question

Which statement must be mentioned in explaining why amphipathic molecules line up at a water surface?

answer

Polar groups attract one another.

question

Dissolving is best described as

answer

mingling of molecules and/or ions.

question

Water is a source of ______________ for chemical reactions in cells.

answer

Oxygen and Hydrogen.

question

Which statement is true of water's tensile strength?

answer

(a) It results from hydrogen bonding. (b) It helps to pull water through plants. (c) It involves both cohesion and adhesion. Both (a) and (b). (a), (b), and (c).

question

Water has surface tension because

answer

hydrogen bonds between surface water molecules resist being stretched

question

Which of the following helps most to explain why water has a high specific heat?

answer

A water molecule can make 4 hydrogen bonds.

question

Which factor is important in making it possible to cool yourself by sweating?

answer

(a), (b), and (c). ; Random collisions allow some molecules to accumulate more energy than other molecules. The weakness of hydrogen bonds lets those molecules escape, leaving the cooler molecules behind.

question

Though you add heat, the temperature of boiling water remains constant because

answer

t takes energy to break hydrogen bonds.

question

Which statement helps to explain why ice is less dense than liquid water?

answer

-Water molecules make hydrogen bonds at definite angles. -Cold molecules move less than warm molecules.

question

The open spaces in water's crystal structure make it possible for

answer

aquatic life to exist at the North Pole

question

Why doesn't oil mix with water?

answer

Polar molecules attract one another.

question

Organizing Effects of water

answer

Life realist on the properties of water. Water organizes other kinds of molecules into structures and make up cells. Water organizes molecules on the basis of their polarity. In this respect, molecules fall into three categories; non polar, polar, and amphipathic. Water itself is highly polar.

question

Water

answer

An inorganic molecule composed of an oxygen atom covalently bound to two hydrogen atoms (H2O)

question

Molecules

answer

Two or more atoms held together by chemical bond.

question

Cell

answer

The smallest unit of matter that has all the properties of life, including the ability to maintain and reproduce itself and to conduct metabolism. All organisms consist of one or more cells. The human body contains trillions of cells. (Picture animals cell)

question

Non-polar molecule

answer

Having little or no partial charge on the component atoms. Single pair of bonded atoms or to a molecule as a whole. Bonds are non polar when they join atoms of similar electronegativity, as in bonds between C and H or between two C atoms or two O atoms.

question

Polar molecule

answer

In a molecules or bonds, the presence of distinct regions that have partial positive and negative charges.

question

Amphipathic molecule

answer

Having both polar and non polar parts. Water causes amphipathic molecules to arrange themselves so their polar parts are in the water and their non polar parts are excluded from the water, as in biological membranes and proteins. Thus, amphipathy is fundamental to the structure of life.

question

Oil Molecules

answer

Oil molecules are non polar and cannot form hydrogen bonds. To break into a water mass, they must force water molecules apart, breaking hydrogen bonds. That takes energy. If oil moles do get into water by our shaking the mixture, they form clumps and wander about until water expels them.

question

More Polar Less polar

answer

Dissolves in water easily. (Methanol) Dissolves in water less easily. (Myristic Alcohol) (Butanol: middle)

question

Do molecules break apart when they dissolve?

answer

In water, some molecules break into ions, but most do not. For instance, a sugar cube contains many molecules held together by hydrogen bonds. When a sugar cube dissolves, each molecule stays intact. It trades the old hydrogen bonds for new ones with water. Salt, on the other hand, doesn't consist of molecules; it's just ions that separate water.

question

Does water repel non polar molecules:

answer

There is no repulsion between water and non polar molecules. The two don't mix simplify because water molecules attract one another and won't make room for molecules that lack attractive charged regions. When water expels a non polar molecule, it's because the water molecules pull one another together behind departing non polar molecule.

question

Does water treat all polar molecules alike?

answer

Not at all. Highly polar moles get into water more easily than less polar ones. Molecules vary widely in polarity depending partly on the balance between non polar and polar parts.

