Chemistry Paper 2 Flashcards
How has water vapour created a change in the earths atmosphere ?
• earth cooled after it formed-> water vapour condensed into liquid-> fells as rain creating oceans
How has CO2 increased over the years ?
• CO2 dissolved by water in oceans as they formed-> amount in atmosphere decreased
How has oxygen increased over the years ?
• photosynthesis-> remove CO2 & release oxygen-> CO2 decreased & oxygen increased
What is the greenhouse effect ?
• greenhouse gases absorb heat radiated from Earth-> releases energy which keeps earth warm
What is climate ?
• average weather over long time & over large area
What are the effects of climate change ?
• glaciers & polar ice melting
• sea levels rising
• rainfall changing-> floods or droughts
• habitats changing
What are some ways to limit effects of climate change ?
• building flood essences
• irrigation systems
• planting different crops
Why does reactivity increase as you go down group 1 ?
As you go down-> radius of atom gets larger bc an extra shell is added in each period-> as outer electron gets further away from nucleus-> electrostatic forces become weaker-> easier to form cation by losing outer electron
Why are alkali metals very reactive ?
They have 1 electron in outer shell which they easily lose to form cation
What is the tests for chlorine gas ?
It bleached damp red litmus paper white
Why does the melting & boiling point of halogens increase as you go down group 7 ?
The molecules become larger-> more intermolecular forces which require more energy to break
Why does reactivity decrease as you go down group 7 ?
The elements need to gain 1 electron to become stable-> as you go down, radius gets bigger-> electrostatic forces become weaker-> makes more difficult for larger atoms to gain electrons to form anion
What are the properties & uses of helium ?
• less dense than air, low density, low flammability
• filling weather balloons, airships, balloons
What are the properties & uses of argon ?
• inert-> inert protective shield around hot metal when welding
• doesn’t react with tungsten filament-> filament bulb
Why does melting, boiling point £ density increase as you go down group 0 ?
Radius of atom gets larger so forces are stronger between atoms so it needs more energy to overcome
What needs to happen in order for chemical reaction to happen ?
Reactant particles must collide & have sufficient energy for them to react
How to increase rate of reaction ?
• increase frequency of collisions
• increase energy of reactants when they collide
How does increasing surface area increase rate of reaction ?
Increasing surface area of substance-> increasing amount of particles available to react-> more frequent collisions-> increase rate of reaction
How does increasing concentration increase rate of reaction ?
Greater concentration-> more particles-> more frequent collisions-> increase rate of reaction
How does increasing pressure increase rate of reaction ?
increasing pressure-> particles closer together by reducing space available to them-> frequent collisions
How does increasing temperature increase rate of reaction ?
Heat applied-> energy of particles increase-> reactant particles move more quickly (KE increases)-> frequency of successful collisions between reactant particles increase
What is a catalyst ?
• speeds up rate of reaction
• doesn’t alter products of reaction
• isn’t chemically changed or used up at end of reaction
How does catalyst increase rate of reaction ?
Provides alternative pathway that has lower activation energy than uncalled traction-> increases chance of successful collisions-> bc more particles have energy greater than activation energy
What happens during exothermic reaction ?
• forming bonds
• energy released to surroundings
• temp of surroundings increases
• E.g. handwarmers
