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Science Year 9 > Topic 2 (Chemistry) > Flashcards

Topic 2 (Chemistry) Flashcards

1
Q

What were the key points of Dalton’s atomic model?

A

All matter consists of tiny particles called atoms.
Atoms are indivisible and identical within an element.
Atoms cannot be created or destroyed.

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2
Q

What was JJ Thomson’s plum pudding model and when was it proposed?

A

Description: Atom as a sphere of positive charge with embedded electrons.
Proposed in 1897 after the discovery of the electron.

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3
Q

What experiment did Rutherford conduct, and what were its key findings?

A

Experiment: Directed alpha particles at a thin gold foil.
Findings: Most passed through, some deflected, few reflected.

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4
Q

What conclusions did Rutherford draw from his experiment?

A

Most of an atom is empty space.
There is a positive nucleus at the center.
Electrons orbit the nucleus.

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5
Q

What were the key findings of Rutherford’s gold foil experiment, and what conclusions did he draw from them?

A

In Rutherford’s experiment, most alpha particles passed straight through the gold foil, but some were deflected at large angles, and a few were reflected back. From these results, Rutherford concluded that most of an atom is empty space, there is a dense positive nucleus at the center of the atom, and electrons orbit the nucleus.

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6
Q

What did Bohr observe about the light emitted by heated atoms, and how did he interpret it?

A

Bohr observed that the light emitted by heated atoms always had specific amounts of energy. He concluded that electrons orbit the nucleus in fixed energy levels, and each energy level corresponds to a specific amount of energy. This led to the development of the Bohr model of the atom.

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7
Q

What is sublimation?

A

Sublimation is the process in which a substance transitions directly from a solid to a gas phase without passing through the intermediate liquid phase.

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8
Q

Define melting.

A

Melting is the process in which a solid substance changes to its liquid phase as a result of an increase in temperature.

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9
Q

What is evaporation?

A

Evaporation is the process in which a liquid substance changes to its gas phase at the surface, typically at a temperature below its boiling point.

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10
Q

Describe the characteristics of a solid

A

Arrangement: Closely packed, fixed position.
Movement: Particles vibrate around their fixed positions.
Kinetic energy: The least.

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11
Q

Describe the characteristics of a liquid.

A

Arrangement: Close together, no fixed position.
Movement: Particles can move or flow while maintaining contact with each other.
Kinetic energy: Some.

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12
Q

Describe the characteristics of a gas.

A

Arrangement: Far apart, random position.
Movement: Particles move very fast and randomly.
Kinetic energy: The most.

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13
Q

What is condensation?

A

Condensation is the process in which a gas changes to its liquid phase due to a decrease in temperature.

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14
Q

Define freezing.

A

Freezing is the process in which a liquid substance changes to its solid phase as a result of a decrease in temperature.

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15
Q

What is desublimation?

A

Desublimation, also known as deposition, is the process in which a substance transitions directly from a gas to a solid phase without passing through the intermediate liquid phase.

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16
Q

What is a pure substance?

A

A pure substance is made up of only one type of element or compound.

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17
Q

What is an impure substance or mixture?

A

An impure substance or mixture is made of two or more substances that are not chemically joined together.

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18
Q

Define an element.

A

An element is a substance made of one type of atom only.

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19
Q

Define a compound.

A

A compound is a substance formed when two or more elements are chemically bonded together.

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20
Q

What is an atom?

A

An atom is the smallest part of an element that can exist.

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21
Q

How do pure substances differ from mixtures?

A

Pure substances contain only one type of element or compound, while mixtures contain two or more substances that are not chemically bonded.

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22
Q

Give an example of a pure substance.

A

An example of a pure substance is pure gold (Au) or pure water (H2O).

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23
Q

Give an example of a mixture.

A

An example of a mixture is air, which contains a combination of gases such as nitrogen, oxygen, carbon dioxide, and others.

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24
Q

What is the melting point of a substance?

A

The melting point is the temperature at which a substance changes from a solid to a liquid phase.

