Recap chapter 7

• Scheikunde
• Middelbare school
• havo
• Leerjaar 3

What are we going to do today?

• Recap chapter 7 through questions          
  

Chapter 7 quick review

Conductivity of electricity

simple experiment =>

Different substances conduct electricity in different states.

When do metals conduct electricity?

1. solid and dissolved
2. solid and liquid
3. liquid and dissolved
4. never

Which particles are responsible for electrical conductivity in a liquid metal

1. positively charged metal atoms
2. negatively charged electrons
3. freely moving electrons
4. freely moving electrons en + charged metal atoms

Metals

* Formula consists only of symbols of metals

* Conduct electricity in solid and liquid state due to negatively charged electrons which move can move freely in the metallic lattice. In liquid state the positively charged metal atoms conduct as well.

* Metal bond is very strong => high melting points

Francium is a

1. precious metal
2. semi-precious metal
3. reactive metal
4. highly-reactive metal

Metals

* electrons are also responsible for the flexibility of metals.

* precious, semi-precious, reactive and highly reactive metals. (corrosion)

* Alloys: change characteristics, e.g. less flexibel:

When do salts conduct electricity?

1. solid and dissolved
2. solid and liquid
3. liquid and dissolved
4. never

Salts

* formula consists of symbols of metals and

non-metals.

* Cannot conduct electricity in solid state, because the charged particles (ions) cannot move freely in the ionic lattice.

* Ions are formed because electrons leave the outer orbit (positive) or enter the outer orbit (negative).

Salts

* Ionic bonds are strong, but the ionic lattice is

not flexible (applying force will disrupt the ionic bond and the salt will fall apart.

* Salts in water:

NaCl(s)=>Na+ (aq)+Cl-(aq)

When do molecular substances conduct electricity?

1. solid and dissolved
2. solid and liquid
3. liquid and dissolved
4. never

Barium chloride (BaCl2) is dissolved in water. Choose the correct chemical equation.

1. BaCl(s) =>Ba+(aq)+Cl-(aq)
2. Ba+(aq)+Cl-(aq) =>BaCl(s)
3. BaCl2(s) =>Ba2+(aq)+2Cl-(aq)
4. Ba2+(aq)+2Cl-(aq) =>BaCl2(s)

The melting point of sodium chloride is 801 °C, explain why this is so high.

Molecular substances

* formula consists of symbols of non-metals.

* Attractive forces between molecules => van der Waals forces => result in van der Waals bonding.

=> the greater the molecule mass and surface the stronger the van der Waals bonding.

Molecular substances

* Covalent bond or atomic bond

* Covalency or covalence

* Hydrophylic and hydrophobic (NH- and/or OH-groups!)

* emulsifier

Does the following substance readily dissolve in water?

1. Yes
2. No

Does the following substance readily dissolve in water?

1. Yes
2. No

What is the covalency of Se

1. 1
2. 2
3. 3
4. no covalency

What is the covalency of Sr

1. 1
2. 2
3. 3
4. no covalency

What kind of substance is C2H6

1. Metal
2. Salt
3. Molecular substance

What kind of substance is CaCO3

1. Metal
2. Salt
3. Molecular substance

What kind of substance is Kr

1. Metal
2. Salt
3. Molecular substance

What kind of substance is Hf

1. Metal
2. Salt
3. Molecular substance