Chemistry PDF - States of Matter

Chemistry States of Matter - Everything on Earth is grouped into one of three states of matter: solid, liquid or gas - To determine which state of matter an object is, we examine its properties: - Shape -- the shape of the object and what space it fills - Mass -- the amount of m...

Chemistry States of Matter - Everything on Earth is grouped into one of three states of matter: solid, liquid or gas - To determine which state of matter an object is, we examine its properties: - Shape -- the shape of the object and what space it fills - Mass -- the amount of matter an object has - Volume -- the amount of space the matter takes up Solids - Easy to recognise - Shape -- definitive, does not change - Mass -- does not change mass - Volume -- takes up the same amount of volume - Made of tiny particles called atoms which are closely packed together and hold the definitive shape A group of round objects Description automatically generated Liquids - Shape - Do not have a definitive shape. Liquids take the shape of their containers at the lowest place - Mass - Do have a definitive mass - Volume -- Do have a definitive volume e.g. 100mL of OJ in glass you then spill on the floor -- still 100mL of OJ - Liquids are like solids as their atoms are close together but what makes them different is that these atoms can move around  Gases - Shape - do not have a definitive shape. Gases will take the shape of the container however if not in a container they will spread out indefinitely - Volume -- Do not have a definitive volume. Unlike solids and liquids, gases can be compressed to change the amount of volume they take up. E.g. pumping up tyres or ball - Mass -- still have definitive mass A black and white rectangle with two spheres Description automatically generated Example -- Water  \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ The Particle Model - Matter is made of extremely small particles called atoms, which are difficult to visualise because they are so tiny. - If we imagine the atoms as being tiny balls, this is called The Particle Model of Matter Theory - The particles are always moving -- kinetic refers to the energy of anything moving - Therefore, the Particle Model describes the amount of kinetic energy there is in each state of matter Particle Energy -- People vs Particles - When people are sitting quietly, they have little kinetic energy. This is like a solid, where the particles only vibrate. - In a crowd, people are standing and moving around and have more kinetic energy. This is like a liquid, where the particles jostle about. Particles in a liquid have more kinetic energy than particles in a solid. - When people are running, they have much more kinetic energy. This is like a gas, where the particles move fast and on their own. Particles in a gas have the highest amount of kinetic energy. Mass - Mass is the amount of matter in a substance and is measured in kg. - Mass depends on the number of particles and the mass of each individual particle - A particular volume of a solid or liquid will have a greater mass because it has more particles in it - Lead vs Aluminium -- lead particles are heavier than aluminium even though have the same volume A close-up of a diagram Description automatically generated Diffusion - The spreading out of particles from a high concentration to low concentration e.g. perfume sprayed in lockers can quickly be smelt - Occurs fastest in gases as particles are moving fast and freely - Takes longer in liquids as particles collide with each other e.g. tea bag in water takes longer to diffuse -- how can we speed this up? - In solids, particles are locked in position and only able to vibrate and not move to a new location therefore, diffusion does not occur in solids \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Changing States of Matter - When you heat matter, you are passing on heat energy to the particles - This means they start moving faster and increase kinetic energy - Melting and boiling points are the temperatures at which a substance melts and boils Example -- Gold - Gold is usually a solid at room temperature -- particles all packed tightly together - When given heat energy, gold particles start vibrating faster - At 1064°C, the particles have enough kinetic energy to move around each other just like a liquid -- the gold has melted - If you continue heating gold, it will continue to gain kinetic energy and move faster and take up more space until it finally reaches 2807°C. It turns into a gas Changing States of Matter - The process can happen in reverse - If the temperature is reduced, particles will move more slowly and the attraction to other particles will now keep the particles close together e.g. gas condenses into a liquid - If this liquid loses enough energy, the movement continues to slow until eventually they are locked in place as a solid and has solidified or frozen - The difference between a hot and cold substance is the kinetic energy of the particles! A group of cylindrical containers with blue balls Description automatically generated Heat Causes Expansion - All objects and substances expand (in size and volume) as their temperature increases. These