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Bonding and substances flashcards
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Card 1
How does the strength of forces between particles influence the melting and boiling points of a substance?
The amount of energy needed to change state from solid to liquid and from liquid to gas depends on the strength of the forces between the particles. Stronger forces require more energy to overcome, resulting in higher melting and boiling points for the substance.
Card 2
DEFINITION: Distinguish between boiling and evaporation.
Boiling occurs at a specific temperature (boiling point) where thermal energy causes gas bubbles to form inside the liquid, allowing particles to escape from both the surface and within the liquid. Evaporation, however, occurs over a range of temperatures below the boiling point, only at the surface of the liquid where high-energy particles escape.
Card 3
Why are ionic compounds poor conductors of electricity in the solid state but good conductors when molten or in solution?
In the solid state, ions in an ionic compound are in fixed positions within the giant lattice structure and cannot move to carry a charge. However, when molten or dissolved in water, the ions become mobile and are able to move freely, thus allowing them to conduct electricity.
Card 4
DEFINITION: Define the term 'sublimation' and provide an example of a substance that undergoes this process.
Sublimation is when a solid changes directly into a gas without passing through the liquid state. Examples of substances that undergo sublimation include iodine and solid carbon dioxide.
Card 5
Explain how heating a solid leads to it melting, according to particle theory.
When a solid is heated, its particles absorb thermal energy, which is converted into kinetic energy. This causes the particles to vibrate more intensely. As the temperature increases, they vibrate so much that the bonds between them break, causing the solid to expand and eventually melt.
Card 6
DEFINITION: What are state symbols, and why are they included in chemical equations?
State symbols are abbreviations (s, l, g, aq) written after each chemical formula in brackets to indicate the physical state of a substance. They are included in chemical equations to provide crucial information about the reaction conditions and the physical form of reactants and products.
Card 7
Why do substances consisting of small molecules generally have low melting and boiling points?
Small molecules have strong covalent bonds within the molecules, but only weak intermolecular forces between them. These weak intermolecular forces require little energy to overcome, resulting in relatively low melting and boiling points for these substances.
Card 8
DEFINITION: What is the key difference between the melting point and freezing point of a pure substance?
For a pure substance, the melting point and freezing point are the same specific temperature. Melting is the process of a solid changing to a liquid by absorbing energy, while freezing is the reverse process of a liquid changing to a solid by losing energy at that identical temperature.
Card 9
How does the particle theory model represent the particles in the three states of matter, and what are its limitations?
The particle theory model represents particles as small, solid, inelastic spheres. Its limitations include not considering the differences caused by various types of particles (atoms, ions, molecules) or mixtures, and it fails to account for the specific intermolecular forces between different particles in different substances.
Card 10
DEFINITION: What does the state symbol (aq) represent in a chemical equation?
The state symbol (aq) stands for 'aqueous,' meaning the substance is dissolved in water. It indicates that the substance exists as a solution rather than a pure liquid or solid.
Card 11
Explain why ionic compounds typically have high melting and boiling points.
Ionic compounds have giant lattice structures with strong electrostatic forces of attraction between oppositely charged ions in all directions. A significant amount of energy is required to overcome these strong forces, leading to high melting and boiling points.
Card 12
DEFINITION: What is meant by a 'physical change' in the context of changing states of matter?
A physical change, when referring to changes of state, means that the particles themselves remain the same. Only the forces between the particles change, altering their arrangement and movement, but not their chemical identity.
Card 13
How does increasing the size of molecules affect the melting and boiling points of substances made of small molecules?
As the molecules increase in size, the strength of the weak intermolecular forces between them generally increases. Consequently, more energy is needed to overcome these stronger intermolecular forces, leading to an increase in the melting and boiling points.
Card 14
DEFINITION: Describe the arrangement and movement of particles in a gas according to the simple model of states of matter.
In a gas, particles are randomly arranged and are far apart from each other. They move quickly in all directions, with very weak forces of attraction between them.
Card 15
DEFINITION: What is condensation, and over what range of temperatures does it occur?
Condensation is the process where a gas changes into a liquid upon cooling. It occurs over a range of temperatures as gas particles lose energy, group together, and form a liquid when they lack the energy to bounce away after collisions.
Card 16
How does the charge on ions affect the melting point of an ionic compound?
The greater the charge on the ions in an ionic compound, the stronger the electrostatic forces of attraction between them. This increased force requires more energy to overcome, resulting in a higher melting point for the ionic compound.
Card 17
DEFINITION: What are the three states of matter, and what property typically dictates a substance's state?
The three states of matter are solids, liquids, and gases. A substance's state is typically dependent on temperature, and to a lesser extent, pressure.
Card 18
Explain why the temperature of a substance does not change during a phase change, such as melting or boiling.
