1Matter
- All matter is composed of atoms and has mass.
2What is a chemical reaction?
A process where atoms are rearranged to form new substances.
3What are reactants?
The substances present at the start of a chemical reaction.
4What are products?
The substances formed by a chemical reaction.
5What is a word equation?
A representation of a chemical reaction using words.
6What is a chemical equation?
A representation of a chemical reaction using chemical formulas and symbols.
7What does the law of conservation of mass state?
The total mass of the reactants is equal to the total mass of the products.
8Why must chemical equations be balanced?
To obey the law of conservation of mass.
9What are subscripts in a chemical formula?
Numbers showing the number of atoms of an element in a compound.
10Can subscripts be changed when balancing equations?
No.
11What are coefficients in a chemical equation?
Numbers placed in front of formulas to show the number of molecules or formula units.
12What does (s) mean in a chemical equation?
Solid.
13What does (l) mean in a chemical equation?
Liquid.
14What does (g) mean in a chemical equation?
Gas.
15What does (aq) mean in a chemical equation?
Aqueous or dissolved in water.
16What type of reaction is A + B → AB?
Synthesis reaction.
17What is a synthesis reaction?
A reaction where simpler substances combine to form a more complex product.
18What type of reaction is AB → A + B?
Decomposition reaction.
19What is a decomposition reaction?
A reaction where a compound breaks down into simpler substances.
20What is a neutralisation reaction?
A reaction between an acid and a base producing salt and water.
21What is produced when a metal carbonate reacts with an acid?
Salt, carbon dioxide, and water.
22What is the general formula for a metal reacting with an acid?
Metal + Acid → Salt + Hydrogen Gas
23What gas is produced when acids react with metals?
Hydrogen gas.
24How is hydrogen gas identified?
Using the pop test with a lit match.
25What is corrosion?
The gradual destruction of materials by chemical reactions with the environment.
26What is rusting?
Iron reacting with oxygen and water to form iron oxide.
27How can corrosion be prevented?
By methods such as galvanising.
28What is combustion?
A rapid reaction between a fuel and oxygen producing heat and light.
29What is a fuel?
A substance that releases useful energy quickly and controllably.
30What are hydrocarbons?
Compounds containing hydrogen and carbon.
31What are the products of complete combustion?
Carbon dioxide and water.
32What are the products of incomplete combustion?
Carbon monoxide, water, and sometimes soot.
33What is a precipitation reaction?
A reaction where an insoluble solid forms from two solutions.
34What is a precipitate?
An insoluble solid formed in a reaction.
35What are spectator ions?
Ions that do not take part in the reaction.
36What are exothermic reactions?
Reactions that release energy into the surroundings.
37Give an example of an exothermic reaction.
Combustion.
38What are endothermic reactions?
Reactions that absorb energy from the surroundings.
39Give an example of an endothermic reaction.
Photosynthesis.
40What is reaction rate?
The speed at which a reaction occurs.
41What does collision theory state?
Particles must collide with enough energy and correct orientation to react.
42How does temperature affect reaction rate?
Higher temperature increases reaction rate.
43How does concentration affect reaction rate?
Higher concentration increases reaction rate.
44How does surface area affect reaction rate?
Larger surface area increases reaction rate.
45How does stirring affect reaction rate?
It increases contact between reactants.
46What is a catalyst?
A substance that increases reaction rate without being consumed.
47What is an enzyme?
A biological catalyst.
48What are the properties of acids?
Sour, corrosive, and contain hydrogen ions.
49What pH do acids have?
Less than 7.
50Give an example of an acid.
Hydrochloric acid.
51What are the properties of bases?
Bitter, slippery, and react with acids.
52What pH do bases have?
Greater than 7.
53What is an alkali?
A base that dissolves in water.
54Give an example of a base.
Sodium hydroxide.
55What is neutralisation?
The reaction between an acid and a base.
56What are indicators?
Substances that change colour in acids or bases.
57What does pH 7 represent?
Neutral.
58What is molar mass?
The mass of one mole of a substance in g/mol.
