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STEM core > [Sem 1] Chemistry Basics > Flashcards

[Sem 1] Chemistry Basics Flashcards

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1
Q

What are the five states of matter?

A

Solid, Liquid, Gas, Plasma, Bose Einstein condensates

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2
Q

Describe the characteristics of particles in a solid.

A

Very close and have little energy. They vibrate in a fixed position.

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3
Q

How do particles in a liquid behave compared to those in a solid?

A

Further apart and have more energy. They are not closely bonded, so they can take the shape of any container.

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4
Q

Explain the behavior of particles in a gas.

A

Have a lot of energy and are always moving in many directions. They can be compressed as there is a large amount of space between them.

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5
Q

What happens to particles when the temperature of a substance increases?

A

Melting and evaporating.

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6
Q

How does decreasing temperature affect particles?

A

Condensation, freezing, and sublimation.

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7
Q

Define elements and compounds

A

Elements are pure substances made up of only one type of atom, while compounds are formed when two or more different elements are chemically bonded together.

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8
Q

What are molecules?

A

Any atoms connected together by a bond, describing elements bonded together. For example, O2 represents oxygen molecules.

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9
Q

What are ions?

A

Atoms that have gained or lost electrons are called ions. They do this to become more stable by achieving a full shell of electrons.

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10
Q

What are cations?

A

Atoms that have lost electrons, and are positively charged. Metals tend to lose electrons to form this.

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11
Q

What are anions?

A

Atoms that have gained electrons and are negatively charged. Non-metals often gain electrons to form this.

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12
Q

What are isotopes?

A

Atoms with a different number of neutrons.

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13
Q

Why are many isotopes radioactive?

A

Because they strive to return to a stable state. This often results in a lot of energy being released.

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14
Q

What is radioactive decay?

A

The process by which unstable isotopes lose particles, usually electrons, in order to achieve a more stable configuration.

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15
Q

How are isotopes represented in notation?

A

Written with the element name followed by their atomic mass. E.g. Carbon-14 represents carbon with an atomic mass of 14.

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16
Q

How are periods arranged on the periodic table?

A

In rows from left to right. All elements in the same period have the same number of electron shells.

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17
Q

How are groups arranged on the periodic table?

A

In columns going up and down. Elements in these have the same number of valence electrons on their outer shell.

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18
Q

Trend of going down and across?

A

The atomic number and mass increase due to the increasing number of particles within the nucleus.

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19
Q

Trend of the atomic radius on the periodic table?

A

Increases going down a group and decreases going across a period.

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20
Q

How does reactivity change within groups and periods?

A

Metals are more reactive going down a group, while non-metals are less reactive.

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21
Q

What is core charge and how does it change across a period?

A

Increases across a period. It is calculated as the number of protons minus the number of inner shell electrons.

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22
Q

Define electronegativity and describe its trend across the periodic table.

A

The ability of an atom to attract electrons towards itself. It increases across a period and decreases down a group.

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23
Q

Explain the trend of first ionization energy across the periodic table.

A

Increases across a period and decreases down a group. It represents the energy required to remove one electron from the valence shell.

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24
Q

What is the basic structure of Bohr’s model of the atom?

A

Nucleus of the atom in the middle, surrounded by electron shells. Electrons are arranged in shells following 2,8,8,2 rule.

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25
Q

What is the octet rule?

A

Atoms like to have 8 electrons in their outer shell, making them stable. When they don’t, they react to form stable compounds.

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26
Q

What is ionic bonding?

A

Atoms transfer electrons. It occurs between a metal and a non-metal.

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27
Q

How does ionic bonding work?

A

Metals lose electrons to become positively charged, while non-metals gain electrons to become negatively charged. This creates a strong attraction between them.

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28
Q

What is covalent bonding?

A

Happens between two non-metals. Instead of giving away or taking electrons, they share them.

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29
Q

What is metallic bonding?

A

Occurs between metals. It involves a sharing of detached electrons among positively charged cations.

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30
Q

What holds together in ionic bonds?

A

Positive and negative charges hold together. Positive ions are attracted to negative ions, forming an electrostatic attraction and a lattice structure.

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31
Q

What are electrostatic forces?

A

The forces of attraction between particles of opposite charge.

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32
Q

What happens to electrons in metallic bonding?

A

They leave the outer shells of metal atoms, forming positive metal ions and a ‘sea’ of delocalised electrons.

33
Q

What are delocalized electrons?

A

Not associated with a single atom; they form a ‘sea’ of electrons in metallic bonding.

34
Q

Describe the structure of solid metals.

A

Closely packed metal ions arranged in a regular metallic lattice structure with layers of metal ions.

35
Q

How do metallic bonds contribute to the physical properties of metals?

A

Explains properties such as high melting point, good conductivity of heat and electricity, high density, malleability, ductility, and shiny appearance.

36
Q

What is the effect of metallic bonding on melting and boiling points?

A

High melting and boiling temperatures due to the strong electrostatic forces between metal ions and delocalised electrons.

37
Q

What is an alloy?

A

A metallic substance made of two or more elements, with at least one being a metal, and can be produced in compound or solution form.

38
Q

How are alloys made?

A

Made by heating both elements to form a liquid, turning them into powders and combining them under heat and pressure, or by shooting beams of ions into the surface layer of a metal.

