Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Chemsitry > Energy Changes > Flashcards

Energy Changes Flashcards

1
Q

What is the conservation of energy principle?

A

Energy is conserved in chemical reactions. The amount of energy in the universe at the end of a chemical reaction is the same as before the reaction takes place.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is an exothermic reaction? Give examples

A

A reaction where energy is transferred to the surroundings so that the surroundings temperature increases - combustion, oxidation reactions and neutralisation (acid + alkali) reactions. Negative sign of energy change.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is an endothermic reaction? Give examples

A

A reaction where energy is taken in from the surroundings so the surroundings temperature decreases - thermal decomposition, reaction of citric acid and sodium hydrogencarbonate.
Negative sign of energy change.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is activation energy?

A

Minimum amount of energy that particles need to react

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is a reaction profile?

A

Reaction profile is a graph which shows the relative energies of reactants and product, as well as activation energy of the reaction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What occurs in a chemical reaction in terms of bond energies? Describe exothermic and endothermic reactions in terms of bond breaking/forming.

A

• Energy is supplied to break bonds and energy is released when bonds are made; exothermic - energy released from forming bonds is greater than that needed to break the bonds; endothermic - energy needed to break bonds is greater than energy released making them

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the equation to find enthalpy change in terms of bond energies?

A

Energy of reaction = sum of bonds broken - sum of bonds made

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is a cell?

A

A cell is composed of two electrodes dipped in an electrolyte solution. It produces electricity from a chemical reaction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is a battery?

A

A battery consists of two or more cells connected in series.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What determines the voltage obtained from a cell?

A

Identities of metals used as electrodes and the identity and concentration of an electrolyte.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

State the advantages and disadvantages of using cells and batteries.

A

(+) more or less cheap, some are rechargeable, a convenient source of electrical (-) harmful chemicals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe rechargeable and non-rechargeable cells

A

Rechargeable - chemical reactions are reversed when an external current is supplied
Non-rechargeable - reactants are used up, cannot be recharged

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is a fuel cell?

A

Fuel cells are supplied by fuel and oxygen to oxidise the fuel to generate electricity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the overall reaction in a hydrogen fuel cell? What are the half equations?

A

Cathode: 2 H2 -> 4 H^+ + 4 e1.
Anode: 02 + 4 H^+ + 4 e1. -> 2 H20
Overall: -> 2 H2 + 02 -> 2 H20

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the advantages and disadvantages of hydrogen fuel cells?

A

Advantages: no pollutants, no recharging
Disadvantages: flammable, H2 difficult to store, fossil fuel production, toxic chemicals, expensive production of H2 by electrolysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is an exothermic reaction?

A

An exothermic reaction is one that transfers energy to the surroundings so the temperature of the surroundings increases.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is an example of an exothermic reaction?

A

Combustion, many oxidation reactions and neutralisation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are everyday uses of exothermic reactions?

A

Include self-heating cans and hand warmers.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is an endothermic reaction?

A

An endothermic reaction is one that takes in energy from the surroundings so the temperature of the surroundings decreases.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are examples of endothermic reactions?

A

Endothermic reactions include thermal decompositions and the reaction of citric acid and sodium hydrogencarbonate. Some sports injury packs are based on endothermic reactions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

When do chemical reactions occur?

A

Chemical reactions can occur only when reacting particles collide with each other and with sufficient energy. The minimum amount of energy that particles must have to react is called the activation energy.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are reaction profiles used to show?

A

Reaction profiles can be used to show the relative energies of reactants and products, the activation energy and the overall energy change of a reaction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How is the chemistry of metals seen?

A

• The chemistry of the metals is seen by comparing their characteristic reactions.

24
Q

Why do chemical reactions occur?

A
  • Chemical reactions occur so that elements can achieve a more stable energy state by gaining a full outer shell of electrons.
25
Q

How do elements gain a full outer shell?

A

This is done by chemical bonding (we have already seen ionic and covalent bonding) where old bonds are broken, and new bonds are formed.

26
Q

What does the process of old bonds being broken and new bonds being formed?

A

This process involves the transfer of energy into and out of reaction mixtures.

27
Q

Where does energy come from in heat exchange in reactions?

A
  • The energy comes from the chemical bonds themselves which could be considered as tiny stores of chemical energy.
  • In the majority of reactions, the energy is in the form of heat energy, although sometimes other types of energy are produced such as light or sound
28
Q

What can physical processes involve?

