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chem y9 m1, there are more exothermic reactions than endothermic reactions…

- - - - separate liquid from solid (different states of substances)
      - Apparatus: Round-bottom flask + Condenser + Receiving flask + Burning experiment setup (Gauze + tripod + bunsen burner)
      - The mixture boils off as a gas (at boiling point) --> condenses and turns into liquid in the condenser --> received by the receiving flask
    - - separate mixture with 2+ substance of same state (e.g. all liquid)
      - Apparatus: Fractionating column + Thermometer + Distillation flask + cork + condenser + stopper (prevents gas from escaping)
      - Gas A passes into the condenser as boiling point reached --> condenses and being collected --> Temperature rise until Gas B boiling point is reached --> condensed and collected in a separate beaker
      - the heating curve recorded of the thermometer stops at the different boiling points of the substances. Since during a phase change, all of its heat energy is transferred to kinetic energy.
    - - used to cool the separated gas->liquid
      - out at top, in at bottom to prevent water from escaping
  - - - Chemicals in a mixture have different solubilities and different attractions to the paper, so it travels at different distance on the paper.
        
        Greater solubility, the farther the distance. Vice versa
        
        Greater attraction, the shorter distance. Vice versa
      - works only when the substances in the mixture dissolve in one solvent
    - - distance traveled by the substance / distance traveled by the solvent (solvent front)
      - 0<=Rf<=1
    - - Draw base line --> spot the substances --> Paper stand in solvent (water / alcohol) --> Draw (Observe & mark solvent front) --> Dry (Spray locating agent if needed) --> Measure the distance of dots from the base line--> Calculate Rf value
    - - Spray locating agent at the stage of drying, so it produces color
    - - How many substances are present in a mixture
      - Purity/Solubility of substances
      - Identify substances by the distance they travel
    - - use graphite in the baseline since it's not soluble
      - baseline above solvent, or else the dye will be dissolved directly by the solvent
  - - - Has no particles of other substance mixed with it
      - SHARP & FIXED melting point
    - - Has particles of other substance mixed with it
      - Melting / boiling point is over a RANGE of temp, NOT SHARP. It is because different substance have different melting/boiling points.
    - - Looking at the melting & boiling points of heating/cooling curves
      - Chromatography
- - - - particles are moving all time
      - higher temperature, higher speed OR higher heat energy, higher kinetic energy
      - different movement and arrangement of particles for the three states of matter *mentioned above
      - diffusion
        
        particles (eg.dye) mix and spread by colliding with other particles (eg.water)
        
        usually, particles move from high to low concentration
        
        determinants
        
        particles movement
        
        Thus, gas diffusion is quicker than liquid diffusion. Since particles have greater kinetic energy and greater freedom of movement
        
        temperature
        
        particles take in heat energy, and transfer to kinetic energy, making diffusion faster
        
        mass
        
        lighter gases diffuse quicker as compared to heavier gases. Heavier particles move slower.
      - gas pressure
        
        produced by particles hitting the walls of the container. More often the collision, greater the pressure
        
        determinants
        
        mass
        
        greater the mass=>more particles=>more frequent they collide=>greater gas pressure
        
        temperature
        
        heat=>kinetic *mentioned above
      - random movement of particles
        
        Brownian motion: particles don't move in a straight line
        
        factors
        
        pressure
        
        space between particles
        
        number of particles
        
        temperature
        
        size of container
        
        state of matter
  - - - heating/cooling curve
        
        key elements in any graph
        
        title
        
        X-axis & Y axis with labels and unit
        
        line of best fit
        
        key
        
        observations(heating/cooling curves in water)
        
        heating curve is a mirror image of cooling curve
        
        In a heating curve, the temperature is strictly increasing. In a cooling: curve, the temperature is strictly decreasing
        
        temp. stays at 0C for a moment
        
        0C is the melting point
        
        ice is melting to water (state: Solid and Liquid)
        
        all heat energy in the particle is transferred into kinetic energy for changing the state by breaking the intermolecular bonding
        
        temp. stays at 100C for a moment
        
        water is boiling into vapor (state: Liquid and Gas)
        
        100C is the boiling point
        
        the temperature rises/falls
        
        <0C(below melting point): solid state
        
        0C-100C (above melting point and below boiling point): liquid state
        
        100C(above boiling point): gas state
      - process names:
        
