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From Flashcardlet > C2 > Flashcards

C2 Flashcards

0
Q

What do you get at the negative electrode in electrolysis?

A

positively charged ions gain electrons. This is reduction, and you say that the ions have been reduced.Metal ions and hydrogen ions are positively charged. Whether you get the metal or hydrogen during electrolysis depends on the position of the metal in the reactivity series: The metal will be produced if it is less reactive than hydrogen
Hydrogen will be produced if the metal is more reactive than hydrogen

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1
Q

What happens if an electric current is passed through a concentrated sodium chloride solution

A

hydrogen gas forms at the negative electrode and chlorine gas forms at the positive electrode. A solution of sodium hydroxide forms.

You might have expected sodium metal to be deposited at the negative electrode. But sodium is too reactive for this to happen, so hydrogen is given off instead.

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2
Q

How would you purify copper in copper manufacture?

A

In this case, both electrodes are made from copper. The negative electrode gradually gets coated with pure copper as the positive electrode gradually disappears.

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3
Q

How would you electroplate with silver?

A

The object to be plated, such as a metal spoon, is connected to the negative terminal of the power supply. A piece of silver is connected to the positive terminal. The electrolyte is silver nitrate solution.

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4
Q

What needs to happen for electrolysis to work?

A

For electrolysis to work, the ions must be free to move. Ions are free to move when an ionic substance is dissolved in water or when melted.

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5
Q

What is the electrolyte?

A

A substance which in a solution will conduct an electric current.

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6
Q

How are half-equations balanced?

A

A half-equation is balanced by adding, or taking away, a number of electrons equal to the total number of charges on the ions in the equation.

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7
Q

How would you electroplate with copper?

A

The object to be plated, such as a metal pan, is connected to the negative terminal of the power supply. A piece of copper is connected to the positive terminal. The electrolyte is coppersulfate solution.

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8
Q

How do you write a half-equation?

A

Write the formulae of the reactant and product.
Adjust the number of ions, if needed.
Count the number of charges. Add enough electrons so that both sides have the same total number of charges.

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9
Q

How do you use electrolysis to electroplate objects?

A

The negative electrode should be the object that is to be electroplated
The positive electrode should be the metal that you want to coat the object with
The electrolyte should be a solution of the coating metal, such as its metal nitrate or sulfate

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10
Q

Why is aluminum so expensive?

A

largely because of the amount of electricity used up in the extraction process.

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11
Q

What does a half-equation show you?

A

A half-equation shows you what happens at one of the electrodes during electrolysis

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12
Q

What happens during the electrolysis of sodium chloride solution?

A

Hydrogen ions H+ (from the water) are discharged at the negative electrode as hydrogen gas, H2
Chloride ions Cl– are discharged at the positive electrode as chlorine gas, Cl2
Sodium ions Na+ and hydroxide ions OH– (from the water) stay behind - they form sodium hydroxide solution, NaOH

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13
Q

What happens during electrolysis?

A

Positively charged ions move to the negative electrode during electrolysis. They receive electrons and are reduced.
Negatively charged ions move to the positive electrode during electrolysis. They lose electrons and are oxidised.

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14
Q

What are electrons shown as in half-equations?

A

Electrons are shown as e- in half-equations

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15
Q

What happens during electrolysis in the extraction of aluminum?

A

Aluminium metal forms at the negative electrode and sinks to the bottom of the tank, where it is tapped off. Oxygen forms at the positive electrodes. This oxygen reacts with the carbon of the positive electrodes, forming carbon dioxide, and they gradually burn away. As a result, the positive electrodes have to be replaced frequently. This adds to the cost of the process.

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16
Q

What is electrolysis?

A

Electrolysis is the process by which ionic substances are decomposed (broken down) into simpler substances when an electric current is passed through them.

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17
Q

How is aluminum extracted before electrolysis?

A

The bauxite is purified to yield a white powder - aluminium oxide - from which aluminium can be extracted. The extraction is done by electrolysis. But first the aluminium oxide must be melted so that electricity can pass through it. Aluminium oxide has a very high melting point (over 2000°C) so it would be expensive to melt it. Instead, it is dissolved in moltencryolite - an aluminium compound with a lower melting point than aluminium oxide. The use of cryolite reduces some of the energy costs involved in extracting aluminium.

