AP Bio; Unit 1: Ch 2 The Chemical Context of Life

Matter is made up of

elements

An element is

a substance that cannot be broken down to other substances by chemical reactions

Compounds are made up of

two or more elements in a fixed ratio

What is the smallest unit of matter that still retains the properties of an element

An atom

2 or more atoms help together are called

a molecule

Ionic Bond

Occurs between metals and nonmetals. One atom gives its electron(s) to another atom. The ultimate in polarity.

Polar covalent bond

One atom is more electronegative, atoms don't share electrons equally

Covalent Bonds

Electrons are shared not taken/given. Atoms in a molecule attract electrons to varying degrees

Electronegativity

An atom's attraction for the electrons in a covalent bond

Nonpolar covalent bond

Electronegativity is equal, the atoms share the electron equally

Unequal sharing of electrons causes

partial + or - charge for each eatom or molecule (cations and anions)

Highly polar molecules are

highly different

Hydrogen Bonds

An attractive force between a hydrogen atom covalently bonded to a very electronegative atom such as a N, O, or F atom and another very electronegative atom.

Van der Waals Interactions

Attractions between molecules that are close together as a result of Van der Waals forces

Van der waals forces

If electrons are distributed assymmetrically in molecules or atoms they can result in "hot spots" of positive or negative charges. Slight + or - (H2O)

4 properties of water molecules

Cohesive behavior, ability to moderate temperature, expansion upon freezing, versatility as a solvent

Cohesion of water molecules

water molecules are linked by hydrogen bonds.

Surface Tension

measure of how hard it is to break the surface of a liquid and is due to hydrogen bonding (for ex: water beading of water on a penny)

How does water transport up (against gravity) in plants

Xylem vessels transport water (that sticks to xylem walls through adhesion) and stick to eachother (H2O) through hydrogen bonds/cohesion

Adhesion of water molecules

The clinging of 1 substance to another plays a role in the transport of water in plants (why water travels up paper towels)

Moderation of temperature by water

water absorbs heat from warmer air and releases stored heat to cooler air. water can absorb or release a large amount of heat with only a slight change in its own temperature

Water's specific heat

Water resists changing temp because of its high specific heat due to hydrogen bonding

Heat is ___________ when hydrogen bonds break

absorbed

Heat is _____________ when hydrogen bonds form

released

Water __________________ in frozen state

expands

Water dissolves many molecules including

polar molecules and ionic compounds

Acid __________ H+ concentration of a solution

increases

Bases ____________ H+ concentration of a solution

decreases

Acidic solutions have pH values __________ 7

less than

Basic solutions have pH values ____________7

greater than

Biological fluids have pH values in the _______ range

6-8

As pH gets higher, H+ concentration _____________

decreases

As pH gets lower, H+ concentration _____________

increases

Null Hypothesis

States there is no differences, all outcomes are chance based

Standard deviation

How the data is distributed form the mean formula

Standard error of mean (SEM)

Estimate of how reliable the mean is, requires multiple samples of the same experiment