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WorksheetsC5 Energy changes triple
Total questions: 42
Worksheet time: 21mins
State the law of conservation of energy.
Energy cannot be created or destroyed, it can only transferred from one place to another.
Energy can be created or destroyed, it can only transferred from one place to another.
Energy cannot be light or sound it can only be kinetic energy moving from one place to another.
Energy can destroyed, and then can reform to be transferred from one place to another.
How does the law of conservation of energy apply to chemistry?
In all physical reactions, energy is either transferred to the surroundings or from the surroundings.
In all chemical reactions, energy is either transferred to the surroundings only.
In all chemical reactions, energy is either transferred to the surroundings or from the surroundings.
In all physical reactions, energy is absorbed by the surroundings.
What is an exothermic reaction?
A reaction where energy is transferred from the surroundings.
A reaction where energy is transferred to the surroundings.
A reaction where energy is absorbed into surroundings.
A reaction where energy is absorbed from the surroundings.
Give two examples of exothermic reactions.
Combustion, photosynthesis
Decomposition, respiration
Neutralisation, photosynthesis
Combustion, respiration
What happens to the temperature of the surroundings during an exothermic reaction?
They increase.
They decrease.
They stay the same.
What is an endothermic reaction?
A reaction where energy is transferred from the surroundings.
A reaction where energy is transferred to the surroundings.
A reaction where energy is absorbed into surroundings.
A reaction where energy is absorbed from the surroundings.
Give two examples of endothermic reactions.
Combustion, photosynthesis
Decomposition, respiration
Neutralisation, photosynthesis
Thermal decomposition reactions, citric acid and sodium hydrogencarbonate.
What happens to the temperature of the surroundings during an endothermic reaction?
They increase.
They decrease.
They stay the same.
State two uses of exothermic reactions
Self-heating cans, hand warmers
Making fertilisers and explosives
Fireworks, fire extinguishers
Radiators, Air-conditioning
State uses of endothermic reactions
Self-heating cans, hand warmers
Some cooling sports injury packs
Fireworks, fire extinguishers
Radiators, Air-conditioning
What are reactants?
The substances involved in a chemical reaction
The substances formed when reactants have a chemical reaction
What are products?
The substances involved in a chemical reaction
The substances formed when reactants have a chemical reaction
What is a reaction profile?
A diagram which shows a chemical equation.
A diagram which shows whether the reactants have more or less energy than the products.
A fact file which describes the reactants and the products.
If the reactants have more energy than the products, what kind of a reaction must have taken place?
An exothermic one. The missing energy has been transferred to the surroundings.
An endothermic one. The extra energy has been transferred from the surroundings.
If the reactants have less energy than the products, what kind of a reaction must have taken place?
An exothermic one. The missing energy has been transferred to the surroundings.
An endothermic one. The extra energy has been transferred from the surroundings.
Is breaking bonds endothermic or exothermic?
Endothermic. Chemical bonds are strong so require energy to break (like when you have to put energy in to separate magnets from each other)
Exothermic. Energy is released when chemical bonds are formed (like how two magnets move together when close and generate kinetic energy)
Is making bonds endothermic or exothermic?
Endothermic. Chemical bonds are strong so require energy to break (like when you have to put energy in to separate magnets from each other)
Exothermic. Energy is released when chemical bonds are formed (like how two magnets move together when close and generate kinetic energy)
How do we work out the overall energy change of a reaction?
Add the energy needed to break all the bonds in the reactants to the energy released to form all the bonds in the products.
Work out the difference between the energy needed to break all the bonds in the reactants and the energy released to form all the bonds in the products.
Divide the energy needed to break all the bonds in the reactants from the energy released to form all the bonds in the products.
Multiply the energy needed to break all the bonds in the reactants to the energy released to form all the bonds in the products.
What type of reaction takes place in a chemical cell
Exothermic
Endothermic
No reaction occurs
Why does the voltage from a chemical cell that is connected in a circuit with a lamp eventually reach zero?
The lamp breaks
One of the reactants is used up
The circuit becomes broken
What is produced by a hydrogen-oxygen fuel cell?
Water and Carbon Dioxide
Carbon Dioxide
Water
What happens to hydrogen molecules in a hydrogen-oxygen fuel cell?
They form hydrogen ions, H+ , and electrons, e-
They form hydrogen ions, H+ , and electrons, e+
They form hydrogen atoms, H
What happens to oxygen molecules in a hydrogen-oxygen fuel cell?
They react with electrons to form oxide ions, O2-
They react with hydrogen ions to form hydroxide ions, OH-
They react with hydrogen ions and electrons to form water
Which of these is a disadvantage of cars driven by hydrogen-oxygen fuel cells rather than by petrol engines?
They have fewer moving parts
There are fewer suitable filling stations
They emit little pollution
What is the main reason why hydrogen is more difficult to store than diesel?
Hydrogen is a gas at room temperature but diesel is a liquid
Hydrogen can be liquefied by cooling it
Hydrogen can be stored under pressure
What is a strength of using hydrogen-oxygen fuel cells in manned spacecraft, compared to using chemical cells?
They produce electricity
They produce water that the astronauts can drink
They produce a voltage
In a hydrogen fuel cell used to power a car, where does the oxygen come from?
The air
A catalyst
The fuel
What are the main components of a chemical cell?
An anode, a cathode
An anode, a cathode and an electrolyte
An anode and an electrolyte
A cathode and an electrolyte
What is an electrolyte?
An electric current
The splitting of ionic compounds
A solution containing ions which allows current to flow.
The salts in drinking water.
What does the potential difference of a cell depend on?
The anode and cathode.
The type of electrolyte and fuel
Whether it's alkali or not
The type of electrode and the electrolyte.
What is a battery?
A single cell
Two or more cells connected in series
AA or AAA
An alkaline substance
In non-rechargeable cells, why do the chemical reactions stop over time?
One of the reactants becomes used up.
The energy has depleted.
The products are oxidised.
The electrodes become reactive.
How does the reactivity of the metal electrodes affect the size of the potential difference?
The lower the difference in reactivity, the greater the potential difference.
The greater the difference in reactivity, the lower the potential difference.
The greater the difference in reactivity, the greater the potential difference.
The lower the difference in reactivity, the lower the potential difference.
What is a fuel cell?
A cell which uses hydrogen to generate electricity.
A cell which uses oxygen (or air) to generate electricity.
A cell which uses a fuel to generate electricity.
A cell which uses a fuel and oxygen (or air) to generate electricity.
What are the products in a hydrogen fuel cell?
Water
Oxygen
Hydrogen
State three advantages of hydrogen fuel cells
Do not need to be recharged, no pollutants are produced, can be different sizes for different uses
Hydrogen is highly flammable, hydrogen is sometimes produced through non-renewable means, hydrogen is difficult to store
State three disadvantages of hydrogen fuel cells
Do not need to be recharged, no pollutants are produced, can be different sizes for different uses
Hydrogen is highly flammable, hydrogen is sometimes produced through non-renewable means, hydrogen is difficult to store
Complete the equation which occurs at the negative electrode of a hydrogen fuel cell 2H₂ + 4OH⁻ →
H₂O + 4e⁻
4H₂O + e⁻
4H₂O + 4e⁻
3H₂O + 2e⁻
Complete the equation which occurs at the positive electrode of a hydrogen fuel cell O₂ + 2H₂O →
OH⁻
2OH⁻
3OH⁻
4OH⁻
Why can some cells not be recharged?
Because the reaction is not reversible
Because the reaction is reversible
Because the reactant is used up
Because the products are used up