59What is a mole?
A unit representing (6.022 \times 10^{23}) particles.
60What is Avogadro’s number?
(6.022 \times 10^{23})
61What is the formula for calculating moles?
(n = \frac{m}{MM})
62What is stoichiometry?
The quantitative relationship between reactants and products in a reaction.
63What is the mole ratio in (2H_2 + O_2 ightarrow 2H_2O)?
1:1 between (H_2) and (H_2O)
64What is the balanced equation for water formation?
(2H_2 + O_2 ightarrow 2H_2O)
65What is the balanced equation for methane combustion?
(CH_4 + 2O_2 ightarrow CO_2 + 2H_2O)
66What is the balanced equation for rusting iron?
(4Fe + 3O_2 ightarrow 2Fe_2O_3)
67What is the balanced equation for magnesium reacting with hydrochloric acid?
(Mg + 2HCl ightarrow MgCl_2 + H_2)
68What is the balanced equation for neutralisation of HCl and NaOH?
(HCl + NaOH ightarrow NaCl + H_2O)
69What is the balanced equation for thermal decomposition of calcium carbonate?
(CaCO_3 ightarrow CaO + CO_2)
70What is the balanced equation for electrolysis of water?
(2H_2O ightarrow 2H_2 + O_2)
71What colour is lead iodide precipitate?
Yellow.
72What happens during bond breaking?
Energy is absorbed.
73What happens during bond formation?
Energy is released.
74Why do powdered solids react faster than large chunks?
They have a larger surface area.
75Why do catalysts increase reaction rate?
They lower activation energy.
76What is activation energy?
The minimum energy needed for a reaction to occur.
77What are solubility rules used for?
Predicting whether a precipitate will form.
78What is complete combustion?
Combustion with excess oxygen.
79What is incomplete combustion?
Combustion with limited oxygen.
80What is the general formula for complete combustion?
Hydrocarbon + Oxygen → Carbon Dioxide + Water
81What is the general formula for incomplete combustion?
Hydrocarbon + Oxygen → Carbon Monoxide + Water
82Why is the law of conservation of mass true in chemical reactions?
Atoms are rearranged but not created or destroyed.
83Why can mass appear to change in an open system?
Gases may escape or enter the system.
84What must be equal on both sides of a balanced equation?
The number of each type of atom.
85Why are coefficients changed instead of subscripts when balancing equations?
Changing subscripts changes the substance itself.
86What does the coefficient 2 mean in (2H_2O)?
There are two molecules of water.
87What does the subscript 2 mean in (H_2O)?
There are two hydrogen atoms.
88What happens during a synthesis reaction?
Smaller substances combine into a larger compound.
89What usually provides energy for decomposition reactions?
Heat or electricity.
90What is produced in all neutralisation reactions?
Salt and water.
91Why is hydrogen gas dangerous?
It is highly flammable.
92What evidence shows a chemical reaction has occurred?
Colour change, effervescence (gas formation), luminescence, temperature change, or precipitate formation.
93Why does rusting need water and oxygen?
Both are required for iron to oxidise.
94What metal is commonly used for galvanising?
Zinc.
95Why is zinc used in galvanising?
It protects iron from oxygen and water.
96What is oxidation?
A reaction involving oxygen or loss of electrons.
97Why does combustion release energy?
New bonds formed release more energy than is needed to break old bonds.
98What causes incomplete combustion?
A limited supply of oxygen.
99Why is carbon monoxide dangerous?
It is poisonous and reduces oxygen transport in blood.
100What is soot?
Solid carbon formed during incomplete combustion.
101Why are hydrocarbons commonly used as fuels?
They release large amounts of energy.
102What is a double displacement reaction?
A reaction where ions swap partners.
103How can you identify a precipitation reaction?
An insoluble solid forms.
104What is the precipitate in (Pb(NO_3)_2 + 2KI ightarrow PbI_2 + 2KNO_3)?
Lead iodide.
105Why are spectator ions called spectator ions?
They do not participate in the reaction.