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18
Q

What are the uses of the three products of the electrolysis of concentrated sodium chloride solution

A

Hydrogen is used as a fuel and for making ammonia
Chlorine is used to kill bacteria in water, and to make bleach and plastics
Sodium hydroxide is used to make soap and bleach

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19
Q

What do you get at the positive electrode in electrolysis?

A

At the positive electrode, negatively charged ions lose electrons. This is oxidation, and you say that the ions have been oxidised.

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20
Q

What is the name of aluminum ore?

A

bauxite.

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21
Q

Are nitrates soluble?

A

Yes, all of them are.

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22
Q

What are alkalis?

A

Bases that dissolve in water are called alkalis. Alkaline solutions have a pH of more than 7. The stronger the alkali, the higher the pH number

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23
Q

What ions do acids produce when dissolved in water?

A

When acids dissolve in water they produce aqueous hydrogen ions, H+(aq). For example, looking at hydrochloric acid:

HCl(aq) → H+(aq) + Cl–(aq)

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24
Q

What are neutral solutions?

A

Neutral solutions have a pH of 7.

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25
Q

How do alkalis react with universal indicator?

A

They turn universal indicator paper dark blue or purple if they are strongly alkaline, and blue-green if they are weakly alkaline.

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26
Q

How do alkalis react with litmus paper?

A

Alkalis turn red litmus paper blue.

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27
Q

Are sulfates soluble?

A

Most are, except for Lead sulfate, barium sulfate

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28
Q

Are hydroxides soluble?

A

Most aren’t, except for Sodium hydroxide, potassium hydroxide

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29
Q

How do you make an insoluble salt?

A

You need to react two soluble salts together in a precipitation reaction. if you want to make an insoluble salt XY, mixing X nitrate with sodium Y will always work. The salt forms a precipitate. The precipitate can be filtered, washed with water on the filter paper, and then dried in an oven.

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30
Q

Are chlorides, bromides and iodides soluble?

A

Most are, except for Silver chloride, silver bromide, silver iodide, lead chloride, lead bromide, lead iodide

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31
Q

How do you crystallize salt solutions?

A

If the base dissolves in water, you need to add just enough acid to make a neutral solution. Check a small sample with universal indicator paper. Warm the salt solution to evaporate the water. You get larger crystals if you evaporate the water slowly.If the base does not dissolve in water, you need an extra step. You add the base to the acid until no more will dissolve and you have some base left over (called an excess). You filter the mixture to remove the excess base, then evaporate the water in the filtrate to leave the salt behind.

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32
Q

What are the four state symbols?

A

(s) means solid
(l) means liquid (not the same as dissolved in water - see below)
(g) means gas
(aq) means aqueous (dissolved in water)

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33
Q

How do acids react with universal indicator?

A

They turn universal indicator paper red if they are strongly acidic, and orange or yellow if they are weakly acidic.

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34
Q

Are carbonates soluble?

A

Most aren’t, except for Sodium carbonate, potassium carbonate

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35
Q

What are acids?

A

Substances with a pH of less than 7 are acids. The more strongly acidic the solution, the lower its pH number.

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36
Q

How can we predict the name of the salt formed?

A

The first part of the name is ‘ammonium’ if the base used is ammonia. Otherwise, it is the name of the metal in the base. The second part of the name comes from the acid used:

Chloride (if hydrochloric acid is used)
Nitrate (if nitric acid is used)
Sulfate (if sulfuric acid is used)
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37
Q

How can hydrogen be detected?

A

The hydrogen causes bubbling during the reaction, and can be detected using a lighted splint.

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38
Q

How do acids react with litmus paper?

A

Acidic solutions turn blue litmus paper red.

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39
Q

What ions do alkalis produce when dissolved in water?

A

When alkalis dissolve in water they produce aqueous hydroxide ions, OH–(aq). For example, looking at sodium hydroxide:

NaOH(aq) → Na+(aq) + OH–(aq)

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40
Q

What are the equations for when acids react with bases?

A

acid + metal oxide → salt + water

acid + metal hydroxide → salt + water

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41
Q

What is the neutralization equation?

A

H+(aq) + OH–(aq) → H2O(l)

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42
Q

What is the equation for when an acid reacts with a metal?

A

acid + metal → salt + hydrogen

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43
Q

What are bases?

A

Substances that can react with acids and neutralise them to make a salt and water are called bases. They are usually metal oxides or metal hydroxides.