objects shrink back to original size as they begin to cool (or lose kinetic energy). - Applying heat energy causes the particles in the liquid or gas to gain more energy. The particles jostle more and speed up. As they move around faster, they take up more space and push the other particles further apart - Although this expansion may only be small, it may have a great affect on the object   Physical vs Chemical Changes - Physical Changes - Substance still consists of the same particles but it looks different - Chemical Changes - When two different substances interact and combine to form a new substance - Change in colour, formation of bubbles, change in temperature or formation of new state may occur Diagram of a diagram of liquid Description automatically generated Physical Changes - **Vaporisation** - When a liquid evaporates to become a gas, we say it has vaporised - Gas form of substance that is normally solid or liquid at room temperature - **Condensation** - When a gas changes state to become a liquid, normally by cooling, we say it condenses - Gas to liquid - **Melting** - When a solid is heated and changes state to become a liquid, we say it has melted - **Solidification** - When the liquid loses heat and becomes a solid, it is called solidification or it is sometimes known as freezing Physical Changes: Sublimation - Some substances don't ever exist as liquids - Change straight from gas-to-solid or solid-to-gas - The process is called sublimation - Example: Dry Ice - It is carbon dioxide in gaseous form, dry ice in liquid form - The 'smoke' you see when using dry ice is not Carbon Dioxide, it is clouds of water - When dry ice sublimes to form Carbon Dioxide gas, it cools the air quickly, which causes water vapour in the air to condense and form clouds of water \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Structure of Atoms - Atoms consist of **three smaller particles.** The Differences between the Particles - The protons and neutrons are roughly the same mass, but the electron has a mass that is negligible by comparison. - The proton has a positive electrostatic charge. The electron has a negative electrostatic charge. The neutron has no charge, it is neutral. - For a neutral atom there are always the same number of protons as electrons. Lithium has three protons, so it must have three electrons.  Atomic Number - The number of protons found in the nucleus of an atom - This also is the number of electrons surrounding the nucleus of an atom. Mass Number or Atomic Weight - The number of protons and neutrons in the nucleus of an atom Number of Protons, Electrons and Neutrons - \# of PROTONS = ATOMIC NUMBER - \# of ELECTRONS = ATOMIC NUMBER - \# of NEUTRONS = ATOMIC WEIGHT -- ATOMIC NUMBER \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ What are Elements? - An element is a pure substance made of only one type of atom - Elements cannot be broken down into other substances because they are already the simplest substances Elements - In the solid state, atoms of metals are held in a lattice - Most other elements, which are not metals, are called non-metals -- most of which are gases at normal temperature Elements - Monoatomic - each gas particle is a single atom (mono = one) - Example: neon and helium - Diatomic - atoms of these elements join together in pairs (di = two) - Example: oxygen, hydrogen and nitrogen Periodic Table - The periodic table arranges all the elements in order of the size of their atoms - Metals are found to the left of the zigzag line in the table and non-metals are found to the right - Elements can also be classified on the basis of their chemical properties - E.g. how they react with other substances, such as acids and the oxygen in the air A periodic table of elements Description automatically generated \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ The Structure of the Periodic Table - The periodic table is arranged into groups (vertical columns) and periods (horizontal rows). - Elements are organized by atomic number (number of protons). Elements with similar properties are grouped together. What are Groups? - Groups are **vertical columns** on the periodic table. - There are 18 groups, each with elements that have similar chemical properties. - Example: Group 1 elements are Alkali Metals (e.g., Lithium, Sodium), highly reactive, especially with water. - Each group number (e.g., Group 1, Group 17) indicates the number of electrons in the outer shell for elements in that group. Key Groups to Know - **Group 1 (Alkali Metals):** Highly reactive, 1 valence electron, soft metals. - **Group 2 (Alkaline Earth Metals):** Reactive metals with 2 valence electrons. - **Group 17 (Halogens):** Non-metals, very reactive, 7 valence electrons. - **Group 18 (Noble Gases):** Inert, stable gases with a full outer electron shell. Alkali Metals (Group 1) - **Physical Properties:** - **Soft**, can be cut with a knife. - **Shiny** when freshly cut, though they tarnish quickly when exposed to air. - **Low densities**; some (like Lithium, Sodium, and Potassium) are light enough to float on water. - **Low melting and boiling points** compared to most other metals, and these decrease as you move down