Chemistry Flashcards
What are the states of matter and what determines them?
Solids, liquids, and gases. Can be determined by temperature, as it gives particles more energy, or pressure as the particles are closer together … the intermolecular attraction will be made stronger.
Describe the particles of a solid.
Particles have strong forces of attraction and are in fixed positions with a regular lattice arrangement. They have a definite shape and volume. The particles vibrate about their positions.
Describe the particles of a gas.
Particles have very weak forces of attraction and can move about in straight lines, and are spaced out. They can change volume and will fill any container.
Describe the particles of a liquid.
Particles have have weak forces of attraction, are randomly arranged and can move about. They are constantly moving with random motion. Liquids have a definite volume.
Describe particle changes from solid to liquid to gas.
When a solid is heated the particles gain energy. They vibrate more, and the attraction weakens. They break free from their positions. When changing to a gas they move faster and break their bonds altogether.
What is diffusion?
The gradual movement of particles from high concentrations of that particle to low concentrations of that particle.
How is an atom made up?
The nucleus is in the middle with equal numbers of neutrons and protons. The nucleus has a positive charge with all the protons, and also makes up the atomic mass.
The electrons move around the nucleus in shell levels. They are the same number as the neutrons and cancel out the charge.
What is the atomic number and mass number?
The atomic number is the number of protons, and the mass number is the number of protons and neutrons. From this you can work out the number of neutrons.
What is the difference between compounds, elements, and mixtures?
- Elements have only one element.
- Compounds are two or more elements chemically bonded, with different properties (Eg. Iron Sulphide is not magnetic)
- Mixtures have no chemical bonds and can be easily separated.
How to separate an insoluble solid from a liquid?
Use filtration, filter the filtrate and leave behind the residue.
How do you use crystallisation and recrystallisation?
Recrystallisation can purify compounds, by putting them in solution, and heating them so the compound dissolves and becomes supersaturated. Let this cool and the solvent evaporates, leaving a purer compound.
Crystallisation is just a way of obtaining a solid from a solution in the same way.
How would you separate rock salt?
Grind it up, dissolve the salt in water, filter it to get the sand, then heat the salt water to evaporate the water.
How does chromatography work?
The solvent soaks up the paper, and the dies dissolve in it. They then move up the paper with the solute. How far they move depends on how well they dissolve and how much they stick to the paper.
How does simple distillation work and what would you use it for?
Used to separate out solutions. Heat the solution in a round bottomed flask and let the solvent evaporate. It will condense in the liebig condenser.
How does fractional distillation work and what would you use it for?
Used to separate a mixture of liquids. In the fractionating column liquids evaporate and condense repeatedly until they reach the top and go into the liebig condenser. The liquids with the lowest boiling point will come out first.
What can you say about elements in the same group in the periodic table?
They have the same no. of electrons in the outer shell, and as a result have similar properties.
Describe ionic bonding.
It happens between a metal and a non metal, where electrons are transferred from one atom to another to give each atom full outer shells. Ions are formed, which are attracted to each other.
What do you call negative and positive ions?
Cation +, anion -
What are the characteristics of Giant ionic structures and why?
They have high melting points and boiling points as a lot of energy is required to break the bonds.
How does covalent bonding work?
Two non metals share some electrons so they both have full outer shells. There is a very strong attraction between the shared electrons and the two nuclei.
What are the formulas for ammonia and methane?
NH3 and CH4
What are the characteristics of covalent molecules and giant covalent structures?
- Covalent molecules have weak intermolecular forces and so have low melting points.
- Giant covalent structures have all the atoms bonded together strongly, which takes a lot of energy to break , and so there are high melting points. They usually don’t conduct electricity and are insoluble in water.
Why is diamond so strong?
Each atom has four covalent bonds in a very rigid structure.
What are the characteristics of graphite and why?
It is made up of layers that can slide over each other - easy to break. Good conductor of electricity because it contains delocalised electrons.
What are isotopes?
They are different atomic forms of the same element that have different numbers of neutrons but the same amount of protons.
How would you work out the relative atomic mass of an element?
Multiply the masses of the different isotopes buy their abundance. Then add them together and divide by the abundances put together.
