SC25/26: Qualitative Analysis, Properties of Matter & Nanoparticles Flashcards
SC25a Flame tests and photometry
A) Describe how flame tests are carried out
B) State the flame colour for the certain metal ions
A) To carry out a flame test;
- Light a Bunsen burner and open the air hole to give a hot blue flame.
- Pick up a small sample of the test substance using a wire loop
- Hold the sample in the edge of the flame and observe the flame colour.
B) Different colours are;
- Lithium -> Red
- Sodium -> Yellow
- Potassium -> Lilac
- Calcium -> Orange-red
- Copper -> Blue-green
SC25a Flame tests and photometry
A) Describe what flame photometry is
B) State why machines may be used with flame photometry
A) Flame photometry measures the light instensity of the flame colours produced by ions.
B) Using scientific equipment equipment may improve:
- Sensitivity ( they can detect much smaller amounts )
- Accuracy ( they give values closer to the true values )
- Speed
SC25b Tests for positive ions
A) State the tests to identify the different positive ions.
B) State the test for ammonium ions
A) Different tests include;
- Iron(II) -> Green
- Iron(III) -> Brown
- Copper -> Blue
- Calcium -> White
- Aluminium -> White - Aluminium hydroxide disappears to form a colourless solution when excess sodium hydroxide solution is added.
B) Ammonia gas is produced when the mixture containing ammonia ions are heated, Ammonia has a very sharp smell.
- Ammonia changes the colour of damp red litmus paper to blue.
SC25c Tests for negative ions
Describe the test for;
A) Carbonate ions
B) Sulfate ions
A) Add dilute hydrochloric acid to the test substance and look for bubbling caused by the production of carbon dioxide.
- Since the bubbles could be due to a different gas, you should bubble the bubbles into limewater and if the limewater turns milky, the gas is CO2.
B) Add a few drops of dilute hydrochloric acid to the solution. This acidifies the solution and removes carbonate ions that might also give a precipitate in the test.
- Add a few drops of barium chloride solution. A white precipitate of barium sulfate forms if sulfate ions are present.
SC25c Test for negative ions
Describe the test for halide ions
1. Add a few drops of dilute nitric acid. This acidifies the solution and removes carbonate ions that might also give a precipitate in the test.
2. Then add a few drops of silver nitrate soltion. Different coloured silver halide precipitates form, depending on the halide present.
- Chloride -> White
- Bromide -> Cream
- Iodide -> Yellow
SC25c Core practical - Identifying ions
Describe the chemical test for;
A) Ammonium ions
A) Dissolve a little solid salt in a test tube using distilled water.
- Add dilute sodium hydroxide solution and then warm gently.
- Remove the flame. Hold a piece of damp red litmus paper near the mouth of the test tube, record what happens to its colour.
SC26a Choosing materials
Describe the properties of;
A) Clay ceramics
B) Glass
A) Clay ceramics;
- Change very little when heated
- Chemically unreactive, hard and stiff but brittle
- Poor electrical and thermal conductors, & have high melting points
- Ceramics can be dipped in glaze which forms hard, waterproof, smooth surfaces.
B) Glass;
- Has similar properties to Ceramics
- The atoms in glass are not arranged in a regular way to form crystals, so glass is transparent & not opaque
SC26a Choosing materials
Describe the properties of;
A) Polymers
B) Metals
A) Polymers;
- Can be molded into complex shapes
- Usually strong and chemically unreactive
- Poor electrical & thermal conductors
- Can be made softer by including plasticisers in its manufacturing.
B) Metals
- Strong, shiny and have high melting points
- Good electrical and thermal conductors
- They are malleable, and ductile
- Metals can be mixed together to form alloys, making them stronger.
SC26b Composite materials
A) State what is ment by a composite material
B) Describe how concrete is formed
A) A composite material is a mixture of 2 or more materials, combined to produce a material with improved properties.
B) Concrete is made by mixing cement, sand aggregate ( small stones and gravel ) and water together. As the concrete sets hard, chemical reactions happen that bond the solid components together.
- The sand and aggregate form the reinforcement of the concrete.
- The reinforcement is bonded together by cement, which is the matrix.
SC26b Composite materials
Describe what Laminates are
- Wood is a natural composite material consisting of cellulose fibres in a matrix of a polymer called lignin.
- It is stronger along the grain than it is across its grain. Plywood typically consists of odd numbers of thin sheets of wood, each glued at right angles to the sheet below.
SC26c Nanoparticles
Compare how big Nanoparticles are with cells & atoms.
- Nanoparticles typically consist of just a few hundred atoms, and are 1-100nm in size. Nanoparticles are larger than atoms ( e.g. an oxygen atom is 0.1nm in diameter ) and simple molecules
- Nanoparticles are smaller than cells ( typical bacterium is 1000nm long )
SC26c Nanoparticles
Describe;
A) The uses of Nanoparticles
B) The risks associated with Nanoparticles
A) Some uses are;
- Nanoparticulates are transparent while still absorbing ultraviolet radiation from rays from the sun. This makes it good for almost invisible sunscreen.
- The very large surface area to volume ratio of nanoparticulates makes them useful as catalysts. Stain-resistant clothes treated with nanoparticulate materials stay clean as the nanoparticles catalyse the breakdown of dirt.
B) Some risks are;
- Their small size allows them to be breathed in, or to pass through cell surface membrane.
- Their large surface area to volume ratios allow them to catalyse harmful reactions.
