Chapter 1 Flashcards
What is matter?
Matter is defined as any substance that has mass and volume. It makes up the observable universe and together with energy (light, sounds, etc) forms the basis of all objective phenomena.
What is vacuum?
Space in which there is no matter or in which the pressure is so low that any particles in the space do not affect any processes being carried on there. It is a condition well below normal atmospheric pressure and is measured in units of pressure (the pascal). A vacuum can be created by removing air from a space using a vacuum pump or by reducing the pressure using a fast flow of fluid, as in Bernoulli’s principle.
Do suction cups work in space?
No, because space is a vacuum. A suction cup works by creating a volume of low pressure inside it, which is held in place by atmospheric pressure pushing down onto it from the outside.
What is matter composed of?
Matter is composed of elementary particles known as quarks and leptons (the class of elementary particles that includes electrons). Quarks combine into protons and neutrons and, along with electrons, form atoms of the elements of the periodic table.
What is a chemical? What is a compound?
A chemical is anything made of matter. A compound is a substance made of two or more atoms.
What is a model? Which do chemists use and what are their comparative benefits?
A way or a method of representing a structure or idea. Chemists use space-filling model (useful for seeing relative size of atoms) and ball-and-stick model (for seeing relative position of the centres of constituent atoms).
Is a water molecule straight or bent?
Water molecule is bent! The atoms are not connected in a straight line.
What is risk?
- a situation involving exposure to danger.
- the possibility that something unpleasant or unwelcome will happen.
- a person or thing regarded as a threat or likely source of danger.
What is hazard?
Hazards are components of risk: they are defined as the potential to cause harm and can be an object or a situation that poses a level of threat to life, health, property or environment.
What is control measure?
An action taken to reduce the risk associated with a hazard.
Colour codes for S, Cl, C, O, N, H?
Yellow green black red navy white
Most common elements in human body. How much is water? Third most abundant element in universe by mass.
O oxygen 65.0
C carbon 18.0
H hydrogen 10.0
N nitrogen 3.0
Ca calcium 1.5
P phosphorus 1.2
K potassium 0.4
S sulfur 0.25
Cl chlorine 0.20
Na sodium 0.20
water 70%
Oxygen!!
Size of raindrop in the cloud and as it falls to earth. How many times can you divide the average raindrop before it is not water anymore?
0.01mm (or 10 to the power of -5 metres) . Raindrops coalesce to 2mm as they fall to earth. You can divide an average raindrop 67 and it is still water. After that, you’re splitting the molecule into constituent parts.
Visualise atom v droplet.
One way of trying to visualise the size of an atom within a water droplet is to imagine the water droplet magnified to the size of the Earth; an atom would be roughly the size of a tennis ball.
How to keep a scientific notebook.
Use permanently bound notebooks and number the pages. Never remove pages from the notebook. Loose-leaf should be avoided and any attachments should be stapled.
The notebook should be hard-backed, since this offers more protection against spillages and also adds to its durability in hostile environments.
Do sign and date each entry.
Entries should be made in permanent ink and in chronological order. Avoid using pencils.
Record all the observations that you make during the course of the experiment. Remember to include the units of measurement. Don’t be embarrassed about writing down mistakes or accidents.
Include raw data and also interpreted results, making clear which is which.
Detecting electrons.
Does the strength of the running stream of water affect your results?
Does the size of the object used (comb or inflated balloon) have an effect on your observations?
Is the weather affecting your experiment?
State relative mass of electron versus neutron and proton.
The mass of a neutron is almost the same as the mass of a proton. Both the proton and the neutron have a relative mass of 1. The mass of a proton (or a neutron) is nearly 1840 times that of an electron.
static electricity
form of electricity resulting from the imbalance between positive and negative charges within a material that occurs when electrons (the negatively charged particles in an atom) move from one material to another. If the electron-receiving material is either isolated or not an electrical conductor, it tends to hold on to the electrons, resulting in a buildup of electric charge. Since this charge is not moving, it is referred to as static electricity. When conditions allow the built-up charge to flow, the surplus of static electricity is discharged, and it becomes current electricity.
covalent bonding
A covalent bond is a type of chemical bond characterized by the sharing of an electron pair between two atoms. This bond forms when the total energy of the bonded atoms is lower than that of the atoms when they are widely separated. The electrostatic attraction between the nuclei of the atoms and the shared electrons holds the atoms together. Covalent bonds are typically formed between nonmetal atoms, which are found on the right side of the periodic table, and are common in both inorganic molecules like water (H₂O) and organic compounds.
Covalent bonds can be single, double, or triple, depending on the number of shared electron pairs. Single bonds involve one pair of shared electrons, double bonds involve two pairs, and triple bonds involve three pairs. These bonds are directional, giving molecules specific shapes. Covalent bonds can be nonpolar, with equal sharing of electrons, or polar, with unequal sharing, leading to partial charges on the atoms.
ionic bonding
An ionic bond typically forms between a metal and a non-metal atom through a permanent transfer of an electron which leads to the formation of a negative ion (anion) and a positive ion (cation); the compound is held together by the electrostatic attraction between the two ions.
Ionic bonding is a type of chemical linkage formed from the electrostatic attraction between oppositely charged ions in a compound. This bond occurs when one atom transfers its valence electrons to another atom. The atom that loses electrons becomes a positively charged ion, or cation, while the atom that gains electrons becomes a negatively charged ion, or anion.
Ionic bonds typically form between metals and nonmetals, such as in sodium chloride (NaCl), where sodium donates an electron to chlorine. This results in a sodium ion (Na⁺) and a chloride ion (Cl⁻), each achieving a stable electronic configuration. In ionic solids, the ions are arranged in a lattice structure, where each cation is surrounded by anions and vice versa, balancing the overall charge to zero.
Ionic compounds generally exhibit high melting points, moderate hardness, and poor electrical conductivity in solid form, but they conduct electricity when melted or dissolved in water due to ion mobility
Polarisation
The term polarisation is commonly used to describe this partial separation of charge and can be represented as δ− (delta minus) and δ+ (delta plus). The Greek letter delta δ is used to represent ‘a little bit’, since it amounts to less than one electron’s worth. In Figure 1.12, the oxygen atom has a partial negative charge δ− and the hydrogen atom has a partial positive charge δ+. This is known as a polar bond. Covalent bonds between two different elements will always present some polarisation.
Molecule polarization refers to the distribution of electrical charge over the atoms within a molecule, leading to the formation of polar bonds. This occurs when atoms in a molecule have different electronegativities, causing the shared electrons in a bond to be more attracted to the more electronegative atom. This results in partial charges, with the more electronegative atom acquiring a partial negative charge and the less electronegative atom acquiring a partial positive charge. The presence of these partial charges creates an electric dipole, characterized by a dipole moment, which is the product of the magnitude of the partial charges and their separation distance.
The overall polarity of a molecule depends not only on the presence of polar bonds but also on the molecular geometry. For example, water (H₂O) is a polar molecule because its bent shape prevents the dipole moments from canceling out, whereas carbon dioxide (CO₂) is nonpolar because its linear shape allows the dipole moments to cancel each other.
Is the covalent bond between two atoms of the same element polar or non-polar?
The covalent bond between two atoms of the same element is non-polar because both atoms attract the shared electrons to the same extent.
In which situation can a molecule with polar bonds still be non-polar?
A molecule can have polar bonds and still be non-polar if these bonds are evenly distributed (e.g. in a symmetrical linear molecule).
What is a hydrogen bond?
Due to its bent geometry, water is a polar molecule and this causes the positive hydrogen of one water molecule to be attracted to the negative oxygen of another water molecule (Figure 1.13). This attraction is called a hydrogen bond.
hydrogen bond is a type of intermolecular interaction that occurs when a hydrogen atom, which is covalently bonded to a highly electronegative atom such as oxygen, nitrogen, or fluorine, interacts with another electronegative atom. This interaction can be represented as A–H···B, where A and B are electronegative atoms, and the hydrogen atom lies on a straight line between the nuclei of A and B. Hydrogen bonds are significantly stronger than other types of intermolecular forces and play a crucial role in determining the properties of substances, such as the liquid state of water at normal temperatures and the solid state of many organic molecules containing hydroxyl groups.
Hydrogen bonds are also vital in biological systems, influencing the structure of proteins and DNA. In proteins, hydrogen bonds help maintain the helical and pleated sheet structures, while in DNA, they are responsible for the specific pairing of nucleotide bases, which is essential for genetic information transmission.