Chemistry 1 warm-up session : Foundation tier

Remember, you have learnt all the information on the following slides in your lessons. This is just to refresh your memory of the essentials

Atomic structure

Atoms have a small central nucleus around which there are electrons

A substance that is made of only one sort of atom is called an element Elements O C C C O O O C C C O O C C C O O Eg, Carbon is made up of only carbon atoms Eg, Oxygen is made up of only oxygen atoms A substance that is made of only one sort of atom is called an element

Mass number and Atomic number Number of protons + Number of neutrons 9 Atomic Number = Number of protons Number of electrons 4 Elements in the same group in the periodic table have similar chemical properties Because they have the same number of electrons in their outer shell

Electronic structure 1st shell holds a maximum of 2 electrons 2nd shell holds a maximum of 8 electrons 3rd shell holds a maximum of 8 electrons Electrons are arranged in energy levels or shells around the nucleus. E.g. An Argon atom has 18 electrons. We can represent its electron structure as: 2,8,8.

Noble gases - Group 8 elements Noble gases are unreactive because their atoms have stable arrangements of electrons They have a full outer shell of electrons

Chemical reactions

Chemical reactions - bonding and electrons When elements react, their atoms join with other atoms to form molecules and/or compounds. This is Bonding. Bonding involves giving, taking or sharing electrons to form ions or molecules

Metals bonding with Non-metals Compounds formed from metals and non metals consist of ions. Metals lose electrons to form positive ions. Non metals gain electrons to form negative ions

Word and symbol equations +  Word equation: carbon carbon dioxide oxygen +  Symbol equation: C(s) + O2(g)  CO2(g) Chemical reactions can be represented by word equations or by symbol equations No atoms are lost or made during a chemical reaction so the mass of products equals the mass of the reactants

Limestone Chemical name: Calcium carbonate (alkali) Chemical formula: CaCO3 Found in earth’s crust - is quarried (dug up) Uses: Building materials (cement, glass, concrete, mortar); neutralise substances Heat limestone  breaks down Thermal decomposition reaction

Limestone cycle

Quarrying

Metals

Metal ore Rocks containing metals + other elements Found in the earth’s crust Ores contain enough metal to make it economical to extract the metal

Unreactive metals found in the Earth as the metal itself Native metals eg, Gold Unreactive metals found in the Earth as the metal itself

Properties of Transition metals Like other metals They are good conductors of heat and electricity They can be bent or hammered into shape They are useful as structural materials and for making things that must allow heat or electricity to pass through them easily

Alloys are A mixture of elements ...mainly metal... ...containing other elements... ...which change its properties Steel is an example of an alloy containing iron

Why is steel stronger than pure iron? Pure metals: have a regular arrangement of atoms – all the same size Layers can slide over each other soft and easily shaped - BUT too soft for many uses. Alloys/Steel The different sized atoms : distort the layers in the structure making it more difficult for them to slide over each other, and so alloys (steel) are harder.

Why is recycling of metals important? Saves resources (metal/ore) Saves energy (extraction) Cheaper/saves money Decreases waste material Decreases (a named) pollutant gas – carbon dioxide/sulphur dioxide

Hydrocarbons

Crude oil - hydrocarbons Crude oil consist of molecules made up of hydrocarbons - hydrogen and carbon atoms only

Fractional distillation Crude oil heated Liquid evaporates Cools and condenses at different temperatures Separates into fractions containing similar sized hydrocarbon molecules Long molecules – bottom Short molecules - top

Alkenes Alkanes Unsaturated hydrocarbons Saturated hydrocarbons At least one C=C double bond General formula CnH2n Saturated hydrocarbons Each C atom has 4 single bonds General formula CnH2n+2

alkane  alkane + alkene Cracking Cracking is a process used to break large hydrocarbon molecules into smaller more useful molecules by heating them over a hot catalyst C10H22  C8H18 + C2H4 alkane  alkane + alkene

