Start of year recap test- Yr 9 topics Flashcards
What are all substances made of?
Atoms
What is an atom?
The smallest part of an element that can exist
What are atoms of each element represented by?
A chemical symbol
What is an element?
A substance with only one kind of atom
Where are elements listed?
The periodic table
How many elements are there in the periodic table?
118
What can elements be classified as?
Metals or non-metals depending on their properties
What are the columns in the periodic table called?
Groups
They contain similar elements
What are the rows in the periodic table called?
Periods
Element show a gradual change in properties across a period.
How are compounds formed?
When some elements combine through chemical reactions
What are compounds made from?
Two or more element combined together in fixed proportions.
How can compounds be represented?
Using the symbols of the atoms they were made from e.g. CO2
What does a mixture consist of?
Two or more elements or compounds not chemically combined together
What happens to the chemical properties of the elements in a mixture?
Are unchanged
Do compounds have different properties to they were made from?
Yes
How can compounds be separated into elements?
By chemical reactions
What are the physical processes by which mixtures can be separated?
Filtration, crystallisation, simple distillation,
fractional distillation and chromatography. These physical processes do not involve chemical
reactions.
What type of mixture does simple distillation separate?
Soluble solids
How does simple distillation work?
Liquid boils off and condenses in the condenser.
The thermometer will read the boiling point of the pure liquid.
What type of mixture does crystallisation/evaporation separate?
A soluble solid and a liquid e.g. salt and water.
What type of liquid must the soluble solid not be dissolved in to use evaporation?
Non-flammable
What should we do if we want to create hydrated salt crystals using evaporation?
Don’t evaporate all the water from the mixture
Why is the evaporating basin used in evaporation wide and shallow?
Gives the liquid a wider surface area for quicker evaporation.
What type of mixture does fractional distillation separate?
Soluble liquids with different boiling points e.g. crude oil
Does the fractionating column used in fractional distillation have a temperature gradient?
Yes- It’s hotter at the bottom than it is at the top
How does fractional distillation work?
. Mixture of soluble liquids heated
. All liquids are evaporated
. Liquid with lower boiling point forms greatest % of vapour
. As vapour moves up the fractional column,
it becomes more rich with component with the lowest boiling point (due to vapour mixture condensing and evaporating as it moves up the column)
. Thermometer measures temps of the ‘fractions’ before they condense
. Liquid with lowest boiling point will be the first ‘fraction’ to collect
.
What did the discovery of the electron lead to?
The plum pudding model
What did the plum pudding model suggest about atoms?
That the atom was a ball of positive charge with negative electrons embedded in it
