4.2 Physical and Chemical Properties

Every fire needs each of these components in order to burn with one exception. What is the exception?
1. Carbon
2. Fuel
3. Heat
4. Oxygen
What is the best example of cohesion?

Example 1: Dew sticks to this iris flower

Example 2: Mercury, a metal that exists as a liquid at room temperature, forms a single puddle in a beaker

Example 3: A frog snares its cricket meal

Example 4: This bee is almost completely coated with pollen
1. Example 2
2. Example 3
3. Example 1
4. Example 4
Sodium, seen here in this vial, is a soft lustrous silvery white metal that can be easily cut with a knife. If it were placed in a warm oven (about 100 °C) it would melt into a liquid. Its density is 0.968 g/cm³, very close to that of water, which means it would float depending on the water's temperature. Sodium would not float, however, because it reacts violently with water. Small pea-sized pieces of if would skip and sizzle on the water's surface until they were consumed and larger pieces would explode.

Which part of the description of sodium metal is a chemical description?
1. Sodium reacts with water
2. Sodium is soft and malleable
3. Sodium has a density very close to water
4. Sodium is lustrous and silvery white
Quartz, seen here, can be scratched by topaz (8 on the Mohs scale) but not by feldspar (6 on the Mohs scale).

That means it rates about 7 on the Mohs scale for
1. hardness.
2. malleability.
3. density.
4. ductility.
Passing water through an electrical current can test its purity. Water that contains dissolved salts will allow an electrical current to pass through it much more easily than pure water. This method of testing water purity is based on which physical property of water?
1. Conductivity
2. Viscosity
3. Colour
4. Density
Which statement about chemical properties of substances is false?
1. Heat must always be applied to a substance in order for it to undergo a chemical change
2. A chemical change must occur in order for a chemical property to be observed
3. A chemical change in a substance occurs through a process called a chemical reaction
4. Reactivity with other substances is an example of a chemical property
A dangerous situation can occur if household bleach and a cleanser containing ammonia are used together. The two chemicals interact with each other and a deadly gas called chlorine (Cl₂) is formed. The process can be written as follows:

2NaOCl + 2NH₃ --> 2NaONH₃ + Cl₂

This process is an example of
1. a chemical reaction.
2. sublimation.
3. a physical change.
4. heat formation.
What two physical changes are involved in the process of freeze-drying?
1. Freezing and sublimation
2. Freezing and evaporation
3. Freezing and combustion
4. Precipitation and sublimation
Lead can be deformed under compressive stress but it cannot normally be stretched into other shapes such as a wire. This means that lead is
1. malleable.
2. viscous.
3. ductile.
4. conductive.
The amount of mass in a given volume (of most substances) increases as the temperature is decreased. This is an example of a change in
1. density.
2. mass.
3. viscosity.
4. hardness.