is nothing but that element in that substance e.g. only H2O in water, no chlorine or other gases
What is a mixture?
Several elements and molecules that have not been chemically bonded together
How can you use melting points to determine purity?
Purer substances will have higher melting points than their impure counterparts and will melt at a single temperature rather than over a range
Why is water poured from a filter jug not pure in the scientific sense?
It will still be contaminated by gases in the air and other substances
Why does seawater freeze at a lower temperature than freshwater?
Seawater is a mix of water and salt while freshwater is just pure water