106What happens to the surroundings in an exothermic reaction?
They become warmer.
107What happens to the surroundings in an endothermic reaction?
They become cooler.
108Why do endothermic reactions feel cold?
They absorb heat from the surroundings.
109Why do exothermic reactions feel warm?
They release heat into the surroundings.
110What is the relationship between temperature and particle movement?
Higher temperature increases particle movement.
111Why do higher temperatures increase reaction rate?
Higher temperatures increase reaction rate because particles gain more kinetic energy, causing them to move faster and collide more often. More particles also have enough energy to overcome the activation energy, so a greater number of collisions are successful and produce a reaction.
112Why does increasing concentration increase reaction rate?
There are more particles available to collide.
113Why does increasing surface area increase reaction rate?
More particles are exposed for collisions.
114How does stirring speed up reactions?
It increases contact between reactants.
115What happens to a catalyst during a reaction?
It remains chemically unchanged.
116Why are enzymes important in living organisms?
They speed up biological reactions.
117What pH range is acidic?
Below 7.
118What pH range is basic?
Above 7.
120What colour does universal indicator show in strong acids?
Red.
121What colour does universal indicator show in strong bases?
Purple.
122Why are acids corrosive?
They react chemically with materials.
123What ion do acids release in water?
Hydrogen ions (H+).
124What ion do bases release in water?
Hydroxide ions.
125Why are alkalis different from other bases?
They dissolve in water.
126What is the formula for sulfuric acid?
(H_2SO_4)
127What is the formula for hydrochloric acid?
(HCl)
128What is the formula for sodium hydroxide?
(NaOH)
129What is the formula for calcium hydroxide?
(Ca(OH)_2)
130What is the formula for ammonia?
(NH_3)
131How is molar mass calculated?
By adding the atomic masses of all atoms in a formula.
132What unit is used for molar mass?
g/mol.
133What does the mole measure?
The amount of particles in a substance.
134How many particles are in one mole?
(6.022 \times 10^{23})
135What does stoichiometry use to calculate substance amounts?
Balanced chemical equations.
136Why are mole ratios important?
They show the quantitative relationship between reactants and products.
137What is the mole ratio between (CH_4) and (CO_2) in methane combustion?
1:1.
138What is the first step in stoichiometry problems?
Write and balance the equation.
139What is the second step in stoichiometry problems?
Convert known quantities into moles.
140What is the final step in mass-to-mass stoichiometry?
Convert moles back into mass.
141Why must equations be balanced before stoichiometry calculations?
To get correct mole ratios.
142What is the molar mass of (CO_2)?
44.01 g/mol.
143What is the molar mass of (CH_4)?
16.05 g/mol.
144What gas is formed during complete combustion?
Carbon dioxide.
145What gas is formed during incomplete combustion?
Carbon monoxide.
146What is produced when hydrogen burns in oxygen?
Water.
147What happens if reactant particles collide without enough energy?
No reaction occurs.
148What is the correct orientation in collision theory?
Particles must collide in a suitable arrangement to react.
149Why do powders react faster than lumps?
Powders have greater surface area.
150What is an aqueous solution?
A substance dissolved in water.
151Why are state symbols important in equations?
They show the physical state of substances.
152What is formed when iron rusts?
Iron(III) oxide.
153What is the chemical formula for rust?
(Fe_2O_3)
154Why are chemical equations useful?
They show how atoms rearrange during reactions.
155Predict what happens to the reaction rate when temperature increases and explain why.
The reaction rate increases because particles move faster and collide more often with greater energy.
156Predict what happens to the reaction rate when concentration increases and explain why.
The reaction rate increases because there are more particles available to collide.
157Predict what happens to the reaction rate when surface area increases and explain why.
The reaction rate increases because more particles are exposed for collisions.
158Predict what happens to the reaction rate when a catalyst is added and explain why.
The reaction rate increases because the catalyst lowers activation energy.
159A student crushes a solid reactant into powder before reacting it. Predict what happens to the reaction rate.
The reaction rate increases because the surface area is larger.
