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science 3m2 > Science Chemistry > Flashcards

Science Chemistry Flashcards

1
Q

What are the three states of matter?

A

Solid

Liquid

Gas

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2
Q

State 3 Differences between all three states of matter.

A
  1. Solids have a fixed volume and a fixed shape but liquids have a fix VOLUME but NO fixed shape and gases have no fixed volume and shape.
  2. Solids cannot flow, because their particles cannot move from place to place but Liquids on the other hand can flow and take the shape of their container, because their particles can move around each other and gases can flow and completely fill their container, because their particles can move quickly in all directions
  3. Solids cannot be compressed, because their particles are close together and have no space to move into. liquids cannot be easily compressed, because their particles are close together and have no space to move into Gases can be EASILY compressed, because their particles are far apart and have space to move into
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3
Q

Can a physical change be reverted? why

A

Yes , They can be reversed since their chemical properties of the substance do not change.

This is because the particles themselves do not change -only their arrangement, movement and amount of stored energy.

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4
Q

State HOW a state changes from one to another during :
MELTING , EVAPORTING , BOILING

A

*Energy must be transferred, by heating, to a substance for these changes of state to happen. During these changes the particles gain energy, which is used to break or overcome the bonds between particles during melting and ALL the bonds during evaporating and Boiling

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5
Q

State 2 differences between evaporation and boiling.

A
  1. Evaporation can happen at any temperature, while boiling happens only at the boiling point
  2. Evaporation happens only at the surface while boiling happens everywhere
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6
Q

What are all 6 changes of state?

A
  1. Boiling
  2. melting
  3. condensing
  4. deposition
  5. sublimation
  6. freezing
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7
Q

What does a pure substance consist of?

A

A pure substance consists only of one element or one compound

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8
Q

What is a Atom?

A

The smallest unit of a substance

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9
Q

What is a Element?

A

A substance that is made of only one type of atom

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10
Q

What is a Compound?

A

A substance that contains more than one element chemically joined together

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11
Q

What does a mixture contain?

A

A mixture contains elements and/or compounds that are not chemically joined together. You can use physical processes to separate mixtures into different substances.

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12
Q

What are some differences between pure and impure substances?

A

Pure substances have a sharp melting point but mixtures melt over a range of temperatures. This difference is most easily seen when the temperature of a hot liquid is measured as it cools and freezes.

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13
Q

Can we separate elements?

A

Elementscannot be separated into simpler substances by either physical methods or chemical methods

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14
Q

Can we separate compounds?

A

Since Compound sare two or more elements chemically bonded together, they can be separated by chemical methods but NOT by physical methods

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15
Q

Can we separate mixtures?

A

Mixtures form when elements/compounds are mixed together (combined physically not chemically).
This means that, unlike pure substances, mixtures can always be separated by physical methods

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16
Q

What is a solution

A

A solution is a liquid that is made when one substance dissolves and mixes fully with another

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17
Q

What is a solute

A

The solid that dissolves (e.g. sugar granules) is called the solute

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18
Q

What is a Solvent?

A

The liquid that does the dissolving (e.g. hot water) is called the solvent

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19
Q

What does it mean when a solution is saturated?

A

When no more solute can be dissolved in a solvent the solution is said to be saturated

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20
Q

When is filtration used? How does it work?

A

Filtration is used to separate an insoluble solid from a liquid. It is useful for separating sand from a mixture of sand and water, or excess reactant from a solution.

Filtration works because the filter paper has tiny holes, or pores, in it. These are large enough to let small molecules and dissolved ions through, but not the much larger particles of undissolved solid.

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21
Q

What are the steps to obtain a large regularly shaped crystal? (4)

A

To obtain large, regularly shaped crystals:

*put the solution in an evaporating basin

*warm the solution by placing the evaporating basin over a boiling water bath

*stop heating before all the solvent has evaporated

*After the remaining solution has cooled down, pour the excess liquid away
(or filter it). Dry the crystals using a warm oven or in air.

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22
Q

What is a hazard?

A

A hazard is something that could cause:

*harm to someone

*damage to something

*adverse health effects, either straightaway or later

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23
Q

What is a risk?

A

A risk is the chance that a hazard will cause harm .When evaluating a risk, think about factors such as:

*the way the hazard causes harm

*how likely it is that someone or something will be exposed to the hazard

*how serious the effects of the hazard could be

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24
Q

What is a precaution?

A

A precaution is something that can be done to reduce a risk of harm. Different substances and different practical procedures need different precautions. A risk assessment describes the hazards and risks of harm, and what suitable precautions are needed to work more safely.

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25
Q

What are some hazard and ways of reducing risk during crystallization?