the group. - **Chemical Properties:** - Extremely **reactive**, especially with water and oxygen. - Reactivity **increases down the group** (e.g., Potassium is more reactive than Sodium). Alkaline Earth Metals (Group 2) - **Physical Properties:** - **Harder and denser than alkali metals**, with higher melting and boiling points. - **Appear silver or gray** and are **less reactive** than alkali metals. - All are solid at room temperature and are relatively lightweight. - **Chemical Properties:** - Reactivity is moderate; more reactive than transition metals but less reactive than alkali metals. - Have **2 valence electrons**, which they readily lose to form ions with a +2 charge. The Halogens -- Group 17 - Halogens are located in **Group 17** on the periodic table. - Known as "**salt-formers**" because they easily form salts with metals. - Highly reactive **non-metals** with **seven valence electrons** (one electron short of a full outer shell). - **Properties of Halogens:** - Exist in various states at room temperature: - **Fluorine (F)** -- Pale yellow gas - **Chlorine (Cl)** -- Greenish-yellow gas - **Bromine (Br)** -- Reddish-brown liquid - **Iodine (I)** -- Dark purple solid - Reactivity **decreases down the group**: Fluorine is the most reactive, while Iodine is less reactive. Noble Gases -- Group 18 - Located in **Group 18**. - Characteristics: - Inert - Rarely form compounds, - Full outer electron shell - Examples: Helium (He), Neon (Ne), Argon (Ar). What are Periods on the Periodic Table? - Periods are **horizontal rows** on the periodic table. - There are 7 periods, each representing a new energy level for electrons - Properties change across a period from **metals** on the left to **non-metals** on the right. Metals - Found mostly in **Groups 1-12**. - Characteristics: - **Good conductors** of heat and electricity, - **shiny,** - **malleable.** - Examples: - Iron (Fe), Gold (Au), Silver (Ag), Copper (Cu). - Conductive, malleable, often shiny; mostly found on the left side and middle of the periodic table. Non-metals - Found mostly in **Groups 14-17**. - Characteristics: - Poor conductors, - brittle in solid form, - various colours. - Examples: Carbon (C), Nitrogen (N), Oxygen (O), Sulfur (S) - Poor conductors, brittle in solid form; are mostly found on the right side of the periodic table. Metalloids - Have properties of both metals and non-metals; located along a zig-zag line between metals and non-metals. - **Properties of Metalloids:** - **Semi-Conductive:** Metalloids can conduct electricity but not as well as metals. Their conductivity can vary with temperature, which makes them valuable in electronics. - **Brittle and Solid at Room Temperature:** Unlike metals, metalloids are typically brittle and will shatter if struck. - **Appearance:** Often look metallic (shiny), but behave more like non-metals in their chemical reactions. - **Intermediate Melting Points:** Generally have melting points between those of metals and non-metals. Transition Metals - Found in **Groups 3-12**. - Characteristics: - Form coloured compounds, - Good conductors. - Examples: Iron (Fe), Copper (Cu), Nickel (Ni), Platinum (Pt). The Periodic Table's Layout and Element Properties - Metals, metalloids, and non-metals are arranged in a way that reflects their properties. - **The trend in reactivity**: - Metals become more reactive down a group, - While non-metals become more reactive moving up a group. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Atoms - Particles that could not be broken down any further by chemical means Element - A pure substance made of only one type of atom - Elements cannot be broken down into other substances as they are already the simplest substances Compound - Compounds are formed when 2 or more atoms are chemically bonded - E.g. Water and Carbon Dioxide Mixture - When two or more atoms are mixed together however are not chemically bonded Molecules - Molecular substances can be elements or compounds - E.g. Oxygen is a molecular element -- made up of 2 Oxygen elements. Oxygen gas is made up of millions of oxygen molecules - Molecular Compounds are made of atoms of 2 or more different elements/molecular elements - E.g. Water and Carbon Dioxide - Polymers -- made up of groups of atoms that repeat over and over, like a necklace or chain - E.g. Plastics \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Physical & Chemical Change - Physical and chemical changes both involve changes in the appearance of substances. - The key difference is whether a new substance is formed or not. - A **chemical change** is a change that involves the formation of one or more new substances. - A **physical change** is a change that does not involve the formation of new substances. Types of Physical Change - Physical changes can involve up to four alterations in appearance. - In all cases described, the substances have changed their appearance, but they are still the same substance. Physical Change: Change in Shape - Twisting, bending, tearing, shredding, breaking, crushing, pulverising, stretching and squashing are all ways that the shape of a substance can be altered by the application of a force. - They may result in substances