Chemsitry aqa combined summer exam
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56 Terms
Why do Group 1 metals get more reactive down the group?
Outer electron is further from the nucleus, easier to lose
What did the alpha particle scattering experiment show?
That atoms have a small, dense, positive nucleus
What is the relative atomic mass?
Average mass of all isotopes of an element
What is the law of conservation of mass?
Mass is neither created nor destroyed in a chemical reaction
Why does mass appear to increase in a reaction in air?
A gas (like oxygen) has been added from the air
What is a metal + acid reaction?
Metal + acid → salt + hydrogen
What is the ionic equation for magnesium + hydrochloric acid?
Mg + 2H⁺ → Mg²⁺ + H₂
How do you make soluble salts using an acid and an insoluble base?
Add base to warm acid until in excess, filter, evaporate slowly to crystallise
What is crude oil?
A mixture of hydrocarbons
How does fractional distillation separate crude oil?
By boiling point - lower boiling points come off first
What is the trend in hydrocarbon boiling points with chain length?
Longer chains = higher boiling points
How did Earth's early atmosphere form?
Volcanic activity released gases - mainly CO₂, water vapour, and little oxygen
How did oxygen levels increase?
Photosynthesis by early plants and algae
What human activities increase greenhouse gases?
Burning fossil fuels, deforestation, farming (methane)
What is global warming?
Gradual increase in Earth's temperature due to greenhouse gases
Why do Group 1 metals get more reactive down the group?
Outer electron is further from the nucleus, easier to lose
What did the alpha particle scattering experiment show?
That atoms have a small, dense, positive nucleus
What is the relative atomic mass?
Average mass of all isotopes of an element
What is the law of conservation of mass?
Mass is neither created nor destroyed in a chemical reaction
Why does mass appear to increase in a reaction in air?
A gas (like oxygen) has been added from the air
What is a metal + acid reaction?
Metal + acid → salt + hydrogen
What is the ionic equation for magnesium + hydrochloric acid?
Mg + 2H⁺ → Mg²⁺ + H₂
How do you make soluble salts using an acid and an insoluble base?
Add base to warm acid until in excess, filter, evaporate slowly to crystallise
What is crude oil?
A mixture of hydrocarbons
How does fractional distillation separate crude oil?
By boiling point - lower boiling points come off first
What is the trend in hydrocarbon boiling points with chain length?
Longer chains = higher boiling points
How did Earth's early atmosphere form?
Volcanic activity released gases - mainly CO₂, water vapour, and little oxygen
How did oxygen levels increase?
Photosynthesis by early plants and algae
What human activities increase greenhouse gases?
Burning fossil fuels, deforestation, farming (methane)
What is global warming?
Gradual increase in Earth's temperature due to greenhouse gases
What are Group 1 elements called?
Alkali metals
Why do alkali metals become more reactive as you go down the group?
Outer electron is further from the nucleus and easier to lose
What are Group 7 elements called?
Halogens
What happens when a more reactive halogen reacts with a less reactive halide solution?
A displacement reaction occurs
Who discovered the nuclear model of the atom?
Ernest Rutherford
What did the plum pudding model suggest?
That atoms are a ball of positive charge with electrons scattered throughout
What is the relative formula mass (Mr)?
The sum of the relative atomic masses of all atoms in a compound
What is the formula to calculate percentage mass of an element in a compound?
(Ar × number of atoms of the element ÷ Mr of compound) × 100
What is the law of conservation of mass?
No atoms are lost or made during a chemical reaction
Why might mass appear to increase in a reaction?
A gas from the air has been added
What is a base?
A substance that reacts with an acid to form a salt and water
What is a neutralisation reaction?
Acid + base → salt + water
How can you make a soluble salt from an acid and an insoluble base?
Add base until no more reacts, filter, then evaporate water
What is an example of a neutralisation reaction?
Hydrochloric acid + sodium hydroxide → sodium chloride + water
What are hydrocarbons?
Compounds made of hydrogen and carbon only
What is the general formula for alkanes?
CnH2n+2
What is produced when hydrocarbons combust completely?
Carbon dioxide and water
What is fractional distillation used for?
To separate crude oil into fractions based on boiling point
What is the trend in hydrocarbon properties as chain length increases?
Boiling point increases, viscosity increases, flammability decreases
What is the main cause of the greenhouse effect?
Greenhouse gases like CO₂, methane, and water vapour trapping heat
What are two human activities that increase methane levels?
Cattle farming and landfill
What is carbon monoxide?
A toxic, colourless, odourless gas formed in incomplete combustion
How can we reduce carbon footprint?
Use renewable energy, plant trees, conserve energy
How was Earth's early atmosphere formed?
Volcanic activity released gases like CO₂, water vapour, and nitrogen
How did oxygen levels increase in Earth's early atmosphere?
Photosynthesis by algae and plants
What is the current composition of Earth's atmosphere?
78% nitrogen, 21% oxygen, small amounts of other gases