Testing for unsaturated compounds (alkenes) – use bromine or iodine

Biofuels - ethanol Ethanol can be used as a biofuel Made either by fermentation with yeast or hydrating ethene (from crude oil) Adv of using sugar: - Useful in underdeveloped countries as they can grow sugar cane (have the right climate and enough land) - sugar is renewable source (oil is non-renewable) - uses less fossil fuels (low pollution) Adv of using alkanes: useful in country which has lots of oil faster process economic costs low

Acid rain Greenhouse effect Burning fuels Particulates

Cause and effects of pollutants Pollutant found in air Cause Effect – environmental problem Carbon dioxide Combustion (burning) Respiration Greenhouse effect  leads to Global Warming Carbon monoxide Incomplete combustion (not enough oxygen) Blood cannot carry oxygen so well Sulphur dioxide Burning coal Acid rain Particulates Burning wood and fossil fuels Soot deposits Global dimming Lung damage Nitric oxides High temperature combustion Smog

Polymers and oils

Polymerisation Many small molecules (monomers) join together to form very large molecules (polymers). Alkenes can be used to make polymers such as poly (ethene) and poly (propene).

Uses of polymers Polymers have many uses and new ones are being developed E.g. new packaging materials; waterproof coatings for fabrics; hydrogels; and, smart materials (including shape memory polymers)

Extracting plant oils Plant material Pressed or distilled Water removed Crushed Some fruits, seeds and nuts are rich in oils that can be extracted. The plant material is crushed The oil removed by pressing or in some cases by distillation. Water and other impurities are removed.

Emulsions Emulsions are thicker than oil or water and have many uses that depend on their special properties. They provide better texture, coating ability and appearance, for example in salad dressings, ice creams, cosmetics and paints.

Earth’s structure, movement and atmosphere

The Earth’s layers and movement The Earth’s crust and the upper part of the mantle are cracked into a number of large pieces (tectonic plates) The Earth consists of a core, mantle and crust.

Why can scientists not accurately predict when earthquakes will occur? Earthquakes involve sudden movements... ...between plate boundaries so... ...scientists are unsure what happens under the crust ...so don’t know where or when the force/ pressure is building up – and reaches its limit

Convection currents Convection currents within the Earth’s mantle, caused by heat released by natural radioactive processes, cause the plates to move at speeds of a few centimetres per year

The Earth’s atmosphere today For 200 million years, Earth’s atmosphere has been the same as now: − about 80% nitrogen − about 20% oxygen − small amounts of CO2, water vapour and noble gases.

How was our atmosphere formed? First billion years - intense volcanic activity. Which released the gases that formed the early atmosphere - water vapour that condensed to form the oceans. There may have been water vapour and small amounts of methane and ammonia. When plants evolved they produced the oxygen that is now in the atmosphere

Some scientific terms... Reliable Repeating tests, checking results, having a bigger sample Valid Keep everything the same except the independent & dependent variables Precision Smaller scale division on equipment Range From the smallest to biggest Interval What the values go up by Claims You decide if it is true or false by looking at evidence, independent organisations avoid bias

What is the questions asking you to do? Describe a graph Refer to the pattern e.g. as……...increases………increases etc Explain Describe & give a reason “because…….” Evaluate For & against Compare What is the same & what is different Calculate Show calculations & give units Suggest a reason This should be scientific

Things to think about when evaluating a situation... Economical aspect - money Environmental – pollution/ greenhouse gases/ global warming/ acid rain/ carbon dioxide/ habitat destruction Health risks – body rejection/damage Availability/accessibility Ethical – suffering/human rights Religious

Some final tips... Read the whole Q – 33% of the Qs can be answered from information given to you in text, diagrams, graphs & tables Follow instructions – “tick a box” “tick two boxes” “use info from the table” Don’t write “it” – “the concentration increases” NOT “it increases”

And remember... 1 mark per minute – you have 60 minutes to answer 60 marks Use bullet points for short questions – e.g. 3 marks should mean 3 bullet points Write in ‘good English’ for the 6 mark question Check your answers – read over your answers at the end

Good luck 