Bonding & Substance Properties Flashcards

All 47 cards in this deck

Which two changes of state take place at the melting point?

Melting (solid to liquid) and freezing (liquid to solid).

Which two changes of state take place at the boiling point?

Boiling (liquid to gas) and condensing (gas to liquid).

What are the steps to predict the state of a substance at a given temperature?

e.g. bromine, melting point $-7^\circ$C, boiling point $59^\circ$C, at $100^\circ$C

1. Below the melting point it is a solid: $100 > -7$, so not solid.

2. Between melting and boiling point it is a liquid: $100 > 59$, so not liquid.

3. Above the boiling point it is a gas: bromine is a gas at $100^\circ$C.

What decides how much energy is needed to change a substance from solid to liquid or liquid to gas?

The strength of the forces between the particles, which depends on the type of bonding and the structure of the substance.

True or false? The stronger the forces between the particles of a substance, the lower its melting and boiling points.

False. The stronger the forces, the higher the melting and boiling points, because more energy is needed to overcome them.

True or false? At a temperature above its boiling point, a substance is a liquid.

False. Above the boiling point the substance is a gas.

In the simple model of the three states of matter, how are the particles represented?

As small solid spheres.

Give two limitations of the simple particle model in which particles are solid spheres.

There are no forces shown between the particles, and all particles are shown as solid spheres (molecules are not shown as groups of atoms).

True or false? The simple particle model shows the forces between particles.

False. The model shows no forces, so it cannot explain why energy is needed to change state.

True or false? It is correct to say a single bromine molecule has a boiling point of $59^\circ$C.

False. Boiling point is a bulk property; it depends on the intermolecular forces between many molecules.

In terms of particle theory, what happens to the particles when a solid melts?

The particles gain enough energy to overcome the forces holding them in fixed positions, so they can move past one another.

What are the state symbols used in chemical equations for solid, liquid and gas?

$(s)$ for solid, $(l)$ for liquid, $(g)$ for gas.

What does the state symbol $(aq)$ mean in a chemical equation?

Aqueous — the substance is dissolved in water.

True or false? Liquid water produced in a reaction is written as $\mathrm{H_2O(aq)}$.

False. It is written $\mathrm{H_2O(l)}$; $(aq)$ is only for substances dissolved in water.

What state symbol is given to an insoluble precipitate formed in a solution?

$(s)$, because it is a solid.

e.g. $\mathrm{BaSO_4(s)}$

What are the steps to add state symbols to an equation?

e.g. $\mathrm{HCl} + \mathrm{NaOH} \rightarrow \mathrm{NaCl} + \mathrm{H_2O}$

1. Substances dissolved in water get $(aq)$: $\mathrm{HCl(aq)}$, $\mathrm{NaOH(aq)}$, $\mathrm{NaCl(aq)}$.

2. Pure liquids get $(l)$: $\mathrm{H_2O(l)}$.

3. Insoluble solids get $(s)$ and gases get $(g)$: none here.

What type of structure do ionic compounds have?

A regular giant ionic lattice.

What holds the particles together in a giant ionic lattice?

Strong electrostatic forces of attraction in all directions between oppositely charged ions.

Why do ionic compounds have high melting and boiling points?

Large amounts of energy are needed to break the many strong electrostatic forces between the ions in the giant lattice.

When do ionic compounds conduct electricity, and why?

When melted or dissolved in water, because the ions are then free to move so charge can flow.

True or false? Solid sodium chloride conducts electricity.

False. The ions are held in fixed positions in the lattice, so they are not free to move and carry charge.

True or false? An ionic compound dissolved in water conducts electricity because its electrons are free to move.

False. It conducts because the ions are free to move and carry the charge.

What states are substances made of small molecules usually in at room temperature?

Gases or liquids, because they have relatively low melting and boiling points.

Which forces are overcome when a substance made of small molecules melts or boils?

The weak intermolecular forces between the molecules — not the covalent bonds inside them.

True or false? Simple molecular substances have low boiling points because their covalent bonds are weak.

False. The covalent bonds are strong; it is the intermolecular forces between molecules that are weak.

Why do substances made of small molecules not conduct electricity?

The molecules do not have an overall electric charge, so there is nothing to carry charge.

How do the intermolecular forces of molecular substances change as the molecules get larger?

They increase in strength, so larger molecules have higher melting and boiling points.

What are the steps to explain why one molecular substance has a higher boiling point than another?

e.g. butane boils at a higher temperature than methane

1. State the size difference: butane has larger molecules.

2. Larger molecules have stronger intermolecular forces.

3. More energy is needed to overcome them, so the boiling point is higher.

Why are polymers solids at room temperature?

Their molecules are very large, so the intermolecular forces between them are relatively strong.

What type of bonds link the atoms within a polymer molecule?

Strong covalent bonds.

What features of a bonding and structure diagram show that a substance is a polymer?

A very large molecule made of a repeating unit of atoms joined by covalent bonds.

True or false? The intermolecular forces between polymer molecules are weaker than those between small molecules.

False. Polymer molecules are much larger, so their intermolecular forces are relatively strong.

Name three examples of substances with giant covalent structures.

Diamond, graphite (both forms of carbon) and silicon dioxide (silica).

Why do giant covalent structures have very high melting points?

All the atoms are linked by strong covalent bonds, and many of these bonds must be overcome, needing a lot of energy.

What state are substances with giant covalent structures in at room temperature?

Solids, because of their very high melting points.

True or false? Melting silicon dioxide only involves overcoming weak intermolecular forces.

False. There are no intermolecular forces to overcome; strong covalent bonds throughout the structure must be broken.

What features of a bonding and structure diagram show a giant covalent structure?

Many atoms all joined to their neighbours by covalent bonds in a lattice that continues beyond the diagram.

What type of structure and bonding do metals have?

Giant structures of atoms held together by strong metallic bonding.

Why do most metals have high melting and boiling points?

They have giant structures with strong metallic bonding, so a lot of energy is needed to overcome the bonds.

Why can pure metals be bent and shaped?

Their atoms are arranged in layers, which can slide over each other.

What is an alloy?

A metal mixed with other metals (or elements); alloys are harder than pure metals.

Why are alloys harder than pure metals?

The atoms are of different sizes, so the layers are distorted and cannot slide over each other easily.

True or false? Pure metals are too soft for many uses, which is why they are mixed to make alloys.

True. Alloys are harder because different sized atoms distort the layers of atoms.

Why are metals good conductors of electricity?

The delocalised electrons carry electrical charge through the metal.

Why are metals good conductors of thermal energy?

Thermal energy is transferred by the delocalised electrons.

True or false? Metals conduct electricity because their ions are free to move.

False. It is the delocalised electrons that move and carry the charge; the metal ions stay in place.

True or false? A substance with a high melting point that conducts electricity as both a solid and a liquid is likely to be a metal.

True. Metals have delocalised electrons that carry charge in the solid and liquid state.