Homework 1

True or False: Chemistry is a science that deals with the composition of matter and the changes in the composition of matter.
True
True or False: A theory can never be proven correct, but one experiment can prove it incorrect.
True
True or False: One may test a hypothesis by making measurements, noting color changes, or weighing the amount of a substance that forms in a reaction.
True
Which of the following is a scientific observation?

1. Water freezes at 0°C.

2. If a substance freezes at 0°C, it must be water.

3. When a substance freezes, its molecules lose potential energy.

4. Freezing and boiling are called physical changes.

1. Water freezes at 0°C.
Which of the following is a definition of matter.

1 Anything that takes up space.

2 Anything with mass.

3 Stuff

4 all of the above

5 none of the above

4. all of the above
True or False: A liquid has definite volume but no definite shape.
True
True or False: Of the three states of matter, a gas has its particles farthest apart.
True
Which of the following is not true of particles.

1 They are in constant motion.

2 Energy does not affect their motion.

3 They move in straight lines until they collide.

4 When they collide they bounce off.

5 They can vibrate, rotate or translate.

2. Energy does not affect their motion.
Why does a solid have a definite shape while a liquid does not?

1 In a solid the particles are free to move while in a liquid they are not.

2 In a liquid, the particles are free to move while in a solid they are not.

3 In a liquid the particles do not interact with each other.

4 In a solid the particles have no space between them.

2 In a liquid, the particles are free to move while in a solid they are not.
Is air a element, compound, or mixture?
Mixture: Air is a mixture of nitrogen, oxygen, and other gases.
Is oxygen an element, compound, or mixture?
Element, Oxygen gas is a pure substance.
Is sodium choride an element, compound, or mixture?
Compound: Sodium chloride is a pure substance.
Is wine an element, compound, or mixture?
Mixture: Wine is a mixture of water, alcohol, and other substances.
True or False: The two forms of pure substances are elements and compounds.
True
True or False: A solution is a homogeneous mixture.
True
True or False: Elements are the basic building blocks of all substances.
True
True or False: The symbols for most of the elements contain one or two letters.
True
True or False: The symbol for cobalt can be written as Co or CO.
False
Which of the following is an element?

1 blood

2 iron

3 water

4 wood

2 iron
True or False: Compounds can be decomposed chemically into simpler substances.
True
True or False: A compound is a pure substance and cannot be separated by physical means.
True
True or False: A mixture is a combination of two or more substances in which the substances retain their identity.
True
Which of the following is not true of a gas?

1 A gas is able to be compressed into a very small volume.

2 The particles of a gas are held together by very strong attractive forces but not in a rigid form.

3 A gas presses continuously and in all directions on the vessel walls.

4 Gas particles fill the entire space in which they are contained.

2 The particles of a gas are held together by very strong attractive forces but not in a rigid form.
Air is classified as a mixture because it

1 does not have a definite composition.

2 has a density of 1.29 g/mL.

3 is colorless and odorless.

4 may be liquefied.

1 does not have a definite composition.
When a pure substance was analyzed, it was found to contain carbon and chlorine. This substance must be classified as

1 A compound

2 Both a mixture and a compound

3 An element

4 A mixture

1 A compound
Which of the following is an example of a chemical change?

1 A heated candle turns to a liquid.

2 A sheet of copper is easy to bend and fold.

3 A mixture of baking soda and vinegar fizzes vigorously.

4 Ice changes into water.

3 A mixture of baking soda and vinegar fizzes vigorously.
When a platinum wire is heated in a bunsen burner flame, the platinum gets red hot, but returns to its original appearance on cooling. Has the platinum wire undergone physical change, chemical change, or both when heated?
Physical change only: The wire has undergone physical change on heating. There is no chemical change observed, as the wire appears the same after heating as before.
True or False: The transformation of energy from one form to another is contrary to the law of conservation of energy.
False
True or False: The vaporization of liquid water is a chemical change.
False
True or False: In a chemical change there is a change in the composition of matter.
True
True or False: In a chemical change the mass of the reactants equals the mass of the products.
True
True or False: When copper reacts with oxygen to form copper(II) oxide, a chemical change occurs.
True
Color, taste, odor, density, and boiling point are all physical properties.
True
True or False: An unknown compound is heated; a dark purple vapor and white crystalline solid result. This is an example of a chemical change.
True
True or False: In a chemical change, substances are formed that are entirely different, having different properties and composition from the original material.
True
According to the Law of Conservation of Energy, energy

1 can be destroyed.

2 can be created and destroyed.

3 can be converted from one form to another.

4 can be created.

3 can be converted from one form to another.
True or False: The Law of Conservation of Mass states that no detectable change is observed in the total mass of the substances involved in a chemical change.
True
True or False: Energy is the capacity of matter to do work.
True
When 3.06g of aluminum is burned in air, the resulting product, aluminum oxide, has a mass of 5.78g. What mass of oxygen was reacted with the aluminum?

a) 8.84g

b) 5.78g

c) 1.89g

d) 2.72g

d) 2.72g
Which of the following statements is true for the law of conservation of matter and energy.

1 Matter and energy can be interconverted.

2 All matter always comes from preexisting matter.

3 Energy cannot be created.

4 It only applies to nuclear reactions.

1 Matter and energy can be interconverted.
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