Chemistry: Properties and Changes

Properties and Changes

• Chemistry involves studying substances, their composition, behavior, and applications in everyday life as well as in the laboratory.
• Understanding chemistry helps modify substances into new, useful products and promotes environmentally and socially responsible practices.

Physical and Chemical Properties in Daily Life

• Teeth are not naturally pure white, ranging from off-white to yellow, and naturally darken with age.
• Teeth whitening does not improve teeth health; whitened teeth are still prone to decay and gingivitis.
• Whitening requires repetition to keep teeth white.
• Surface whitening involves using abrasive materials like baking soda to scrape stains off teeth, whereas bleaching chemically uses substances like hydrogen peroxide.
• Physical property is a substance's characteristic, for example hardness, color, density, smell, solubility, taste, melting point, and physical state.
• Chemical property defines a substance's behavior when it transforms into a new substance. Hydrogen peroxide's ability to bleach coloured substances is an example.

Physical and Chemical Changes

• A physical change does not create a new substance; changes of state like melting or dissolving are examples.
• Physical changes are reversible, for example dissolving sugar in water, but some aren't, for example cutting logs.
• A chemical change results in a formation of new substances.
• Confirming a chemical change requires testing products to see if they differ from the original materials.
• Many chemical changes, such as a forest fire, are irreversible, but some, like those in rechargeable batteries, can be reversed.

Cadmium Cleanout

• Nickel-cadmium (NiCd) batteries were an early type of rechargeable battery for small electronics.
• NiCd batteries lose their ability to hold a charge over many discharge-recharge cycles.
• The batteries end up in landfill sites, leaking toxic cadmium into groundwater; more than 50% of cadmium in landfills comes from NiCd batteries.
• Cadmium cannot be broken down and is a human carcinogen which is linked to lung, liver, and kidney disorders.

Workplace Hazardous Materials Information System (WHMIS)

• WHMIS is a Canadian system ensures safe handling, usage, and information about hazardous products for Canadian workers.
• Employers are legally obligated to provide WHMIS information through product labels, safety data sheets, and worker training.
• WHMIS product labels alert users to potential hazards, come in two types: supplier and workplace labels.
• Supplier labels include a hatched border, bilingual text, product name, hazard symbols, supplier information, and reference to the MSDS.
• Workplace labels must show the product name, safe handling information, and an MSDS reference but do not need a hatched border.
• Materials Safety Data Sheets (MSDS) contain safety information, safe handling and storage advice and first aid help.

Patterns and the Periodic Table

• The periodic table is a powerful tool used to predict and explain the properties of the elements
• Elements are pure substances that cannot be broken down into simpler substances.
• Includes metals, non-metals, and metalloids that have individual properties.
• Metals are generally shiny, solid at room temperature (except mercury), malleable, are good conductors of electricity. Non-metals have properties that vary.
• A period is a horizontal row in the periodic table.
• A group is a vertical column that contain elements with comparable properties -- alkali metals, alkaline earth metals, halogens, and noble gases.
• Alkali metals (Group 1) are soft, highly reactive metals.
• Alkaline earth metals (Group 2) are light and reactive.
• Halogens (Group 17) are highly reactive.
• Noble gases (Group 18) are very stable and rarely react

Atomic Structure

• The structure of atoms leads to properties of elements.
• Developed by scientists into a model of the atom.
• Mass is in a small, dense, positively charged core called the nucleus.
• Atoms are made up of 3 subatomic particles: protons (positive charge in nucleus), neutrons (neutral charge in nucleus), electrons (negative charge that orbit nucleus).
• Each element's atomic number is its number of protons in the nucleus.
• In neutral atoms, the amount of electrons equals the number of protons.
• A Bohr-Rutherford diagram is a model to show electron arrangement in orbits around the nucleus.
• Orbits hold a limited amount of electrons, with two in the first and eight in the second and third.
• Elements are in order of increasing atomic number.

Electron Outer Orbit Arrangement

• Lithium-7 (mass number 7) has three protons and four neutrons, with three electrons orbiting, two in the first orbit and one in the second.
• The second electron orbit in Fluorine can accommodate up to eight electrons.
• The noble gases that are known for their nonreactivity are Helium, Neon, and Argon.
• Because noble gases all have completely filled outer orbits, they’re very stable.
• Chemists infer that the electrons in the atom's outermost orbit determine an element's reactivity.
• Reactive elements combine to form compounds and stable compounds contain two or more elements in set ratios.

Atoms and lons

• Excessively drinking water to dilute sodium in blood is hyponatremia, which has symptoms that include poor balance.
• Sodium with too little sodium concentration in the blood can lead to fatality.
• In blood the body needs calcium, phosphorus and iron ions.
• Atom is neutral with proportionate electrons and protons
• Ion is charged having gained or lost electrons
• Atoms are made of equal electrons and protons, an ion is created when electrons are gained or lost.
• Sodium atoms lose one electron and have 11 protons and 10 electrons, resulting in ionic charge of +1 represented as Na1+ or Na+.
• The other alkali metals also form ions with a single positive charge.
• Fluorine forms a fluoride ion (F-) by gaining an electron, resulting in a negative charge of -1. All halogens do this.