160A student breaks marble chips into smaller pieces before adding acid. Predict what happens to the reaction rate.
The reaction rate increases because more particles are exposed.
161Why does powdered magnesium react faster than a magnesium ribbon?
Powdered magnesium has a larger surface area.
162Why do wood shavings burn faster than a large log?
Wood shavings have a larger surface area exposed to oxygen.
163Why does food spoil faster in warm temperatures?
Higher temperatures increase reaction rates.
164Why do reactions usually slow down in the fridge?
Lower temperatures reduce particle movement and collisions.
165Why does a hot fire burn things faster than a small flame?
Higher temperatures increase collision frequency and energy.
166Why do enzymes in the body work more slowly when body temperature drops?
Particles move slower and collide less effectively.
167Predict the products when hydrochloric acid reacts with sodium hydroxide.
Sodium chloride and water.
168Predict the products when sulfuric acid reacts with potassium hydroxide.
Potassium sulfate and water.
169Predict the products when nitric acid reacts with calcium hydroxide.
Calcium nitrate and water.
170Predict the products when hydrochloric acid reacts with magnesium oxide.
Magnesium chloride and water.
171Predict the products when magnesium reacts with hydrochloric acid.
Magnesium chloride and hydrogen gas.
172Predict the products when zinc reacts with sulfuric acid.
Zinc sulfate and hydrogen gas.
173Predict the products when iron reacts with hydrochloric acid.
Iron chloride and hydrogen gas.
174Predict the products when calcium reacts with nitric acid.
Calcium nitrate and hydrogen gas.
175A gas produced in a reaction makes a popping sound with a lit match. Identify the gas.
Hydrogen gas.
176A student reacts magnesium with acid and hears a squeaky pop during testing. What gas was formed?
Hydrogen gas.
177What gas is identified using the pop test?
Hydrogen gas.
178Why is the pop test useful in metal-acid reactions?
It confirms hydrogen gas is produced.
179Predict the products of complete combustion of methane.
Carbon dioxide and water.
180Predict the products of complete combustion of propane.
Carbon dioxide and water.
181Predict the products of complete combustion of ethane.
Carbon dioxide and water.
182Predict the products of complete combustion of butane.
Carbon dioxide and water.
183Predict the products of incomplete combustion of methane.
Carbon monoxide and water.
184Predict the products of incomplete combustion of propane.
Carbon monoxide, water, and soot.
185Predict the products of incomplete combustion of butane.
Carbon monoxide and water.
186Why does incomplete combustion form carbon monoxide?
There is not enough oxygen for complete combustion.
187A student mixes two clear solutions and a yellow solid forms. What type of reaction occurred?
A precipitation reaction.
188What evidence suggests a precipitation reaction occurred?
An insoluble solid formed.
189Two aqueous solutions are mixed and the solution becomes cloudy. What most likely formed?
A precipitate.
190Why does a precipitation reaction occur?
An insoluble product forms when ions combine.
191Balance the equation: (H_2 + Cl_2 ightarrow HCl).
(H_2 + Cl_2 ightarrow 2HCl)
192Balance the equation: (N_2 + H_2 ightarrow NH_3).
(N_2 + 3H_2 ightarrow 2NH_3)
193Balance the equation: (Fe + O_2 ightarrow Fe_2O_3).
(4Fe + 3O_2 ightarrow 2Fe_2O_3)
194Balance the equation: (CH_4 + O_2 ightarrow CO_2 + H_2O).
(CH_4 + 2O_2 ightarrow CO_2 + 2H_2O)
195Classify the reaction: (CaCO_3 ightarrow CaO + CO_2).
Decomposition reaction.
196Classify the reaction: (N_2 + 3H_2 ightarrow 2NH_3).
Synthesis reaction.
197Classify the reaction: (HCl + NaOH ightarrow NaCl + H_2O).
Neutralisation reaction.
198Classify the reaction: (CH_4 + 2O_2 ightarrow CO_2 + 2H_2O).
Combustion reaction.
199A student notices the temperature around a reaction increases. Is the reaction exothermic or endothermic?
Exothermic.
200A cold pack becomes colder when activated. Is the reaction exothermic or endothermic?
Endothermic.
201Combustion produces heat and light. Is it exothermic or endothermic?
Exothermic.
202Photosynthesis absorbs energy from sunlight. Is it exothermic or endothermic?
Endothermic.
203Why does rusting happen faster in wet conditions?
Water helps iron react with oxygen.
204Why do coastal areas increase rusting of metals?
Salt water speeds up corrosion.
205Why is galvanising used on iron?
To protect it from rusting.
206Why does iron rust slower in dry environments?
Less water is available for corrosion.
207Calculate the number of moles in 18 g of water ((H_2O, MM = 18 g/mol)).
1 mole.
208Calculate the number of moles in 44 g of carbon dioxide ((CO_2, MM = 44 g/mol)).
1 mole.
209Calculate the number of moles in 32 g of oxygen gas ((O_2, MM = 32 g/mol)).
1 mole.
210Calculate the number of moles in 16 g of methane ((CH_4, MM = 16 g/mol)).
1 mole.
211How many moles of water are produced from 2 moles of hydrogen in (2H_2 + O_2 ightarrow 2H_2O)?
2 moles.
212How many moles of ammonia are produced from 1 mole of nitrogen in (N_2 + 3H_2 ightarrow 2NH_3)?
2 moles.
213How many moles of carbon dioxide are produced from 3 moles of methane in combustion?
3 moles.
214How many moles of oxygen are needed to react with 2 moles of methane?
4 moles.
215A solution has a pH of 2. Is it acidic or basic?
Acidic.
216A solution has a pH of 12. Is it acidic or basic?
Basic.
217A solution has a pH of 7. Is it acidic, basic, or neutral?
Neutral.
218A substance turns blue litmus paper red. Is it an acid or base?
Acid.
219A reaction releases light and heat. What type of energy change occurred?
Exothermic.
220A reaction absorbs heat from the surroundings. What type of energy change occurred?
Endothermic.
221Why do hand warmers feel hot?
They use exothermic reactions.
222Why do instant cold packs feel cold?
They use endothermic reactions.
223Why does increasing temperature increase reaction rate?
Particles gain more kinetic energy, causing more frequent and energetic collisions
224Why does a powder react faster than a solid lump?
It has a greater surface area exposed for collisions
225Why can stirring speed up a reaction?
It keeps reactants in contact and removes products blocking the reaction
226If reactant particles do not collide with enough energy, what happens?
No reaction occurs
227What does collision theory state?
Particles must collide with enough energy and correct orientation for a reaction to occur
228Why does increasing concentration increase reaction rate?
There are more particles in a given volume, causing more collisions
229If a reaction releases heat and light, what type of reaction is it?
Exothermic
230Why do surroundings feel colder during an endothermic reaction?
The reaction absorbs energy from the surroundings
231If products have less stored energy than reactants, what type of reaction occurred?
Exothermic
232Why is photosynthesis endothermic?
It absorbs energy from sunlight
233What happens to energy during an exothermic reaction?
Energy is released to the surroundings
234What happens to energy during an endothermic reaction?
Energy is absorbed from the surroundings
235Why are catalysts important in industry?
They increase reaction rates without being consumed
236How does a catalyst increase reaction rate?
It provides an alternative pathway or better surface for collisions
237Why are enzymes considered catalysts?
They speed up biological reactions without being used up
238If a catalyst is unchanged after a reaction, what does this mean?
It is not consumed in the reaction
239Why must chemical equations be balanced?
To obey the law of conservation of mass
240What does the law of conservation of mass state?
Mass is neither created nor destroyed in a chemical reaction
241Why are subscripts not changed when balancing equations?
Changing them changes the substance itself
242What do coefficients in equations represent?
The number of molecules or moles involved
243In the equation 2H2 + O2 → 2H2O, how many hydrogen atoms are on each side?
4
244In the equation 2H2 + O2 → 2H2O, how many oxygen atoms are on each side?
