B1- Core Science Concepts (Chemistry) Flashcards
How were the elements in the early periodic table arranged?
Newland’s arranged elements in increasing order of atomic mass
How are elements arranged in the modern periodic table?
Arranged in order of increasing atomic number in rows and periods.
What is the general name for the unreactive elements in the periodic table?
The noble gases
Why do metals get more reactive going down a group?
The attraction between the nucleus (of the atoms) and the outer shell electrons gets weaker
Where are the transition metals found?
Groups 3-12 of the periodic table
Why do the halogens have low melting and boiling points?
Because the forces of attraction between the molecules are weak
Why are the elements in group 1 called the ‘alkali metals’ ?
When they react with water they become an alkali
Why are the noble gases so unreactive?
The atoms of noble gases already have a complete outer shell
Why did Mendeleev leave gaps in his periodic table?
For the discovery of new elements
What are the three types of sub-atomic particle?
Proton, neutron and electron
What are the differences between the plum pudding model and the nuclear model?
Plum pudding - space between electrons is positively charged “soup”
Nuclear model - mostly empty space
Who proposed the plum pudding model?
JJ Thomson
How does a positive ion form?
Atoms colliding with an energetic electron
when an atom loses an electron
How many protons, neutrons and electrons are there in an atom of aluminium (AN=13 MN=27) ?
13 protons
13 electrons
14 neutrons
Which law states that the mass of products formed in a reaction is equal to the mass of reactants?
The law of conservation of mass
Why do elements in a group have similar chemical properties?
Because they have the same number of electrons in the outershell
What determines the order of the elements in the periodic table?
The elements atomic number
What type of substances are shown in the periodic table?
Elements
What type of substance is sodium chloride (NaCl)?
Salt is a compound
What is the trend in the melting points down group 7?
The melting and boiling points increase going down group 7 because the molecules get larger
How was Mendeleev’s periodic table an improvement on Newland’s table?
Mendeleev left gaps for new element discoveries
Which process could you use to separate ethanol and water?
Fractional distillation
Why are the alkali metals stored in oil?
So they don’t react with the oxygen in the air or water
How would the reaction of Sodium and water differ to the reaction of Lithium and water?
The Sodium and water is more vigorous than Lithium
Relationship between the atomic structure and physical/chemical properties
Stronger bonds between atoms make them more difficult to separate and stronger bonds are typically harder, with higher bp/mp
The relationship between the atomic structure and conductivity of metals
‘aligned positive ions’ (cations) in a “sea” of delocalised electrons. This means that the electrons are free to move throughout the structure, and gives rise to properties such as conductivity.
Chemical properties of G1
- Alkali metals soft solids and can be easily cut
- Low densities
- Good conductors of heat + electricity
- Low mp/bp
Reactivity of group 1 metals with water and oxygen
reactivity increases going down
reactions with water produce metal hydroxides and hydrogen gas
reactions with oxygen - oxidise when with oxygen. they also burn vigorously when heated and placed in a glass jar of oxygen.
Reactivity of group 1 metals in terms of their electronic configurations
Reactivity of group 1 metals increases as you go down the group because the atoms get larger, the outer electron gets further from the nucleus - the attraction between the nucleus and outer electron gets weaker so the electron is more easily lost.
Reactivity of transition metals with oxygen and acids
Transition metals react with oxygen / oxidise to form metal oxides e.g. rust
they react with acids to form metals, salts, carbon dioxide and water
Difference in properties of transition metals compared with group 1 metals
The transition metals are different from Alkali Metals in Group 1 in the following ways:
• they have higher melting points;
• they have higher density;
• they are less reactive with water;
• they react and form ions with different charges, but Group 1 metals only form 1+ ions.
The relationship between the structure and properties of composite materials
How the arrangement of the electrons is linked to the way in which elements are situation within groups in the period table
Elements with the same number of electrons in the outer shell are in the same group of the periodic table
What are the physical properties of acids?
- Irritant or corrosive
- Neutralise bases
- React with metals to form H2
- pH less than 7
Strong and weak acids (as distinct from dilute and concentrate solutions)
- Strong acids are completely ionised in aqueous solutions e.g. sulphuric, hydrochloric and nitric
- weak acids are only partially ionised in aqueous solution (for example ethanoic and carbonic)
- or a given concentration of aqueous solution, the stronger the acid, the lower the pH
- as the pH of an acid decreases by one unit, the hydrogen ion concentration of the solution increases by a factor of 10
How do you determine the name of a salt produced in acid-base reactions
Acid + Base→Salt + Water
E.g. HCL + NaOH → NaCL +H2O
What are the principles of collision theory
- Molecules must collide
- Molecules must collide with enough energy to break and reform bonds
- Molecules must be in the correct spacial orientation
What is the effect of temperature on rates of reaction?
- An increase in temperature makes molecules move faster, resulting in increased collisions and rates of reaction.
- Lower temperatures result in decreased collisions and rates of reaction.
What is a catalyst?
What is the role of catalyst in a reaction?
Catalysts are substances that increase the rate of a chemical reaction without being permanently chemically changed themselves.
What is thin layer chromatography used for?
- Used to separate substances based on their affinity for a mobile (solvent) or stationary phase (on a coated plate)
- used to detect the number of components
- used to identify the compounds and their purity
What is column chromatography used for?
To separate a single chemical compound from a mixture (in a vertical column)
What is gas chromatography used for?
Used to separate and analyse compounds that can be vaporised (in a capillary or packed column)
What is high performance liquid chromatography used for?
To separate substances based on their affinity for a mobile (pressurised solvent) or stationary phase (in a capillary or packed column)
What is mass spectronomy used for?
Used to separate substances due to their mass to charge ratio and to identify molecular ions and ion fragments
Used to identify the components of an unknown sample due to their molecular weights
Name the tests that could be used to quantify components in a mixture
- Gas chromatography
- High performance liquid chromatography
- Mass spectrometry
What is the principle of titration?
- Determining the volume of acids and alkalis required for neutralisation to occur