A
  1. Solvent or Solution may get into your eyes.

Precaution : Wear a labcoat and goggles

  1. Crystals may jump out when heated

Precaution : Wear goggles and lab coat
Remove from fire or heat slowly

  1. Bunsen Burner may burn skin or hair

Precaution : Tie hair back
Have Bunsen burner with safe flame when not in use

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26
Q

What is Chromatography?

A

Chromatography is a process that separates compounds (such as dyes) from a mixture (such as ink).

27
Q

Name the two phases and state what they are.

A

*The stationary phase is the paper, as this does not move.

*The mobile phase is the liquid or gas that flows through the stationary phase, separating the mixture.

28
Q

Why do compounds separate?

A

The compounds are separated because they have different solubilities.

29
Q

What are all the material needed for Chromatogram? (4)

A
  1. Filter paper
  2. Pencil
  3. selection of inks
  4. Some Water
30
Q

When is Simple Distillation used?

A

Simple distillation is used to separate a solvent from a solution. It is useful for producing water from salt solution

31
Q

When is Fractional Distillation used?

A

Fractional distillation is used to separate different liquids from a mixture of liquids. It is useful for separating ethanol from a mixture of ethanol and water, and for separating different fractions from crude oil.

32
Q

What are two ways of obtaining different liquids from the column?

A
  1. By collecting different liquids from different parts of the column. The substance with the lowest boiling point is collected at the top of the column.
  2. By continuing to heat the mixture to increase the temperatures in the column. The substance with the lowest boiling point is collected first.
33
Q

State a difference between Simple and Fractional distillation.

A

Simple distillation is used for separating a solute and a solvent but Fractional distillation on the other hand is used for separating two solvents

34
Q

Why do we need to use distilled water in a Chemical analysis?

A

distilled water needs to be used because dissolved salts may react to form unwanted cloudy precipitates, leading to incorrect results

35
Q

What are all the steps needed to treat fresh water for drinking? State all the names for each step and their purpose. (4)

A
  1. Screening: filter to remove leaves and twigs
  2. Sedimentation: silt and grit, sink to the bottom of the water by sedimentation
  3. Filtration through beds of sand and gravel: to remove very small insoluble particles
  4. Chlorination: to kill bacteria since they are too small to be removed by filtration
36
Q

Where are the protons , electron and neutrons found in the atom?

A

The protons and neutrons exist in a dense core at the center of the atom. This is called the nucleus.

The electrons surround the nucleus in electron shells

37
Q

State the mass and charge of all three sub atomic particles.

A

Protons relative mass is 1 and a charge of +1
neutrons relative mass is 1 and a charge of 0
Protons relative mass is 1/1840 (negligible) and a charge of -1

38
Q

What is the atomic number? What does it consist of?

A

the atomic number is the number of protons in an atom

39
Q

How do you figure out the mass number?

A

mass number = Neutrons + protons

40
Q

Why do atom have no overall charge?

A

Atoms have no overall electrical charge and are neutral because they have an equal number of positive protons and negative electrons

41
Q

What is an Isotope?

A

Atoms of the same element which have the same number of protons but different number of neutrons

42
Q

What is the unit used to measure the mass of an atom?

A

This unit is the amu(atomic mass unit). This is defined as the 1/12 of the mass of Carbon-12.

43
Q

How do you calculate RAM (Relative Atomic Mass)?

A 
                                                                    100
44
Q

State 2 difference between the old and new periodic table.

A

Mendeleev (old period table) arranged these elements in order of relative atomic mass while in the modern periodic table, the elements are arranged according to their atomic number -not their relative atomic mass.

Also Mendeleev left gaps for undiscovered elements in his periodic table while the modern one had no gaps

45
Q

State 2 Similarities between the old and new periodic table.

A

Both have groups and periods

Both have metals and non metals

46
Q

State the maximum amount of electron that can be held in the first 3 shells.

A

First = 2
Second = 8
Third = 8

47
Q

What are two ways the electronic configuration is related to the elements place in the periodic table?

A

*the number of circles in the electronic configuration of an element is represented in the periodic table as the period number that element is situated in

*the number of electrons in the outermost shell of an element is represented in the periodic table as the group number that element is situated in

*the number of electrons in all shells of an element is represented in the periodic table as the element’s atomic number

48
Q

Why do atoms with the same outer electrons have similar reacting properties?

A

When atoms collide and react, it is the outer electrons that meet and interact. So, elements in the same group have similar chemical properties because they have the same number of electrons in their outer shell.

49
Q

What is rate of reaction?

A

The rate of a reaction is the speed at which reactants are turned into products.