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44
Q

What are the uses of precipitation reactions?

A

Precipitation reactions can be used to remove unwanted ions in solution. This is useful for treating drinking water and waste water.

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45
Q

How do neutral solutions react with litmus paper?

A

They do not change the colour of litmus paper

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46
Q

What is the equation of ammonia in a solution?

A

NH3(aq) + H2O(l) → NH4+(aq) + OH–(aq) (small numbers)

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47
Q

How do neutral solutions react with universal indicator?

A

they turn universal indicator paper green

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48
Q

Describe the reaction between anhydrous copper sulfate and water

A

Water is driven off from hydrated copper sulfate when it is heated, so the forward reaction is endothermic - energy must be transferred from the surroundings for it to happen. The backward reaction is exothermic - energy is transferred to the surroundings when it happens. This is easily observed. When water is added to anhydrous copper sulfate, enough heat is released to make the water bubble and boil.

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49
Q

What are some examples of endothermic reactions?

A

Electrolysis
The reaction between ethanoic acid and sodium carbonate
The thermal decomposition of calcium carbonate in a blast furnace

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50
Q

What are endothermic reactions?

A

These are reactions that take in energy from the surroundings. The energy is usually transferred as heat energy, causing the reaction mixture and its surroundings to get colder.

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51
Q

What are some examples of exothermic reactions?

A

Combustion (burning)
Many oxidation reactions, for example rusting
Neutralisation reactions between acids and alkalis

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52
Q

What do exothermic reactions do?

A

Exothermic reactions transfer energy to the surroundings. The energy is usually transferred as heat energy, causing the reaction mixture and its surroundings to become hotter.

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53
Q

What are some uses of exothermic reactions?

A

Exothermic reactions can be used for everyday purposes. For example, hand warmers and self-heating cans for drinks (such as coffee) use exothermic reactions.

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54
Q

If something decomposes, what is the reaction that happens?

A

endothermic - energy must be transferred from the surroundings for it to happen.

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55
Q

What are some uses of endothermic reactions?

A

Endothermic reactions can be used for everyday purposes. For example, certain sports injury cold packs use endothermic reactions.

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56
Q

Describe the decomposition of ammonium chloride

A

Ammonium chloride decomposes when it is heated, so the forward reaction is endothermic - energy must be transferred from the surroundings for it to happen. The backward reaction is exothermic - energy is transferred to the surroundings when it happens.

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57
Q

How are substances measured when calculating the rate of reaction?

A

The mass of a substance - solid, liquid or gas - is measured with a balance
The volume of a gas is usually measured with a gas syringe, or sometimes an upside down measuring cylinder or burette

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58
Q

Why does using a catalyst increase the rate of reaction?

A

Catalysts increase the rate of reaction without being used up. They do this by lowering the activation energy needed. With a catalyst, more collisions result in a reaction, so the rate of reaction increases. Different reactions need different catalysts.

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59
Q

What is activation energy?

A

The minimum energy needed for particles to react

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60
Q

Why does increasing the temperature increase the rate of reaction?

A

The reactant particles move more quickly
More particles have the activation energy or greater
The particles collide more often, and more of the collisions result in a reaction
The rate of reaction increases

61
Q

What needs to happen for a chemical reaction to occur?

A

For a chemical reaction to occur, the reactant particles must collide. Collisions with too little energy do not produce a reaction.The collision must have enough energy for the particles to react.

62
Q

What increases the rate of reaction?

A

The rate of a reaction increases if:

The temperature is increased
The concentration of a dissolved reactant is increased
The pressure of a reacting gas is increased
Solid reactants are broken into smaller pieces
A catalyst is used
63
Q

What are the two ways to measure the rate of reaction?

A

Measure the rate at which a reactant is used up
Measure the rate at which a product is formed
The method chosen depends on the reaction being studied. Sometimes it is easier to measure the change in the amount of a reactant that has been used up; sometimes it is easier to measure the change in the amount of product that has been produced.

64
Q

What is the formula for the rate of reaction?

A

Amount of reactant used or amount of product formed divided by the time taken.

65
Q

Why does breaking a solid reactant down into smaller pieces increase the rate of reaction?

A

Its surface area is increased
More particles are exposed to the other reactant
There is a greater chance of the particles colliding
The rate of reaction increases

66
Q

Why does increases the concentration of a dissolved reactant, or the pressure of a reacting gas increase the rate of reaction?

