Chemical Composition and Properties of Matter – Assessment (Chapter 2 and 13)
In this assessment, questions are based on chemical composition, states and properties of matter, compounds and mixtures.
Name two categories used to classify properties of matter.
Intensive and Extensive
Explain why all samples of a substance have the same intensive properties
every sample of a substance have the same chemical composition
Why can samples of gold(Au) and copper (Cu) have the same extensive properties but not the same intensive properties?
Samples of gold and copper can have the same mass and volume(extensive properties), but have different intensive properties because they have different chemical composition
Name three states of matter
solid, liquid and gas
Describe the two categories use to classify physical changes
reversible and irreversible
Is the freezing of mercury(Hg) a reversible or irreversible physical change?
Reversible because solid mercury can be melted
Which property most easily distinguishes sodium chloride (NaCl) from the other solids in Table 2.1?
Color-sodium chloride is the only white solid on the table
How are liquids and solids alike?How are they different?
They are alike because they have definite volumes but different because a solid has a definite shape while a liquid has an indefinite shape
What physical properties could be used to separate iron filings(Fe) from table salt(NaCl)?
Iron is magnetic, salt is not magnetic; salt dissolves in water, iron will not dissolve in water.
How are mixtures classified?
homogeneous of heterogeneous
What type of properties can be used to separate mixtures?
differences in physical properties such as: particle size, phase , solubility, boiling point
Explain the term phase as it relates to homogeneous and heterogeneous mixtures.
A phase is any part of a sample, with a uniform composition. There is one phase in a homogeneous mixture and two or more in a heterogeneous mixture.
Classify each of the following as a homogeneous or heterogeneous mixture:Food Coloring, Ice cubes in liquid water, mouthwash, and mashed, un-peeled potatoes
homogeneous, heterogeneous, homogeneous, and heterogeneous
How are a substance and a solution similar? How are they different?
Both substances, and a solution have a uniform composition throughout. For differences, a substance has a definite composition where as a a solution has a variable composition
When would you use filtration to separate a mixture? When would you use distillation to separate a mixture?
in a heterogeneous mixture;to separate a liquid from substances dissolved into liquids
Describe a procedure that could separate a mixture of sand and table salt.
Add water to the mixture to dissolve the salt, filter the mixtures the sand will remain in the filter paper, the salt solution will pass through, evaporate the water from the salt solution to obtain the salt
Liquid A and Liquid B are clear liquids. They are placed in evaporating dishes and allowed to evaporate. When evaporation is complete, there is a white solid container B but no solid in container A. What can you infer about the two liquids?
Liquid A is probably a pure substance while liquid B is a mixture
How is compound different from an element?
Compounds can be broken down into simpler substances by chemical means, but elements cannot be broken down further
How can you distinguish a substance from a mixture>
a substance has a fixed composition, whereas the composition of a mixture may vary
What are chemical symbols and chemical formulas used for?
Chemical symbols represent elements, chemical formulas represent compounds
Name two methods that can be used to break down compounds into simpler substance.
heat, electric current
Classify each of these samples of matter as an element, compound, or mixture.
Write the chemical symbol for each element
Name the chemical elements for each symbol: C, Ca, Fe, K, Au, Cu
carbon, calcium, iron, potassium, gold and copper
How does a chemical change affect the composition of matter?
the composition of matter always changes during a chemical change
Name four possible clues that a chemical change has taken place.
a transfer of energy, a change in color, the production of a gas and the formation of precipitate
In a chemical reaction, how does the mass of the reactants compare with the mass of the products?
the mass of the products is always equal to the mass of the reactants
What is the main difference between physical changes and chemical changes?
Physical change, the chemical composition of a substance does not change
Classify the following changes as physical changes or chemical changes.
salt dissolves in water
milk turns sour
According to the law of conservation of mass, when is mass conserved?
mass is conserved in every physical change of chemical reaction
Hydrogen and oxygen react chemically to form water. How much water would form if 4.8 grams of hydrogen reacted with 38.4 grams of oxygen?
4.8 g hydrogen+ 38.4 g oxygen=43.2 g water
Briefly describe the assumptions of kinetic theory as applied to gases.
a gas is composed of tiny particles whose motion is rapid, constant, and random; collisions between particles are perfectly elastic
Use kinetic theory to explain what causes gas pressure.
Gas pressure is the result of simultaneous collisions of billions of rapidly moving particle with an object
how is the Kelvin temperature of a substance related to the average kinetic energy of its particles ?
The kelvin temperature is directly proportional to the average Kinetic energy of the particles
Convert the following pressures to kPa
45 mm Hg
By what factor does the average kinetic energy of the oxygen molecules in the cylinder decrease if a cylinder of oxygen gas is cooled from K(27 degrees Celsius) to 150 K (-124 degrees Celsius)
What factors help determine the physical properties of liquids?
the interplay between the disruptive motions of particles in a liquid and the attractions among the particles
In terms of kinetic energy, explain how a molecule in a liquid evaporates.
a molecule with a certain minimum kinetic energy can escape from the surface of the liquid and vaporize
A liquid is in a closed container and has a constant vapor pressure. What is the relationship between the rate of evaporation of the liquid and the rate of condensation of the vapor in the container?
Rate of evaporation of the liquid equals the rate of condensation of the vapor
What conditions must exist for a liquid to boil?
particles throughout the liquid must have enough kinetic energy to vaporize
Use figure 13.9 to determine the boiling point of each liquid.
ethanoic acid at 27kPa
chloroform at 80 kPa
ethanol at 50 kPa
76 degree Celsius
52 degree Celsius
62 degree Celsius
Explain why the boiling point of a liquid varies with atmospheric pressure
Boiling occurs when the vapor pressure of a liquid equals the external pressure. If the atmospheric pressure changes, the boiling point will change
Explain how evaporation lowers the temperature of a liquid
When the molecules with the highest kinetic energy escape from the liquid, the average kinetic energy of the remaining particles is lower and the temperature decreases
In general, how are particles arranged in solids?
Particles in solids are packed tightly together in an orderly arrangement. The locations of the particles are fixed
What does the shape of a crystal tell you about the structure of a crystal?
The shape of a crystal reflects the arrangement of the particle within the solid
How do allotropes of an element differ?
Allotropes are different molecular forms of the same element in the same physical state
What phases are in equilibrium at a substance’s melting point?
solid and liquid
How do the melting points of ionic solids generally compare with those of molecular solids?Explain.
Ionic solids generally have, higher melting points than molecular solids
What is the difference between a crystal lattice and a unit cell?
a crystal lattice is a repeating array of unit cells