50
Q

How does the gradient (curve) of the graph indicate the rate?

A

-The steeper the curve -> the greater the rate, the faster the reaction, the less the time required to get from the reactants to the products.

-The shallower the curve -> the smaller the rate, the slower the reaction, the more the time required to get from the reactants to the products.

51
Q

How can I measure the rate of reaction?

A

-Measure the change in mass or volume of the reactants or products.

-Some reactions produce gases So if you weigh the container in which the reaction is happening you will see mass decreasing per minute. Because gases escape.

-OR you can collect the gas produced and measure its volume per minute.

52
Q

What is the minimum amount of energy needed for a reaction to occur called?

A

activation energy.

53
Q

How can You speed up a reaction? (5)

A

1.Increase concentration of liquid reactants
2.Increase surface area e.g. make reactants into smaller pieces
3.Increase pressure of gas reactants
4.Increase temperature
5.Add catalyst

54
Q

What is a catalyst?

A

Catalysts are substances that speed up chemical reaction with ought being permanently changes themselves and without altering the products of the reaction.

55
Q

How does a catalyst work?

A

a Catalysts provides a alternative rout with a lower activation energy so more molecules have enough energy to successfully collide

56
Q

How was the earths atmosphere change?

A

*As the young Earth cooled, water vapor in the atmosphere condensed and formed oceans.

*Carbon dioxide then dissolved in the oceans, reducing the amount of carbon dioxide in the atmosphere.

*Sea creatures used the dissolved carbon dioxide to form shells made of calcium carbonate, CaC03. This then allowed more carbon dioxide to dissolve in the oceans

57
Q

How do scientists know when oxygen was first present in our atmosphere?

A

Further evidence comes from iron pyrite, a compoundthatisbrokendownbyoxygenandsoonlyformsifthereisnooxygen. It is often found in very ancient rock.

About 2.4 billion years ago, rocks containing bands of iron oxide started to form. This oxidation of iron suggests that oxygen levels increased at this time. There is fossil evidence of microorganisms that may have produced this oxygen. SC21aThe Early Atmosphere

So, scientists think that oxygen from these microorganisms reacted with iron in the early oceans, to produce insoluble iron oxides that formed layers on the seabed. Some geologists suggest that it was only after microorganisms had produced enough oxygen to oxidize the iron in the ocean that atmospheric oxygen levels could rise.

58
Q

How did oxygen form?

A

*Some organisms use energy from the Sun to make food by photosynthesis. These organisms change the atmosphere because photosynthesis uses up carbon dioxide and releases oxygen.

*More Carbon Dioxide is absorbed during this

59
Q

State the test for Oxygen.

A

The glowing splint test.

A splint is lit, allowed to burn for a few seconds, then blown out by mouth or by shaking. Whilst the ember at the tip is still glowing hot, the splint is introduced to the gas sample that has been trapped in a vessel. Upon exposure to concentrated oxygen gas, the glowing ember flares, and re-ignites to produce a sustained flame.

60
Q

Describe the greenhouse effect?

A
  1. Heat from the sun enters the Earth atmosphere.

2.Higher levels of greenhouse gases trap more of the Suns heat . raising global temperatures.

  1. Burning fossil fuel releases carbon dioxide and water vapor into the atmosphere
61
Q

How can scientist prove that CO2 absorbs infrared radiation ?

A

*We can show experimentally that CO2does absorb infrared.

*Also satellite data confirm that as CO2levels have increased, there has been a reduction in the infrared waves from the Earth leaving the atmosphere.

*This provides a causal link between temperature rise and CO2

62
Q

Which is more threatening as a greenhouse gas methane or Co2

A

Methane (CH4) is a more powerful greenhouse gas than CO, because it is much better at absorbing infrared radiation from the Earth.

63
Q

How is Methane released into the atmosphere?

A

Methane is the main component of natural gas, and is released into the atmosphere when oil and natural gas are extracted from the ground and processed.

Livestock farming (especially cattle) also produces a lot of methane. Cattle have bacteria in their stomachs to digest tough grass. Some of the bacteria produce methane. Soil bacteria in landfill sites and in rice ‘paddy’ fields also produce a lot of methane.

64
Q

State 3 negative effects of Climate Change?

A

*Ice melts and sea level rises.
*Loss of sea ice at the poles.
*Flooding.
*Some animals and plants may become extinct if they cannot survive at warmer Ts or find new places to live.
Some areas will get drier, other will get wetter
.More extreme weather events (e.g. heavy rain, storms, heat waves) affecting wildlife and crops that people depend on.
*More acidic gas (C02) to dissolve in the oceans harming organisms living there.

science 3m2 (3 decks)

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