chemistry test

Chemistry Revision

• definition of matter
• states of matter - identify solid/liquid/gas
• changes of state
• conservation & mass
• definitions & examples of pure substances, mixtures, compounds, & elements
• definitions & examples of physical & chemical changes
• meaning of soluble/insoluble
• definition of solvent, solute, solution(dilute, concentrated, saturated)
• melting point
• reactions - exothermic & endothermic (definition & example)
• factors effecting rate of reaction (particle size, concentration, type of reactants)

Matter

• anything that takes up space and has a mass
• Mass
• the amount of matter in an object
• Volume
• the amount of space an object takes up

States of Matter

• Solids:
• particles tightly packed
• definite shape & volume
• Liquids:
• particles touch each other & can flow
• no definite shape, but definite volume
• Gases:
• particles loosely packed, they can flow freely
• no definite shape/volume

Changes of State

• Solid --------------> Liquid
• add heat(melting)

Changes of State

• 
• Bildunterschrift: Diagram

Conservation of Mass

• - in a closed system the total mass will remain the same even if there are physical/chemical changes made
• A Closed System
• prevents anything already in the system from leaving
• doesn't allow anything else to get into the system
• An Open System
• lets everything in the system escape into the air
• allows everything to get into the system

Classifying Materials

• Matter
• / \
• pure substances mixtures
• / \ / \
• elements compounds solutions other
• Pure substances - is made of particles that are exactly the same as each other Eg. water, oxygen, carbon dioxide
• Mixture - is made of 2 or more different particles mingles together Eg. air
• Element - is a pure substance that cannot be broken down into simpler substances by chemical means Eg. sulfer (S), carbon (C)

Classifying Materials

• Compound - is a pure substance made from 2 or more different elements chemically combined
• Eg. Sodium Chloride is made from Sodium & Chloride

Physical & Chemical Changes

• Physical Change:
• is one in which no new substance is formed
• Eg. Water -> Ice,
• Mixing sand & water
• Boiling water
• Sublimation of dry ice into carbon dioxide vapour
• Breaking a bottle
• Chemical Change:
• causes new substances to form
• Eg. Iron(Fe) & Sulphide(S) -> Iron Sulphide(FeS)
• Milk turning sour
• Wood burning
• Iron rusting on a bike
• Fireworks
• Cooking an egg

Solutions

• Solution:
• is a mixture of a solute & solvent
• Solution = Solute + Solvent
• Solute:
• is a substance that dissolves in a solvent
• ​​​​​​​Solvent:
• the liquid in which a solute dissolves in
• Soluble Substance:
• are able to dissolve in a liquid
• Insoluble Substance:
• ​​​​​​​does not dissolve in a liquid

Solutions (examples)

• 1. Water + Sugar = sugar is a soluble substance
• water = solvent, sugar = solute
• 2.Water + Sand = sand is an insoluble substance

Types of Solutions

• 1.Concentrated Solution contains a lot of solute in a little solvent
• Eg. A lot of MiWadi in a tiny bit of water
• 2.Dilute Solution contains a little solute in a lot of solvent
• Eg. A tiny drop of MiWadi in a lot of water
• 3.Saturated Solution is one in which no more solute will dissolve
• Eg. When so much sugar is added to water that is will no longer dissolve

Melting & Boiling Point

• Melting Point
• the temperature at which a substance changes from a solid state to a liquid state
• Eg. when the temperature is hot enough to melt our ice-cream/chocolate
• Boiling Point
• the temperature at which a substance changes from a liquid to a gas
• Eg. the boiling point of water is 100 degrees, while the boiling point of alcohol is 78 degrees

Exothermic & Endothermic Reactions

• Endothermic Reaction:
• is one which takes in heat
• Eg. icicles melting, baking bread, sweat evaporating from skin, snow forming, an egg frying
• Exothermic Reaction:
• is one which gives out heat
• Eg. a candle burning, bomb exploding, breath condensing on a cold morning, a log fire

Factors affecting rate of reaction

• particle size
• concentration
• temperature
• catalysts