Chemistry C2 OCR gateway gcse

What is relative atomic mass?

the mean mass of an atom compared to a carbon 12 atom

What does the chemical formula tell you?

tells you how many atoms of each element there are in a unit of a substance

What is relative formula mass?

the mean mass of a unit of substance compared to 1/12 the mass of a carbon 12 atom

What is emperical formula?

shows the simplest whole number ratio of the atoms of each element in a compound

What is a pure substance?

a substance that consists of only one type of element

are mixtures pure or impure?

impure as they consist of more than one type of element

What is an alloy?

a mixture of metals with one or more elements

What would the melting point of a pure substance would be?

it is a single temperature

What would the melting point of an impure substance be?

- less than a pure substance

- often melts over a range of temperatures

What is the solute?

the substance that dissolves

What is the solvent?

the substance that it dissolves in

What is a solution?

when one substance dissolves in another

What does filtration do?

it separates an insoluble substance in its solid state

What does crystallisation do?

the solvent evaporates leaving the solute behind

What does simple distillation do?

separates a solvent from a solution

What does fractional distillation do?

separates two or more substances from a mixture in the liquid state

What two different phases does chromatography rely on?

-stationary phase

-mobile phase

For paper chromatography what is the stationary phase?

the absorbent paper

For paper chromatography what is the mobile phase?

the solvent in the liquid state

For gas chromatography what is the stationary phase?

the thin layer of silica or alumina powder packed into a metal column

For gas chromatography what is the mobile phase?

an unreactive carrier gas

What does gas chromatography do?

It separates the components of a mixture and also measures their amounts

What are the physical properties of a metal?

-shiny

-high melting and boiling points

-solid at room temperature

-malleable (bend without shattering)

-ductile (pulled into wires)

-good conductors of heat and electricity

What are the physical properties of a non-metal?

-dull

-low melting and boiling points

-half gas, half solid at room temperature

-brittle

-non-ductile

-poor conductors of heat and electricity (they are insulators)

What solution do metal oxides produce?

alkaline solution

What solution do non-metal oxides produce?

acidic solutions

Explain the structure of an atom?

-the nucleus made up of protons and neutrons

-electrons formed in shells around the nucleus

What are ions?

an electrically charged particle formed when an atom or group of atoms lose or gain electrons

How are ionic compounds formed?

when a metal reacts with a non-metal. The metal transfers electrons to the non-metal

What is the arrangement of an ionic compound?

giant ionic lattice

What is a covalent bond?

This is when 2 non-metal atoms share electrons

What is a giant covalent structure?

it consists of many non-metal atoms joined together by covalent bonds

What is the structure of metals?

they form to create a giant metallic lattice

What are metallic bonds?

the strong electrostatic forces of attraction between delocalised electrons

What are allotropes?

they are different forms of an element in the same state but with different atoms arrangement