Science Chapter 3

Electronegativity

The ability of an atom to pull shared electrons toward itself.

Polar molecule

A molecule with an uneven distribution of electrical charge.

Water polarity

Water is polar because oxygen pulls shared electrons more strongly than hydrogen.

Partial negative charge (δ−)

The slightly negative charge on the oxygen end of a water molecule.

Partial positive charge (δ+)

The slightly positive charge on the hydrogen ends of a water molecule.

Covalent bond

A bond formed when atoms share electrons.

Polar covalent bond

A covalent bond in which electrons are shared unequally.

Ionic bond

The attraction between oppositely charged ions after electrons are transferred.

Ion

An atom or group of atoms with an electrical charge.

Cation

A positively charged ion.

Anion

A negatively charged ion.

Sodium ion (Na⁺)

A positive ion formed when sodium loses an electron.

Chloride ion (Cl⁻)

A negative ion formed when chlorine gains an electron.

Hydrogen bond

A weak attraction between a slightly positive hydrogen and a slightly negative atom on another molecule.

Cohesion

The attraction of water molecules to other water molecules.

Adhesion

The attraction of water molecules to other substances.

Surface tension

The resistance of water's surface to being broken or stretched.

Capillary action

The movement of water up a narrow tube or through small spaces against gravity.

Hydration sphere

A layer of water molecules surrounding a dissolved ion.

Water as a solvent

Water dissolves many ionic and polar substances because of its polarity.

Water freezing

Hydrogen bonds arrange frozen water molecules into an open crystal structure.

Density

Mass per unit volume.

Why ice floats

Ice is less dense than liquid water because its molecules spread farther apart.

Water's maximum density

Liquid water is most dense at approximately 4°C (39°F).

Water at 0°C

Liquid water at 0°C is less dense than liquid water at 4°C.

Insulating layer of ice

Floating ice helps keep the water below liquid for aquatic organisms.

Carbohydrate

An organic molecule made mostly of carbon hydrogen and oxygen used for quick energy energy storage or structural support.

Monomer

A small molecular building block that can join with others to form a larger molecule.

Monosaccharide

A single sugar molecule and the simplest carbohydrate.

Simple sugar

Another name for a monosaccharide.

Glucose

A monosaccharide used for quick energy by cells.

Fructose

A monosaccharide that combines with glucose to form sucrose.

Galactose

A monosaccharide that combines with glucose to form lactose.

Monosaccharide formula

C₆H₁₂O₆.

Disaccharide

A carbohydrate made of two monosaccharides joined together.

Sucrose

A disaccharide made of glucose and fructose.

Lactose

A disaccharide made of glucose and galactose.

Maltose

A disaccharide made of glucose and glucose.

Disaccharide formula

C₁₂H₂₂O₁₁.

Polysaccharide

A large carbohydrate made of many monosaccharides linked together.

Poly-

A prefix meaning many.

Starch

A polysaccharide plants use to store energy.

Glycogen

A polysaccharide animals use to store glucose especially in the liver and muscles.

Cellulose

A structural polysaccharide found in plant cell walls that humans cannot digest and that acts as dietary fiber.

Chitin

A structural polysaccharide found in fungal cell walls and arthropod exoskeletons.

Arthropod exoskeleton

A hard external supporting structure found in arthropods such as insects and crabs.

Dehydration synthesis

A reaction that joins smaller molecules by removing water.

Dehydration

Removal of water.

Synthesis

Building a larger molecule from smaller components.

Dehydration synthesis equation

Monosaccharide + monosaccharide → disaccharide + H₂O.

What happens to water during dehydration synthesis

Water is removed as smaller molecules join together.

Energy storage carbohydrate in plants

Starch.

Energy storage carbohydrate in animals

Glycogen.

Structural carbohydrate in plant cell walls

Cellulose.

Structural carbohydrate in fungal cell walls

Chitin.

Structural carbohydrate in insect and crab exoskeletons

Chitin.

Cohesion example

Water droplets beading up on a waxy surface.

Adhesion example

Water sticking to the sides of a glass or plant-cell walls.

Surface tension example

Some insects can walk on water.

Capillary action example

Water traveling upward through plant xylem from roots to leaves.

Water orientation around Na⁺

The negative oxygen ends of water molecules face the positive sodium ion.

Water orientation around Cl⁻

The positive hydrogen ends of water molecules face the negative chloride ion.

Why water dissolves salt

Water polarity allows its molecules to surround dissolved sodium and chloride ions.

Why ice insulates lakes

Floating ice forms a layer that helps the water underneath remain liquid.

Starch example foods

Bread rice and potatoes are examples of foods containing starch.

Glycogen storage locations

The liver and muscles.

Plant cell walls' main carbohydrate

Cellulose.

Monosaccharide meaning

One sugar unit.

Disaccharide meaning

Two sugar units.

Polysaccharide meaning

Many sugar units.

Bond within one water molecule

Polar covalent bond.

Attraction between separate water molecules

Hydrogen bonding.

Two properties responsible for capillary action

Cohesion and adhesion