Samenvatting door B woorden 7 oktober keer beoordeeld. Scheikunde. Chemistry Summary Chapter 1 & 2 By riverbit

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Samenvatting door B. 1418 woorden 7 oktober 2016 7 18 keer beoordeeld Vak Methode Scheikunde Chemie overal Chemistry Summary Chapter 1 & 2 By riverbit Summary for test chapter 1 & 2 Chapter 1 1.

1 Samenvatting door B woorden 7 oktober keer beoordeeld Vak Methode Scheikunde Chemie overal Chemistry Summary Chapter 1 & 2 By riverbit Summary for test chapter 1 & 2 Chapter Safety: Do not kill yourself Never use a yellow flame for heating substances, only use it when you are not using the burner for a while A colourless flame is used for heating small amounts of substance A rustling flame is used for heating large amounts of substance In a wash bottle you can find distilled water. Distilled water is water that has been cooked and all the solutes have been removed. In Chemistry class we use demi-water, water that has been demineralised. 1.3 Substances and their properties Every substance has a mass Every substance has its own properties Examples are: Colour, taste, solubility in water, combustibility and phase at room temperature. Every substance has its own unique combination of properties. Melting and boiling points of a substance are also known as constants of a substance. A constant is a property you can express by a number followed by a unit. Density is also a constant of a substance. Density is mass divided by volume and the unit is g/cm3 Substances can and will kill you if not handled properly because of their properties. There are safety signs for dangerous chemicals. We have P and H statements, with P of Precaution and H of Hazard. There are the following types of materials Metals Natural polymers like starch, rubber, protein Pagina 1 van 5

2 Synthetic polymers, plastics or synthetic rubber Composites, a mixture of two or more metals A material safety data sheet contains the physical properties along with the dangers and what to do if something goes wrong with the substance 1.4 Structure of matter Every substance has its own type of molecule. A mixture has different substances combined. A pure substance is one substance that only consists of all identical molecules. There are tens and millions of molecules. Molecules are super tiny. Molecules consist of atoms. There are about 110 different atoms. Two or more atoms combine to make a molecule. 1.5 Phases, transition and separation There are different states of matter Solid Liquid Gas Kelvin is a scientific measurement for temperature. 20 C to K = = 239 K 300 K to C = = 27 From gas to solid is called deposition, from a solid to a gas is sublimation From liquid to solid is called solidifying, from a solid to a liquid is melting From liquid to gas is called evaporation, from a gas to a solid is condensation A pure substance will, when being heated, maintain a constant temperature. In a mixture the temperature will rise gradually. It is also possible to separate substances from a mixture, there are 3 ways to do that. Extraction: Using an extractive agent or extraction solvent you can take out different molecules. Like water. Filtration: Using a filter in a funnel you can separate a solid from a liquid, the dissolved substance will pass through the filter with the liquid. Evaporation: When there is a difference in boiling points you can bring it to a temperature where one will evaporate and one will stay a liquid. The phase is determined by - the distance between the molecules - the position of the molecules In every phase the molecules of a substance remain the same. A temperature line contains the temperatures when a substance is a solid, a liquid and a gas. Pagina 2 van 5

3 van der Waals forces influence at what temperature a substance will melt or evaporate. The greater the mass, the stronger the van der Waals forces. For a pure substance there is a boiling point and for mixtures there is a boiling range. 1.6 Kinds of Atoms Every element has its own name and symbol. The periodic table has vertical columns called the groups and horizontal rows called the periods. Most substances are compounds. It was Mendeleev who discovered the periodic table. All metals have: a shiny surface conduct heat and electricity malleable mixable We have the following types of metals, based on their reactivity precious metals semi-precious metals reactive metals highly reactive metals Light metals have a small density and may even float on water Heavy metals have a big density and are like, heavy. They can also pollute the soil Group 1: Alkaline metals Group 2: Earth-alkaline metals Group 17: Halogen Group 18: noble gases An alloy is a mixture of two metals that have formed a new metal. ALLOYS METAL COMPONEMENTS BRASS Zinc and copper STAINLESS STEEL Iron, chromium or nickel SILVER AMALGAM Tin and lead DURALUMIN Copper and aluminium BRONZE Copper and tin SOLDER Tin and lead 1.7 Structure of atoms and bonds between atoms The model of atoms by Dalton is schematically drawn Rutherford s model is more detailed, and says that an atom has: A nucleus with protons and neutrons A cloud of electrons The cloud is negative The number of electrons equals the number of protons in the nucleus. There are also bonds between atoms Covalent bonding is one of them, here atoms are shared between atoms. There are also ionic bonds, these have to do with electrons. The valence of atoms is the number of Pagina 3 van 5