During a phase change, the heat energy absorbed is used to overcome the forces between particles rather than increasing their kinetic energy. This energy is used to break bonds or increase the distance between particles, so the temperature remains constant until the entire substance has changed state.
Card 19
DEFINITION: How do the arrangement and closeness of particles differ between a solid and a liquid?
In a solid, particles are in a regular arrangement and are very close together. In contrast, in a liquid, particles are randomly arranged, but still close to each other, allowing them to move around each other.
Card 20
Describe the process of freezing and its relationship to the melting point.
Freezing is when a liquid changes into a solid, which is the reverse of melting. This process occurs at the same specific temperature as the melting point for a pure substance, requiring a significant decrease in temperature or loss of thermal energy.
Card 21
DEFINITION: What are 'intermolecular forces' in the context of small molecules?
Intermolecular forces are the weak attractive forces that exist between individual molecules in a substance. These forces are distinct from the stronger covalent bonds that hold atoms together within each molecule.
Card 22
Why is it important to specify 'ions' moving and carrying a charge when explaining the conductivity of molten or dissolved ionic compounds, rather than 'electrons'?
It is crucial to specify 'ions' because ionic compounds conduct electricity due to the movement of their charged ions, not free electrons. Unlike metals, ionic compounds do not have delocalised electrons, and their conductivity relies solely on the mobility of their constituent ions.
Card 23
DEFINITION: What is the 'boiling point' of a substance?
The boiling point is the specific temperature at which a liquid changes into a gas through the process of boiling. At this temperature, bubbles of gas form throughout the liquid, allowing particles to escape from both the surface and within the liquid.
Card 24
How does particle theory explain the expansion of a solid when heated, prior to melting?
According to particle theory, when a solid is heated, its particles absorb thermal energy and convert it into kinetic energy, causing them to vibrate more vigorously. This increased vibration forces the particles to move slightly further apart from their fixed positions, leading to the overall expansion of the solid.
Card 25
Explain why ionic compounds are poor conductors of electricity in the solid state but good conductors when molten or in solution.
In the solid state, ions in an ionic compound are held in fixed positions within a giant lattice structure by strong electrostatic forces, preventing them from moving and carrying a charge. However, when melted or dissolved in water, these forces are overcome, allowing the ions to become mobile and thus conduct electricity.
Card 26
DEFINITION: Distinguish between the bonds found within small molecules and the forces found between small molecules.
Within small molecules, atoms are held together by strong covalent bonds. Between small molecules, there are weak intermolecular forces. It is these weak intermolecular forces that are overcome during melting and boiling, not the strong covalent bonds.
Card 27
DEFINITION: Define what a polymer is and how it is formed from monomers.
A polymer consists of very large molecules formed by linking together a large number of smaller molecules called monomers. The atoms within the polymer molecules are connected by strong covalent bonds, forming long chains.
Card 28
Explain why giant covalent structures, such as diamond, have high melting points.
Giant covalent structures have high melting points because they consist of a huge number of non-metal atoms bonded together via strong covalent bonds. A significant amount of energy is required to overcome these strong covalent bonds throughout the entire lattice structure.
Card 29
DEFINITION: What is the primary characteristic of metallic bonding that allows metals to conduct electricity?
Metallic bonding involves a lattice of positive metal ions surrounded by a 'sea' of delocalised electrons. These delocalised electrons are not bound to any specific atom and are free to move throughout the structure, carrying an electrical charge.
Card 30
How does the presence of delocalised electrons contribute to metals being good conductors of heat?
The delocalised electrons in metals are free to move and collide with each other and the positive metal ions. This movement allows them to efficiently transfer thermal energy throughout the metallic structure, making metals good conductors of heat.
Card 31
DEFINITION: What is an alloy, and how does its structure differ from a pure metal?
An alloy is a mixture of two or more metals, or a metal with a non-metal. Its structure differs from a pure metal because it contains atoms of different sizes, which distort the regular layering found in pure metals.
Card 32
Explain why alloys are typically harder than pure metals.
Alloys contain atoms of different sizes, which distort the regular arrangement of layers found in pure metals. This distortion makes it more difficult for the layers of atoms to slide over each other when a force is applied, thus increasing the hardness of the alloy.
Card 33
DEFINITION: What is the significance of the state symbol (aq) compared to (l) when describing a substance like ethanol?
The state symbol (l) indicates that a substance is a pure liquid at room temperature, such as pure ethanol. In contrast, (aq) signifies that the substance is dissolved in water, forming an aqueous solution, which is how alcohol is often used.
Card 34
Why do ionic compounds generally have high melting and boiling points?
Ionic compounds form giant lattice structures with strong electrostatic forces of attraction between oppositely charged ions in all directions. A large amount of energy is required to overcome these strong forces, leading to high melting and boiling points.
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