Cell Compounds and Biological Molecules
What are some negative effects of acid precipitation on an ecosystem?
- harm organisms in aquatic ecosystems - makes soil acidic which then holds fewer nutrients. This effects the plants.
Why is cohesion of water important for living organisms?
1. It is important in plants when water gets pulled up from the roots because cohesion allows the water molecules to stick together. 2. Water bugs can "walk" on water due to cohesion of the water molecules.
Why is it important to living things that ice is less dense than water?
1. This is important for fish because it means lakes and ponds freeze on top but remain liquid underneath so that the fish survive. 2. Frozen ice sheets in the Arctic create hunting ground for polar bears and living space for other animals.
What are some examples of how the "moderating" effect of water is important to living things?
1. Water helps to cool animals when they perspire. Perspiration cools the animal because when the water evaporates off of the skin heat is removed from the animal in order to break apart the hydrogen bonds in the water to cause the evaporation to occur. 2. Water does not cool down or heat up very quickly because of the hydrogen bonds. THis is useful because our bodies are composed in large part out of water and this allows us to maintain our body temperature at 37 degrees C.
How much greater is the concentration of hydrogen ions in a solution with a pH of 2 than a solution with a pH of 7?
10x10x10x10x10 = 100 000 more hydrogen ions
Value for neutral pH?
7
Solution, Solvent, Solute?
A liquid consisting of a homogeneous mixture of two or more substances consisting of a dissolving agent called the solvent and the substance that is dissolved called the solute.
pH scale?
A scale that describes how acidic or basic a solution is. The scale runs from 0-14.
Ion?
An atom that has lost or gained electrons so that it has a charge. An atom that gains electrons becomes negatively charged and an atom that loses electrons becomes positively charged.
Composition of an atom?
Atoms are made of protons and neutrons found in the middle part of the atom and electrons that float around the outside in electron shells
Isotope?
Atoms of the same element with different numbers of neutrons. (note: their proton number stays the same)
Why does it take a lot of heat energy to raise the temperature of a body of water?
Because water has hydrogen bonds it take a lot of energy to break the bonds before the water molecules can absorb enough kinetic energy to move faster.
How do we make pure water acidic?
By adding hydrogen ions (H+) to the water. For example, adding HCl to the water would increase the number of Hydrogen ions (H+), making the water more acidic.
How do we make pure water basic?
By adding hydroxide ions (OH-) to the water. For example, adding NaOH to the water would increase the number of Hydroxide ions (OH-), making the water more basic.
How does an atom gain stability in its outer shell?
By gaining or losing electrons so that the outer shell (valence shell) is full.
Cohesion of water molecules?
Cohesion means water molecules stick to each other. Cohesion results from hydrogen bonds.
Why is water more dense than ice?
Due to hydrogen bonds, when water molecules freeze the spaces between the water molecules becomes greater making ice less dense than water.
What causes acid precipitation?
Fossil fuels burning create sulphur oxide and nitrogen oxide which then react with H2O in the atmosphere to create nitric acid and sulphuric acid.
Hydrophilic?
Hydrophilic means water loving. Hydrophilic substances dissolve in water (things that are polar and ionic).
Hydrophobic?
Hydrophobic means water hating. Hydrophobic substances do not dissolve in water (eg. things that are non-polar such as oil).
What sorts of solutes will dissolve in a non-polar solvent?
Non-polar solutes.
What is meant by the term "like dissolves like"?
Non-polar substances only dissolve in another non-polar solvent. Polar or ionic substances will dissolve in a polar solvent
What are the main elements in the human body?
Oxygen (65%), Carbon (18.5%), Hydrogen (9.5%), Nitrogen ( 3.3 %) - remember CHON
What types of solutes will dissolve in a polar solvent?
Polar and ionic solutes will dissolve in a polar solvent.
Acid precipitation?
Precipitation (eg. rain, snow, fog) with a pH less than 5.6.
If salt is dissolved in water to make a salt solution, which part is the solvent and which part is the solute?
Salt is the solute and Water is the solvent.
What types of solutes will dissolve in water?
Since water is polar, polar and ionic solutes will dissolve in water.
Why do living organisms contain buffers?
So that the pH in the organism remains constant. Chemcal reactions that occur in organisms can't occur if the pH in the organism changes.
Temperature?
Temperature is a measure of the average amount of kinetic energy of molecules in a body of matter.
What has a higher amount of heat: A 1 Litre container at 20 degrees C or a 5 Litre container at 20 degrees C?
The 5 litre container contains more heat because it is bigger and therefore has more energy because it has more molecules.
Ionic bond?
The bond that forms between a positive and negative ion.
Covalent bond?
The bond that forms between atoms when electrons are shared equally. This happens between two non-metals.
Adhesion of water molecules?
The clinging of water molecules to another substance.
Valence shell?
The outermost electron shell of an atom
When salt (NaCl) dissolves in water, what is actually happening?
The salt is breaking apart (dissociation) into its ion components.
Heat?
The total amount of kinetic energy (energy due to the movement of atoms and molecules) in a body of matter.
Hydrogen bond?
The weak bond that occurs between water molecules due to the attraction of the positive hydrogen side of one water molecule to the negative oxygen side of another water molecule.
How can radioactive isotopes be useful in biology?
They can be used as radioactive tracers to follow molecules as they undergo chemical change in the organism.
What does in mean when we say that in pure water some of the water moecules are dissociated?
This means that some of the water molecules break apart into the ions H+ and OH -.
Why is adhesion important in living organisms?
Water molecules stick to the cell walls of plant's thin veins which helps prevent the water from falling backwards due to gravity.
Polar covalent bond?
When elctrons are not shared equally in a covalent bond. As a result one side of the molecule becomes slightly negative and the other side becomes slightly positive. Water is an example of a polar covalent bond. The oxygen side is more negative than the hydrogen side.
Double covalent bond?
When two pairs of electrons are shared between atoms.
What does each pH unit represent?
a 10 fold increase or decrease in the concentration of hydrogen ions. The more hydrogen ions present the more acidic the solution and the lower the pH.
Buffer?
a chemical that keeps the pH constant even when acids or bases are added.
Values for a basic pH?
greater than 7 to 14.
Values for acidic pH?
less than 7 to 0.
