Unit 3 - Lesson 12: Tests for Water and Gas Flashcards
What do humans need to survive?
H2O (water), O2 (oxygen), CO2 (carbon dioxide), and N (nitrogen)
What do plants produce for us?
O2 (oxygen)
How can we test a sample of ice to see if it has water?
Add anhydrous copper (II) sulfate to a sample of the ice. If it has water, it will turn blue. If it stays white, it doesn’t have water.
https://i.pinimg.com/736x/e8/4a/0a/e84a0a5e86eb06192e19f8058d722c23.jpg
What is an endothermic reaction?
An endothermic reaction is one which takes in energy from the surroundings, usually in the form of heat and usually shown by a fall in temperature of the surroundings.
What is an exothermic reaction?
An exothermic reaction is one which gives out energy to the surroundings, usually in the form of heat and usually shown by a rise in temperature of the surroundings.
What is the meaning of anhydrous?
A substance is anhydrous if it contains no water.
What kind of reaction is adding water?
An exothermic reaction. It releases heat energy.
What kind of reaction is removing water?
An endothermic reaction because to take away the water, you need to heat it.
What substance can we use to test an atmosphere for CO2?
Limewater. If it turns cloudy, CO2 is present.
How can we test for oxygen?
How can we test for hydrogen?
Oxygen, in a test tube, will relight a glowing splint.
Hydrogen, in a test tube, will make a lit splint go pop!
State the names and proportions of gases we’d need on Mars to be just like Earth.
Nitrogen - 78%
Oxygen - 21%
Argon - 0.9%
Carbon Dioxide - 0.04%
Describe 2 practicals that could be used to investigate the proportion of oxygen in the atmosphere.
Practical 1 → Finding the proportion of oxygen in an air sample using the metal ‘Iron’ (Fe).
Firstly, soak iron wool in acetic acid.
Secondly, push the wool into a measuring cylinder.
Thirdly, invert this into a beaker of water.
Fourthly, record the starting position of the water.
Fifthly, the water in the measuring cylinder will rise as oxygen enters to react with the Fe (iron).
Sixthly, leave for one week or until it stops rising; this is the final volume of air.
Practical 2 → Finding the proportion of oxygen in an air sample using the non-metal ‘Phosphorus’ (P).
Firstly, place phosphorus in a tube and attach a glass syringe at either end.
Secondly, make sure one of the syringes is filled with air and the other empty.
Thirdly, heat the phosphorus and use the syringes to pass air over it.
Fourthly, the air will decrease as oxygen is used up. Measure starting and final volumes using the scales on the syringes.
State the formula used to calculate the percentage of oxygen in a sample.
Percentage of oxygen = Start volume - Final volume/Start volume x 100
(% of Oxygen = Start volume (subtract) Final volume (divided by) Start volume (multiplied by) 100)
Mars already has an atmosphere rich in CO2. State an experiment you could do to make CO2 in a planet with no CO2.
- What apparatus is needed?
- What is the chemical equation?
- What is the method?
You could use thermal decomposition to make CO2. For example:
Copper (II) carbonate →(heat) metal oxide + carbon dioxide
The apparatus needed: clamp stand, delivery tube, clamp, test tubes, metal carbonate, Bunsen burner, and limewater.
Firstly, heat copper (II) carbonate. It’s a green powder.
Secondly, copper (II) oxide will be made, which is black.
Thirdly, the CO2 will turn the limewater cloudy.
What could happen to the temperature of Mars if there was too much CO2?
The temperature would increase.
A scientist finds water trapped in a large salt plains on a new planet. State the name of a salt with water molecules incorporated into its lattice. Choose one option from a - d.
a) Anhydrous
b) Hydrated
c) Crucible
d) Oxidised
b) Hydrated
(Relating to Q16) State the name of the water trapped in the salt. Choose one option from a - d.
a) Water of crystallisation
b) Anhydrous water
c) Water vapour
d) Evaporated residue
a) Water of crystallisation
How many moles of water are there in these salts?
a) CuSO4.4H2O
b) MgSO4.5H2O
a) 4
b) 5
Find the X in BaCl2.XH2O using the results table below.
Mass of crucible | 30g
Mass of crucible + BaCl2.XH2O | 32.44g
Mass of crucible + BaCl2 | 32.08g
BaCl2.2H2O.
Explanation:
Step 1: Mass of hydrated salt + anhydrous salt
32.44 - 30 = 2.44
32.08 - 30 = 2.08
2.44 + 2.08 = 4.52
Step 2: Number of moles of water lost = mass / Mr
32.44 - 32.08 / (1x2) + 16
= 0.36 / 18
= 0.02 mol
Step 3: Number of moles of anhydrous salt made = mass / Mr
32.08 - 30 / 137 + (35.5 x 2)
= 2.08 / 208
= 0.01 mol
Step 4: Work out the ratio of moles of anhydrous salt to moles of water
Anhydrous salt : water
0.01 : 0.02
1 : 2
Therefore, BaCl2.2H2O
You take a sample of air after 30 years terraforming on Mars. You take it back to your on-site lab for testing.
a) Describe a test for CO2.
b) Describe a test for ammonia.
c) Describe a test for hydrogen gas.
a) Pass a sample of air through limewater. If it turns cloudy, CO2 is present.
b) The simplest test is the presence of a bad smell. However, because ammonia is a danger to your eyes, nose, throat & respiratory system, it’s safer to check for the gas with damp red litmus paper. If it turns blue, ammonium (NH^4+) is present.
c) Place a burning splint near the gas and it’ll make a pop sound.