A

There are more reactant particles in the same volume
There is a greater chance of the particles colliding
The rate of reaction increases

67
Q

What is the reversible reaction involving white anhydrous copper(II) sulfate and blue hydrated copper(II) sulfate,

A

anhydrous copper(II) sulfate + water (double headed arrow) hydrated copper(II) sulfate

68
Q

How do you calculate the formula of a compound?

A

First, you find the masses of elements (usually given to you in the question.) And then you divide it by the relative atomic mass of each element. Then, divide each number by the smaller number produced in order to find the ratio. (If one of the numbers ends in 0.5, multiply all the numbers by 2 - this is because you cannot have half-atoms in a compound.)

69
Q

What is the relative atomic mass?

A

The relative atomic mass of an element (Ar) is an average value for the isotopes of the element. For example, the Ar for chlorine is 35.5 because it contains two different isotopes.

70
Q

What is the retention time?

A

The time taken for a substance to travel through the column is called its retention time.

71
Q

What does the conservation of mass mean?

A

Mass is never lost or gained in chemical reactions. We say that mass is conserved. In other words, the total mass of products at the end of the reaction is equal to the total mass of the reactants at the beginning.

72
Q

Why is it not always possible in practice to get the entire calculated amount of product?

A

Reversible reactions may not go to completion
Some product may be lost when it is removed from the reaction mixture
Some of the reactants may react in an unexpected way

73
Q

What are the advantages of instrumental methods of analysis?

A

Some are suitable for detecting and identifying elements, while others are better suited to compounds. In general, instrumental methods of analysis are:

Fast
Accurate (they reliably identify elements and compounds)
Sensitive (they can detect very small amounts of a substance in a small amount of sample)
74
Q

What is the actual yield?

A

The actual yield is the mass of product you get when you actually do the reaction

75
Q

Why does paper chromotography work?

A

Paper chromatography works because some of the coloured substances are better at dissolving in the liquid than they are at bonding with the paper, so they travel further up the paper.

76
Q

What is paper chromotopraghy used for?

A

Paper chromatography is used to analyse coloured substances

77
Q

How do you work out the relative formula mass?

A

To find the relative formula mass of a substance, you just add together the relative atomic mass values for all the atoms in its formula.

78
Q

How would you work out how much of a reactant/product you can make? For example: If we have 50g of CaCO3, how much CaO can we make?

A

If you have a balanced equation for a reaction, you can calculate the masses of reactants and products.
First, work out the Mr values for the two compounds:

Mr of CaCO3 is 40 + 12 + 16 + 16 + 16 = 100

Mr of CaO is 40 + 16 = 56

This means that 100 g of CaCO3 would yield 56 g of CaO in this reaction. In the question we are told we have only half of that amount of CaCO3, 50 g. So we will get half the amount of CaO, 28 g.

So the mass of CaO we can make = 28 g

79
Q

What is the method of paper chromotography?

A

Samples of each substances are spotted onto a pencil line drawn on a sheet of chromotography paper. The paper is suspended in a container with a shallow layer of a suitable solvent or mixture of solvents in it. It is important that the solvent level is below the line with the spots on it. The container should be covered. As the solvent slowly travels up the paper, the different components of the ink mixtures travel at different rates and the mixtures are separated into different coloured spots.

80
Q

What is the test for the presence of water?

A

The reaction between anhydrous copper(II) sulfate and water is used as a test for water. The white solid turns blue in the presence of water.

81
Q

How do you work out the percentage of mass of an element in a compound?

A

Find the relative atomic mass of the element you want ( if there is more than one atom of the element in the compound, you need to multiply your answer by the number of atoms.) Then divide this number by the relative formula mass of the compound, and then times by 100 to get the percentage.

82
Q

How does gas chromatography work?

A

The sample is dissolved in a solvent, then injected into one end of the column.
An unreactive gas - usually nitrogen - carries the sample through the column.
Different substances in the sample travel through the column at different speeds and so become separated from each other.
The separated substances leave the column one after the other. As they leave, they are detected by a detector.

83
Q

What does the conservation of mass help you work out?

A

This fact allows you to work out the mass of one substance in a reaction if the masses of the other substances are known. It also helps you calculate the theoretical mass of product expected in a chemical reaction

84
Q

What is the symbol for relative atomic mass?

