Flashcards in Chemistry Deck (116)
What's an isotope?
Atoms of the same element but with a different number of neutrons.
They have the same number of protons and electron but a different number of neutrons.
They have the same chemical properties but different physical properties because of their different masses. Some are unstable and radioactive.
What's ionic bonding?
The giving or taking of an electron between a metal and a non-metal.
(Ionic compounds are neural since the charges cancel each other out)
What's an ion?
An atom or molecule with a net electric charge due to the gaining or losing of one or more electrons.
What happens to sodium and chlorine during ionic bondng?
Sodium loses an electron and becomes a positive ion and chlorine gains an electron and becomes a negative ion.
How do ions bond?
One ion is negative and one is positive so they are attracted to each other.
This is called electrostatic attraction and forms an ionic bond.
Ionic compounds are neutral as the charges on the ions cancel each other out.
What's covalent bonding?
The sharing of a pair of electrons between a non metal and a non metal
What happens with the covalent bonding of hydrogen?
As hydrogen has 1 (/2) electron on its (first) outer shell, it needs 1 more electron for a full shell so they bond together and share a pair of electrons.
What happens with the covalent bonding of oxygen?
As oxygen has 6 electrons on its outer shell, there has to be a double covalent bond as it wouldn't be able to share a pair of electrons and have a full outer shell.
Common properties of metals
Good conductor of heat (delocalised electrons)
Good conductor of electricity (delocalised electrons)
Solid at room temp (except mercury)
High melting and boiling point
Have free, delocalised electrons
Why are metals malleable?
The atoms are the same size and arranged in layers so the layers can easily slide over each other.
Why do metals have high melting points?
Because there is high electrostatic attraction between the metal ions and electrons so lots of energy is needed to overcome the attraction and melt the metal.
How does a calcium atom change to a calcium ion with a 2+ charge?
It loses two of its electrons and becomes positively charged.
What type of structure is graphite and diamond and why do they have high melting points?
Because they have strong intramolecular bonds which require lots of energy to break.
What are hydrocarbons?
A compound of hydrogen and carbon from crude oil.
What are the simplest alkane hydrocarbons?
What's the formula for alkanes?
They are saturated and have the formula CnH2n+2
What are the simplest alkene hydrocarbons?
What's a polymer?
Really long chains of molecules (monomers)
What are monomers?
A molecule which can bond to form long chains of polymers.
What's bad about polymers (plastics)
Made from crude oil - limited
Incineration emits toxic gasses
Landfills take up space and lots of time to decompose
What are the 2 types of plastic?
Thermosoftening / thermoplastic:
Can be heated and remoulded
Have weak intermolecular forces which break when heated - these allow the polymer chains to slide over each other.
Made up of individual polymer chains that are tangled together which when heated become soft and hard and is one called
Rigid and have a high melting point
Can't be remoulded
Have strong cross links between polymers which don't break when heated
What are the 4 things which affect the rate of a reaction?
How does temperature affect the rate of a reaction?
The higher the temperature, the faster the rate of reaction.
It gives the particles more energy so they move around faster, therefore colliding more often in the same amount of time, meaning the reaction occurs faster.
How was concentration affect the rate of reaction?
The higher the concentration, the faster the rate of reaction.
If there is an increase in concentration, this means there are more particles in the same volume of the substance therefore there will be more, successful collisions and a higher rate of reaction.
How does surface area affect the rate of reaction?
The large the surface area (smaller the surface area) the faster the rate of reaction.
You increase the surface area each time the object is cut smaller so small substances react faster. This is because, as smaller objects has larger surface areas, there are more atoms exposed on these surfaces, ready to react.
What's a catalyst?
A substance that speeds up the rate of reaction without actually being used up in the reaction itself.
They never produce more product, just the same amount more quickly.
Most lower the reactions activation energy (Ea) meaning they require less energy (minimum energy required).
What gas is given off when calcium carbonate reacts with hydrochloric acid and how can the volume of gas given off be measured?
1) measure the loss in mass on a balance as the reaction happens.
2) collect the gas in a measuring cylinder filled with water or in a gas syringe.
When are reactions usually at their fastest?
At the start.
Which would react fastest in dilute acid, the same mass of iron nails, iron wool or iron filings?