A

Involve heat exchange.

29
Q

What are examples of physical processes?

A
  • freezing.
  • melting.
  • which involve a change in state.
30
Q

What happens in endothermic reactions?

A

In exothermic reactions energy is given out to the surroundings so the temperature of the surroundings increases.

31
Q

What are the different types of exothermic reactions?

A
  • combustion
  • oxidation
  • neutralisation
32
Q

What are hand warmers based on?

A

Hand warmers used in the wintertime are based on the release of heat from an exothermic reaction.

33
Q

What do self-heating cans and drinks use?

A

Self-heating cans of food and drinks such as coffee and hot chocolate also use exothermic reactions in the bases of the containers.

34
Q

What happens in endothermic reactions?

A

In endothermic reactions energy is taken in from the surroundings so the temperature of the surroundings decreases.

35
Q

What is more common an endothermic reaction or exothermic reaction?

A

These types of reactions are much less common than exothermic reactions.

36
Q

What is an example of an endothermic reaction?

A

Electrolysis, thermal decomposition reactions, the first stages of photosynthesis and the reaction between citric acid and sodium hydrogencarbonate are typical endothermic reactions.

37
Q

What do sport injury treatment use which relates to endothermic reactions?

A

Sports injury treatment often use cold packs based on endothermic reactions to take heat away from a recently injured area to prevent swelling.

38
Q

What happens if energy is transferred to its surroundings?

A

So, if energy is transferred to the surroundings during a chemical reaction, then the products formed must have less energy than the reactants by the same amount as that transferred.

39
Q

What happens in a neutralisation reaction?

A

These always give energy out.

40
Q

What happens in displacement reactions?

A

These can either take energy in or give it out.

41
Q

What happens in a combustion reaction?

A

These always give energy out.

42
Q

What is a summary of exothermic reactions?

A

In exothermic reactions, the temperature of the surroundings increases and the heat content of the system falls.

43
Q

What is a summary of endothermic reactions?

A

In endothermic reactions, the temperature of the surroundings falls and the heat content of the system increases

44
Q

What are the materials that should be used in the Investigating Temperature Changes?

A
  • Dilute hydrochloric acid
  • Dilute sodium hydroxide solution
  • Styrofoam (polystyrene) calorimeter & lid
  • 25 cm3 measuring cylinder
  • Thermometer & stirrer
45
Q

What is the method for investigating Temperature Changes ?

A
  1. Using a measuring cylinder, place 25 cm3 of the NaOH solution into the calorimeter.
  2. Measure and record the temperature of the solution.
  3. Add 5 cm3 of the dilute HCl and stir.
  4. Measure and record the highest temperature reached by the mixture.
  5. Repeat steps 1 – 4 increasing the amount of acid added by 5 cm3 each time.
46
Q

What is the conclusion for Investigating Temperature Changes?

A

The larger the difference in the temperature the more energy is absorbed or released.

47
Q

Why do chemical, reactions occur?

A

Chemical reactions occur so that elements can achieve a more stable energy state by gaining a full outer shell of electrons.

48
Q

How do chemical reactions occur?

A

This is done by chemical bonding (we have already seen ionic and covalent bonding) where old bonds are broken, and new bonds are formed.

49
Q

What does the process of a chemical reaction involve?

A

This process involves the transfer of energy into and out of reaction mixtures.

50
Q

What is the process that involves the transfer of energy called?

A

The terms used to describe this are the system (what happens in the chemical reaction) and the surroundings.

51
Q

Where does the energy come from in chemical reactions?

A

The energy comes from the chemical bonds themselves which could be considered as tiny stores of chemical energy.

52
Q

Where does the energy in reactions come from?

A

In the majority of reactions, the energy is in the form of heat energy, although sometimes other types of energy are produced such as light or sound.

53
Q

What happens in an exothermic reaction?

A

In exothermic reactions energy is given out to the surroundings so the temperature of the surroundings increases.

54
Q

What are examples of exothermic reactions?

A

Combustion, oxidation, and neutralisation reactions are typical exothermic reactions.

55
Q

What different factors come into play when analysing collisions?

A
  • energy
  • orientation
  • number of collisions per second

Chemsitry (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions