P1: Atomic Structure & Periodic Table Flashcards
What is an atom?
The smallest part of an element that can exist.
What is an element?
A substance made of one type of atom only.
What does the group it is in suggest about an element?
The number of electrons it has on its outer shell
What is a compound?
A substance that contains two or more elements that are chemically combined.
What is an ion?
An electrically charged particle that is formed when an atom or molecule gains or loses electrons
What does the law of conservation of mass state?
No atoms are lost or made during a chemical reaction
So the total mass of products = total mass of reactants
What is a pure substance?
A substance that consists of only one element or one compound.
What does a mixture consist of?
Two or more different substances, not chemically joined together.
What is filtration used for?
To separate an insoluble solid from a liquid.
List the equipment needed for filtration.
Funnel, filter paper, beaker.
Explain simply filtration.
A mixture is poured through filter paper that sits in a funnel, and the insoluble solid stays on top of the filter paper while the liquid goes through and falls into the beaker below.
What is crystallisation?
The process of producing crystals from a solution by evaporating the solvent.
State the equipment needed for crystallisation.
Evaporating basin, bunsen burner, (heat mat optional)
What are the products of crystallisation?
Crystals.
Explain simply how crystallisation works.
A solution is placed in an evaporating basin and heated with a Bunsen burner. The liquid in the solution evaporates, while solid particles begin to form in the basin. Finally, all the liquid evaporates, leaving solid crystals behind.
How do you obtain large, regularly shaped crystals from crystallisation?
Use a boiling water bath instead of a Bunsen burner, and stop heating the solution when crystals begin to form around the edge of the basin.
How do you sterilise the crystals after crystallisation?
Either use a warm oven or pat them with filter paper.
What is distillation?
A separation method used to separate a solvent from a solution.
What is distillation most commonly used for?
Producing pure water from seawater.
State the equipment needed for distillation.
Bunsen burner, distilling flask, condenser, thermometer, receiving flask.
Simply explain the process of distillation of saltwater.
Salty water is heated, and travels up the beaker, through the tubes into the condenser. The condenser cools down the water vapour and it drips into a beaker. The water has been condensed into a new beaker, and the salt is left behind.
What is fractional distillation?
Distillation of a mixture of several substances.
State the two ways that fractional distillation can be done.
-By collecting different liquids from different parts of the distillation column (the substance with the lowest boiling point collected at the top).
-By continuing to heat the mixture to increase the temperatures in the column (the substance with the lowest boiling point collected first).
What is paper chromatography used for?
Separating mixtures of soluble substances.
Explain simply how chromatography works.
-Ink is dotted along a pencil line on a piece of paper
-The paper is placed into the water, just enough to ALMOST reach the pencil line. The water spreads up the paper, and some of the dye spreads up the paper too
-The paper has now absorbed the solvent and the dye has spread further up the paper.
What are the two different phases of chromatography?
The stationary phase and the mobile phase.
What causes the dissolved substances to move at different rates through the paper?
Their varying attraction to the paper
What does chromatography produce?
A chromatogram
How many spots does a pure substance produce on the chromatogram?
One.
How can you tell if two substances are the same when reading a chromatogram?
-By seeing if they produce the same number of spots that match in colour.
-By seeing if the spots travel the same distance up the paper.
What is an Rf value?
The measure of how far a component travelled in chromatographic separation.
How do you calculate the Rf value?
Distance travelled by the component over the distance travelled by the solvent.
What does a small Rf value mean in chromatography?
It means the dye is more attracted to the paper, so it spends a greater time distributed in the paper than the solvent.
Who created the Plum Pudding Model of the atom?
JJ Thompson.
What did JJ Thompson discover?
The electron.