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CC1,2H SC1,2H
GCSE Pearson Combined and Separate Chemistry Higher
| Term | Definition |
|---|---|
| Define mixture | A substance made of more than one thing not chemically bonded together |
| What are the 3 states of matter? | Solid, liquid and gas |
| What is the change from a solid to a liquid called? | Solid à liquid – melting |
| If the temperature is above the melting point of a substance but below the boiling point of a substance what state will it be in? | Liquid |
| If the temperature is below the melting point of a substance and below the boiling point of a substance what state will it be in? | Solid |
| If the temperature is above the melting point of a substance and above the boiling point of a substance what state will it be in? | Gas |
| What is the change from a liquid to a gas called? | Liquid to gas – evaporation |
| What is the change from a gas to a liquid called? | gas to liquid – condensation |
| What is the change from a liquid to a solid called? | liquid to solid – freezing |
| Describe the arrangement of the particles in a solid | particles closely packed, in a regular arrangement |
| Describe the arrangement of the particles in a liquid | particles closely packed, but in a random arrangement |
| Describe the arrangement of the particles in a gas | particles spaced far apart in a random arrangement |
| A substance has a melting point of 25 oC and a boiling point of 235 oC What state is it at 5oC? | Solid |
| A substance has a melting point of -125 oC and a boiling point of -35 oC What state is it at 15oC? | Gas |
| A substance has a melting point of -25 oC and a boiling point of 35 oC What state is it at 25oC? | liquid |
| Describe how the particles change in arrangement when a solid turns into a liquid | Forces between particles weaken and they move more freely The particles are not arranged in order |
| Describe how the particles change in arrangement when a liquid turns into a solid | Forces between particles weaken and they move freely They are spaced far apart |
| Describe how the particles change in arrangement when a gas turns into a liquid | Forces strengthen, particles move closer together |
| Describe how the particles change in arrangement when a liquid turns into a gas | Forces strengthen, particles move close together in ordered rows |
| Describe the arrangement of particles in a gas | Random and far apart |
| Describe the arrangements of particles in a liquid | Random and close together |
| Describe the arrangements of particles in a solid | Regular and close together |
| Describe the movement of particles in a gas | Fast in all directions |
| Describe the movement of particles in a liquid | Move fast around each other |
| Describe the movement of particles in a solid | Vibrate around fixed positions |
| What is the name in change of state from gas to liquid? | Condensation |
| State the meaning of sublimation | The change in state from solid to a gas |
| How can you see from a cooling or heating curve that a pure substance is changing state? | The temperature does not change during a change of state of a pure substance |
| The boiling point of ethanol is 78oC the melting point of ethanol is -114oC What state is ethanol at 90oC? What state is ethanol at -150oC? | Gas and Solid |
| Describe the arrangement of particles in a gas | Random and far apart |
| Describe the arrangements of particles in a liquid | Random and close together |
| Describe the arrangements of particles in a solid | Regular and close together |
| Describe the movement of particles in a gas | Fast in all directions |
| Describe the movement of particles in a liquid | Move fast around each other |
| Describe the movement of particles in a solid | Vibrate around fixed positions |
| What is the name in change of state from liquid to solid? | Freezing |
| State the meaning of evaporation | The change in state from liquid to gas |
| How can you see from a cooling or heating curve that a mixture is changing state? | The temperature changes during a change of state of a pure substance |
| The boiling point of a substance is -80oC the melting point of ethanol is -200oC What state is ethanol at -85oC? What state is ethanol at -250oC? | Liquid and Solid |
| Define and element | A substance made of only one type of atom |
| Define a compound | A substance made from two or more different elements bonded together |
| Define a mixture | A substance made of two or more substances (elements or compounds) mixed but not bonded together |
| How is the melting point of a mixture different from the melting point of a pure substance? | Mixtures do not melt at a fixed temperature but melt gradually over a range of temperatures |
| What types of mixtures can be separated filtration? | A mixture of a liquid and a solid |
| Define a solution | A mixture of a solute dissolved in a solvent |
| What are the risks of crystallisation and how do you reduce them? | As the solvent boils away the hot solution can spit so wear safety goggles to protect your eyes |
| State the five steps of the chromatography method | "1 Draw pencil line on paper 2 Place sample spot on line, 3 Place paper in solvent, with solvent below pencil line, 4 Allow solvent to soak up the paper,5 Stop when solvent near top, and mark how far it gets |
| What is stationary phase and what is the mobile phase in a chromatography experiment? | The paper is the stationary phase, The solvent is the mobile phase |
| What are the three uses of chromatography | To tell between pure and impure substances, To identify substances by comparison with known ones, To identify substances by calculating Rf |
| What is chromatography? | A process to separate the constituents of a mixture |
| In paper chromatography, what is the stationary phase and what is the mobile phase | Paper is stationary, solvent (usually water or ethanol) is mobile |
| How can chromatography show the difference between pure and impure substances? | Pure ones will not separate into a number of spots |
| How is the Rf value calculated? | distance moved by spot/distance moved by solvent |
| What does a substance's Rf value depend on? | How soluble it is in the solvent |
| In chromatography, why must the substances be placed on a pencil line? | Pencil will not dissolve in the solvent |
| In chromatography why must the solvent height be lower than the pencil line? | So that the substances do not dissolve into the solvent off the paper |
| How is the melting point of a pure substance different from that of an impure substance? | Pure substance has one specific melting point Impure substance has a melting range |
| What is simple distillation used to separate? | A liquid from a solid |
| What is fractional distillation used to separate? | Two liquids with different boiling points |
| What is filtration used to separate? | An insoluble solid from a liquid |
| What is crystallisation? | Forming crystals of a soluble solid from a solution |
| What is potable water? | Drinking water |
| How can sea water be made potable? | By distillation |
| What are the stages used to make water potable | Sedimentation, filtration and chlorination |
| What is a pure substance? | A substance made of one type of atom or molecule only |
| How would you separate water from salt water? | Simple distillation |
| How would you separate salt from salt water? | Crystallisation |
| Why must analysis be done with pure water? | Because dissolved salts in non pure water would give false positive results |
| How is the melting point of a mixture different from a pure substance? | A pure substance has a single melting temperature, a mixture has a range of melting points |
| What is distillation? | A method to collect a pure liquid from a solution |
| What is the role of a condenser in a distillation experiment? | It condenses hot gases back into liquids by cooling them down |
| When is the method of fractional distillation used? | To separate mixtures of two or more liquids |
| If a mixture of alcohol boiling point 78OC and water boiling point 100oC undergoes fractional distillation, which will boil first? | Alcohol |
| Why will be certain that the first liquid being collected is alcohol, and water is not being collected as well? | The temperature will stay at 78oC until all the alcohol has boiled |
| Define potable water | Water that is safe to drink |
| Define desalination | Producing pure water from sea water |
| Why is desalination not more widely used to produce drinking water around the world | It takes a lot of energy so is expensive |
| Why do chemists carry out tests with pure water not tap water? | Dissolved substances in tap water could interfere with the results |
| What are the three stages of water treatment in the UK | Sedimentation, Filtration, Addition of Chlorine |
| Why is chlorine added to drinking water? | To kill bacteria |
Created by:
Davenant Foundation School
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