Elements & Compounds
Which of the following is an example of an element?
A) Water (H20)
B) Carbon Dioxide (CO2)
C) Oxygen (O2)
D) Table Salt (NaCl)
C). Oxygen (O2)
Which of the following is an example of a physical change?
A) Burning a log of wood
B) Melting an ice cube
C) Baking a cake
D) Mixing vinegar and baking soda to produce gas
B) Melting an ice cube
When sugar is dissolved in water, what role does the water play?
A) Solute
B) Solvent
C) Precipitate
D) Mixture
B). Solvent
Which of the following actions will INCREASE the rate at which sugar dissolves in water?
A) Cooling the water before adding sugar
B) Stirring the sugar-water mixture rapidly
C) Using large sugar cubes instead of granulated sugar
D) Letting the mixture sit still without touching it
B) Stirring the sugar-water mixture rapidly
Which of the following is an indicator that a chemical change has taken place?
A) A ice cube melts into liquid water.
B) A piece of paper is shredded into tiny pieces.
C) Vinegar and baking soda mix, producing gas bubbles and foam.
D) Sugar is stirred into hot tea until it dissolves.
C) Vinegar and baking soda mix, producing gas bubbles and foam.
What is the smallest unit of an element that retains all of its chemical properties?
A) Molecule
B) Atom
C) Compound
D) Mixture
B) Atom
Which evidence most strongly indicates that a chemical change—rather than a physical change—has taken place?
A) A shape change from solid to powder
B) An unexpected color change or formation of a precipitate
C) A substance changing from a solid state to a liquid state
D) Dissolving salt into warm water
B) An unexpected color change or formation of a precipitate
What happens to the solubility of most solid solutes in water as temperature increases?
A) It decreases
B) It increases
C) It stays the same
D) It drops to zero
B). It increases
Why does crushing a solid solute into a powder make it dissolve faster?
A) It increases the total surface area exposed to the solvent.
B) It changes the chemical formula of the solute.
C) It lowers the temperature of the solvent.
D) It reduces the amount of solvent needed.
A) It increases the total surface area exposed to the solvent.
True or False: If a substance changes color when painted, a chemical change has occurred.
False (Painting is a physical change because no new chemical substance is formed).
Which representation below is a chemical formula for a compound?
A) Au
B) He
C) C6H12O6
D) Fe
C). C6H12O6
Chopping a wooden board into smaller pieces is considered a physical change because:
A) A new material with different chemical properties is created.
B) The wood undergoes a phase change into gas.
C) The chemical identity of the wood remains unchanged.
D) Heat was absorbed during the chopping process.
C) The chemical identity of the wood remains unchanged.
In a lemonade solution, powder/lemon juice is the ________ and water is the ________.
solute, solvent
In a liquid solvent, how does increasing temperature affect the rate of dissolution for a solid solute?
A) It slows down particle movement, decreasing the rate.
B) It has no effect on how fast the solute dissolves.
C) It speeds up particle movement, increasing the rate.
D) It stops the solute from dissolving completely.
C) It speeds up particle movement, increasing the rate.
When an iron nail is left outside and rusts, what is happening at the atomic level?
A) The iron atoms are freezing into a different shape.
B) Iron atoms chemically react with oxygen atoms in the air to form a new substance.
C) The iron atoms are evaporating into the atmosphere.
D) The iron is physically breaking down without changing its chemical makeup.
B) Iron atoms chemically react with oxygen atoms in the air to form a new substance.
An ________ consists of only one type of atom and cannot be broken down into simpler substances by chemical means.
element
During a ________ change, the size, shape, or state of matter may change, but its chemical composition stays the same.
physical
Stirring a solution increases the rate at which a solid solute dissolves because it increases contact between the ________ and the ________.
solute, solvent
Heating a liquid solvent causes its particles to move ________, which makes collision with the solute more frequent and energetic.
faster (or quicker)
Cooking an egg is a chemical change because heat causes the proteins in the egg to undergo a chemical reaction and form ________ bonds.
new (or chemical)
In the chemical formula for water, H2O, the subscript "2" indicates that there are two atoms of ________.
Hydrogen
A solid that forms and settles out of a liquid mixture during a chemical reaction is called a ________.
precipitate
A solution with a small amount of solute dissolved in a large amount of solvent is described as ________, while one with a large amount of solute is ________.
dilute, concentrated
Fine table salt dissolves faster than coarse rock salt because fine salt has a larger ________ ________.
surface area
The release of gas bubbles when water boils is proof of a chemical change.
False (Boiling water is a physical phase change from liquid to gas; the gas is still H2O)