39
Q

What are reactants in a chemical reaction?

A

The starting substances in a chemical reaction.

40
Q

What are products in a chemical reaction?

A

The substances formed at the end of a chemical reaction.

41
Q

How do you know a chemical reaction has occurred?

A

By the presence of smoke, a change in color, the formation of a new substance, or a change in smell.

42
Q

What is the law of conservation of mass?

A

In a chemical reaction, the total mass of the reactants is equal to the total mass of the products. Mass is neither created nor destroyed.

43
Q

Why do we need to balance chemical equations?

A

To satisfy the law of conservation of mass, ensuring that the same amount of each element is present on both sides of the equation.

44
Q

How do you balance chemical equations?

A

Adjust coefficients to ensure the same number of atoms of each element on both sides of the equation.

45
Q

What do coefficients in a chemical equation represent?

A

They indicate the number of molecules of each reactant or product.

46
Q

What do subscripts in a chemical equation represent?

A

They indicate the number of atoms of a particular element in a molecule.

47
Q

What happens in a synthesis reaction?

A

Two or more substances combine to form a more complex substance.

48
Q

What happens in a decomposition reaction?

A

A more complex substance breaks down into simpler parts, opposite of synthesis reaction.

48
Q

What happens in a single replacement reaction?

A

One element replaces another in a compound, forming a new compound and a free element.

49
Q

What happens in a double replacement reaction?

A

Cations and anions of two compounds switch places, forming two new compounds.

50
Q

What is a precipitation reaction?

A

When two aqueous ionic compounds form an insoluble ionic compound called a precipitate.

51
Q

What is a neutralization reaction?

A

Occurs between an acid and a base to form a salt (ionic compound) and water.

52
Q

What is a combustion reaction?

A

When a fuel combines with oxygen, producing heat, light, carbon dioxide, and water.

53
Q

What is complete combustion?

A

Oxidation of a hydrocarbon producing only carbon dioxide and water.

54
Q

What is incomplete combustion?

A

Oxidation of a hydrocarbon producing carbon monoxide and carbon (soot).

55
Q

What is self-ionization of water?

A

When a small amount of water molecules dissociate to form equal numbers of hydrogen (H+) ions and hydroxide (OH–) ions.

56
Q

How do acids affect the pH of a solution?

A

Increase the amount of hydronium ions (H3O+) in a solution, making it more acidic. The stronger the acid, the more readily it donates H+ ions.

56
Q

What are acids?

A

Substances that dissolve in water and produce hydrogen (H+) ions.

57
Q

What are bases?

A

Substances that dissolve in water to produce hydroxide (OH–) ions.

58
Q

What is the pH scale?

A

A scale used to measure the acidity or basicity (alkalinity) of a substance. It ranges from 0 to 14, with lower values indicating acidity (H+ ions) and higher values indicating alkalinity (OH– ions).

58
Q

How do bases affect the pH of a solution?

A

Increase the amount of hydroxide ions (OH–) in a solution, making it more basic. The stronger the base, the more readily it donates OH– ions.

59
Q

What does a neutral solution have on the pH scale?

A

Equal amounts of hydronium ions (H3O+) and hydroxide ions (OH–), appearing as pH 7 on the scale. Water.

60
Q

What is activation energy?

A

The minimum amount of energy required to start a chemical reaction.

61
Q

What is collision theory?

A

For a chemical reaction to occur, molecules must collide with each other in the correct orientation and with enough energy to break bonds and form new ones.

62
Q

How does temperature affect reaction rates?

A

Higher temperatures increase reaction rates by providing more energy for molecular collisions, while lower temperatures decrease reaction rates as molecules have less energy and are less likely to collide.

63
Q

How does pressure affect reaction rates, especially in gases?

A

Increasing pressure in gases leads to a greater density of molecules, increasing the likelihood of collisions and thus reaction rates. Decreasing pressure has the opposite effect.

64
Q

How does concentration affect reaction rates?

A

Higher concentrations of reactants increase reaction rates by increasing the frequency of collisions. Lower concentrations decrease reaction rates.

65
Q

How does surface area/particle size affect reaction rates?

A

Smaller particle sizes (e.g., powders) have higher reaction rates due to their larger surface area available for collisions. Larger particle sizes (e.g., lumps) have lower reaction rates as only the surface particles can participate in collisions.

66
Q

What are polymers?

A

A substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits.

67
Q

What are monomers?

A

Molecules that can bond together with other identical molecules to form a polymer.

68
Q

What are co-polymers?

A

Polymers with more than one repeating monomer in a chain, formed when two different monomers form a long chain.

69
Q

How are polymers made?

A

By joining repeating units of monomers together through a chemical reaction called polymerisation.

69
Q

What are synthetic polymers?

A

Manufactured materials, such as plastics. Example: Teflon.

70
Q

What are natural polymers?

A

Include materials like cotton, wool, leather, and rubber.

71
Q

What is condensation polymerisation?

A

Occurs when two monomers join together, losing a small molecule like water in the process.

72
Q

What are thermoplastics?

A

Polymers that soften when heated and can be moulded into different shapes. Example: Polythene.

73
Q

What are thermosetting plastics?

A

Do not soften when heated but char instead. They are hard, rigid, and sometimes brittle. Example: Bakelite.

74
Q

What percentage are you getting on the test?

A

0%

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