Chemistry: 1. States of Matter

Syllabus

OC1Name three states of matter and know their characteristics

Student Notes

Characteristics of Solids, Liquids and Gases

Solids / Liquids / Gases
Definite shape / No definite shape / No definite shape
Definite volume / Definite volume / No definite volume
Hard to compress / Hard to compress / Easy to compress
Do not flow / Flow easily / Diffuse to fill all available space

Explanation

These particles are so small that two million of them would fit into the full stop at the end of this sentence!

It’s not surprising that it took thousands of years before people believed that atoms exist. In fact many scientists, including Einstein, were doubtful that atoms existed until just over 100 years ago.

We can now see atoms using special hi-tech microscopes.

These ‘atoms’ are always moving (jiggling), no matter how hot or cold the object is, and it is this movement that determines whether the object is a solid, a liquid or a gas.

In a solid the atoms jiggle around a fixed position but don’t actually move anywhere. Now as you heat the solid the atoms jiggle more quickly and push over and back over a greater area. So although you can’t see the atoms moving, the solid itself actually expands slightly!

If you keep heating the solid then eventually the atoms get so much energy that they are able to leave their fixed position and whole groups of atoms start to move off, sliding over each other while all the time continuing to jiggle.

We say that the solid is turning to a liquid.

If you keep heating the liquid even further then eventually the atoms get so much energy and vibrate so much that they leave the rest of the liquid altogether and end up in the air. We say that the liquid is turning to a gas.

Jiggling atoms and temperature

Can you explain why the level of alcohol in the thermometer rises when you dip a thermometer into a beaker of hot water?

Answer

The atoms in the hot water are jiggling rapidly and bang off the atoms in the glass part of the thermometer. The glass is solid so the atoms in the glass don’t move anywhere but because they are getting battered by the atoms in the water outside they start to jiggle more rapidly. Some of these atoms are in contact with the alcohol so now these atoms start to jiggle more rapidly and as a result the alcohol rises a little on top due to all this movement.

So what a thermometer is actually responding to the jiggliness of the atoms – the more the atoms jiggle the higher the thermometer reading!

Evaporation and Boiling Point

At room temperature some of the atoms in water get enough energy to leave the liquid and become part of the air. This happens slowly and we call this evaporation.

However at a certain temperature (100 0C) every atom can leave the liquid and when this starts to happen we say that the water is boiling.

Condensation is the changing of a gas to a liquid e.g. steam meeting cold glass.

Sublimation is the changing of a solid directly to a gas on heating e.g. iodine, dry ice, volcano sulfur.

Exam Questions

  1. [2006 OL]

The diagrams on the right show the arrangement of particles in a solid, a liquid and a gas.

(i)Which diagram A, B or C shows a gas?

(ii)Name the physical change that takes place when A changes into B.

  1. [2007 OL]

The three states of matter are solid, liquid and gas.

The diagram shows the arrangement of particles in the three states of matter.

(i)In the table write the letter S beside the arrangement of particles in a solid.

(ii)Write the letter G beside the arrangement of particles in a gas.

  1. [2006]

Study the diagram carefully. It shows the ways that the particles of gases and solids occupy space.

The particles of gas have lots of space and move randomly at high speeds in three dimensions and collide with each other and with their container.

The arrows represent the velocities of the gas particles.

The particles of a solid are packed closely together and cannot move around but they can vibrate.

Give one property of a gas and one property of a solid that you have observed and is consistent with (matches) this micro-view of these states of matter.

  1. [2009]

There are three states of matter: solid, liquid and gas.

(i)Give one property that liquids and gases have in common.

(ii)Give one property in which liquids and gases differ.

  1. [2009 OL]

The three states of matter are solid, liquid and gas.

The diagram shows the arrangement of particles in the three states of matter.

(i)In the table write the letter L beside the arrangement of particles in a liquid.

(ii)Write the letter G beside the arrangementof particles in a gas.

Chemistry: 2. Elements, Compounds and Mixtures

Syllabus

OC3Understand what an element is and recall that all known elements are listed in the Periodic Table; understand what a compound is and what a mixture is; recall that when elements combine to form compounds they may lose their individual properties

OC4Examine a variety of substances and classify these aselements or compounds (using the Periodic Table as a reference)

OC12Compare the properties of the simple compounds H2O, CO2, MgO and FeS to those of the constituent elements

OC13Compare mixtures and compounds made from the same constituents, and understand that an alloy is a mixture

OC41Understand how atoms of elements combine to form compounds

Student Notes

We saw in the last chapter (States of Matter) that everything is made of atoms.

It turns out that there are many different types of atom (over 100 in fact), and some substances are made from just one type of atom, while other substances are made from combinations of different types of atom.

Elements

The different types of atom are arranged in terms of their size in a table called the Periodic Table of elements.

Molecules

Some atoms form a very strong attachment (‘bond’) to another atom or atoms and as a result they always go around in groups of two or more atoms. We call these guys ‘molecules’.

