Detergents

Question 1

Low temperature washing

Answer 1

• It is good for the environment to wash clothes at 40 °C instead of at higher temperatures.
• Washing machines have to heat up a lot of water. This needs energy, so the lower the temperature of the water less energy is used and smaller volumes of greenhouse gases are put into the atmosphere.
• Washing clothes at low temperatures is also good for coloured clothes - many dyes are easily damaged by high temperatures.

Question 2

What does a detergent do?

Answer 2

• A detergent lifts the grease stain off into the water.
• When clothes are washed, dirt is lifted off the clothes and put into water. If the dirt is made from oil or grease it will not dissolve in water. Detergents remove fat or oil stains by forming strong intermolecular bonds with both the oil and water.

Question 3

What are the parts of the detergent molecules?

Answer 3

Question 4

What do the detergent moles ends do?

Answer 4

• The hydrophobic end forms intermolecular bonds with molecules of oil and grease.
• The hydrophillic end forms strong intermolecular bonds with molecules.

Question 5

Process of grease lifting

Answer 5

1. The hydrophobic end of detergent molecules form strong intermolecular forces with the molecules of grease. This leaves the hydrophilic ends on the outside.
2. Eventually, so many detergent molecules have form strong intermolecular forces with the grease that the outside of the grease is covered in hydrophilic ends.
3. The grease is now surrounded by hydrophilic ends that form strong intermolecular forces with the water molecules, and so it lifts off the clock into the water.

Question 6

Why is dry cleaning used?

Answer 6

• Some fabrics will be damaged if they are washed in water - they must be dry cleaned.
  
  • A dry-cleaning machine washes clothes in an organic solvent. The ‘dry’ does not mean that no liquid are used, just that the liquid is not water.

Question 7

Dry cleaning solvent

Answer 7

• Grease-based stains do not dissolve in water but they do dissolve easily in a dry cleaning solvent.
• The solvent molecules then surround of grease and pull them from the fabric.

Question 8

Molecules of grease and solvent.

Answer 8

• Molecules of grease form intermolecular forces with molecules of grease.
• Molecules of solvent form intermolecular forces with molecules of solvent.

Question 9

Molecules of Water and Grease

Answer 9

• Molecules of water are held together by stronger intermolecular forces to other molecules of water.
• Molecules of water cannot form intermolecular bonds with the molecules of grease because the attractive forces are much too strong between themselves.