1 Principles of Chemistry Flashcards
What are the three states of matter?
Solids, liquids and gases
What are the four state changes
Melting (solid → liquid) when heating up
Freezing (liquid → solid) when cooling down
Boiling (liquid → gas) when heating up
Condensing (gas → liquid) when cooling down
What is the arrangement of particles, the movement of particles, and the closeness of particles for solids?
Regular arrangement, vibrate about a fixed position, very close.
What is the arrangement of particles, the movement of particles, and the closeness of particles for liquids?
Randomly arranged, move around each other, close.
What is the arrangement of particles, the movement of particles, and the closeness of particles for gases?
Randomly arranged, move quickly in all directions, far apart.
Interconversion:
Melting = ?
Boiling = ?
Freezing =?
Evaporation = ?
Condensation = ?
Sublimation = ?
Solid to a liquid
Liquid to a gas
Liquid to a solid
Liquid to a gas
Gas to a liquid
Solid to a gas
Solutions table:
1. Solvent meaning and example?
2. Solute meaning and example?
3. Solution meaning and example?
4. Saturated solution meaning and example?
5. Soluble meaning and example?
6. Insoluble meaning and example?
- The liquid in which a solute dissolves - the water in sea water.
- The substance which dissolves in a liquid to form a solution - the salt in seawater.
- The mixture formed when a solute is dissolved in a solvent - seawater.
- A solution with the maximum concentration of solute dissolved in the solvent - seawater in the dead sea.
- Describes a substance that will dissolve - salt is soluble in water.
- Describes a substance that won’t dissolve - sand is insoluble in water
Element definition and examples?
Substances that cannot be broken down into anything simpler because they are made of only one type of atom. Hydrogen, oxygen, carbon
Compound definition and examples?
A pure substance made up of two or more elements chemically combined together. They cannot be separated by physical means. Calcium carbonate, carbon dioxide.
Mixture definition and examples?
A combination of two or more substances that are not chemically joined together. Can be separated by physical means. Salt and water (seawater), air.
How do you determine whether a substance is pure?
Pure substances melt and boil at specific and sharp temperatures e.g. pure water has a boiling point of 100 degrees celcius and a melting point of 0 degrees celcius.
How do you determine whether a substance is a mixture?
Mixtures have a range of melting and boiling points as they consist of different substances that tend to lower the melting point and broaden the melting point range.
What is simple distillation?
It is used to separate a liquid and soluble solid from a solution (e.g. water from a solution of salt water) or a pure liquid from a mixture of liquids.
What is fractional distillation?
This is used to separate two or more liquids that are miscible with one another (e.g. ethanol and water from a mixture of the two)
How do you carry out a fractional distillation experiment?
The solution is heated to the temperature of the substance with the lowest boiling point
This substance will rise and evaporate first, and vapours will pass through a condenser, where they cool and condense, turning into a liquid that will be collected in a beaker
All of the substance is evaporated and collected, leaving behind the other components(s) of the mixture
For water and ethanol
Ethanol has a boiling point of 78 ºC and water of 100 ºC
The mixture is heated until it reaches 78 ºC, at which point the ethanol boils and distills out of the mixture and condenses into the beaker
When the temperature starts to increase to 100 ºC heating should be stopped. Water and ethanol are now separated.
What is filtration?
It is used to separate an undissolved solid from a mixture of the solid and a liquid/solution (e.g. sand from a mixture of sand and water)
How to carry out a filtration experiment?
A piece of filter paper is placed in a filter funnel above a beaker
A mixture of insoluble solid and liquid is poured into the filter funnel
The filter paper will only allow small liquid particles to pass through as filtrate
Solid particles are too large to pass through the filter paper so will stay behind as a residue.
What is crystallisation?
It is used to separate a dissolved solid from a solution, when the solid is much more soluble in hot solvent than in cold (e.g., copper sulphate from a solution of copper (II) sulphate in water)
How to carry out a crystallisation experiment?
The solution is heated, allowing the solvent to evaporate, leaving a saturated solution behind. Test if the solution is saturated by dipping a clean, dry, cold glass rod into the solution. If the solution is saturated, crystals will form on the glass rod. The saturated solution is allowed to cool slowly. Crystals begin to grow as solids will come out of solution due to decreasing solubility
The crystals are collected by filtering the solution, they are washed with cold distilled water to remove impurities and are then allowed to dry.
What is paper chromatography?
This technique is used to separate substances that have different solubilities in a given solvent (e.g. different coloured inks that have been mixed to make black ink)
How to carry out a paper chromatography experiment?
A pencil line is drawn on chromatography paper and spots of the sample are placed on it. Pencil is used for this as ink would run into the chromatogram along with the samples
The paper is then lowered into the solvent container, making sure that the pencil line sits above the level of the solvent, so the samples don’t wash into the solvent container
The paper is called the stationary phase
The solvent travels up the paper by capillary action, taking some of the coloured substances with it; it is called the mobile phase
Different substances have different solubilities so will travel at different rates, causing the substances to spread apart
Those substances with higher solubility will travel further than the others
This will show the different components of the ink / dye
If two or more substances are the same, they will produce identical chromatograms
If the substance is a mixture, it will separate on the paper to show all the different components as separate spots
An impure substance will show up with more than one spot, a pure substance should only show up with one spot
Rf Values
These values are used to identify the components of mixtures The Rf value of a particular compound is always the same but it is dependent, however, on the solvent used. If the solvent is changed then the value changes. Calculating the Rf value allows chemists to identify unknown substances because it can be compared with Rf values of known substances under the same conditions. These values are known as reference values
How to calculate the Rf value?
Rf = distance travelled by substance ÷ distance travelled by solvent.
The Rf value will always lie between 0 and 1; the closer it is to 1, the more soluble is that component in the solvent
The Rf value is a ratio and therefore has no units
What is the definition of an atom?
The smallest particles of an element that consists of electrons surrounding a nucleus that contains protons and neutrons.