It is very hard to break these ‘bonds’ and we say that in this case the atoms are ‘chemically combined’. We will look at this bonding in detail in another chapter later.

Basically a molecule is like a very small group of atoms that go around together (they are still too small to see).

Hydrogen usually goes around in pairs of hydrogen atoms, so we say that H2 is a hydrogen molecule.

A water molecule is made up of one atom of oxygen together with two atoms of hydrogen; that’s why it has the symbol H2O.

Compounds

My head hurts; what’s the difference between a compound and a molecule?

All compounds are molecules, but not all molecules are compounds (e.g. H2 is a molecule because it is composed of two atoms chemically combined, but because they are both hydrogen atoms the molecule is not a compound).

Remember when we said that atoms are so small that you can’t see them? Well molecules are made up of small groups of atoms so you won’t be able to see them either.

A compound however might be something like table-salt; you can hold it in your hand. It is a compound because it is made up of two different types of atom – in this case sodium and chlorine. The chemical name for table-salt is NaCl.

The interesting thing is that both sodium and chlorine can be fatal if ingested (swallowed) but when the two go together to form table salt the result is perfectly safe (once you don’t eat too much!).

We can summarise this as follows:

When elements combine to form compounds they may lose their individual properties.

Mixtures

If a substance is made up of different components but they are just mingled together rather than combined at an atomic level then we call this a mixture.

I don’t know what needs to be learnt for the rest of this chapter !!!!!

Exam Questions

  1. [2006 OL]

Table Salt
Carbon
Air
MIXTURE / COMPOUND

Complete the table below identifying one mixture and one compound from the list on the right.

Element
Compound
  1. [2009 OL]

Complete the following sentence using the words from the list on the right.

Water is an example of a ______and hydrogen is an ______found in water.

  1. [2007 OL]

Write the name of each of the two elements present in water.

Aluminium
Copper
  1. [2009 OL]

In each case write the symbol of the metallic element beside its name in the table on the right.

  1. [2007]

Marie Curie showed the existence of the element radium and she produced 0.1 g of the compound radium chloride in 1902 by processing tons of pitchblende ore obtained from mines in Bohemia.

Explain the underlined terms.

Other Test Questions

  1. What is an element?
  1. What is a compound?
  1. Give four examples of compounds.
  1. What is a molecule?
  1. What is a mixture?
  1. Explain the difference between a physical change and a chemical change in chemistry:

Physical:

Chemical:

  1. Give one example of a physical change and a chemical change that you have observed

Physical:

Chemical:

  1. A student carried out an investigation comparing the properties of a mixture of iron and sulphur and the compound iron sulphide.

Name and explain a method that the student could use to separate the iron from the sulphur in the iron and sulphur mixture.

Method of separation:

Explanation:

Could the method of separation that you have suggested be used to separate the iron from the sulphur in the compound iron sulphide?

Explain your answer.

  1. Which two of the following five examples represent a chemical change?

(i)Rusting of iron

(ii)Melting of ice

(iii)Burning of gas

(iv)Grinding of coffee beans

(v)Magnetising of steel

Chemistry: 3. Separating Mixtures

Syllabus

OC2Separate mixtures using a variety of techniques: filtration, evaporation, distillation and paper chromatography

OC32Carry out a simple distillation, and obtain a sample of water from sea-water

Student Notes

e.g. soil and water.

Use filter paper, filter funnel and conical flask.

The problem is that it loses the solvent. e .g. water and salt.

By boiling the mixture the solvent e.g. water, will evaporate and will leave you with the solute.

A: Thermometer

B: Water out to sink

C: Condenser

D: Cold water in

E: Tripod stand

F: Bunsen

Put an ink spot just above the water line as shown.

Water rises up through the chromatography paper and takes the various colours which were in the ink spot to different heights.

To obtain a sample of water from sea-water using simple distillation

  1. Set up as shown

Part A is called a liebig condenser; an outer tube used to cause the water vapour to condense. Cold water goes in through Y and out through X.

  1. Flask A contains sea-water
  2. The water evaporates from flask A, travels through the condenser where it condenses and flows into flask B as pure water.

Exam Questions

  1. [2006]

How would you show that water contains dissolved solids?

  1. [2008 OL]

Describe, with the aid of a labelled diagram, how you could carry out an experiment to separate soil from a mixture of soil and water.

Use the headings below.

Labelled diagram, Equipment, Procedure, Result

  1. [2007 OL]

(i)What is the name given to the separation technique shown in diagram?

(ii)Name two substances which could be separated using this technique.

  1. [2009]

Draw a labelled diagram of an apparatus that could be used to separate an insoluble solid from a liquid.

  1. [2006 OL]

Separation techniques are very important in chemistry.

(i)What is the name given to the separation technique shown in the diagram?

(ii)Name two substances which could be separated using this technique?

