The mass number tells you the total number of protons and neutrons. Electron aren't counted in this number because their relative atomic mass is negligible extremely large negative( negligible, extremely large, negative ).
Which of these 2 statements describes a compound?
Compounds are two or more elements chemically bonded together
Compounds are two or more elements which are not chemically bonded together
Isotopes are different atomic forms of the same element which have the same number of neutrons but a different number of protons.
In ionic bonding, atoms lose or gain electrons to form charge particles (ions). Atoms from groups 1 and 2 are more likely to ❌ electrons.
Which of the following statements are true about ionic compounds?
They have giant ionic lattices
There are very strong electrostatic forces of attraction between oppositely charged ions
They have high melting and boiling points
They dissolve easily in water
They have small ionic lattices
There are very weak electrostatic forces of attraction between oppositely charged ions
They have low melting and boiling points
They don't dissolve easily in water
Covalent bonding involves sharing electrons to obtain full outer shells. These are strong bonds.
Which of these are features of simple molecular substances?
They have weak intermolecular forces
They don't conduct electricity
They have strong intermolecular forces
Thy have high melting and boiling points
They conduct electricity
Graphite is the only non-metal which is a good conductor of heat and electricity. This is because each carbon atom has one .
Metals can be bent or shaped as the delocalised electrons allow the layers of atoms to slide over each other.
What size are nanoparticles?
1-100 nm across
100-1000 nm across
0-1 nm across
Many new uses of nanoparticles are being developed: which of these can they be used for?
Catalysts
Sun cream and deodorants
Nanomedicine
Lubricant coatings
Electrical circuits
Hand warmers
Plastic bags
Making alloys
Thermosetting polymers have which hold the chains together in a solid structure.
How do you work out number of moles?
mass/relative formula mass
relative formula mass/mass
relative formula mass * mass
Yields are always less than 100%, this may be because:
the reaction is reversible
when you filter a liquid to remove solid particles, you usually lose some of the liquid/solid
unexpected reactions happen
there are no reactants
you don't do the experiment in industrial conditions
Name two ways of identifying substances.
Paper Chromatography
Gas Chromatography
Solid Chromatography
Colour Chromatography
The rate of a reaction depends on four things: temperature, , catalyst and surface area.
Which of these methods of measuring the rate of a reaction is the most accurate?
Precipitation: observing a mark through the solution and measuring how long it takes for the mark to disappear
Change in mass: carry experiment out on a mass balance and observe how mass disappears (as gas is released)
Volume of gas given off: Use a gas syringe to measure volume of gas given off
The reaction between HCl acid and marble chips can be sped up by using finer particles of solid as it has a larger smaller( larger, smaller ) surface area.
Higher temperature increases the number and energy of collisions which means it takes more time for the particles to have enough energy to start the reaction.
A is a substance which speeds up a reaction without being changed or used up in the reaction.
Which of these are disadvantages of catalysts?
Very expensive to buy
Different reactions require different catalysts
Catalysts can be poisoned by impurities
They are harmful to people
They are very rare
Which of these are examples of exothermic reactions?
Combustion
Neutralisation reactions
Respiration
Sports injury packs
Photosynthesis
An alkali is a that dissolves in water.
Acid + Metal ------> Salt + Oxygen
Ammonia + Nitric acid ------->
Which of these are methods of making soluble salts?
Using a metal/insoluble base
Using an alkali
Precipitation reactions
An electrolyte contains free ions electrons atoms( ions, electrons, atoms ) which conduct electricity.
Oxidation is loss of electrons and reduction is gaining electrons.
In electrolysis, at the ❌ electrode, if metal and H+ ions are present, the metal ions will stay in solution is the metal is ❌ reactive than hydrogen.
Uses of chlorine:
Bleach
Plastics
Plating metals
Cryolite is used to the temperature needed to melt aluminium oxide.
In electroplating, you put the thing you want to plate at the positive electrode.