A

Ar (small r)

85
Q

What is one mole of a substance?

A

The relative formula mass of a substance - shown in grams - is called one mole of that substance. For example, the Mr of carbon monoxide (CO) is 28. This means that one mole of carbon monoxide has a mass of 28 g. You should be able to see that:

14 g of carbon monoxide contains 14 ÷ 28 = 0.5 moles
56 g of carbon monoxide contains 56 ÷ 28 = 2 moles
86
Q

What are instrumental methods of analysis?

A

Instrumental methods of analysis rely on machines. There are several different types of instrumental analysis.

87
Q

Why is it important that the container is covered?

A

The reason for covering the container is to make sure that the atmosphere in the beaker is saturated with solvent vapour. Saturating the atmosphere in the beaker with vapour stops the solvent from evaporating as it rises up the paper.

88
Q

What do you work out the relative atomic mass (chlorine is provided as an example)?

A

75 per cent of chlorine atoms are 35Cl and 25 per cent of chlorine atoms are 37Cl.

This means that in 100 chlorine atoms, 75 will be 35Cl and 25 will be 37Cl.

The total Ar for these chlorine atoms will be (75 × 35) + (25 × 37) = 2625 + 925 = 3550.

So the average Ar for chlorine is 3550 ÷ 100 = 35.5.

89
Q

What is chromatography used for?

A

Chromatography is used to separate mixtures of substances into their components.

90
Q

What does the mass spectrometer do?

A

The mass spectrometer can be used to identify substances quickly and accurately, and in very small amounts. It can also provide the relative formula mass of the substances separated by gas chromatography. If a GC machine is linked to a mass spectrometer, this combined GC-MS method allows the separated substances leaving the column of the GC machine to be detected.

91
Q

What does Gas chromatography do?

A

Gas chromatography allows a mixture of compounds to be separated.

92
Q

What are isotopes?

A

Atoms of the same element with different numbers of neutrons are called isotopes. The different isotopes of an element have identical chemical properties. However, some isotopes are radioactive.

93
Q

What does the graph produced by the detector show?

A

A detector produces a graph where each substance is represented by a peak:

The number of peaks shows the number of compounds present in the sample
The position of each peak shows the retention time for each compound
94
Q

What does ammonium chloride break down to form?

A

ammonium chloride (a white solid) can break down to form ammonia and hydrogen chloride. It also shows that ammonia and hydrogen chloride (colourless gases) can react to form ammonium chloride again.

95
Q

What does a gas chromatography machine consist of?

A

The GC machine consists of a long glass tube packed with a powdered solid material, which is fitted into an oven. The tube is called the column, even though it is usually wound into a coil so that it fits into the oven.

96
Q

How do you calculate the percentage yield?

A

percentage yield = (actual mass of product) ÷ (theoretical mass of product) × 100

97
Q

What is the standard atom?

A

The mass of the 12C (upper 12) isotope is the ‘standard atom’ that the masses of other atoms are compared to. The Ar of 12C is defined as 12. This is also Avogadro’s number, which is the amount of amounts in 12 grams of carbon-12, which is 6.02x10^23

98
Q

What is the molecular ion peak?

A

The peak furthest to the right in a mass spectrum is called the ‘molecular ion peak’. Its relative mass is the relative formula mass of the substance being analysed.

99
Q

What is the theoretical yield?

A

The theoretical yield is the maximum theoretical mass of product in a reaction (calculated using the idea of conservation of mass)

100
Q

What is the percentage yield?

A

The percentage yield is the ratio of actual mass of products obtained compared with the maximum theoretical mass.

101
Q

How do we show a reversible reaction?

A

When writing chemical equations for reversible reactions, we do not use the usual one-way arrow. Instead, we use two arrows, each with just half an arrowhead - the top one pointing right, and the bottom one pointing left.

102
Q

What will all atoms of a particular element have the same?

A

The atoms of a particular element will all have the same number of protons. Their atomic number will be the same.

103
Q

What is the symbol for relative formula mass?

A

Mr (small r)

104
Q

What is the name of the ion formed by fluorine?

A

fluoride.

105
Q

What is group 1 of the periodic table called?

A

The alkali metals

106
Q

Why are alloys harder than pure metals?

