Ch 12, 14-16 PSC

What happens to the chemical identity of a substance during a physical change?

Nothing. During a physical change, the chemical identity of a substance remains the same.

What is the main difference between an ionic and a covalent bond?

One is sharing a pair of electrons, the other transfers at least one electron.

Which of the following elements will most likely form an ion with a 2- charge?

S

Element, Compound or Mixture, and Justify your classifications: Salt

Salt, sodium chloride; classification: compound.

Element, Compound or Mixture, and Justify your classifications: Stainless Steel

Stainless steel, mix of iron and carbon; classification: mixture.

Element, Compound or Mixture, and Justify your classifications:Sugar

Sugar, chemical name: sucrose; classification: compound.

Element, Compound or Mixture, and Justify your classifications: Tap Water

Tap water, dihydrogen oxide plus impurities; classification: mixture

Which statement best describes a compound?

a material that is made up of a combination of atoms bonded together

Water and ethanol can be separated by heating the ethanol until it boils away from the water. What type of change is this? (Think about it.)

a physical change

What does the following element description actually mean? 238 U 92

a uranium atom with 92 protons and 146 neutrons

Which of the following elements is an alkali metal?

lithium (Li)

A chemical change results in

new materials.

Which of the following best describes ionic bonding?

one atom giving up some of its electrons to another atom.

Which of the following can be classified as matter?

water, sand, granite, ice cream

Which of the following would be considered a homogeneous mixture?

wine

If a neutral element has the following chemical symbol, how many electrons does it have? 18 O 6

6

What is a chemical bond?

A chemical bond is the electrical attraction that holds two atoms together.

To become a negative ion, does an atom lose or gain electrons

A gain of electrons causes a negatively charged ion.

Ch. 16 Practice Problems What defines a material as being a mixture?

A material is a mixture if it contains more than one substance.

Why is the freezing of water considered to be a physical change?

Because the water remains as water. The only thing that changes is water's physical form.

Element, Compound or Mixture, and Justify your classifications: Butter

Butter, natural product; classification: mixture.

An atom loses an electron to another atom. Is this an example of a physical or chemical change?

Chemical change involving the formation of negative and positive ions.

Classify each change as physical or chemical. Be able to defend your answer. a. Grass grows. b. An infant gains 10 lbs. c. A rock is crushed to powder. d. A tire is inflated with air.

(a) chemical. (b) chemical. (c) physical. (d) physical.

Classify each change as physical or chemical. Even if you are incorrect in your assessment, you should be able to defend why you chose as you did. a. Grape juice turns to wine. b. Wood burns to ashes. c. Water begins to boil. d. A broken leg mends itself.

(a) chemical. (b) chemical. (c) physical. (d) chemical.

If a neutral element has the following chemical symbol, how many neutrons does it have? 18 O 6

12

How many valence electrons does boron (B) have?

3 valence electrons

If an element has 15 protons, 16 neutrons and 15 electrons, what is the mass number of the element?

31

Element, Compound or Mixture, and Justify your classifications: Aluminum

Aluminum, metal; classification: in pure form—element (Sold commercially as a mixture of mostly aluminum with trace metals, such as magnesium.)

Ch. 12 Practice Problems How many times of atoms can you expect to find in a pure sample of any element?

An element consists of only one type of atom.

What is the difference between an element and a compound?

An element has only one type of atom. A compound has combinations of different types of atoms.

The air we breathe is not considered by chemists to be an element. Why not?

An element is a material made of only one type of atom. Air is a mixture of different kinds of atoms, mostly nitrogen and oxygen.

How does an ion differ from an atom?

An ion has a charge and an atom does not.

Distinguish between atomic number and mass number.

Atomic number is the number of protons in the nucleus. Mass number is the total number of protons and neutrons in the nucleus.

Element, Compound or Mixture, and Justify your classifications: Cherry-Flavored Cough Drops

Cherry flavored cough drops, pharmaceutical; classification: mixture.

