chemistry of life - quia · chapter 3 chemistry of life . ... adapted from holt biology 2008...

Chapter 3

Chemistry of Life

Content Objectives Write these down!

I will be able to identify:

• The make-up of matter.

• Why atoms form bonds.

• Some important interactions between substances in living things.

Adapted from Holt Biology 2008

Chapter 3 Section 1: Matter & Substance

Key Vocabulary Terms


Atom

The smallest unit of matter that cannot be

broken down by chemical means.

The smallest unit of an element that maintains

the chemical properties of that element.


Element

A substance that cannot be separated or broken

down into simpler substances by chemical

means.

A substance made up of atoms that have the same

number of protons.


Valence Electron

An electron that is found in the outermost shell of

an atom and that determines the atom's chemical properties.


Compound

A substance made up of atoms of two or more

different elements joined by chemical bonds.


Molecule

A group of atoms that are held together by chemical forces (covalent bonds); a molecule is the smallest unit of matter that can exist by itself and retain

all of a substance's chemical properties .


Ion

An atom, radical, or molecule that has gained

or lost one or more electrons and has a negative or positive

charge.


Mass

A quantity representing the amount of matter in a

particle or object. The standard unit of mass in the International System

(SI ) is the gram ( k ).


Protons

A subatomic particle with a positive electric charge of 1 elementary charge.

One or more protons are present in the nucleus of

each atom along with neutrons.


Electrons

A subatomic particle carrying a negative

electric charge which has no known components or

substructure.


Neutrons

A subatomic particle with no net electric charge and a mass slightly larger than

that of a proton.

Except for Hydrogen the nuclei of atoms consist of

protons & neutrons.


Polar

Molecules with partial charges on opposite ends are said to be polar. The water molecule is polar.


Chapter 3 Section 1: Matter & Substance

Supplementary Words


Electron Cloud

The region of an atom in which the electrons move

around the nucleus.


Isotopes

Variants of atoms of an element which have a different number of

neutrons.


Valence Shell

The outermost shell of an atom.


Chemical Bond An attraction between atoms that allows the formation of chemical

substances that contain two or more atoms.

The bond is caused by the electromagnetic force

attraction between opposite charges, either between electrons and

nuclei, or as the result of a dipole attraction.


Covalent Bond

A form of chemical bonding that is

characterized by the sharing of pairs of

electrons between atoms.


Ionic Bond

A type of chemical bond formed through an

electrostatic attraction between two oppositely

charged ions.


Polarity

Equally bonding electrons are shared between

atoms causing

a condition where the molecule has opposing physical properties at

different points, or slight electric charges at

opposite poles.


Solubility In general, solubility is an ability of a substance to

dissolve. In the process of dissolving, the substance

which is being dissolved is called a solute and the substance in which the

solute is dissolved is called a solvent. A mixture of solute and solvent is

called a solution.


Hydrogen Bond The attractive interaction of a hydrogen atom with an electronegative atom, such as nitrogen, oxygen or fluorine, that comes

from another molecule or chemical group. The hydrogen must be

covalently bonded to another electronegative atom to create the bond.


Chapter 3 Section 1:

Matter & Substance

Notes

Section 1: Matter and Substances

Preview

• Matter

• Atoms

• Chemical Bonds

• Polarity

Matter

Matter is anything that has mass and takes up space. All living and

non-living things are made of matter.

http://my.hrw.com/sh2/sh07_10/student/flash/visual_concepts/75004.htm

Atoms

An atom is the smallest unit of matter that cannot be broken

down by chemical means.

Atoms, continued

The nucleus of an atom is made up of positively charged protons

and uncharged neutrons.

Atoms, continued

Negatively charged electrons have very little mass and move around the

nucleus in a large region called the electron cloud.

Atoms, continued

An element is a substance made up of atoms that have the same

number of protons.

Elements


Atoms, continued

For example, each atom of the element carbon has six protons.

Elements

Atoms, continued

Atoms of an element may have different numbers of neutrons. These atoms are called isotopes of elements.

Elements

Think, Share, Write #1

What is a neuron?


What is a proton?

A proton is a positively

charged particle that is part

of the nucleus of an atom.

Chemical Bonds

Electrons in the outermost level, or shell, are called valence electrons.

Chemical Bonds

When atoms combine, a force called a chemical bond holds them

together.

Chemical Bonds, continued

Atoms become stable when they have eight electrons in the valence shell.


When atoms of different elements combine, a compound forms. A compound is a substance made of the bonded atoms of two or more elements.



YOUR TURN

With a partner, read the Chapter 3 Section 1 Active Reading – Matter and Substances

1st - Take turns reading the questions aloud to each other, alternating questions.

2nd - Take turns reading the selection aloud to each other, alternating sentences or paragraphs.

Adapted from Holt Biology 2008 Adapted from Holt Biology 2008

YOUR TURN

As you read discuss the content.

Reread and discuss each question. Write down the best answer to the question using full descriptive sentences.

• Be prepared to share with the class.


2


Occurs when atoms bond by sharing valence electrons and form a covalent bond.

Covalent Bonding



A molecule is a group of atoms held together by chemical bonds.

Covalent Bonding



A water molecule, H2O, forms when an oxygen atom forms covalent bonds with two hydrogen atoms.

Covalent Bonding


What is a chemical bond?


What is a chemical bond?

A chemical bond is the

attractive force that holds

atoms or ions together.


An ion is an atom or group of atoms that has an electric charge because it has gained or lost electrons. (to

become stable)

Ionic Bonding




The attractive force between oppositely charged ions is an ionic bond.

Ionic Bonding


Ionic Bonding in Salt

Polarity

In some covalent bonds one end (pole) of the molecule has a partial

negative charge (-), while the

opposite end has a partial positive (+) charge.

Polarity

Molecules with partial charges on opposite ends are said to be polar.

Polarity, continued

The partially charged ends of polar molecules attract opposite charges.

Water molecules are polar.

Solubility

Polarity, continued

Because of this behavior, polar molecules can dissolve other polar

molecules and ionic compounds. For example, water can dissolve sugar

and salt.

Solubility

Polarity, continued

Nonpolar substances, such as oil, grease, and wax, do not dissolve

well in water.

Solubility


Ionic Compounds in Water

Polarity, continued

When bonded to an oxygen, nitrogen, or fluorine atom, a

hydrogen atom has a partial charge nearly as great as a proton’s charge.

Hydrogen Bond

Polarity, continued

A hydrogen bond, is stronger than attractions between other

molecules, but not as strong as covalent bonds.

Hydrogen Bond

Polarity, continued

Hydrogen bonding plays an important role in many of the molecules that

make up living things.

Hydrogen Bonding



Why does salt dissolve in water?


Why does salt dissolve in water?

Salt dissolves in water because the

partial positive charge of the H atoms in

water molecules (H2O) attracts the

negatively charged chloride ions in salt

crystals (NaCl). The partially negative

charge of the O atom of water molecules

attracts the positively charged sodium

ions in salt crystals.

chemistry of life - quia · chapter 3 chemistry of life . ... adapted from holt biology 2008...

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