Questions - Chemistry

1) What is Matter ?
Anything that has mass and takes up space is recognised as matter. All stuff/materials are matter.

2) What is a Particle ?
Matter is made up of particles.
A particle can be an atoms, molecules or ions.
Particles are very small and cannot be seen with a microscope

3) What is a Vacuum ?
A space with no particles of matter in it.

4) What is Particle Theory ?
All matter is made up of particles.
Matter can exist in 3 states: solid, liquid or gas
Matter can change state.
This explains how particles are arranged in solids, liquids and gases and what properties they have
At a certain temperature the particles have enough energy to break the strong forces holding them together (melting, solid to liquid)
At a certain temperature the particles have enough energy to break the weak forces holding them close together (boiling, liquid to gas)

5) Can you give some physical properties of a Solid ?
It is a solid when the temperature of the material is lower than the melting point.
hard/strong, fixed shape, fixed volume, high density
cannot be compressed easily

6) Can you give some physical properties of a Liquid ?
It is a liquid when the temperature of the material is between the melting point and boiling point.
can flow/be poured, fixed volume, medium density
cannot be compressed easily
shape changes to fill bottom of a container

7) Can you give some physical properties of a Gas ?
It is a gas when the temperature of the material is greater than the boiling point.
does not keep the same shape or volume
can diffuse, low density
can be compressed
gases have the same shape and volume as the container they are in

8) What does Permeable mean ?
This is the name given to a material that allows liquids and gases to pass through it or soak into it.
eg Sandstone

9) What does Impermeable mean ?
This is the name given to a material that does not allow liquids or gases to pass through it.
eg Marble

10) What is Diffusion ?
This is the process where particles of one gas (or liquid) substance spread out in between the particles of another gas (or liquid) substance.
Diffusion in gases is much faster than diffusion in liquids
The particles spread out and move from an area of high concentration to an area of low concentration.
The following three factors affect the rate of diffusion: temperature, particle size and concentration

11) What are the different ways that state can be changed ?
Melting - solid to liquid, increase in energy, particles break free from fixed position
Freezing - liquid to solid, decrease in energy
Boiling - liquid to gas, increase in energy, fill container (also includes evaporation)
Condensation - gas to liquid, decrease in energy - happens at any temperature below the boiling point
Sublimation - solid to gas, particles break free from fixed position, increase in energy
Deposition - gas to solid, decrease in energy

12) Is Boiling and Evaporation the same thing and explain why ?
They are both processes that change a liquid to a gas but they are not the same thing.
Boiling is faster, only occurs are boiling temperature and occurs everywhere. The state slowly changes to gas creating bubbles that rise to the surface to escape.
Evaporation only occurs on the surface and can happen at any temperature.

13) What piece of equipment is used to measure temperature ?
Thermometer

14) What is Conduction ?
Conductors are materials that allow heat to easily pass through it (metals)
Insulators are materials that are poor conductors (non-metals, gases, plastic)

15) What is an Atom ?
The atom is the smallest unit of matter.
It is composed of three sub-atomic particles: the proton, the neutron, and the electron.

16) What is Ionisation ?
This is the removal of an electron from an atom.

17) What is an Element ?
Made of only one type of atom. Everything in the periodic table is an element.
O - one Oxygen atom
H2 - two Hydrogen atoms

18) What is the Periodic Table ?
Every element has a name and a symbol (one or two letters)
Depending on the temperature every element can be changed into solid, liquid or gas.
The periodic table provides a list of all the different elements
The table is divided into groups (which go down) and periods (which go across)
For example the first group are all soft, shiny metals
All the elements in a column/group have similar properties
The properties of the elements change as you go down the column.
Elements at the bottom of the column/group act more violently than those at the top.

19) How many elements are there in the periodic table ?
118. 95 metals (including 7 metalloids), 22 non-metals

20) Can you list the 7 metalliods ?
Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium and Polonium

21) What are the Symbols for the following elements ?
Sulpur - S
Iron - Fe
Hydrogen - H
Carbon - C
Magnesium - Mg
Aluminium - Al
Sodium - Na
Chlorine - Cl
Calcium - Ca
Zinc - Zn
Oxygen - O
Copper - Cu
Potassium - K
Silver - Ag
Gold - Au

22) What is a Molecule ?
Made of two or more atoms chemically bonded, due to a chemical reaction. They may or may not be the same type of atom.
H2 - two Hydrogen atoms
O2 - two Oxygen atoms
CO2 - different atoms

23) What is a Compound ?
Compounds are molecules that have different types of atoms
All compounds are molecules.
CO2

24) What is the difference between Molecules and Compounds ?
Molecules can be elements or compounds

25) What is the difference between Molecules and Elements ?
Elements are made up of only one type of atom.
Molecules can be made up of different types of atoms.

26) Give an example of a Molecule that is not a Compound ?
Molecules are elements when they are only made up of one type of atom
H2 - is not a compound

27) Give an example of a Compound that is also a Molecule ?
All compounds are molecules.
CO2

28) Do all Compounds have a Chemical Formula ?
Yes. The formula contains the symbols of the elements that make up the compound.
In a chemical reaction you start with "Reactants" and you end up with "Products".

29) What is a Chemical Reaction ?
This is a process in which one or more substances are converted into one or more different substances.