A

Alloys contain atoms of different sizes. These different sizes distort the regular arrangements of atoms. This makes it more difficult for the layers to slide over each other, so alloys are harder than the pure metal.

107
Q

What is a covalent bond?

A

A covalent bond forms when two non-metal atoms share a pair of electrons. The electrons involved are in the highest occupied energy levels - or outer shells - of the atoms. An atom that shares one or more of its electrons will complete its highest occupied energy level.

108
Q

What are the properties of ionic compounds?

A

Ionic bonds are very strong so a lot of energy is needed to break them. Ionic compounds contain many of these strong bonds so they have high melting and boiling points.Ionic compounds conduct electricity when they are dissolved in water or when they are melted. This is because their ions are free to move and carry the current. However, ionic compounds do not conduct electricity when they are solid. This is because their ions cannot move around in their lattice structure.

109
Q

What is graphite and what are its properties?

A

Graphite is a form of carbon in which the carbon atoms form layers. Each carbon atom in a layer is joined to only three other carbon atoms.The layers can slide over each other because there are no covalent bonds between them. This makes graphite much softer than diamond. It is used in pencils and as a lubricant. Graphite conducts electricity

110
Q

What are thermosofting polymers?

A

Thermosoftening polymers soften when heated and can be shaped when hot. The shape will harden when it is cooled, but can be reshaped when heated up again. Poly(ethene) is a thermosoftening polymer. Its tangled polymer chains can uncoil and slide past each other, making it a flexible material.

111
Q

What is the formula of iron (III) hydroxide and why is it written like that?

A

Fe(OH)3 is the formula for iron(III) hydroxide.The formula is written like this because the oxygen and hydrogen atom often act together.

112
Q

How can you work out the number of covalent bonds a chemical can make?

A

There is a quick way to work out how many covalent bonds an element will form. The number of covalent bonds is equal to eight minus the group number

113
Q

What is diamond and what are its properties?

A

Diamond is a form of carbon in which each carbon atom is joined to four other carbon atoms, forming a giant covalent structure. As a result, diamond is very hard and has a high melting point. It does not conduct electricity.

114
Q

What ions do non-metal atoms form?

A

Non-metal atoms gain an electron, or electrons, from another atom to become negatively charged ions

115
Q

What is the reaction between calcium and chlorine?

A

calcium + chlorine → calcium chloride

116
Q

What happens during ionic bonding?

A

When metals react with non-metals, electrons are transferred from the metal atoms to the non-metal atoms, forming ions. The resulting compound is called an ionic compound. There is a strong electrostatic force of attraction between these oppositely charged ions, called an ionic bond.

117
Q

What are the properties of substances formed by covalent bonds?

A

Covalent bonds are strong - a lot of energy is needed to break them. Substances with covalent bonds often form molecules with low melting and boiling points, such as hydrogen and water.

118
Q

How many covalent bonds can hydrogen, chlorine, oxygen, nitrogen and carbon form?

A

Hydrogen and chlorine can each form one covalent bond, oxygen two bonds, nitrogen three, while carbon can form four bonds.

119
Q

Drawing dot and cross diagrams

A

You know how to do this, but just remember that the two ions need to balance out. So, if one ion has a 2- charge, and the other has a + charge, than you need two +’s.

120
Q

What are nanotubes?

A

The tube fullerenes are called nanotubes.

121
Q

What can nanotubes be used for?

A

These are very strong. They are useful in reinforcing structures where lightness and strength are needed - for example, in tennis racket frames.

122
Q

How do you work out the formula of a compound?

A

The formula of a compound can be worked out if the ions in it are known. For example, the compound formed from Na+ and SO42- will consist of two Na+ ions to every one SO42- ion so that the compound is neutral overall. The formula is therefore Na2SO4.

123
Q

What is the structures of metal?

A

Metals form giant structures in which electrons in the outer shells of the metal atoms are free to move. The metallic bond is the force of attraction between these free electrons and metal ions. Metallic bonds are strong, so metals can maintain a regular structure and usually have high melting and boiling points.

124
Q

What is the chemical formula of ammonia?

A

NH3 (little 3)

125
Q

What are simple molecules?

A

These contain only a few atoms held together by strong covalent bonds.

126
Q

What are the properties of simple molecules?

A

Low melting and boiling points - This is because the weak intermolecular forces break down easily.
Non-conductive - Substances with a simple molecular structure do not conduct electricity. This is because they do not have any free electrons or an overall electric charge.

