Science A (Core): Chemistry (I) - The Basics Flashcards
What is an atom made up of?
Atoms contain a nucleus (made of protons and neutrons) and electrons which orbit around in shells
How are the number of protons and electrons related?
The number of protons = the number of electrons (atoms have no overall charge)
How many types of atom does an element have?
An element has only one type of atom (there are around 100 different types of atom, e.g. gold, oxygen, copper etc…)
How are elements represented and where are they found?
Elements are shown by a symbol beginning with a capital letter
All elements are shown in the periodic table
Where are elements with similar properties found in the periodic table?
Elements with similar properties are put into columns (e.g. group 1 are all similar, group 2 are all similar etc…)
Which group are the noble gases found in and where are the alkali metals found in?
Noble gases are found in group 0
Alkali metals are found in group 1
In the periodic table what does the mass number and atomic number of an element shown?
Mass number: protons + neutrons
Atomic number: protons (∴ electrons)
How do electrons fill up around atoms in the shells?
Electrons are found in shells: 2 can fill the first shell then 8 can fill the others
Draw out the electrons surrounding nitrogen (which has 7 electrons)
2 electrons in the first shell and 7 in the second shell
How do atoms join together to form compounds?
Atoms can give / take electrons (ionic bonding)
Atoms can share electrons (covalent bonding)
Draw an example of a covalent bond between two non-metals
Two non-metal atoms share a pair of electrons
Draw an example of an ionic bond between a metal and a non-metal
The metal atom loses an electron (becomes a +ve ion) and the non-metal atom gains an electron (becomes a –ve ion)
What happens to the number of atoms during a reaction?
Atoms are not lost or made in a chemical reaction (the reactants you start with = the products you end with)
What is limestone and what is it used for?
Limestone is calcium carbonate (dug up from the ground and used as a building material)
What happens when limestone (CaCO3) is heated?
Calcium carbonate is thermally decomposed into calcium oxide + carbon dioxide
Calcium carbonate → calcium oxide + carbon dioxide
What happens when limestone (CaCO3) is added to acid?
Calcium carbonate is broken down into a salt, water and carbon dioxide
This is why buildings can get damaged from acid rain
What happens when calcium oxide is added to water?
Calcium oxide reacts with water to form calcium hydroxide (limewater)
Calcium oxide + water → calcium hydroxide
How is limestone useful?
Limestone is used to make cement (heated with clay)
Cement can be mixed with sand and water to make mortar
Cement can be mixed with sand, water and gravel to make concrete
What are the advantages and disadvantages of using limestone as a building material?
Advantages: limestone is cheap, is easily cut and concrete is extremely useful
Disadvantages: quarrying limestone causes noise, pollution and is ugly. Limestone is also damaged by acid rain
How can metals be extracted?
Some metals are found as ores – they can be mined, extracted and purified
Which metals can be extracted using carbon?
Metals below carbon can be extracted using it (reduction)
What is electrolysis?
Electrolysis uses electricity to break down substances (like purifying aluminum)
Electricity breaks the substance into ions which move to a charged electrode
Draw a simple diagram of electrolysis
More reactive metals than carbon must be extracted using electrolysis
What is bioleaching?
Bioleaching uses bacteria to extract copper from an ore
What is phytomining?
Phytomining is where plants are grown in soil with copper in it – the plants absorb the copper and when burnt leave the copper behind
Why is recycling important?
There are finite resources so recycling is important (less rubbish; saves energy; saves money etc…)
What are the properties of metals?
Metals are strong, bendy and conduct well (some like aluminum are light / some like titanium don’t rust etc…)
What is an alloy?
An alloy is a mixture of two materials (one of which is a metal) getting the best properties of each
E.g. iron + carbon make steel which is easily shaped, hard and does not corrode
What is crude oil and how is it used?
Crude oil is a hydrocarbon – it needs to be split into fractions to be useful (such as petrol, diesel, natural gas etc…)
What is an alkane?
An alkane is a hydrocarbon with the formula:
CnH2n+2
What is an alkene?
An alkene is a hydrocarbon (with a double bond) with the formula:
CnH2n
How is crude oil used and what associated problems are there?
Crude oil is used as a fuel – however it will run out one day and also produces a lot of CO2 when burnt which can lead to global warming
Fossil fuels also release sulfur dioxide when burnt which can lead to acid rain
What is global warming?
Global warming is caused by carbon dioxide released due to burning fossil fuels causing the Earth’s temperature to warm
What is global dimming?
Global dimming is caused by particles from fossil fuel burning blocking sunlight
What is cracking and how does it work?
Cracking makes long hydrocarbons shorter (which are more useful)
Cracking requires heat to break down the hydrocarbons
Draw out a diagram for cracking and say what it produces
Cracking produces alkanes and alkenes
What is the test for an alkene?
Bromine water – goes from red/orange to colourless if an alkene is present (containing a double bond)
How is ethanol (alcohol) produced?
What can be used to make polymers?
Alkenes can be joined together to form polymers (e.g. many ethane molecules form poly(ethane))
What are the properties and uses of polymers?
Polymers are used for waterproof clothing, tooth fillings, plasters etc… however most do not biodegrade (meaning they need to be recycled)
How are plant oils obtained and used?
Plant oils can be crushed and pressed to release their oil
Vegetable oils are used in foods (have lots of energy) and are used in cooking as they have higher boiling points than water so they cook the food quicker
They can also be used as fuels such as biodiesel
What is the difference between saturated and unsaturated?
Saturated: no double bond; bromine water stays red/orange if added; carry a high risk of heart disease
Unsaturated: C=C double bond; change bromine water colourless; lowers risk of heart disease
What is an emulsion?
An emulsion is something which does not mix (such as oil and water) – they are thick and used as ice cream, moisturisers, salad dressing etc…
What is an emulsifier?
Emulsifiers are added to emulsions to stop them separating
What is Wegener’s theory of continental drift?
Continents fit like a jigsaw and matching fossils and rocks suggest the continents are constantly shifting
What is the structure of the Earth like?
Earth has an inner core, outer core, mantle and crust
Tectonic plates are constantly shifting around (but can move quickly such as during an earthquake)
What is contained in Earth’s atmosphere?
The atmosphere is made of nitrogen (79%); oxygen (20%); argon (1%) and other gases
How has Earth’s atmosphere changed over time?
Early atmosphere lots of methane and carbon dioxide
Water condensed to form oceans and much less carbon dioxide (with tress beginning)
Trees release oxygen and carbon dioxide levels reduced