How can you work out the relative formula mass of a compound?
Find out the relative formula masses of the different atoms, multiply them by how many of those atoms there are and add everything together.
What is the empirical formula?
It is the smallest whole number ratio of atoms in a compound.
How can you work out the empirical formula of a compound used in an experiment?
Write down the different masses of the different elements used, and divide them by their relative formula masses to work out roughly how many atoms were used. Then multiply/ divide them to get a whole number.
How can you work out the molecular formula of a compound used in an experiment?
Find out the relative formula mass of the compound and then divide the mass used by that. Multiply all the elements in the empirical formula by this.
How can you work out the masses used / made in reactions if you know one already?
- First write out the balanced equation.
- Find the relative atomic masses of the different ingredients.
- Multiply/ divide them to get the answer.
How can you work out the number of moles in a substance?
Divide the mass of the substance by the molar mass.
What is the structure of a hydrated salt?
It is a lattice of positive and negative ions with the water in between.
How can you work out how much water of crystallisation a salt contains.
- First work out the number of moles of salt and the number of moles of water used by dividing masses used by the molar mass.
- Multiply/ divide these to get a close to whole number ratio.
How much space does one mole of any gas occupy?
24 dm^3 (24 litres)
What do you measure concentration in?
Moles per dm^3
What is an electric current?
It is the flow of electrons or ions.
Can ionic compounds conduct electricity and why?
They can conduct it when in solution or when molten because the ions are free to move around. When solid the ions are not free to move around.
Why can metals conduct electricity and heat well?
Because they are made up of positive ions surrounded by a sea of electrons. The free electrons can make up an electrical current, and carry thermal energy quickly.
How does electrolysis work?
- An electric current is passed through an ionic substance (called an electrolyte).
- The positive ions flow towards the cathode (-), and loose electrons.
- The negative ions flow towards the anode (+), and gain electrons.
- They form atoms or molecules.
Describe what happens to lead bromide during electrolysis.
The Pb2+ ions from PbBr2 are attracted to the cathode and are given 2e-, which together makes Pb.
The 2Br- ions are attracted to the anode and give away two electrons, making Br2 + 2e-
What are periodic table rows and columns called, and how are whey organised? What is the the top of the staircase?
Periods have the same number of electron shells.
Groups have the same no. of electrons in the outer shell.
Al
Which type of oxides are basic and acidic?
Metal oxides are basic.
Non-metal oxides are acidic.
Why do alkaline metals get more reactive?
The electrons are further away from the nucleus, so the attraction is weaker, and the bonds can break more easily.
Describe what happens when you put different alkaline metals in water.
Lithium fizzes on the surface slowly producing lithium hydroxide and hydrogen.
Sodium fizzes rapidly around the surface producing sodium hydroxide and hydrogen.
Potassium reacts vigorously and burns with a lilac flame, producing potassium hydroxide and hydrogen.
What are the colours and physical states of the halogens?
Chlorine is a green gas.
Bromine is a red-brown liquid.
Iodine is a grey solid.
How do the properties of the halogens change and why?
They get less reactive as you go down, because the atoms get larger, so the attraction to the nucleus decreases. Therefore, electrons are harder to gain.
The boiling points get higher as you go down, because there are larger atoms, and greater intermolecular attraction.
What does hydrogen chloride gas do in water?
It dissociates to produce H+ ions and Cl- ions, making hydrochloric acid.
What is a displacement reaction?
When a more reactive element displaces a less reactive element from a compound.
what is the loss/gain of electrons?
Oxidation is loss, reduction is gain.
What do you call the elements that swap in a displacement reaction?
An oxidising agent accepts electrons and gets reduced.
A reducing agent gives electrons and gets oxidised.
When this happens at the same time it is a redox.
What happens when an acid reacts with a metal?
It produces a metal salt and hydrogen.
What happens when a metal reacts with water (or steam)?
It will give a metal hydroxide and hydrogen.
What is the first ten in the reactivity series?
Potassium, Sodium, Lithium, Calcium.
Magnesium, Aluminium, Zinc.
Iron, Copper.
Silver, Gold.