1.1 Flashcards
What is an element?
A substance made up of one type of atom.
What is a compound?
Two or more elements chemically bonded together in fixed proportions.
- Chemically separated.
What is a mixture?
Two or more elements that are not chemically bonded together.
- Physically separated
What is a molecule?
Two or more of the same or different atoms that are chemically bonded.
Name the reason and simple method of filtration.
- Remove insoluble solids from solution.
1) Set up filter paper in filter funnel that is on conical flask
2) Pour solution in filter funnel with filter paper so residue collects in filter paper.
Name the reason and simple method of crystallisation.
- Remove soluble solids from solution.
1) Set up water bath
2) Pour solution into evaporating dish.
3) Gently heat solution to evaporate the liquid.
4) Once liquid has evaporated, turn off the bunsen burner and wait.
5) Collect crystals once cooled.
Name the reason and simple method for simple distillation.
- Separate soluble solid from liquid, whilst keeping the liquid.
1) Set up simple distillation apparatus.
2) Pour solution into flask and heat it until it boils and evaporates.
3) Vapour cools and condenses as it passes through condenser [due to change in temperature].
5) Turn off bunsen burner when solids are left in flask and liquid is collected in beaker.
Name the reason and simple method for fractional distillation.
- Separate several liquids with different boiling points.
1) Set up fractional distillation apparatus.
2) Gently heat solution until it turns into vapour.
3) Liquids travel through fractionating column.
4) Lower BP vapour condenses and purer version of that solvent is collected.
5) As the temperature increases, the higher BP vapour begins to condense purer version of that solvent is collected.
Name the reason and simple method for paper chromatography.
- Separate substances in mixtures.
1) Draw pencil line near bottom of chromatography paper.
2) Plot substances as dots on pencil line at equal distances.
3) Clip chromatography paper to wooden stick and fill beaker with solvent.
4) Place chromatography paper so it’s touching the solvent in beaker.
5) Remove paper when solvent has moved 3/4 of paper and let it dry.
Explain why some substances reach different distances in paper chromatography.
- Different substances have difderent solubilities.
- The more soluble a substance is the more attracted it is to the mobile phase,
- Therefore it moves further up the stationary phase.
Describe the plum pudding model of atomic structure.
Ball of positive charge with negative charges randomly distributed within it.
Describe how the results of the alpha scattering experiment led to the nuclear model.
- Majority of alpha particles went straight through the gold foil - Majority of atom is empty space.
- Some alpha particles changed direction when going through - centre of atom has positive charge.
- Few bounced straight back - centre of atom is massive (contains a great deal of mass).
Describe the nuclear model of atomic structure
- Mostly empty space
- positive nucleus that contains most of the mass of the atom
- electrons on the edge
Describe how nuclear model was modified by the discoveries of electron energy levels, the proton and neutron.
1) Bohr - suggested electrons orbit nucleus at specific distances.
2) Scientist found out that the positive charge of the nucleus is due to tiny positive particles called protons.
3) Chadwick - discovered neutral particles also in the nucleus called neutrons.
What is the radius of an atom and a nucleus?
- Atom: 0.1nm (1x10-10m)
- Nucleus: 1x10-14m (less than 1/10000th of an atom)
What are the relative charges and atomic masses of the sub-atomic particles?
Proton
- Charge = 1+
- Mass = 1
Neutron
- Charge = 0
- Mass = 1
Electron
- Charge = 1-
- Mass = nearly 0/very small
What is the atomic number?
The amount of protons in an atom (and therefore electrons) - smallest number.
What is the atomic mass?
The amount of protons and neutrons in an atom - larger number
What is an isotope?
Atoms of the same element with different numbers of neutrons.
What is an ion?
Atoms that have lost or gained an electron to gain an overall charge.
What is relative atomic mass?
An average value of the mass of an atom taking into account the abundance of each of its isotopes.
What is the equation to calculate the relative atomic mass?
((mass number of isotope 1 x its abundance percentage) + (mass number of isotope 2 x its abundance percentage)) / 100
How do you determine the group number of an atom of an element?
The amount of electrons in its outer shell corresponds to the group number.
Describe early attempts to arrange the elements into a periodic table.
- Triads - Doberoëiner saw elements that reacted similarly often occurred in threes.
- Octaves - Newland ordered in increasing atomic weight and saw every 8th element reacted similarly.
Explain why Dimitri Mendeleev’s periodic table successfully predicted the properties of elements.
1) Ordered elements in increasing atomic weight
2) but switched order of elements to fit the chemical properties of the elements in the group.
3) Left gaps for undiscovered elements
4) Predicted properties of the unknown elements based on other elements in the same group.
Describe how the elements are arranged in the modern periodic table.
- Ordered in atomic number which removes problem of isotopes.
- Group 0 discovered
- Elements in groups have similar chemical properties.