4 electrons that can be added or removed from a specific atom Chapter 2: Water 2.2 Water: a very special substance Water influences our climate We depend on water Water is special in 4 different things: Density, the density in liquid is MORE than in solid Water has a high heat capacity Water has a high boiling point A high dissolving capacity. 2.3 Water as a solvent When a substance dissolved, all bonds will be broken, including the bond between molecules of the solvent. A solution is a mixture that is always clear. A suspension is always turbid. The solid substance did not dissolve. Solid particles are floating around in the substance. The solubility of a substance the maximum number of Grams in a kilogram of a certain solvent. For solids, the higher the temperature, the higher the solubility. When the temperature of water is higher, less oxygen can be dissolved in water. 2.4 Hydrogen bonds Atoms are kept together by covalent bonds When electrons are shared equally, we call it a non-polar covalent bond. Quite often the electrons that are shared are attracted by one of the two atoms involved. A polar covalent bond is created. Between molecules containing OH-groups or NH-groups, a hydrogen bond is also present A hydrophilic substance can dissolve in water and is attracted by water. A hydrophobic substance can t dissolve in water and hates water A high surface tension means that it has a very strong hydrogen bond Hydrophilic substances don't mix well with hydrophilic substances 2.5 Quality of water The process of producing water from the sea is called desalination. You can clean water by: Pagina 4 van 5

5 Membrane filtration Distillation Distillation is using the difference in boiling points between salt and water. Salt will boil earlier and as long as you don t boil the water, the salt will evaporate. Later, it is cooled down and will end separated. Adsorption is a method to remove dyes, flavours and fragrances from water. Norit is one of some products that can be used to remove these. You can also use a membrane; this is a small piece of a certain material which only water molecules or salt molecules can pass thru. MDI stands for maximum daily intake. It is how much you can consume in mg of a certain substance per kg of body weight. Water can be soft or hard water. Hard water means there is a high level of lime. It is not dangerous only more difficult to clean and it looks not nice. Lime is actually good for your body. 2.6 Cosmetics Water and oil don t mix well; we call this an emulsion. We add an emulsifier to force them to be mixed. It has a hydrophilic head and a hydrophobic tail. ph means acidity. A ph level between 0 and 7 is called acidic, 7 is called neutral and 7 until 14 is called alkaline. 2.7 Cleansing agents Cleansing agents are things like soap, decalcified, all-purpose cleaner etc. Acidic cleansing agents are things to remove limestone Alkaline cleansing agents are used to remove things like greasy dirt and fat in general. Notes An emulsion = liquid + liquid A suspension: solid + liquid An emulsion ALWAYS has an emulsifier We have 4 types of separation Extraction (to remove sand from salt, add water) Filtration (filter sand from water) Absorption (dissolving) Adsorption (using Norit to remove the blue from spiritus) Evaporation Pagina 5 van 5

Year 8 Exam Revision. Theme 1 & 2 Chemistry. TBAT gain your target grade on the Year 8 exam

Year 8 Exam Revision. Theme 1 & 2 Chemistry. TBAT gain your target grade on the Year 8 exam Year 8 Exam Revision Theme 1 & 2 Chemistry TBAT gain your target grade on the Year 8 exam Key Questions- Chemistry Theme 1 1. Particles move faster when they have more.this happens when you increase the.