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25
Define the boiling point of a substance.
The boiling point is the temperature at which a substance changes from a liquid to a gas phase.
26
How can the physical state of a substance be predicted using its melting and boiling points?
If the temperature is below the melting point, the substance is in a solid state. If it is between the melting and boiling points, it is in a liquid state. If it is above the boiling point, it is in a gaseous state.
27
Provide an example illustrating the prediction of a substance's physical state based on its melting and boiling points.
For example, water has a melting point of 0°C and a boiling point of 100°C. If the temperature is 52°C, water would be in a liquid state because it is between its melting and boiling points.
28
What physical state is a substance in if the temperature is below its melting point?
If the temperature is below the melting point, the substance is in a solid state.
29
At what temperature is a substance in a gaseous state?
A substance is in a gaseous state when the temperature is above its boiling point.
30
What physical state is a substance in if the temperature is between its melting and boiling points?
If the temperature is between the melting and boiling points, the substance is in a liquid state.
31
What do heating/cooling curves show?
Heating/cooling curves show the changes in temperature of a substance as it is being heated or cooled.
32
Describe the behavior of particles in a solid as it is heated
Particles in a solid vibrate faster on their fixed position, and their kinetic energy increases.
33
What happens to the temperature at the melting point of a substance?
At the melting point, the temperature remains constant because the attractive forces between solid particles are being overcome, causing particles to vibrate faster.
34
How does the heating curve of a pure substance differ from that of an impure substance?
The heating curve of a pure substance will have horizontal lines at the melting and boiling points, indicating a constant temperature during phase change. In contrast, the heating curve of an impure substance will have a shallow gradient at the melting and boiling points due to different particles melting/boiling over a range of temperatures.
35
Why do heating curves of pure substances have horizontal lines at the melting and boiling points?
At the melting and boiling points of pure substances, the energy is used to overcome attractive forces between particles, resulting in a phase change rather than a temperature change. This leads to horizontal lines on the heating curve.
36
What causes the shallow gradient at the melting and boiling points in the heating curve of an impure substance?
In an impure substance, different particles have different melting and boiling points. This leads to a range of temperatures over which melting or boiling occurs, resulting in a shallow gradient on the heating curve.
37
Keyword: Dissolving
Definition: The process of a substance mixing uniformly with a solvent to form a solution. Diagram: [Illustration showing solute particles mixing with solvent particles] Example: When salt dissolves in water to form saltwater.
38
Keyword: Solute
Definition: A substance that dissolves in a solvent to form a solution. Diagram: [Illustration showing solute particles dissolving in solvent] Example: Salt is the solute in seawater.
39
Keyword: Solvent
Definition: The liquid in which a solute dissolves to form a solution. Diagram: [Illustration showing solute particles dissolving in solvent] Example: Water is the solvent in seawater.
40
Keyword: Solution
Definition: A homogeneous mixture formed when a solute dissolves in a solvent. Diagram: [Illustration showing solute particles uniformly distributed in solvent] Example: Seawater is a solution of salt dissolved in water.
41
Keyword: Insoluble
Definition: A substance that cannot dissolve in a particular solvent. Diagram: [Illustration showing solute particles not dissolving in solvent] Example: Sand is insoluble in water.
42
Keyword: Soluble
Definition: A substance that is capable of dissolving in a particular solvent. Diagram: [Illustration showing solute particles dissolving in solvent] Example: Sugar is soluble in water.
43
Keyword: Dilute
Definition: Describes a solution with a low concentration of solute particles in a given volume of solvent. Diagram: [Illustration showing fewer solute particles in solvent] Example: A dilute solution contains only a small amount of salt dissolved in water.
44
Keyword: Concentrated
Definition: Describes a solution with a high concentration of solute particles in a given volume of solvent. Diagram: [Illustration showing many solute particles in solvent] Example: A concentrated solution contains a large amount of salt dissolved in water.
45
Keyword: Saturated solution
Definition: A solution in which no more solute can dissolve at a given temperature. Diagram: [Illustration showing excess solute settling at the bottom of the container] Example: When no more salt can dissolve in water, the solution is saturated.
46
Keyword: Filtration
Definition: A method used to separate an insoluble substance from a liquid or solution. Procedure: Pour the mixture through a filter paper into a conical flask. The insoluble substance (residue) remains in the filter paper, while the liquid or solution (filtrate) passes through into the flask. Filtrate: The liquid or solution that passes through the filter. Residue: The material remaining in the filter after the filtrate has passed through.
47
Keyword: Crystallisation
Definition: A method used to separate a soluble substance from a solvent by evaporating the solvent. Procedure: Heat the mixture to evaporate the solvent (usually water), leaving behind the solute as crystals. The rate of evaporation determines the size of the crystals formed. Crystallisation: The process of forming crystals from a dissolved solute. Solvent: The substance that is evaporated during crystallisation. Solute: The substance left behind as crystals after the solvent has evaporated