You want to test the ice caps of Mars for water. Describe the test to use.
Add anhydrous copper (II) sulfate (CuSO4) to a sample of the melted ice. If the CuSO4 turns blue, water is present.
State the boiling point of pure water.
100 degrees Celsius
State the freezing point of pure water.
0 degrees Celsius
What change of state is occurring at the boiling point of pure water?
Liquid to gas
Give the name of the process of turning a solid to a gas.
Sublimation.
Describe the particles in a water ice cap & compare this to the particles in a melted liquid water.
The ice is solid, so the particles can only vibrate in a fixed position (because they have strong forces of attraction between them). They have low energy and are arranged in a lattice structure.
Particles in the liquid water can move randomly due to their weak forces of attraction. They have more energy than the particles in the solid.
Write a method for a rest for chlorine that can be pinned up in your lab for newcomers.
Use damp litmus paper or universal indicator paper. If Cl2 is present in a sample, it’ll bleach/turn white. If blue litmus paper is used, it’ll turn red before white.
Give an example of an exothermic reaction that could be used to test for water.
Add water (H2O) to anhydrous copper (II) sulfate (CuSO4)
Steel is stronger than iron and does not rust like iron. Name two ways to prevent rusting.
- Barrier method → painting, coating in plastic or smearing in oil/grease to prevent air and water reaching the iron.
- Sacrificial method → coat in or add a bolt of a more reactive metal than iron.
- Sacrificial method → galvanise; coat the iron in zinc (Zn) which is more reactive.
How will bolting some Mg onto a piece of Fe prevent rusting?
Mg is more reactive than Fe, so it’ll react with the air and water instead of the Fe doing so.
Are covalent bonds between non-metals and non-metals OR metals?
Non-metals
Is a covalent bond the loss or gain of electrons OR sharing of electrons?
Sharing of electrons
Is there a strong OR weak electrostatic attraction between the negatively charged shared electrons and the positively charged nuclei of the atoms involved?
Strong
How many electrons are shared in a single covalent bond?
2
How many double bonds does Ethene have?
1
What is the chemical formula of Fullerene?
C60
What is the chemical formula of chloromethane & provide an image of the covalent compound diagram for chloromethane.
CH3Cl
https://i.pinimg.com/736x/ab/8d/e9/ab8de99ba0cc27cc1b721840eb5b8476.jpg
Draw a dot cross diagram for H2O.
https://i.pinimg.com/736x/e0/0c/26/e00c262d8d33fec1dc3bd2c395c34cec.jpg
Draw a dot cross diagram for CO2.
blob:https://uk.pinterest.com/52c6c0d1-695e-4a76-9fc1-8e5ead22a6df
Draw a dot cross diagram for HCl.
blob:https://uk.pinterest.com/6dbbc773-88d8-47ff-a484-70b6979fdb40
Describe the structure of diamond.
Diamond is made only from carbon atoms covalently bonded in a rigid lattice structure. Each carbon atom is bonded with 4 other carbon atoms.
Are ionic bonds between metals and non-metals OR metals?
Non-Metals
Is an ionic bond the loss or gain OR sharing of electrons?
Loss or gain
Will group 1, 2 & 3 elements lose OR gain electrons to form positive ions?
Lose
Will group 5, 6 & 7 elements lose OR gain electrons to form negative ions?
Gain
What do square brackets around an electron configuration diagram tell us about its contents? Is it an ion OR a compound?
An ion.
State the chemical ionic formula (including charge) of the ion formed from each compound.
a) Sulfate
b) Nitrate
c) Hydroxide
d) Ammonium
a) SO4^2-
b) NO3^-
c) OH^-
d) NH4^+
Draw a dot cross diagram for the ionic compound: Magnesium Oxide (MgO)
https://i.pinimg.com/736x/4f/68/60/4f6860334859e1fc4617554ac675082e.jpg
Draw a dot cross diagram for the ionic compound: Lithium Sulfide (Li2S)
https://i.pinimg.com/736x/2b/e4/7d/2be47da5c032f01c4aa2d61b5721c825.jpg
Ionic compounds aren’t electrical conductors when they’re solid. What would you have to do to the solid to make it electrically conductive?
Melt it. I.E, put in molten state or dissolve in water to make an aqueous solution.
Write out the ionic formula for these compounds:
a) Calcium Oxide
b) Potassium Chloride
a) CaO
b) KCl