looking very different, but they remain the same substances, just in a different form. Physical Change: Change in State of Matter - The six types of state changes are: melting, freezing, vaporisation, condensation, sublimation and deposition. - These result from changes in temperature (and/or pressure). Physical Change: Dissolving and Crystallising - Dissolution occurs when a soluble substance (solute) separates and disperses throughout another substance (solvent). - Crystallisation occurs when a solid solute comes out of a solution, due to evaporation of solvent from a saturated solution, or cooling of a supersaturated solution. Physical Change: Formation of Mixtures - The dissolving of salt mentioned above is an example of the formation of a type of mixture called a solution. - The formation of any type of mixture is a physical process as all the original substances are still present. Signs of a Chemical Change - There are many types of chemical change, - It is not always easy to distinguish whether a chemical change has taken place or whether a change in appearance is purely physical. - This is because chemical changes will usually involve physical changes as well. - For example, the burning of a candle is a chemical change. - It involves the conversion of wax and oxygen to carbon dioxide and water. - However, this is accompanied by physical changes as well, such as melting of the wax. - There are certain signs which indicate that a chemical change may have taken place. - Although they are not proof of a chemical change, chemical changes usually involve one or more of the following indicators. Signs of a Chemical Change: Colour Change - A colour change **may** indicate that a new substance has been formed. - Not all colour changes are chemical changes. - the mixing of blue and yellow paint to make green paint is a physical change, as separate blue and yellow pigments still exist. Signs of a Chemical Change: Formation of Bubbles or Odours - Bubbles or odours **may** indicate that a new substance -- a gas -- has been produced. - Not all bubbling and odours are chemical changes. - The bubbling that occurs when a substance boils, or the smell of a substance when it vaporises, are both the result of changes of state. Signs of a Chemical Change: Formation of a Solid - The formation of a solid **may** indicate that a new substance has been formed. - When the solid results from the mixing of two liquids, or a gas and a liquid, it is called a precipitate. - Solids **aren't always** produced from chemical changes. - For example, the formation of ice on a cold windscreen, or the formation of crystals in a cave, are a result of physical changes. Signs of a Chemical Change: Temperature Change - Chemical changes involve the transfer of heat energy, resulting in an increase or decrease in temperature. - Sometimes the release of heat is accompanied by light, and occasionally, sound. - Temperature changes **aren't always** the result of chemical change. - For example, heat caused by friction is not due to a chemical reaction, but the transfer of kinetic energy to heat energy. - Similarly, the production of light in electric devices, such as light globes, is due to the conversion of electrical energy to light energy, not as a result of a chemical reaction. The Process of Chemical Change - Chemical change involves the breaking and forming of chemical bonds between atoms. - Atoms and molecules are rearranged, but the number and type of each atom remain the same.  - Chemical change involves the breaking and forming of chemical bonds between atoms. - Atoms and molecules are rearranged, but the number and type of each atom remain the same. - Consequently, the total mass of reactants is equal to the total mass of products. - This is known as the Law of Conservation of Mass. Energy Transfer During Physical and Chemical Changes - All chemical changes involve energy changes and the transfer of heat energy. - Depending on the particular example, energy can be released or absorbed. - When energy is released, it is known as an **exothermic** chemical change. - Energy is released in the form of heat, but occasionally also as light, or even sound. - As a result, the surrounding environment experiences an increase in temperature. - Since energy is released, the new substances contain less stored chemical energy than the original substances. - When energy is absorbed, it is known as an **endothermic** chemical change. - Heat energy is absorbed from the surrounding environment - As a result, the surrounding environment experiences a decrease in temperature. - Since energy is absorbed, the new substances contain more stored chemical energy than the original substances. - Physical changes can also be exothermic or endothermic. - For example, dissolving calcium chloride in water is an exothermic process, whereas dissolving ammonium nitrate is endothermic. Reversibility of Physical and Chemical Change - Most physical and chemical changes are reversible - Generally, physical changes are easier to reverse than chemical changes. - This is because physical processes do not require as much energy as chemical processes, as they do not involve the breaking of chemical bonds.