Sodium and Fluorine

• Group 18 is the noble gases with stable outer orbits.
• Sodium ions and fluoride ions are also stable.
• Bohr-Rutherford diagrams are helpful in explaining sodium and fluorine non-reactivity; neon is closest to sodium and fluorine on periodic table.
• Process of a sodium atom reacting to lose electron is most likely from the outer orbit.
• As a result, the sodium ion has the stable electron arrangement of neon.
• Fluorine has one less electron than neon, tends to react with other atoms to gain electron.
• Fluorine, which gains electron, has 10 electrons and nine protons becoming fluoride ion F-.

Aluminum

• Aluminum's electrons are shown by the Bohr-Rutherford diagram.
• Aluminum ions have ionic charge +3: Al3+
• Experiments show that metals lose electrons, while nonmetals gain them.
• Sulfur needs 6 electrons in its 3rd orbit.
• To be stable, sulfur atoms gain two electrons and will form sulfur ions with the symbol S2-.
• Positive ions are categorized as cautions and are positively charged, while anions are negatively charged with negative charges.

Formation and Stability

• Elements gain/lose electrons to form stable ions.
• Atoms that gain/lose electrons to form the ions are called anions/cations.
• Atoms have complete outer orbits and are stable.
• Positive ions have less electrons than protons = positive charge.
• Atoms/ions can be represented through diagrams.
• Ion concentration is necessary for good health

lonic Compounds

• Violent reaction between sodium and chlorine forms NaCl (table salt).
• Metals lose electrons and become positive ions (cations).
• Non-metals gain electrons and become negative ions called anions.
• Non-metal chlorine takes electrons away from metal sodium which causes both to occur.
• Metal's hold is weakest, while the nonmetal attracts the electrons.
• By doing this the result is that all ions have a noble gas filled outer shell/arrangement.

Molecular Compounds

• Attraction leads to positively charged ions and is made of sodium Na+ and Cl-.
• When it comes to only two elements 1 is usually metal and the other is non-metal and there is attraction that happens in the compound ionic bond

Crystals and Solvents

• Sodium and chloride join together to form an ionic crystal.
• Cubic NaCl is a ratio of 1:1
• Always consist of sodium many ions and chloride ions.
• Some ionic compounds are soluble in water, and separate into ions when dissolving, where molecules prevent rejoining by the crystal.
• Positive and negative ions are pushed by water that allows for more arrangement

Aluminum and Dissolving

• Three electrons available to chlorine from aluminum makes for reaction by chlorine and aluminum atom with one extra energy
• Aluminum reacts with formula of chemical aluminum chloride
• Ions allow for dissolving of aluminum/sodium from water in solutions

Ionic Compound Properties

Ionic compounds have properties that include:

• Hard
• Brittle
• High melting points
• Electrolytes and dissolve to conduct electronic current
• Presence of ions improve electric conductivity of liquids
• Pure doesn’t conduct well The compounds are essential to stay out of pools during lightning and water.

Formation of Ionic Compounds

• Metals combine with non-metals to form an ionic compound.
• During the reaction, the metallic ions are held together by non-metallic interactions, like atoms.
• Depends completely the amount that both gain and lose to combine effectively.
• The point of metals is to stay balanced.
• Ionic crystals are built in different dimensions with many combinations of metal and non-metal to make an effective product.

Molecules

• Polyatomic ions can be expressed in different quantities.
• They allow for cleaning and fertilizing properties.
• Anions lead to negative charge
• Important to be necessary.
• Most can be applied when looking at problems because they are required for necessary things

Formulas Involving Elements

• Use element symbols when naming compounds, including in order of listing.
• Use chemical formulas.
• There must be a specific number for everything.
• Apply all the steps when first thinking of chemical charges.
• This leads to chemical charges that you learned already.
• There are charges on the metal.

Polyatomic lons

• Strategy for naming polyatomic follows steps learned by previous sections.
• Difference: named according to polyatomic ions by elements.
• The formulas is needed to use brackets when necessary.
• Use Roman Numeral to show charge.

Polyatomic Atoms

• The reactions that occur create polyatomic charges
• They require the specific amount of oxygen.
• The method to be used with everything and is needed to apply with polyatomics.
• It requires brackets to put around everything as well

Chemicals

• Both types of chemical actions in nature and is helpful/harmful. 2.4. The reactions show the electrons that connect and make non-metal effective- A variety of steps allow for the release of dangerous spills on the environment

Compounds in Molecular Actions

• Most are good but others make life good.

Forming Connections

• Requires the bond to create action with each other and for all to get close.
• The strong actions make both atoms get pulled toward each
• Both results are tug-of-war that share electrons
• Process called covalent bond by having each other close through what is needed