127
Q

What is the chemical formula of sodium chloride?

A

NaCl

128
Q

What are the properties of metals?

A

Metals are malleable - they can be bent and shaped. This is because they consist of layers of atoms. These layers can slide over one another when the metal is bent, hammered or pressed. Metals are good conductors of electricity and heat. This is because the free electrons can move throughout the metal.

129
Q

Name three differences between HDPE and LDPE?

A

There are many branches on the polymers of LDPE, but not on HDPE. LDPE is quite weak, whereas HDPE is quite strong. The maximum usable temperature for LDPE is 85, and for HDPE it is 120

130
Q

What may nanoscience lead to the development of?

A

New catalysts
New coatings
New computers
Stronger and lighter building materials
Sensors that detect individual substances in tiny amounts
New cosmetics such as sun screen and deodorants.

131
Q

What is an ion?

A

Ions are electrically charged particles formed when atoms lose or gain electrons.

132
Q

What can fullerenes be used for?

A

Fullerenes may be used for drug delivery systems in the body, in lubricants and as catalysts.

133
Q

What is the chemical formula of hydrogen chloride?

A

HCl

134
Q

What are alloys?

A

An alloy is a mixture of two or more elements, where at least one element is a metal. Many alloys are mixtures of two or more metals.

135
Q

What is group 7 of the periodic table called?

A

the halogens.

136
Q

What is it that breaks down in simple molecules?

A

When one of these substances melts or boils, it is these weak ‘intermolecular forces’ that break, not the strong covalent bonds.

137
Q

What are fullerenes?

A

These are cages and tubes with different number of carbon atoms. Buckminsterfullerene is one type of fullerene. Its molecules are spherical and contain 60 carbon atoms.

138
Q

How large are nanoparticles?

A

Nanoparticles range in size from about 100 nm down to about 1 nm. They are typically the size of small molecules, and far too small to see with a microscope.

139
Q

What is the reaction between magnesium and oxygen?

A

magnesium + oxygen → magnesium oxide

140
Q

What is the reaction between sodium and chlorine?

A

sodium + chlorine → sodium chloride

141
Q

What is a nanometre?

A

A nanometre, 1 nm, is one billionth of a metre (or a millionth of a millimetre).

142
Q

What are macromolecules?

A

Macromolecules have giant covalent structures. They contain a lot of non-metal atoms, each joined to adjacent atoms by covalent bonds. Their atoms are arranged into giant lattices, which are strong structures because of the many bonds involved.

143
Q

What are shape-memory alloys and what are there uses?

A

Shape memory alloys can return to their original shape after being bent or twisted. Nitinol is a shape memory alloy made from nickel and titanium. It is used in dental braces and spectacle frames.

144
Q

What are thermosetting polymers?

A

Thermosetting polymers have different properties to thermosoftening polymers. Once moulded, they do not soften when heated and they cannot be reshaped. Vulcanised rubber is a thermoset used to make tyres. Its polymer chains are joined together by cross-links, so they cannot slide past each other easily

145
Q

What is the chemical formula of methane?

A

CH4 (little 4)

146
Q

What are the properties of nanoparticles?

A

Nanoparticles have a very large surface area compared with their volume, so they are often able to react very quickly. This makes them useful as catalysts to speed up reactions.Nanoparticles also have different properties to the same substance in normal-sized pieces.

147
Q

What ions do metal atoms form?

A

Metal atoms lose the electron, or electrons, in their highest energy level and become positively charged ions

148
Q

What is Silica, and what are its properties?

A

Silica, which is found in sand, has a similar structure to diamond. It is also hard and has a high melting point. However, it contains silicon and oxygen atoms instead of carbon atoms.

149
Q

How do you draw the chemical structure of a double and triple covalent bond and what are they?

A

a double covalent bond - meaning they have two shared pairs of electrons - or a triple covalent bond - three shared pairs of electrons. A double covalent bond is shown by a double line, and a triple bond by a triple line.

150
Q

What are the properties of graphite?

A

Graphite is a good conductor of heat and electricity. This is because, like metals, graphite contains delocalised electrons. These electrons are free to move through the structure of the graphite.Graphite is soft and slippery because there are only weak intermolecular forces between its layers.

From Flashcardlet (66 decks)

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