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Chemistry > Fundamentals (1.1) > Flashcards

Fundamentals (1.1) Flashcards

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1
Q

What is an atom?

A

the smallest part of an element that can exist

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2
Q

What is an element?

A

A substance made of only one type of atom

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3
Q

How many different elements are there roughly?

A

100

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4
Q

What is a compound?

A

a substance containing two or more elements chemically combined (bonded) in fixed proportions

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5
Q

What are compounds formed from?

A

elements by chemical reactions

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6
Q

2 needed

What do chemical reactions always involve?

A

the formation of one or more new substances, and often involve a detectable energy change

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7
Q

What can compounds only be separated into by chemical reaction?

A

elements

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8
Q

What is a mixture?

A

a substance containing two or more elements or compounds not chemically combined (bonded) together

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9
Q

What happens to the chemical properties of each substance in a mixture?

A

They are unchanged

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10
Q

How can mixtures be separated?

A

Through physical processes such as filtration, chromatography, crystallisation, etc

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11
Q

What do physical processes do separate mixtures not involve?

A

do not involve chemical reactions and no new substances are made

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12
Q

How would you separate sand from salt solution mixture by filtration?

A
  1. Put filter paper inside a funnel and place beaker underneath
  2. Pass solution through funnel, the sand (residue) will be collected by the filter paper (as is a bigger particle) and the salt solution (filtrate) will pass through
  3. Wash the sand to remove the rest of the salt particles
  4. Dry in warm oven
  5. Collect sand
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13
Q

How would you separate a mixture by simple distillation?

A
  1. Pour solution into flask
  2. Apply heat using bunsen burner
  3. Substance with lowest boiling point (solvent) will evaporate first leaving the solid solute in the flask
  4. Vapour (solvent) then passes through a condenser (acts as cooling jacket) where it is cooled and condensed and collected in a beaker
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14
Q

When and why is fractional distillation used?

A

to separate (liquids) that have a similar boiling point, which is hard to separate during simple distillation

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15
Q

How would you separate a mixture by fractional distillation?

A
  1. Pour solution into flask
  2. Apply heat using bunsen burner
  3. Both substances will rise up the fractionating column (hotter at bottom, cooler at top)
  4. The substance with the higher boiling point will condense at the glass beads in the column, where they condense and drip back down
  5. The substance with the lower boiling point will rise above the glass beads and pass through a condenser and condense, being collected in a beaker
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16
Q

What is chromatography used to do?

A

to separate (often coloured) dissolved substances and provide information to help identify them

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17
Q

How would you separate a mixture by chromatography?

A
  1. A pencil line is drawn on chromatography paper and spots of the sample are placed on it
  2. The paper is then lowered into the solvent container, making sure that the pencil line sits above the level of the solvent so the samples don’t wash into the solvent container
  3. The solvent travels up the paper by capillary action, taking some of the coloured substances with it
  4. Those substances with higher solubility (how well they dissolve) will travel further than the other, operating the mixture
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18
Q

In chromatography, why is a pencil lien used, rather than a line of ink?

A

as ink would run into the chromatogram (results) along with the samples

19
Q

What may lead to a scientific model being changed or replaced?

A

New experimental evidence

20
Q

Before the discovery of the electron, what were atoms thought to be?

A

tiny spheres that could not be divided

21
Q

The discovery of the electron led to which model?

A

the plum pudding model of the atom

22
Q

Describe the plum pudding model

A

that the atom is a ball of positive charge with negative electrons embedded in it

23
Q

What did the results from the alpha particle scattering experiment show?

A

that the mass of an atom was concentrated at the centre (nucleus) and that the nucleus was charged

24
Q

Which model did the results from the alpha particle scattering experiment lead to, replacing the plum pudding model?

A

The nuclear model

25
Q

How did Niels Bohr adapt the nuclear model? How did he prove this?

A

by suggesting that electrons orbit the nucleus at specific distances (in shells)

the theoretical calculations of Bohr agreed with experimental observations

26
Q

How did later experiments lead to the discovery of the proton?

A

They led to the idea that the positive charge of any nucleus could be subdivided into a whole number of smaller particles, each particle having the same amount of positive charge. The name proton was given to these particles.

27
Q

What did the experimental work of James Chadwick prove the evidence to show?

A

the existence of neutrons within the nucleus

28
Q

How long was there between Chadwick’s proof of the neutron and the nucleus becoming an accepted scientific idea?

A

about 20 years

29
Q

How did the alpha particle scattering experiment lead to a change in the atomic model?

A

Geigar and Marsden fired very dense, positive particles, known as alpha particles, at a thin piece of gold foil. They expected all particles to pass straight through and be detected using a screen. However, while most did, many diverged and some rebounded.

Thus, Rutherford theorised that the atomic model must be wrong as the alpha particles must have rebounded off a centre of dense positive particles (nucleus) with electrons orbiting it.

30
Q

What is the difference between the plum pudding and nuclear models?

A

In the plum pudding model, the atom as a ball of positive charge with negative electrons embedded within it, whereas in the nuclear model, the positive charged is concentrated at a dense centre (nucleus)

Also the later nuclear model has shells of electrons orbiting it at specific distances (after Bohr’s work)

31
Q

What are the relative electrical charges of the particles in atoms?

A

proton: +1
neutron: 0
electron: -1

32
Q

What is the relationship between the number of protons and electrons within an atom?

A

They are the same

33
Q

All atoms of a particular element, have the same number of..

A

protons (and electrons)

34
Q

Atoms of different elements have a different number of…

A

protons (and electrons)

35
Q

What is the radius of an atom/small molecule?

A

1 x 10-10 m

36
Q

What is the radius of the nucleus?

A

about 1 x 10-14 m (1/10 000 of the atom)

37
Q

What are the relative masses of protons, neutrons and electrons?

A

protons: 1
neutrons: 1

Electrons: negligible

38
Q

What is the mass number of an atom?

A

the sum of the number of protons and neutrons

39
Q

What are isotopes?

A

Atoms of the same element that have different numbers of neutrons

40
Q

Where are the mass number and atomic number (proton number) represented on a symbol?

A

mass number - top left

atomic number - bottom left

41
Q

What is the relative atomic mass?

A

an average value that takes account of the abundance of the isotopes of the element

42
Q

How do you calculate the relative atomic mass of an element?

A

(abundance percentage1 x isotopic mass1) + (abundance percentage2 x isotopic mass2)…

continue until all isotopes included

43
Q

What do electrons in an atom occupy first?

A

the lowest available energy levels (innermost available shells)

44
Q

What is the electronic structure of sodium (11 electrons) in numbers and in a diagram?

A

2,8,1

Chemistry (34 decks)

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