question

Chemical Reactions with Water

answer

Water provides hydrogen (H) and (O) atoms for making biological molecules. This plant is conducting photosynthesis. using the O from water to make atmospheric oxygen (O2), ad combining the H from water with carbon dioxide (CO2) to make sugar (C6H12O6). Many other reactions transfer OH from water to biological molecules. This happens when we digest proteins and starch.

question

Hydrogen (H)

answer

The chemical element composed of atoms that have 1 proton in the nucleus; symbolized by the letter H. The smallest and lightest atom, one of the four most abundant elements in biological molecules, and the most abundant element in the universe.

question

Oxygen O2

answer

The chemical element composed of atoms that have 8 protons in the nucleus; symbolized by the letter O. One of the four most abundant element in biological molecules, and the most abundant element ( on a weight basis) in Earths crust, water, and atmosphere.

question

Photosynthesis

answer

The metabolic pathway by which light energy is used to combine carbon dioxide and water into sugar and molecular oxygen.

question

Carbon Dioxide

answer

Two oxygen atoms bound to one carbon atom by double bonds; CO2. This simple, low-energy compound is life's principal source of carbon. Organisms release it into the air as they process fuels for energy. Some organisms, chiefly plants, convert CO2 back to sugars with the air of light energy (the process of photosynthesis).

question

Sugar (C6h12O6)

answer

An organic molecule that has the formula CnH2nOn, and that has at least one O atom bound to each C atom. Sugars are the simplest carbohydrates.

question

Tensile Strength of water

answer

Water evaporates from leaves, which stay moist by pulling water up from roots against the pull of gravity. This stretches the water in the tree, but the water molecules resist breaking apart because of tensile strength. Tensile strength results from hydrogen bonds that link water molecules to one another (cohesion) and to cell walls (adhesion)

question

Tensile Strength

answer

The ability of a material to resist breaking when stretched.

question

Hydrogen Bond

answer

An electric attraction that occurs when a hydrogen atom with a partial positive charge comes near another atom (typically O or N) with partial negative charge. The partial charges derive from the atoms being engaged in covalent bonds with aims that differ great in electronegativity.

question

Cohesion

answer

The binding together of like molecules, often by hydrogen bonds.

question

Cell wall

answer

A protective layer external to the plasma membrane in plant cells, bacteria, fungi, and some protists. In the case of plant cells, the wall is formed of cellulose fibers embedded in a polysaccharide-protein matrix. The primary cell wall is thin and flexible, whereas the secondary cell wall is stronger and more rigid, and the primary constituent of wood.

question

Adhesion

answer

The tendency of different kinds of molecules to stick together.

question

How high can tress lift water

answer

The tallest tress (pacific coast redwoods) lift water over 100 meters (365ft) against the pull of gravity. Laboratory experiments suggest that water has enough tensile strength to be pulled to the tops of tress three times that heights.

question

Why do paper towels absorb water?

answer

Paper towels are made of molecules from plant cell walls, which form hydrogen bonds with water. As randomly moving water molecules enter the towel, they adhere to the towel molecules, and cohesion pulls more water molecules after them. All these events forces result from hydrogen bonds.

question

What does adhesion contribute to tensile strength?

answer

Adhesion maintains the width of water mass by holding water to cell walls (or, in pipes, to the metal of the pipe). Without that effect, any force pulling on the water would make the water mass thinner and thinner until it's so narrow that it breaks.

question

Surface tension of Water

answer

The cohesion of water creates a force called surface tension that resists the entry of water-repellent objects such as this water strider. To overcome surface tension, a non polar object must push hard enough to break many hydrogen bonds. Water striders don't weigh enough to exert such force. This means little to us, but can be vital to a tiny insect.

question

Surface Tension

answer

A measure of how difficult it is to stretch or break the surface of a liquid. Water has a high surface tension because of the hydrogen bonding of surface molecules.

question

Non-polar

answer

Having little or no partial charge on the component atoms. The term can apply to a single pair of bonded atoms or to a molecule as a whole. Bonds are non polar when they join atoms or similar electronegativity, as in bonds between C and H or between two C atoms or two O atoms.

