1. Unit 2 Check For Understanding

2. Question 1: What best describes matter?
Answer: D. Anything that has mass and takes up space.
Notes:
Everything is made up of matter.
All matter is made up of atoms.
There are four states of matter (solid, liquid, gas, plasma).

3. Question 2: What are the basic units of of a chemical element called?
Answer: D. Atoms
Notes:
Atoms make up all matter.
Atoms have specific properties and specific names according to their protons and properties. (examples Carbon, Hydrogen, Calcium)
Atoms are made up of electrons, protons, and neutrons.

4. Question 3: The picture below represents an atom of the element nitrogen. How many electrons are in this atom?
Answer: B. 7
Notes:
The number of protons and electrons is equal
The electrons orbit the nucleus in a random motion

5. Question 4: There are six elements that make up most of the human body
Question 4: There are six elements that make up most of the human body. Which of the following is not one of these six elements?
Answer: D. Cu
Notes:
Cu is copper and is not an element found in the human body.
There are 6 major elements found in the human body that are used to form structures like bones and hair, water, and energy molecules.
Hydrogen, Oxygen, Carbon, Nitrogen are the four main elements.

6. Question 5: What is the most common molecule in living things?
Answer: A. H2O
Notes:
Water is composed of 2 molecules of hydrogen and 1 molecule of oxygen.
Water is held together by hydrogen bonds a type of covalent bond in which electrons are shared between

7. Question 6: Which produces an ionic bond?
Answer: A. Creating an electrostatic attraction.
Notes:
Electrostatic attrations occur between atoms that have a positive and a negative charge. (opposite charges attract)
For example sodium (Na) has a positive charge and cholrine has a negative charge (Cl) when they combine it forms NaCl (table salt)
Ionic bonds are weak bonds and are easily broken by other elements that maybe attracted to them.

8. Question 7: Which pair of atoms will form an ionic bond?
Answer: A. Na and Cl
Notes:
Their oppositely charged and will be attracted to each other.
Their charges comes from the number of electrons they want or need in order to be happy, stable atoms.

9. Question 8: The complicated molecules that make up living things usually contain carbon. Why is carbon so important in these molecules?
Answer: B. Carbon can form 4 strong covalent bonds.
Notes:
Covalent bonds are the strongest type of bond because they involve sharing electrons between 2 atoms or elements.
Carbon forms 4 bonds because it need 4 more electrons in order to be a stable, happy atom.

10. Question 9: The molecules that make up food contain energy
Question 9: The molecules that make up food contain energy. How does the human body get energy from the food molecules?
Answer: B. By breaking the bonds in the molecules.
Notes:
Anytime a bond is broken energy is released.
The more bonds there are the more energy is released.
The stronger the bonds are the more energy is released.
Therefore, covalent bonds between Carbon atoms release the most energy!