Section 1 - Particles and Matter

Question 1

solids

Answer 1

• strong forces of attraction between particles
• holds particles close together in fixed positions
• solids have definite shape and volume and don’t flow because particles don’t move
• particles vibrate. hotter = more vibrate (causing solids to expand slightly when heated

Question 2

liquids

Answer 2

• weak force of attraction between particles arranged randomly free to move but tending to stay closer together
• definite volume but not definite shape and will flow to fill bottom of container
• particles are constantly randomly moving hotter = more vibrate (causing liquids to expand slightly when heated

Question 3

gases

Answer 3

• force of attraction between particles is very weak, they’re free to move and far apart the particles travel in straight lines
• don’t have definite shape or volume and flow to fill container particles move constantly with random motion ( hotter = faster so when heated a gas can either expand or increase pressure)

Question 4

physical changes of states

Answer 4

(solid) - melt - (liquid) - evaporating - (gas)

(gas) - condensing - (liquid) - freezing - (solid)

(solid) - subliming - (gas)

Question 5

melting

Answer 5

1) when a solid is heated its particles gain more energy
2) this makes particles vibrate more, weakening the forces that hold the solid together making it expand
3) at a certain temperature particles have enough energy to break free from their positions solid turns to liquid

Question 6

evaporation

Answer 6

1) when liquid is heated particles get energy
2) this makes particles move faster which weakens and breaks bonds holding liquid together
3) at a certain temp the particles have enough energy to break their bonds. this is called evaporating and liquid turns into a gas

Question 7

solution

Answer 7

a mixture of a solute and a solvent that does not separate out

Question 8

solute

Answer 8

the substance being disolved

Question 9

solvent

Answer 9

the liquid the substance is dissolving into

Question 10

saturated solution

Answer 10

a solution where the maximum amount of solute has been dissolved and no more solute will dissolve into the solution

Question 11

atoms

Answer 11

made up of three subatomic partcles
- protons (heavy and positively charged)
- neutrons (heavy and neutral)
- electrons ( hardly any mass and negatively charged )the

Question 12

the nucleous of an atom

Answer 12

1) its in the middle
2) contains protons and neutrons
3) has a positive charge (because of the protons)
4) almost whole mass of atom is concentrated in nucleus
5) compared to overall size of atom nucleolus is tiny

Question 13

facts ab the

the electrons

of an atom

Answer 13

• move around nucleus in energy levels called shells
• negitavely charged
• tiny but orbitals cover a lot of space
• size of orbitals determine size of atom
• electrons have virtually no mass

Question 14

electons and protons in an atom

Answer 14

number of electrons = number of protons
- neutral atoms have no overall charge, but if electrons are added or removed the atom becomes charged and is now an ion

Question 15

on the periodic table

Answer 15

atomic number - tells you how many protons
- same elements have same number of protons
- mass number = total of protons and neutrons so to get number of neutrons subtract atomic number from mass number

Question 16

molecules

Answer 16

atoms join together to from molecules. Thy can be made from one or more elements (H2 or H20)

Question 17

isotopes

Answer 17

isotopes are different atomic forms of the same element, which have the same number of protons but different numbers of neutrons
ie carbon-12 and carbon-13

Question 18

relative atomic mass (Ar)

Answer 18

its the average mass of all the isotopes of an element according to their relative abundance (which can be ratio fraction or percentage)
Calculate:
- multiply the mass of each isotope by its relative abundance, add those together and divide by the sum of the relative abundace

Question 19

elements contain atoms

Answer 19

of only one type

Question 20

compouds

Answer 20

• two or more different elements chemically bonded together
• very difficult to separate them
• properties are totally different to properties of original elements

Question 21

mixtures characteristics

Answer 21

• no chemical bond and can be separated by physical methods
• properties are a mixture of properties of separate parts

Question 22

pure substances

Answer 22

• if they are made up completely of a sigle element or compound
• every pure substance has a specific sharp melting and boiling points
• mixture isn’t pure so it will boiL/ melt over a rage of temperatures

Question 23

crystallisation

Answer 23

separates a soluble solid from a solution
- pour solution into an evaporation dish and gently heat solution, some water will evaporate and solution will get more concentrated
- once all the water has evaporated or when you start seeing crystals form (point of crystaillisation) remove dish and let solution cool
- salt will start to form crystals as it becomes insoluble in the cold, highly concentrated solution
- filter crystals out of the solution and leave in a warm place to dry. You can use a drying oven or desiccator to remove exccess water

Question 23

filtration

Answer 23

if the product of a reaction is an insolube solid you can use filtration to separate it from the liquid reaction mixture
- it can be used in purification , for example solid impurities can be separated out of a reaction mixture using filtration
- you have to put some filter paper into a funnel and pour the mixture. The liquid runs through paper leaving behind a solid residue

Question 24

rock salt separation

Answer 24

rock salt is a mixture of salt and sand (salt is soluble and sand is not) to separate them:
- first grind them up with pestle and mortar
- then dissolve
- then filter to separate the insoluble sand from the salt dissolved in the water
- then crystalise to separate salt from water

Question 25

how cromatography separates mixtures

Answer 25

• different dyes move up paper at different speeds because some stick to paper while others dissolve in the solvent and travel quicker. The distace they travel depeds on solvent and paper you use

Question 26

Rf value

Answer 26

= distance travelled by solute / distance travelled by solvent

• measure from baseline to centre of spot
• chromatography is often carried out to see if a certain substance is present in a mixture. if samples have same rf value they are likely to be the same

Question 27

SRMs

Answer 27

chemists use samples of pure sustances called standard reference materials next to a mixture to check the identities of components, as they have controlled concentrations and purities