(iii)Name the part of the apparatus labelled X in the diagram.

(iv)What is the name given to the separation technique shown in the second diagram on the far right?

  1. [2008 OL]

Separation techniques are very important in chemistry.

(i)What is the name given to the separation technique shown in the diagram?

(ii)Name two substances which could be separated using this technique.

  1. [2007]

The apparatus shown in the diagram can be used to separate mixtures.

(i)Name part A.

(ii)Which connection, X or Y, is attached to the cold tap?

(iii)Flask A contains seawater. Name the liquid that collects in flask B.

(iv)Name a constituent of seawater that does not move from flask A to flask B.

  1. [2009]

(i)Name the separation process shown in the diagram.

(ii)Name the item labelled C in the diagram.

(iii)Identify the part A or B of item C which is connected to the cold tap.

(iv)How could you show that the water collected contains no salt?

  1. [2009 OL]

Separation techniques are very important in chemistry.

The apparatus in the diagram below was used to separate a mixture of water and a dissolved dye. Study the diagram.

(i)Complete the table correctly matching the labels A – F in the diagram with words/phrases in the table.

(ii)What is the name given to the separation technique shown in the diagram above?

(iii)A colourless liquid was collected in container E during the separation. Name a substance you could use to show that this liquid was water.

(iv)What colour change is observed in this test to show that water is present?

  1. [2007 OL]

Separation techniques are very important in chemistry.

The apparatus in the diagram was used to separate sea-water.

Study the diagram.

(i)Complete the table correctly matching the labels A – F in the diagram with words/phrases in the table.

(ii)What is the name given to the separation technique shown in the diagram?

  1. [2008 OL]

A solution of dye can be separated into its constituent colours using the method shown in the diagram.

(i)Identify a liquid X that can be used in this separation.

(ii)What name is given to this type of separation?

  1. [2008]

(i)Describe an experiment, using a labelled diagram in the box provided, to investigate the composition of inks in markers containing water-soluble inks, to see if they are a single-colour ink or a mixture of coloured inks.

(ii)On completion of the experiment how is it possible to distinguish between a marker containing a pure single-colour ink and a marker containing mixture of coloured inks.

  1. [2006]

A spot of water-soluble ink was put on a piece of chromatography paper and set up as shown in the diagram. The ink used was a mixture of different coloured dyes.

(i)What happens to the ink spot as the water moves up the paper?

(ii)What would happen to a spot of water-soluble ink consisting of a single coloured dye if it were used in the above experiment?

Separating Mixtures

  1. Describe briefly with the aid of a diagram how to separate salt from water.
  1. Describe briefly with the aid of a diagram how to separate alcohol from water by distillation.
  1. Describe briefly with the aid of a diagram how to separate a mixture of inks using paper chromatography.
  1. How does filtration work?
  1. How does crystallisation work?
  1. A student attempts to separate water from a salt water solution using the apparatus shown.

(i)What’s left in the round bottomed flask at the end of the experiment?

(ii)Name the part labelled X and explain how it functions.

(iii)Name the method of separation shown in the diagram.

(iv)Identify a mixture that could be separated by using this method.

(v)How does the design of X enable it to carry out its job?

(i)The ink in a biro is an example of a mixture. Explain what is meant by a mixture.

(ii)What technique, in a laboratory, could be used to separate the mixture of pigments in biro ink?

(i)Name the piece of apparatus shown in the diagram.

(ii)Name the separation technique that uses this piece of apparatus.

  1. Alcohol and water can be separated by distillation.

(i)What is the difference between the two liquids that allows them to be separated by this technique?

(ii)Which liquid is the distillate?

(i)Give two safety precautions when heating a substance in a test tube.

(ii)Name a solvent and a solute that would dissolve in it.

  1. Name a substance, other than water, that forms crystals.

Give one difference between crystalline and non-crystalline solids.

  1. Give two methods that a student could use to make dilute copper sulphate solution more concentrated when making copper sulphate crystals.

Chemistry: 4.The Atom

Syllabus

OC39Describe the structure of the atom, state the location, relative charge, and atomic mass of the sub-atomic particles, and define atomic number and isotope

OC40Draw the Bohr structure of the first 20 elements

Student Notes

In other words, an atom of iron is the smallest piece of iron that shows all of the properties of copper.

Structure of the atom

The atom has a solid central section called the nucleus with particles in orbit around it.

The tiny particles found inside the atom are called “sub-atomic particles”.

There are three particles; protons, neutrons and electrons

The electrons revolve around the nucleus of an atom in fixed paths called orbits (shells) to form an electron cloud.

Particle / Location / Mass / Charge
Proton / Inside the nucleus / 1 Unit / +1
Neutron / Inside the nucleus / 1 Unit / 0
Electron / Outside the nucleus / 2000 times smaller than the mass of a proton / -1

All atoms are neutral. Therefore, the number of protons must equal the number of electrons.

Atomic number