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Unit 5: Atoms, purity and climate

GRADE 7 – Unit 5: Atoms, purity and climate — HIA International - Grade 7 Revision Notes & Topical Questions

5 min read 9 parts Lesson 1 of 6 1 quiz

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Lesson summary

GRADE 7 - Unit 5: Atoms, purity and climate — HIA INTERNATIONAL notes: Describe atomic structure, purity, weather and climate, past climates and changes to the atmosphere.Particles — protons and neutrons in the nucleus, electrons moving around it.Charges — proton positive, neutro…

  • Pure element
  • Percentage purity
  • Single product
  • More than one product
  • Importance
  • Glacial period

Section 1 of 9Structure of the atom

Structure of the atom
Particles
  • Particles protons and neutrons in the nucleus, electrons moving around it.
Charges
  • Charges proton positive, neutron none, electron negative, with equal numbers of protons and electrons in a neutral atom.
Mass
  • Mass protons and neutrons have the same mass, and electrons have almost none.
Model
  • Model developed by Thomson, Rutherford and Chadwick, who discovered the electron, the nucleus and proton, and the neutron.

Section 2 of 9Purity

Pure element
  • Pure element all atoms are the same type.
Percentage purity
  • Percentage purity parts that are the pure substance ÷ total parts × 100.
Gold
  • 24 carat is pure and 18 carat is 75% gold.
Silver
  • Silver the mark 925 means 925 parts per 1000, which is 92.5% silver.
Diamonds
  • Diamonds pure diamond is only carbon, while other atoms such as nitrogen or boron change its colour.
Seawater
  • Seawater about 350 g of salts per 1000 g, and only about 68% of those are sodium chloride.

Section 3 of 9Making pure products

Single product
  • Single product only one product forms, for example magnesium + oxygen gives magnesium oxide.
More than one product
  • More than one product the products are mixed together and may be mixed with unused reactants, so they must be separated and purified.
Importance
  • Importance medicines must be free from impurities that could harm the patient.

Section 4 of 9Weather and climate

FeatureWeatherClimate
TimeMinutes to weeksMore than 30 years
MeaningState of the atmosphere at a place and timeAverage weather and its extremes
StudyMeteorologyClimatology
FactorsTemperature, humidity, cloudiness, precipitation, visibility and windTemperature and precipitation

Section 5 of 9Climate zones

ZoneClimate
PolarVery cold and dry all year
TemperateCold winters and mild summers
AridHot and dry all year
TropicalHot and wet all year
MediterraneanMild winters and hot, dry summers
Mountains, tundra, taigaVery cold all year

Section 6 of 9Ice ages and evidence

Glacial period
  • Glacial period a very cold period when ice spreads much further from the poles.
Interglacial period
  • Interglacial period a warmer period between glacials, and the Earth is in one today.
Ice age
  • Ice age a long cold period containing glacial and interglacial periods.
Evidence
  • Evidence boulders moved by glaciers, scratched rocks, fossils of cold-adapted organisms and pollen in peat bog cores.

Section 7 of 9Atmosphere and climate

Early atmosphere
  • Early atmosphere formed from volcanic gases, mostly carbon dioxide with little or no oxygen.
Oxygen rise
  • Oxygen rise photosynthesis by microorganisms and plants made oxygen from carbon dioxide.
Today
  • Today about 78% nitrogen, 21% oxygen and 0.04% carbon dioxide.
Carbon dioxide rise
  • Carbon dioxide rise burning fossil fuels, deforestation and cement making.
Greenhouse effect
  • Greenhouse effect greenhouse gases trap heat, and increasing them causes global warming.
Reducing the effect
  • Reducing the effect use renewable resources such as wind, tidal and solar power.

Section 8 of 9Key terms

TermMeaning
AtomThe smallest particle of an element.
NucleusThe centre of an atom.
PurityHow much of a sample is the pure substance.
WeatherThe state of the atmosphere at a place and time.
ClimateThe average weather of an area over many years.
Glacial periodA very cold period when ice spreads widely.
Greenhouse effectHeat trapped by gases in the atmosphere.
Global warmingA rise in the Earth's average temperature.

Section 9 of 9Exam technique

1
Confusing weather with climate — climate is the average over many years.
2
Saying a pure substance means natural — scientifically it contains only one substance.
3
Saying the greenhouse effect is entirely harmful — without it the Earth would be much colder.
4
Saying electrons are in the nucleus.
5
Saying an ice age is the same as a glacial period.

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