30) How do you Create a Compound ?
All compounds are formed from chemical reactions.
Some of these chemical reactions occur naturally, for example water (H2O) and carbon dioxide (CO2).
Water Synthesis is a chemical reaction in which two molecules of hydrogen combine with one molecule of oxygen.

31) How do you Separate a Compound ?
You need a chemical reaction to separate any atoms that have been chemically bonded.

32) What is a Substance ?
It has the same properties all the way through.
Substances can be pure or impure.

33) What is a Pure Substance ?
A pure substance is made from just one type of element or one type of compound.
** Is the air we breath a pure or impure substance ?
Impure because it contains different elements (nitrogen, oxygen) and compounds (cardon dioxide)
** Is Salt a pure or impure substance ?
Pure because it only contains one type of compound (sodium chloride symbol - NaCl).

34) What is a Mixture ?
Two or more different substances that have not been chemically bonded together.
In a mixture the different substances can be separated using a physical process.
A substance is not a mixture
For exampe iron and sulphur

35) How do you Create Mixtures ?
One way to create a mixture is to add a solid to a liquid and watch it Dissolve. For example salt in water.
The strong forces holding the particles together are broken down allowing the solid particles to mix with the liquid particles.
Solvent - The name given to the liquid substance that the solid is being dissolved into
Soluble - A solid substance is called soluble if it will dissolve
Insoluble - A solid substance is called insoluble if it will not dissolve
Solution - The name given to a mixture of a solid (solute) with a liquid (solvent) that does not separate out.

36) Can you describe what happens when a solid dissolves ?
When something dissolves it does not disappear
There is no change in mass
If you evaporate off the liquid you will see the solid particles

37) How do you Separate Mixtures ?
If particles are not chemically bonded they can usually be separated.
There are a number of separation techniques (or physical methods) that can be used:
Filtration
This technique separates pieces of solid that are mixed with a liquid by pouring through filter paper.
Evaporation
This technique separates a soluble solid from a liquid (creating crystals)
Distillation
This technique separates a liquid from a solution (water can be separated from salty water) Uses evaporation and condensation to obtain a solvent from a solution
Chromatography
This technique separate different coloured liquids

38) Can you describe how you would separate rock salt which is a mixture of salt and sand.
Grind the rock and mix it with water.
The salt will dissolve because it is soluble.
The sand will fall to the bottom it is insoluble.
The sand could be seperated by using filtration using filter paper
The salt could then be separated by using evaporation
The water could be seperated by using condensation by colling down the water vapour.

39) Some changes are called Reversible ?
These materials will change when heated and then return to how they were before, when cooled down.
For example salt in water

40) Some changes are called Irreversible ?
Bicarbonate of soda will dissolve in vinegar

41) What is the difference between Chloride and Chlorine ?
Chloride is formed from chlorine.
Chloride is what is created when Chlorine gains an electron and combines with other elements

42) Can you give some examples of chemical reactions ?
Sodium + Hydrogen = Sodium Hydride
Hydrogen + Oxygen = Water
Sodium + Hydrochloric Acid = Sodium Chloride + Hydrogen
Hydrogen + Carbon = Methane Gas

43) What is Water ?
It is the H2O compound in its liquid state.

44) Can you describe some physical properties of Metals ?
Metals conduct electricity
Metals conduct energy
Metals are strong and tough
Metals are shiny when polished
Metals are sonorous
Metals are ductile
Metals have high densities
Metals have high melting and boiling points

45) Can you describe some physical properties of Non-Metals ?
Non-metals don't conduct electricity
Non-metals don't conduct energy (by heating well)
Non-metals are not strong or hard wearing
Non-metals are dull
Non-metals are brittle
Non-metals have low densities
Non-metals have low melting and boiling points

46) Can you describe some different types of polymers (or plastics)
nylon, polythene, PVC

47) Can you describe some different types of ceramics ?
glass and porcelain

48) What are Composite Materials ?
These are materials that are made from two or more materials stuck together
eg - Fibre Glass (glass fibre and plastic)
eg - Concrete - sand, gravel and cement

49) What are Chemicals ?
This is the name given to substances that are used in a chemical reaction
Chemicals is another word for substances
The chemicals you start with are called the reactants
The chemicals you finish with are called the products
Chemical formulas are used to indicate what is happening in a chemical reaction
These chemical formulas are called symbol equations.

50) Can you describe what happens in a chemical reaction ?
atoms are not changed or destroyed
atoms move around
the mass does not change (the products weigh the same as the reactants)
there is always a transfer of energy to or from the surroundings

51) Can you give the names of different types of chemical reactions
Oxidation - this is when a substance reacts with oxygon releasing energy (heat and light)
* Combustion is an oxidation reaction
* Rusting is an oxidation reaction (iron + oxygon = iron oxide)
Thermal Decomposition - this is when a substance is heated and breaks down
Neutralisation -

52) What is an Exothermic Reaction ?
This is a chemical reaction that transfers energy to the surroundings

53) What is an Endothermic Reaction ?
This is a chemical reaction that takes energy from the surroundings

54) What is the name of the scale used to measure how Acid or Alkaline a substance is ?
The PH scale (from 0 to 14)
Substances with a PH less than 7 are called acids (hydrochloric acid)
Substances with a PH more than 7 are called alkaline (sodium hydroxide)
Substances with a PH equal to 7 are considered neutral (water)