Chemistry OCR gcse C4
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What is the charge and relative mass of a proton?
What is the charge and relative mass of a neutron?
What is the charge and relative mass of an electron?
What is the atomic number?
The number of protons
What is the mass number
The total number of protons and neurons
What is an isotope?
Atoms of the same element with a different number of neutrons, i.e. the same atomic number but a different mass number
What is an ion?
A charged atom (or group of atoms)
How does an atom become an ion?
A positive ion is made by the atom(s) losing electrons. A negative ion is made by the atom(s) gaining electrons.
What happens in ionic bonding?
A metal atom loses all outer shell electrons to become positive. The non-metal gains electrons to became negative because of this they attract eachother
What are giant ionic lattices?
Several Positive and negative ions joined together through ionic bonding. e.g NaCl
What are the properties of giant ionic lattices?
- High melting points- as they have strong attraction
- Conduct electricity when molten or in solution.
What is covalent bonding?
When atoms (non-metal) combine by sharing a pair of electrons.They don't conduct electricity as there aren't any free electrons. They also have weak bonds so low melting points.
Why do elements have similar properties to the other elements in the same group?
Elements in the same group have the same numbers in their outer shell.
What properties do group 1 elements have?
They react with water and air. They react more vigorously as you more down the group, as it is easier to lose an electron because the outer shell is further from the nucleus.
What happens to group 1 elements (alkali metals) in water?
- They produce hydrogen and a hydroxide. (an exothermic reaction)
- Li reacts gently
- K melts and burns with a lilac flame
- Rb can shatter a glass beaker
As you move down group 7 what happens to their reactvity? Why
- They become less reactive. This is because there are more full shells. making it harder to gain an electron.
- A more reactive halogen will displace a less reactive one when in solution. for ex. 2KI+Br2 -> 2KBr+I2
What properties do metals have that makes then useful?
- Lustrous- used in jewlery
- Hard with high density- steel in drill parts
- High tensile strength- steel in bridges
- Good conductors- copper in wires
- high melting points- tungsten in lightbulbs
Why do metals have high melting and boiling points?
Metals are held together with strong metallic bonds. These are electro static attractions between metal ions and delocalised electrons.
What is a super conductor?
Some metals become super conductors at low temperatures. These have little or no resistance to electricity. Useful in electro-magnets and super computers. They only work below -200c, tis is expensive and impractical.
To drink water it first has to be treated. What is the treatment process?
- 1)sedimentation - insoluble particles sink
- 2)filteration - removal of fine particles
- 3)chlorination - kills microbes in water
to obtain pure water it must also be distilled
What pollutants can be found in our water supply?
- Nitrates- fertiliser run off
- lead compounds - old pipes
- pesticides - spraying crops near the water supply
What colour precipitates are formed when mixed with silver nitrate?
- Silver nitrate detects halide ions
- -chlorides form white precipitates
- -bromides form a cream precipitate
- -iodides form a pale yellow precipitate
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