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C3 science
- Atoms have a nucleus
which is positively charged,
and electrons which are
negatively charged.
- Atoms can form bonds to make molecules or compounds. It's
the electrons that are involved in making bonds. Sometimes
an atom loses or gains one or more electrons and this gives it a
charge (positive if it loses an electron and negative is it gains
one.)
- Charged atoms are known as ions. If a positive ion
meets negative ion they'll be attracted to one another
and join together.
- The other main type of bond is called a covalent
bond. When non-metal atoms combine together
they form covalent bonds by sharing pairs of
electrons. Because the bond is a shared pair, no
atom loses electrons.
- The other main type of bond is called a covalent
bond. When non-metal atoms combine together
they form covalent bonds by sharing pairs of
electrons. Because the bond is a shared pair, no
atom loses electrons.
- Charged atoms are known as ions. If a positive ion
meets negative ion they'll be attracted to one another
and join together.
- Atoms can form bonds to make molecules or compounds. It's
the electrons that are involved in making bonds. Sometimes
an atom loses or gains one or more electrons and this gives it a
charge (positive if it loses an electron and negative is it gains
one.)
- Combustion is an exothermic reaction -- heat's given out. The
best example of an exothermic reaction is burning fuels. In an
endothermic reaction, heat is taken out. Endothermic reactions
are less common and less easy to spot. One example is thermal
decomposition.
- Energy must always be supplied to break bonds, and
energy is always released when bonds form.
- Energy must always be supplied to break bonds, and
energy is always released when bonds form.
- Reactions happen is particles collide. So if you increase the number of
collisions, the reaction happens more quickly.
- Increasing the temperature means the
particles are going faster and have more
energy. This means they will have more
collisions, therefore the reaction will happen
faster.
- Increasing the concentration (or
pressure) means the particles and more
crowded together. More collisions will
happen.
- More surface area means other particles can get to it more easily. If one of
the reactants is a solid then breaking it up into smaller pieces will increase
its surface area. This means the particles around it will have more area to
work on so the frequency of collisions will increase.
- A catalyst increase the number of successful collisions. A catalyst is a substance
which increases the speed of a reaction, without being chemically changed or
used up in the reaction. Catalysts tend to be very fussy about which reactions they
catalyst though -- you can't just stick any old catalyst in a reaction and expect it to
work.
- Increasing the temperature means the
particles are going faster and have more
energy. This means they will have more
collisions, therefore the reaction will happen
faster.
- In the periodic table, the elements all have
two number. The bigger one is the relative
atomic mass.
- To figure out the relative formula mass, all your need
to do is add all the relative atomic masses together.
- In a chemical reaction, mass is always
conserved. During a chemical reaction no atoms
are destroyed and no atoms are created. This
means there are the same number and types of
atoms on each side of a reaction equation.
- In a chemical reaction, mass is always
conserved. During a chemical reaction no atoms
are destroyed and no atoms are created. This
means there are the same number and types of
atoms on each side of a reaction equation.
- To figure out the relative formula mass, all your need
to do is add all the relative atomic masses together.
- A lot of reactions make more than one product. Some of them will be useful,
but others will just be a waste (e.g when you make quicklime from limestone,
you also get carbon dioxide which is a waste product.
- The atom economy of a reaction tells you how much of the mass of
the reactants is wasted when manufacturing a chemical.
- Atom economy = total Mr of desired products divided by total Mr of all products x 100.
- 100% atom economy means that all the atoms in the reactants
have been turned into useful (desired) products. The higher the
atom economy the 'greener' the process.
- Atom economy = total Mr of desired products divided by total Mr of all products x 100.
- The atom economy of a reaction tells you how much of the mass of
the reactants is wasted when manufacturing a chemical.
- The predicted yield of a reaction can be calculated from the balanced reaction equation.
Percentage yield is given by the formula: Percentage yield = actual yield (grams) divided by
predicted yield (grams) x 100.
- Percentage yield is always somewhere between 0 and 100%. 100% yield means that you got all the product you expected to get.
0% yield means that no reactants were converted into product (no product at all was made.) Industrial processes want as high
a percentage yield as possible to reduce waste and reduce cost.
- You never get 100% yield because some product or
reactant will always get lost along the way. This depends
on what sort of reaction it is and what apparatus is being
used. Things that can go wrong are: Evaporation,
filtration, and transferring liquids.
- Percentage yield is always somewhere between 0 and 100%. 100% yield means that you got all the product you expected to get.
0% yield means that no reactants were converted into product (no product at all was made.) Industrial processes want as high
a percentage yield as possible to reduce waste and reduce cost.
- Batch production only operates at certain times. Batch production is often
the most cost-effective way to produce small quantities of different drugs to
order because it's flexible, start-ip cost are relatively low, it's labour intensive
and it can be tricky to keep the same quality from batch to batch.
- Continuous production runs all the time. The haber process for
making ammonia uses continuous production because the
production never stops, so you don't waste time emptying the
reactor and setting it up again. It runs automatically, and the
quality of the product is very consistent.
- Continuous production runs all the time. The haber process for
making ammonia uses continuous production because the
production never stops, so you don't waste time emptying the
reactor and setting it up again. It runs automatically, and the
quality of the product is very consistent.
- Diamond is used in jewellery and cutting tools. They're lustrous (sparkly) and
colourless. Each carbon of atom forms four covalent bonds in a very rigid giant
covalent structures. These take a lot of energy to break and give diamond a very high
melting point. It doesn't conduct electricity because it had no free electrons or ions.
- Graphite makes the lead of your pencil. It's black but still kind of shiny. Each carbon
atom only forms three covalent bonds, creating sheets of carbon atoms which are free to
slide over each other.The layers are held together weakly so they are slippery. Graphite
has a high melting point and they can conduct electrons.
- Fullerenes are molecules of carbon, shaped like closed tubes or hollow balls. Fullerenes can be
used to cage other molecules as the structure forms around another atom or molecule.
- Nanotubes have a huge surface area, so they could help make great industrial catalysts.
- Nanotubes have a huge surface area, so they could help make great industrial catalysts.
- Fullerenes are molecules of carbon, shaped like closed tubes or hollow balls. Fullerenes can be
used to cage other molecules as the structure forms around another atom or molecule.
- Graphite makes the lead of your pencil. It's black but still kind of shiny. Each carbon
atom only forms three covalent bonds, creating sheets of carbon atoms which are free to
slide over each other.The layers are held together weakly so they are slippery. Graphite
has a high melting point and they can conduct electrons.
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