chemistry chapter 2
How are mixtures classified?
As heterogeneous or homogeneous.
According to the law of conservation of mass, when is mass conserved?
Mass is conserved in every physical change or chemical reaction.
Hydrogen and oxygen chemically react to form water. How much water would form if 4.8 grams of hydrogen reacted with 38.4 grams of oxygen?
43.2 g
Explain the term phase as it relates to homogeneous and heterogeneous mixtures.
A phase is any part of a sample with uniform composition. There is one phase in a homogeneous mixture and two or more phases in a phases in a heterogeneous mixture.
How can you distinguish a substance from a mixture?
A substance has a fixed composition. The composition of a mixture may vary.
Name four possible clues that a chemical change has taken place.
A transfer of energy, a change in color, the production of a gas, the formation of a precipitate.
Write the chemical symbol for each element. A. lead B. oxygen C. silver D. sodium E. hydrogen F. Aluminum
A. Pb B. O C. Ag D. Na E. H F. Al
Classify each of these samples of matter as an element, a compound, or a mixture. A. table sugar B. tap water C. cough syrup D. nitrogen
A. compound B. mixture C. mixture D. element
Describe a procedure that could be used to separate a mixture of sand and table salt.
Add water to dissolve the salt. Pour the resulting mixture onto a piece of closely woven cloth. The sand will remain on the cloth, and the salt solution will pass through. Use evaporation to remove the water from the salt solution, leaving solid salt behind.
How are a substance and a solution similar? How are they different?
Both have a uniform composition throughout. A substance has a definite composition; a solution has a variable composition.
What elements make up the element acetaminophen, chemical formula C8H9O2N? Which element is present in the greatest proportion by number of particles?
Carbon, hydrogen, oxygen, and nitrogen; hydrogen is present in the greatest proportion by number of atoms.
What are chemical symbols and chemical formulas used for?
Chemical symbols are used to represent elements. Chemical formulas are used to represent compounds.
Which property in Table 2.1 can most easily distinguish sodium chloride from the other solids?
Color; sodium chloride is the only white solid listed.
How is a compound different from an element?
Compounds can be broken down into simpler substances by chemicals means, but elements cannot.
What type of properties can be used to separate mixtures?
Differences in physical properties.
.Explain why all samples of a given substance have the same intensive properties.
Every sample of a given substance has the same chemical composition.
In general, when would you use filtration to separate a mixture? When would you use distillation to separate a mixture?
Filtration separates solids from a liquid in a heterogeneous mixture. Distillation can separate a liquid from substances dissolved in a liquid.
Name two methods that can be used to break down compounds into simpler substances.
Heating or an electric current.
Classify each of the following as a homogeneous or a heterogeneous mixture. a. food coloring b. Ice cubes in liquid water c. Mouthwash d. Mashed, unpeeled potatoes
Homogeneous Heterogeneous Homogeneous Heterogeneous
What is the main difference between physical changes and chemical changes?
In a physical change, the chemical composition of a substance does not change. In a chemical change, the chemical composition of the reactants changes as one or more products form.
Name two categories used to classify properties of matter.
Intensive and extensive properties
. In what way are liquids and gases alike? In what way are liquids and solids different?
Liquids and gases have an indefinite shape. The shape of a solid is definite; the shape of a liquid is indefinite.
Describe the two categories used to classify physical changes.
Physical changes are either reversible or irreversible. Reversible changes can be "undone," or reversed. Irreversible changes can not be undone.
Explain why samples of gold and copper can 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). They can not have the same set of intensive properties because they have different chemical compositions.
Name three states of matter.
Solid, Liquid, Gas.
How does a chemical change affect the composition of matter?
The composition of matter always changes during a chemical change.
Is the freezing of mercury a reversible or irreversible physical change? Explain your answer.
The freezing of mercury is reversible because solid mercury can be melted.
. 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.
Name the chemical elements represented by the following symbols. a. C b. Ca c. K d. Au e. Fe f. Cu
a. Carbon b. Calcium c. Potassium d. Gold e. Iron f. Copper
2. Classify the following changes as physical or chemical changes. a. Water boils b. Salt dissolves in water c. Milk turns sour c. A metal rusts
a. physical b. physical c. chemical c. chemical
