Biology Chapter 2 Flashcards
Give an example of an element.
Carbon gold aluminum etc. anything found on the periodic table of the elements
Everything in the universe is made of how many different elements?
92
Living things contain a maximum of how many elements?
25
What are the four most important elements that make up 96% of the human body?
Carbon, hydrogen, oxygen, nitrogen (CHON)
Most of the rest of the body is made up of what four elements?
Calcium, potassium, phosphorus, sulfur (CaK PS)
What is a compound?
Two or more elements joined by chemical bonds.
Give three examples of compounds.
Salt, water, plastic
What is an Atom?
The smallest unit of an element.
Name the three particles an Atom is made up of.
Protons, neutrons, electrons
Where is a proton located?
In the nucleus of an atom
Where is a neutron located?
In the nucleus of an atom
Where is an electron located?
On the shell(s) of an atom.
What is the weight of a proton?
One Dalton (amu)
What is the weight of a neutron?
One Dalton (amu)
What is the weight of an electron?
1/2000 dalton (amu)
What is the charge of a proton?
+1
What is the charge of a neutron?
0
What is the charge of an electron?
-1
What does the atomic number tell you about an Atom?
The number of protons and the number of electrons. They are the same. The periodic table arranges elements in order of their atomic number.
Name the first 10 elements in order of their atomic number.
Hydrogen helium lithium beryllium boron carbon nitrogen oxygen fluorine neon
What does the atomic mass tell you about an atom?
Number of protons plus neutrons
What is an isotope?
And Atom of the same element that differs in the number of neutrons
What are radioactive atoms?
Large isotopes that break apart, releasing energy
Name the three types of energy that can be released from a radioactive atom.
Alpha particles, beta particles, gamma rays
The energy released from a radioactive atom, that is weak and cannot penetrate paper is called?
Alpha particles
The energy that is released from a radio active Atom, that is stronger and can penetrate paper but not metal is?
Beta particles
The energy that is released from radioactive Atoms, that is very strong and can penetrate metal and harm living things is?
Gamma rays
What can radioactive Atoms be used for?
- To track chemicals in the body
- To work out the age of fossils (radiocarbon dating)
- To track the movement of individual animals (e.g. butterflies)
Which is the only particle of an Atom that is involved in chemical bonds?
Electrons
What are valence electrons?
Electrons in the outer shell of an atom. All atoms try to fill their valence shell with electrons when they form chemical bonds.
What is the maximum number of electrons in the first shell of an atom
2
What is the maximum number of electrons in the second shell of an atom?
8
What is the maximum number of electrons in the third shell of an Atom?
8
What is a molecule?
Two or more atoms joined by chemical bonds.
Name two characteristics of covalent bonds.
- Very strong
- Atoms share electrons
Example hydrogen gas (H2), water (H2O)
Name two characteristics of ionic bonds.
- Strong
- One Atom gives electrons to another
Example NaCL (Table salt)
Name 3 characteristics of hydrogen bonds.
- Weak
- A hydrogen atom is attracted to a slight negative charge on a different molecule.
- Important in sending signals from nerves to muscles.
Name five characteristics of water.
- Good solvent
- Cohesive
- High specific heat
- High heat of vaporization
- Expands when it freezes
Why is water a good solvent?
Many chemicals dissolve in it.
How can some animals walk on water?
The molecules in water stick together with hydrogen bonds.
What is meant by high specific heat?
It takes a lot of energy to heat
What is meant by high heat of vaporization?
It takes a lot of Energy to evaporate water
What makes ice float?
Water expands when it freezes so ice floats.
At what temperature is water most dense?
4°C (39°F)
What is an acid?
A substance that gives off hydrogen ions (H +)
Give an example of an acid.
Hydrochloric acid (HCl)
What is a base (alkali)?
A substance that absorbs hydrogen ions.
Give an example of a base.
Sodium hydroxide (NaOH)
What does the pH scale measure?
How acidic or basic a chemical is.
What is the pH of stomach acid?
2
What is the pH of coffee?
5
What is the pH of ammonia?
11
What is the pH of oven cleaner?
13
The pH scale is logarithmic. What does that mean?
If pH drops by one unit the number of hydrogen ions increases by 10 times. (pH 5 has 10 times the number of hydrogen ions as pH 6).
What is the pH of natural (unpolluted) rain?
5.5
What is the pH of Florida rain?
4.5
What is the pH of NE US rain?
3.5
What is an element?
A substance that cannot be broken down by chemical reaction