question

Hydrogen Bond

answer

An electric attraction that occurs when a hydrogen atom with a partial positive comes near another atom (typically O or N) with a partial negative charge. The partial charges derive from the atoms being engaged in covalent bonds with atoms that differ greatly in electronegativity.

question

Why don't all small objects float on water?

answer

Even if it's small, an object will sink into water if it concentrates enough weight on a small area (as in the point of a needle). With such a concentration, there aren't enough hydrogen bonds to resist the force. Also, an object will sink if it can make hydrogen bonds and soak up water, as with paper.

question

High specific heat of water

answer

With its oceans, Earth has a milder climate than a dry planet. You see the same effect in comparing seacoasts with the desert. This is due to water's high specific heat--water can gain or lose heat with little change in temperature, because of the heat is used to break hydrogen bonds. At night, hydrogen bonds return, releasing heat so the temperature does not drop far.

question

Specific heat

answer

The amount of heat that must be absorbed or lost for 1g of a substance to change its temperature 1C.

question

How does water's specific heat affect organisms

answer

Stored water, as in these cacti, helps to stabilize an organism's temperature, so it doesn't rise as far during the day or fall as far at night. This occurs because water has a high specific heat--that is, much heat can be gained or lost with only a small change in temperature. This results from hydrogen bonding in water.

question

How does heat relate to temperature

answer

Heat is the total kinetic energy stored in random motion of atoms or molecules. Two cups of boiling-hot tea have twice as much heat energy as one cup. Temperature measures the heat energy of the aerate atom or molecule. It's same for two cups of tea as for one cup, because its an average rather than a total.

question

Why do hydrogen bonds cause high specific heat

answer

much of the heat absorbed by water is used to break hydrogen bonds. only a small amount of heat is left over to increase molecular motion. Since temperature measures molecular motion, the temperature rises only slightly. Molecules that don't make hydrogen bonds, like CO2, attract each other more weakly , so a larger fraction absorbed heat can raise temperature.

question

Cooling by Evaporation

answer

Sweating cools you off because the fastest-moving (hottest) water molecules break every hydrogen bond and escape, carrying away heat. The escape is evaporation, so this way of losing heat is called evaporating cooling. Plants and many animals cool themselves in this way. It can be dangerous if too much water is lost, but it's worth the risk if the alternative is fatal overheating.

question

Evaporative cooling

answer

The property of a liquid whereby the surface becomes cooler during evaporation, owing to a loss of high kinetic molecules to the gaseous state.

question

What gives some molecules more energy?

answer

When two molecules collide and rebound, one molecule may give energy to the other. Because collisions occur at varied speeds and angles, the average molecule gains energy as often as it loses energy. But sometimes, by chance, a molecule gains energy in several successive collisions, giving it much more energy than the average molecule.

question

Boiling

answer

Boiling occurs when all the water molecules have so much energy that their motion break most of the hydrogen bonds. Then the liquid rapidly changes to gas bubbles (steam). If you keep adding heat to boiling water, the temperature stays the same because all the heat is used to break hydrogen bonds. The free molecules (steam) carry away energy.

question

Freezing

answer

If the temperature drops below about 0c (The freezing point), water changes from liquid to a crystalline solid (ice). With too little energy to break hydrogen bonds very often, each water molecule forms four hydrogen bonds that pull the molecules into a regular arrangement (a lattice).

question

Crystalline

answer

A group of atoms or molecules that are uniformly arranged in space.

question

Lattice

answer

A regular arrangement of points in space, marking the positions where particular atoms or molecules occur in a crystal.

question

What's a lattice

answer

A lattice is a regular arrangement of points in space. In ice, each oxygen atom of water molecule occurs at a point of the lattice. The water molecules are held in place by hydrogen bonds.

question

Can Ice evaporate?

answer

When it's very cold, ice may evaporate without melding. This change from solid ice directly to gaseous vapor is called sublimation. sublimation occurs because even in the cold, molecules occasionally gain enough energy in collisions without molecules to break away from the solid ice lattice.

Chemistry Review-Water properties of water

Unlock all answers in this set

Haven't found what you were looking for?

Search for samples, answers to your questions and flashcards