        S->L: melt
        
        S->G: sublimes
        
        L->S: freeze
        
        L->G:boil/evaporate
        
        G->S: deposition
        
        G->L: condense
      - it is a physical reaction
        
        endothermic
        
        absorbing heat energy when reacting (can be chemical or physical)
        
        eg. heating
        
        solid->liquid->gas
        
        particles take in heat energy and change into kinetic energy
        
        gradually more spacing between particles
        
        exothermic
        
        releasing heat energy when reacting (can be chemical or physical)
        
        eg. cooling
        
        gas->liquid->solid
        
        particles loses energy and slows down
        
        the forces of attraction takes over
        
        gradually fewer spacing between
        
        To change states of matter, we can apply or remove heat
        
        Since state changing is a physical process, its particles do not change. Only the movement, arrangement, and inter-molecular force changes
    - - liquid
        
        close & touching
        
        irregular arranged
        
        less strong molecular force than solid
        
        movement: vibrate & slide past another
        
        volume doesn't change, since the particles are all touching, they have small gaps between each other
      - gas
        
        far apart
        
        randomly arranged
        
        no molecular force
        
        movement: vibrate & move freely
        
        volume can be easily changed by compressing, since there are large gaps between particles and small molecular attractions
      - solid
        
        close & touching
        
        regularly arranged
        
        strong molecular force
        
        movement: vibrate
        
        volume doesn't change, since the particles are all touching, they have small gaps between each other
- - - - isotopes
        
        def: elements with the same number of protons and electrons but different number of neutrons and consequently mass number
        
        behave the same way during chemical reactions, because they have the same number electrons. However, their density is different.
        
        some isotopes are radioactive as they decay due to their unstable nuclei
        
        the radioactivity has both dangers and industrial/medical uses such as killing cancer cells
      - ions
        
        def: charged atoms where the number of protons and electrons are not equal
        
        achieved by an atom losing or gaining electrons
        
        the overall charge of an ion depends on the original atom's valance electrons (number of electrons in the outmost layer)
        
        positive ions
        
        <=4 valance electrons
        
        more protons than electrons
        
        atoms lost electrons
        
        +1, +2 or +3
        
        negative ions
        
        =5 valance electrons
        
        less protons than electrons
        
        atoms gain electrons
        
        -1, -2, or -3
      - components (subatomic particles)
        
        nucleus
        
        protons
        
        positively charged / "+"
        
        relative mass: 1
        
        neutrons
        
        not charged / neutral
        
        relative mass: 1
        
        occupies a small amount of an atom, but it's dense
        
        electrons
        
        negatively charged
        
        arranged in shells outside the nucleus
        
        each shell has a maximum number of electrons. the first layer 2, the second layer 8, the third layer 8, etc.
        
        shells further from the nucleus have higher energies
        
        shells are filled starting with the one lowest in energy
        
        relative mass: 1/1840 or almost zero
      - def: the smallest unit of element that make up everything
    - - elements: contains one type of atom
      - compound: made up of atoms of elements chemically bonded to atoms of other elements
        
        compound properties are different from the properties of the elements in it
      - mixture: consists of different substances not chemically bonded
        
        homogeneous: uniform composition (eg. coffee)
        
        heterogeneous: not uniform composition (eg. salad)
    - - proton number
        
        In an atom, the proton number equals to the number of electrons, so that there is no overall charge in an atom.
        
        def: the number of protons
        
        Elements have a fixed proton number. The proton number tells you which element it belongs to
        
        In an ion, the proton number doesn't equal to the number of electrons, making it charged
      - nucleon number
        
        the number of protons + the number of neutrons
      - mass number
      - atomic number
        
        it determines the order the periodic table is arranged
      - relative atomic mass
        
        average mass of naturally occurring atoms of an element
        
        its calculation is similar to calculating the expected value. if you have a list of elements a, and its corresponding list abundance, or probability p, the expected value is the sum of all ai x bi, given that i is a number from 1 to n, n being the number of elements.
        
        eg: the relative mass of chlorine with mass number 35 and abundance 75% and isotope chlorine with mass number 37 and abundance 25% is 35*75%+37&25%=35.5