2
245Why is rusting considered oxidation?
Iron reacts with oxygen to form iron oxide
246Why is rusting a slow exothermic reaction?
It releases energy slowly over time
247How does galvanising prevent corrosion?
A zinc coating protects the iron from oxygen and water
248What is produced when a metal reacts with an acid?
A salt and hydrogen gas
249If bubbles form when metal reacts with acid, what gas is likely produced?
Hydrogen gas
250What is produced when an acid reacts with a carbonate?
Salt, water, and carbon dioxide
251How can you identify carbon dioxide in a reaction?
It can turn limewater milky
252Why are hydrocarbons commonly used as fuels?
They release large amounts of energy during combustion
253What are the products of complete combustion of hydrocarbons?
Carbon dioxide and water
254Why is carbon monoxide dangerous?
It is toxic and reduces oxygen transport in blood
255If oxygen supply is limited during combustion, what gas may form?
Carbon monoxide
256What type of reaction is combustion?
A rapid exothermic reaction with oxygen
257What is formed in a neutralisation reaction?
Salt and water
258Why is neutralisation useful?
It reduces acidity or alkalinity
259What happens to pH during neutralisation?
It moves closer to 7
260If a solution has pH 2, what can you infer?
It is a strong acid
261If a solution has pH 12, what can you infer?
It is a strong base
262What does a pH of 7 indicate?
A neutral solution
263Why do acids conduct electricity?
They contain ions in solution
264What ion do all acids contain?
Hydrogen ions (H+)
265Why do alkalis feel slippery?
Because of the hydroxide ions in solution
266What is an alkali?
A base that dissolves in water
267If blue litmus paper turns red, what does this indicate?
An acid is present
268If red litmus paper turns blue, what does this indicate?
A base is present
269Why is universal indicator more useful than litmus paper?
It shows a range of pH values
270What causes ocean acidification?
Carbon dioxide dissolving in water to form carbonic acid
271Why does ocean acidification harm coral reefs?
It reduces carbonate ions needed for shells and skeletons
272What type of reaction is photosynthesis?
A synthesis and endothermic reaction
273What type of reaction is electrolysis of water?
A decomposition reaction
274Why does decomposition often require energy input?
Bonds must be broken apart
275What happens during a synthesis reaction?
Simpler substances combine to form a more complex compound
276Why is precipitation evidence of a chemical reaction?
An insoluble solid forms
277What is a precipitate?
An insoluble solid formed in a solution
278If two clear solutions form a solid when mixed, what reaction likely occurred?
A precipitation reaction
279Why are balanced equations important in chemistry?
They show the correct ratio of reactants and products
280What state symbol is used for gases?
(g)
281What state symbol is used for aqueous solutions?
(aq)
282Why does increasing surface area not affect reactions between only liquids?
Surface area mainly affects solids
283If particles move faster, what happens to collision frequency?
It increases
284Why do catalysts not violate conservation of mass?
They are regenerated and not consumed
285If mass appears lost in a reaction, what may have happened?
A gas may have escaped
286Why does methane burn with oxygen?
Combustion reactions require oxygen
287What is the fuel in a combustion reaction?
The substance that releases energy during reaction
288If reactants are rearranged into new substances, what has occurred?
A chemical reaction
289What type of compound is formed between a metal and a non-metal?
An ionic compound
290What type of bonding occurs in molecular compounds?
Covalent bonding through sharing electrons
291Why does NaCl conduct electricity when dissolved in water?
Its ions are free to move
292Why do ionic compounds usually have high melting points?
Strong electrostatic attractions exist between ions
293What is the chemical formula for sodium hydroxide?
NaOH
294What is the chemical formula for magnesium chloride?
MgCl2
295What is the chemical formula for methane?
CH4
296What is the chemical formula for carbon dioxide?
CO2
297What is the chemical formula for rust?
Fe2O3
298What is the chemical formula for ammonia?
NH3
299What is the chemical formula for glucose?
C6H12O6
300What is the chemical formula for octane?
C8H18