48
Keyword: Filtration Key Point
Only particles small enough to fit through the gaps in the filter paper will pass through during filtration; larger particles are retained as residue.
49
Keyword: Crystallisation Key Point:
The substance with the lower boiling point (usually the solvent) evaporates during crystallisation, leaving behind the other substance as crystals.
50
Keyword: Hazard
Definition: Something that can cause harm, such as headaches, dizziness, cuts, or burns.
51
Keyword: Risk
Definition: The likelihood and consequences of a hazard happening.
52
Keyword: Moderate health hazard
Meaning: Causes skin irritation.
53
Keyword: Toxic
Meaning: Could cause death if swallowed or inhaled.
54
Keyword: Harmful to the environment
Meaning: Could cause damage to animal or plant life.
55
Keyword: Oxidising
Meaning: Makes flammable substances burn more easily.
56
Keyword: Corrosive
Meaning: Damages skin and clothing.
57
Keyword: Flammable
Meaning: Catches fire easily.
58
Keyword: Distillation
Definition: A technique used to separate a pure liquid from a mixture by evaporating the liquid and then condensing it for collection.
59
Keyword: Simple distillation
Definition: A separation method used to separate a solvent from a solution, where the dissolved solute has a much higher boiling point than the solvent. Process: Heat the solution. The solvent vaporizes and rises. The vapor is cooled and condensed. The remaining solution becomes more concentrated in solute.
60
Keyword: Fractional distillation
Definition: A separation method used when different liquids in a mixture have different boiling points. Process: Heat the mixture. Vapors rise through a column with varying temperatures. Vapors condense at temperatures below their boiling points. Different liquids are collected from different parts of the column.
61
Keyword: Chromatography
Definition: A technique used to separate mixtures of soluble substances by allowing them to move at different rates through a stationary phase, typically a chromatography paper.
62
Keyword: Chromatogram
Definition: The result of chromatography, where the separated components of a mixture are visible as spots or bands at different distances on the chromatography paper.
63
Keyword: Soluble
Definition: Capable of being dissolved in a solvent.
64
Keyword: Solute
Definition: The substance that is dissolved in a solution.
65
Keyword: Solvent
Definition: A substance capable of dissolving other substances.
66
Key Point: In chromatography
In chromatography, solutes are carried by their solvent, and different solutes move different distances along the chromatogram, causing them to spread out.
67
Key Point: In chromatography about particles
Key Point: Particles with larger mass or those with weak attractive forces move less distance along the chromatogram paper.
68
diagram for chromatogprahy
69
What does Rf stand for in chromatography?
Rf stands for Retention factor.
70
What do Rf values indicate in chromatography?
Rf values indicate how soluble a solute is in a particular solvent.
71
How is the Rf value calculated?
he Rf value is calculated using the equation: Rf = distance moved by sample / distance moved by solvent.
72
What does an Rf value less than 1 indicate?
An Rf value less than 1 indicates that the solute traveled a shorter distance than the solvent on the chromatogram.
73
What are the steps for conducting chromatography?
The steps include drawing a pencil line on the chromatography paper, placing dots of the sample on the line, placing the paper in the solvent, and allowing the solutes to move up the paper.
74
How many dots of the ink mixture are typically placed on the chromatography paper?
Three dots of the ink mixture are typically placed on the chromatography paper.
75
What does each dot on the chromatography paper represent?
Each dot represents a different sample or component of the mixture being analyzed.
76
EWhat is the significance of the distance moved by the sample and the solvent in chromatography?
The distance moved by the sample and the solvent helps determine the Rf value, which indicates the relative solubility of the sample in the solvent.
77
What does a higher Rf value indicate about the solute?
A higher Rf value indicates that the solute is more soluble in the solvent and travels further up the chromatogram.
78
Why is it important to use a pencil line when conducting chromatography?
Using a pencil line ensures that the starting point of the chromatogram is consistent and allows for accurate measurement of distances.
79
How is sea water desalinated to obtain drinking water?
Sea water is desalinated using simple distillation, where the water is evaporated and then condensed to form pure water, leaving the salt behind due to its higher boiling point.
80
Why is simple distillation not suitable for large-scale desalination of sea water?
Simple distillation requires a lot of energy, making it unsuitable for large-scale desalination unless there is abundant energy available.
81
What is the first step in the process of obtaining drinking water from sea water?
Small insoluble particles are allowed to settle to the bottom.
82
What is the purpose of filtering sea water through sand and gravel?
Filtering sea water through sand and gravel acts like filter paper, removing impurities and large particles from the water.
83
Why is chlorine added to drinking water during the purification process?
Chlorine is added to kill any microorganisms that might cause disease, ensuring the safety of the drinking wate
84
Why is distilled water used for laboratory experiments?
Distilled water is used in laboratory experiments to ensure there are no dissolved ions or impurities that could interfere with the experimental results
85
drinking water diagram

Science Year 9 (3 decks)

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