Flashcards in Module 1 Deck (60):
How do emulsion paints dry?
The solvent in the paint (water) evaporates
How do oil paints dry?
The solvent in the paint (hydrocarbon oil) evaporates and then oxygen oxidises the hydrocarbon molecules
What are thermochromic substances?
A substance that changes colour according to temperature (e.g. baby spoons and thermometers)
How do phosphorescent pigments work?
They absorb energy when they are in light, and then they can glow in the dark. They are used in road signs and clocks.
Why are phosphorescent pigments safer than radioactive pigments?
Because radioactive pigments can cause damage to cells and cause cancer.
What is a colloid?
A paint mixture when particles are mixed and dispersed in a liquid but are not dissolved
Why do the components of colloids not settle?
Because the particles are too small to settle
Name 3 examples of fossil fuels
Crude oil, coal and gas
What type of resource is a fossil fuel?
They are finite resources which means they are no longer being made or made extremely slowly. And they are non renewable which means they are used faster than they are formed
What is crude oil?
A mixture of hydrocarbons , a hydrocarbon contains ONLY hydrogen and carbon atoms
How does fractional distillation work?
The coolest part is at the top and the hottest part is at the bottom. It works because the different hydrocarbons have different boiling points. The low boiling points exit the top and the high boiling points exit at the bottom. The larger the hydrocarbon molecules the stronger the intermolecular force which is why they are at the bottom because they need a higher temperature to break the intermolecular forces.
What are the problems with oil?
Damage to wildlife/beaches and oil slicks
What are alkanes?
Hydrocarbons that contain single covalent bonds between carbon atoms
What are alkenes?
Hydrocarbons which contain a double covalent bond
Molecules with double bonds are said to be what?
When is a double covalent bond formed?
When 2 atoms share 2 pairs of electrons
What is used for testing unsaturation?
Bromine water is orange and if it's unsaturated a colourless dibromo compound is formed
What is an atom?
The smallest part of an atom that can exist
How many elements are there approximately?
What are compounds and how are they formed?
Compounds are formed from elements by chemical reactions. Compounds contain two or more elements chemically combined.
How can compounds be separated?
Only by chemical reactions
What is a mixture?
A mixture consists of 2 or more elements that are not chemically combined, the chemical properties of a mixture are unchanged
How can mixtures be separated?
4) Fractional Distillation
5) Simple Distillation
(These do not involve chemical reactions)
What is the radius of an atom?
What is an atom?
A nucleus surrounded by electrons
Where are the protons and neutrons?
Mass and charge of a proton?
Mass - 1
Charge - +1
Mass and charge of neutron?
Mass - 1
Charge - 0
Mass and charge of an electron?
Mass - very small
Charge - -1
What is atomic number?
The number of protons in an atom
What is mass number?
The total number of protons and mass number in an atom
When are positive ions formed?
When an atom loses electrons
When are negative ions formed?
When an atom gains an electron
What are elements in Group 0 called?
Why are noble gases unreactive?
Because their atoms have stable arrangements of electrons
What happens when you go down the group?
The boiling point increases
How are the elements in the periodic table arranged?
In order of atomic number
Why is it called the periodic table?
Because similar properties occur at regular intervals
Why do elements in the same group have similar chemical properties?
Because they have the same number of electrons in their outer shell
What does periods tell you about the element?
The number of shells the electrons fill
How was the periodic table ordered before now?
In order of atomic weights
What did Mendeleev do?
He sorted some problems by leaving gaps for undiscovered elements and changed the order in some places. The gals were the filled and knowledge of isotopes made it possible to explain why the order of atomic weights wasn't always correct.
What was the problem with Döbereiner's ideas?
He could not explain his observations
Why was Newland's version of the periodic table dismissed?
He ordered them in order of relative atomic mass but it only worked for first 20 elements, up to Calcium
Why was Mendeleev's ideas accepted?
He swapped some elements around and left gaps for undiscovered elements
Which elements form positive ions?
Where are metals in the periodic table?
Left and towards the centre
Name the properties of metals
Good conductor of electricity
Good conductor of heat
High melting point
Why is iron used in buildings?
Because it is strong and has a high melting point
Why is copper used in wires?
Because it is ductile and a good conductor of electricity
What elements from negative ions?
Where are non metals found?
To the right and top of the periodic table
How many electrons do Group 1 have in their outer shell?
Why are Group 1 metals stored in oil?
Because they are so reactive
Why are they called alkali metals?
Because when they react they produce alkaline solutions
What are the Group 1 elements like?
They have a low density, the first 3 metals are less dense than water
How do Group 1 metals react with water?
They are white solids that dissolve in water to form colourless solutions
Hydrogen is formed
They all react vigorously with water
Metal hydroxide is formed that dissolves in water to give alkaline solutions
Reactivity increases down the group
What type of elements are the Group 7 elements?
Non metals, that consist of molecules which are made up of pairs of atoms. They react with metals to form ionic compounds which the halide iron carries a charge of -1
Trends in Group 7
Decreases in reactivity down the group
Boiling and melting point increases
A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt