SCH3U Units 1 & 2 Flashcards
What is chemistry?
It is the study of matter and its composition.
Name 6 things scientists do to be able to observe matter.
- Developing models
- Conducting experiments
- Seeking patterns
- Observing various types of chemical reactions
- Performing calculations based on known data
- Building continuously on the work and discoveries of other scientists.
What is matter?
It is anything that has mass and volume (takes up space).
Give some examples of qualitative physical properties.
Physical state, colour, odour, crystal shape, malleablility, ductility, hardness, brittleness, clarity, taste, texture.
Give some examples of quantitative physical properties.
Melting point, boiling point, density, solubility, electrical conductivity, thermal conductivity, height, mass, volume.
Give some examples of chemical properties.
Combustibility, toxicity, decomposition, and reactivity with water, air, pure oxygen, acids, pure substances.
What are the four rules of significant digits?
- All non-zero numbers are significant
- All seros that are located between two non-zero numbers are significant
- Zeros that are located to the left of a value are NOT significant.
- Zeros located to the right of a value may or may not be significant.
What is accuracy?
Accuracy refers to how close a given quantity is to an accepted or expected value.
What is precision?
Precision may refer to the exactness of a measurement.
What are physical properties & how can they be observed?
They can be observed without changing on form of matter into the other. They can be either quantitative or qualitative.
What are chemical properties and how can they be observed?
They are properties that can only be observed by changing matter from one form to the other.
What are physical changes?
PHysical changes are changes in appearance, but not what the substance is (appearance changes, but composition doesn’t).
What are chemical changes?
They change what the matter is (change the composition of the matter).
What are 5 indicators of a chemical change?
- Heat/light
- Precipitate
- Gas produced
- New colour
- Difficult to reverse
What is the rule for the number of significant digits that should be recorded in the answer to a multiplying or dividing calculation?
The value with the fewest number of significant digits going into the calculation is how many significant digits should be recorded in your answer.
What is the rule for how many significant digits should be recorded in the answer to a adding or subtracting calculation?
The value with the fewest decimal places going into the calculation indicates the number of decimal places you should record in your answer.
If a number that ends in 5 is being rounded, should the number be rounded up or down?
If the number preceding the 5 is odd, the number should be rounded up, but if it is even, the number should be rounded down.
What does the law of conservation of mass state?
During a chemical reaction, the total mass of the substances involved does not change.
What does the law of definite proportions state?
Elements always combine to form compounds in fixed proportions by mass.
Define: atom
An atom is the smallest partical of an element that still retains the identity and properties of the element.
What three particles are atoms made up of? Which are found in the nucleus?
Electrons, protons and neutrons. Protons and neutrons are found in the nucleus.
Define: atomic number
The number of protons in the nucleus of an atom of the element.
Define: mass number
The total number of protons and neutrons in the nucleus of one atom.
Define: Isotopes
Atoms of an element that have the same number of protons but different number of neutrons.
Define: Radioactivity
The process in which unstable nuclei spontaneously decay, releasing energy and subatomic particles.
Define: Radioisotopes
An unstable isotope of an element, which undergoes radioactive decay.
State the four points of Dalton’s Atomic Theory.
- All matter is made up of tiny particles called atoms. An atom cannot be created, destroyed, or divided into smaller particles.
- The atoms of one element cannot be converted into the atoms of any other element.
- All the atoms of one element have the same properties, such as mass and size. These properties are different from the properties of the atoms of any other element.
- Atoms of different elements combine in specific proportions to form compounds.
State the four points of the Modern Atomic Theory.
- All matter is made up of tiny particles called atoms. Each atom is made up of smaller subatomic particles: protons, electrons and neutrons.
- The atoms of one element cannot be converted into the atoms of any other element by a chemical reaction.
- Atoms of one element have the same properties such as average mass and size. These properties are different from the properties of the atoms of another element.
- Atoms of different elements combine in specific proportions to form compounds.
T or F: A defined constant such as pi, p = 3.141559, has an infinite number of significant digits.
T
True or False: A slight rise in air temperature can accompany the onset of snowfall. This rise in temperature is evidence of a chemical change
False
True or False: The following three values for the density of water at 34 degrees celcius were determined by experiment: 0.99g/cm³, 1.04g/cm³, and 0.94g/cm³. These values are accurate, but not precise.
True
Define: Atomic radii
The distance from the centre of the nucleus to the valence level.
What is the group trend for atomic radii?
The atomic radii increases as you move down the group - higher energy levels are occupied.
What is the periodic trend for atomic radii?
Generally, atomic radii decreases as we move from left to right. This is because the number of protons and electrons in an atom increases across a period, so there is a greater attraction between the nucleus and the orbitals, pulling the valence level closer.
Define ionization energy.
The energy required to remove an electron from a neutroal gaseous atom.
What is first ionization energy?
The energy required to remove the most weakly held valence electron from an atom.
What is the group trend for ionization energy?
Generally, ionization energy decreases as we move down a group.
What is the periodic trend for ionization energy?
The ionization energy increases from left to right.
The increase in electrostatic attraction (which reduces atomic radii) also means that greater energy is needed to overcome it, and steal a valence electron
Define electron affinity
The energy released when an electron is added to a neutral gaseous atom to form an anion.
What is the group trend for electron affinity?
Generally, the electron affinity decreases as we move down a group.
What is the periodic trend for electron affinity?
The electron affinity generally increases as we move across a period.
What are some properties of alkali metals?
- Very reactive with H2O to form an alkaline/basic solution and hydrogen gas
- Conductive
- Metallic
- Relatively soft
- Opaque
What are some properties of alkaline earth metals?
- React with oxygen to form compounds called oxides, which react with H2O to form alkaline/basic solutions
- Shiny
- Metallic
- Lustrous
- Silver-white colour
What are some properties of Halogens?
- They combine with other elements to form compounds called “salts”
- They are poisonous
- Different elements from the group exist in all three states of matter at room temperature
Name some properties of noble gases
- Gases at room temperature
- Stable
- Non-reactive