Which of the following elements is a halogen?

Chlorine (Cl)

What changes during a chemical reaction?

During a chemical reaction there is a change in the way atoms are bonded together.

What doesn't change during a physical change?

During a physical change the chemical composition of a substance does not change.

How do the electron-dot structures of elements in the same group in the periodic table compare with one another?

Electron dot structures of elements in the same group have the same number of valence electrons

Which elements tend to form ionic bonds?

Elements on opposite sides of the periodic table tend to form ionic bonds.

Which elements tend to form covalent bonds?

Elements that tend to form covalent bonds are primarily non-metallic elements.

Which element has the atomic number 9?

F (fluorine)

PV 14 Which of the following is an example of a chemical change?

Gasoline being burned in an engine of a car producing exhaust.

Element, Compound or Mixture, and Justify your classifications: Ice

Ice, dihydrogen oxide; classification: in pure form—compound; when made from impure tap water—mixture.

What is the valence shell?

It is the outermost shell of electrons in an atom, responsible for bonding.

Which of the following elements will most likely form an ion with a 1+ charge?

K

Element, Compound or Mixture, and Justify your classifications: Maple Syrup

Maple syrup, natural product; classification: mixture.

Distinguish between mass number and atomic mass.

Mass number is the count of nucleons in an isotope. Atomic mass is a measure of the total mass of an atom.

Element, Compound or Mixture, and Justify your classifications: Milk

Milk, natural product; classification: mixture.

Ch. 14 Practice Problems Are atoms made of molecules or are molecules made of atoms?

Molecules are made of atoms. Atoms link together to form larger but still small basic units of matter called molecules.

Are most elements metallic or nonmetallic?

Most of the known elements are metallic.

Oxygen atoms are used to make water molecules. Does this mean that oxygen, O2, and water, H2O, have similar properties?

No, compounds are uniquely different from the elements from which they are made.

Why are the atomic masses listed in the periodic table not whole numbers?

The atomic masses are average atomic masses.

PV 16 What is the difference between a compound and a mixture?

The components of a mixture are not chemically bonded together.

Which element within a compound is given first in the compound's name?

The element found closer to the left side of the periodic table is first shown within the compound's name.

When two elements come together to form a compound, which element is named first within the name of the compound?

The element toward the left hand side of the periodic table.

The nucleus of an electrically neutral iron atom contains 26 protons. How many electrons does this iron atom have?

The iron atom is electrically neutral when it has 26 electrons to balance its 26 protons.

What do chicken soup and garden soil have in common?

They are both examples of heterogeneous mixtures.

Why isn't water classified as an element?

Today, an element is identified as a material consisting only one kind of atom.

Ch. 15 Practice Problems Which electrons are represented by an electron-dot structure?

Valence electrons are represented in an electron-dot structure.

Element, Compound or Mixture, and Justify your classifications:Vanilla Extract

Vanilla extract, natural product; classification: mixture.

Which of the following statements describes an isotope?

an element with the same number of protons but a different number of neutrons.

Which of the following is an example of a chemical change?

baking a pizza

Which of the following is a pure substance?

baking soda

Classify the following changes as physical or chemical. Wood burns to ashes; water begins to boil, grass grows, a rock is crushed to powder.

chemical; physical; chemical; physical

A combination of two or more substances in which they no longer retain their chemical properties is called a(n)

compound.

Ch. 12 Homework An element is best described as a material

consisting of only one type of atom.

PV. 12 An element is best described as a material

consisting of only one type of atom.

Classify the following bonds as ionic or covalent. O with F Ca with Cl S with N

covalent, ionic, covalent

Which of the following would be considered a heterogeneous mixture?

salad dressing

Which statement best describes a mole?

the amount of molecules or atoms in 1 gram of something

Which of the following is an example of a physical change?

water boiling and being converted to steam