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Grade 8 Science > Chemistry > Flashcards

Chemistry Flashcards

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1
Q

What is a Solution?

A

When one substance dissolves into another, the mixture is called a solution.

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2
Q

What happens when a substance dissolves?

A

It’s split into particles that no longer have contact with the other particles from the original substance, and are evenly distributed.

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3
Q

Are solutions impure?

A

Yes

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4
Q

What is a solute?

A

The substance in a solution that dissolves is called a solute.

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5
Q

What is a solvent?

A

The substance that the solute dissolves in is called a solvent.

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6
Q

True or False: If a solute cannot dissolve in a particular solvent, then it is insoluble in that solvent. For example, oil is insoluble in water.

A

True

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7
Q

True or False: A solute that is able to dissolve in a particular solvent is said to be soluble in that solvent. For example, sugar is soluble in water.

A

True

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8
Q

Provide a written example of when one substance in soluble to another.

A

Example: Acetone is used as a nail polish remover because the nail polish is soluble to the acetone - not water.

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9
Q

What does concentration mean?

A

The amount of dissolved solute in a solution

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10
Q

True or False: Solutions with higher concentrations have less solvent or more solute

A

True

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11
Q

What does dilute mean?

A

A solution is dilute when their is less solute than a given volume of solvent.

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12
Q

What does it mean if a solution is saturated?

A

The solvent can’t take anymore solute because the solvent becomes ‘full’ and their is no space for more particles, so the solute just piles at the bottom of the glass.

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13
Q

What is a suspension?

A

A suspension is the opposite of a solution, because the particles and substances are non-soluble. Usually, after a while the substances will separate, and the heaviest substance will sink to the bottom. An example of this is oil and water. If water and oil are both poured into a beaker and stirred, both substances will mix but won’t dissolve in each other. Eventually, they will both “sit” (when two insoluble substances seperate and the lighter (the oil) floats as a single mass to the top of the beaker and is no longer mixed with the heavier (the water) substance).

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14
Q

What is sedimentation?

A

When one of a suspensions substances are a solid object (eg. dead animal, dirt, sand, silt…) that falls to the bottom (the object is then called sediment).

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15
Q

What is Decanting?

A

Decanting is the process of removing the liquid part from a suspension. This is done by pouring the top layer of a suspension into another beaker/test tube.

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16
Q

State when straining can be used.

A

When a suspension needs to be separated.

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17
Q

What is filtration?

A

Filtration involves passing a suspension through a filter, which is a material that has lots of very small holes.

(eg. In a coffee machine, tiny holes allow only some substances to pass through and not others. A coffee filter lets water pass through, but keeps the coffee grounds separate.)

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18
Q

What makes filter paper useful in a lab?

A

It has tiny holes that let most liquids through, but not solids.

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19
Q

True or false: The solid particles that cannot pass through the holes of a filter are called residue.

A

True

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20
Q

True or false: The liquid that can pass through the filter paper; is called filtrate.

A

True. Note that… This method of separation is useful because both the residue and filtrate can be saved and used elsewhere.

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21
Q

What type of folds are used as filter paper?

A

Fluted and conical. (Research the shapes and how to fold them)

22
Q

You are given a mixture of muddy water and are asked to clean it to create water that is more pure. Choose one method (either decanting, straining and filtering) and explain how this method could be used to clean the water, and why the others won’t work as well. In your answer, identify what the different parts of the separated solution would be called.

A

To clean the muddy water, i’d filter it. Decanting wouldn’t work due to how I’d have to pour the top layer (there is none) into another beaker. Straining would help a bit by separating any solids - but filtration will do that, plus filter it a little more. The residue could then be used for other uses, whilst the filtrate would be relatively clear - but not drinkable.

23
Q

“When a suspension is spun quickly, so that the heaviest substances fall to the bottom.” What is this called?

A

centrifuging

24
Q

What is gravity separation?

A

Gravity separation is when gravity is the prominent force used to separate substances in a suspension.

25
Q

What are some examples of ways to separate a solution?

A

Evaporation, regular distillation, cold distillation, fractional distillation, chromatography.

26
Q

True or False: Usually, solute particles have high boiling points, and will not turn into gas with the solvent.

A

True

27
Q

True or False: Solutions become saturated if the solvent evaporates.

A

True

28
Q

If a saturated solution is evaporated, there will now be too much solute. So what does it do?

A

It solidifies out of the solution.

29
Q

True or False: If a solution becomes saturated and a solid starts to form, plus all the solvent boils away (for some reason) leaving behind a dry solute.

A

True

30
Q

What is distillation?

A

Distillation is the process of heating a solution to the lowest boiling point so that the substance vaporizes. As this occurs, the gases are captured in a condenser and become distillate and condense back into liquid form inside a beaker.

(Read the following) For example, water has a boiling point of 100 degrees Celsius, and ethanol has a boiling point of 78 degrees Celsius. So if we heat the mixture to 78 degrees Celsius, we will boil away the ethanol but leave the water as a liquid. Ethanol will leave the solution as a gas and we trap it in a cooled pipe called a condenser. The gas turns into a liquid again as it is condensed and we call this liquid the distillate. Solids will generally be left behind because they have high boiling points. They are left as a solid or liquid (if they melt) in the original container.

31
Q

When is fractional distillation used?

A

When the boiling point of the solute and solvent are very similar.

32
Q

Explain what happens when a solution is put through fraction distillation.

A

The solution is put through a distillation column where different sections of the column have different temperatures. A furnace then heats the distillation column. Then the various gases produced are condensed at different heights (depending on their boiling point) and are collected separately.

33
Q

What is an example of a solution that commonly goes through the process of fractional distillation? (if you don’t know, research it - than mark it as “Not at All”)

A

Crude oil

34
Q

What is cold distillation (also known as vacuum distillation)?

A

Cold distillation is when we lower the pressure (This is usually done in a vacuum) on a mixture (with a high boiling point). This reduces the boiling point of the components to a temperature that can be created in a lab. The solution is then boiled at this temperature and regular distillation takes place.

35
Q

A whiskey manufacturer wants to create a new line of whiskey that has a high alcohol content. However, she only has a solution of alcohol in water that is quite dilute. Conclude why distillation would be a better choice than evaporation if she wants to remove the water from solution. Remember that alcohols boiling point is 78 degrees Celsius, and waters boiling point is 100 degrees Celsius. Vocalise your answer.

A

Answers vary.
Include the words:
*evaporate_
*distillate
*dilute_
*solution

36
Q

Research and create a sketch of a fractional distillation.

A

Save the sketch to the Distillation files.

37
Q

When is chromatography used?

A

Chromatography is used to separate solutions with very small concentrations of coloured solutes.

38
Q

State what all forms of chromatography have in common.

A

All forms of chromatography involve passing the solution through another substance - to separate the different parts of the solution.

39
Q

True or False: Different solutes have different properties - meaning that different solutes will travel faster than others through substances.

A

True

40
Q

Name a real-life situation where paper chromatography can be used.

A

Forensics (the study of crime scenes), uses chromatography to identify unknown substances such as drugs, blood, explosives and other fluids.

41
Q

Research chromatography used in forensics.

42
Q

Describe the process of crystallization.

A

Crystallisation occurs when a saturated solution begins to cool. As the temperature drops, the dissolved particles can no longer stay dissolved and they solidify and leave the solution. When a particle leaves a solution, it attaches to the easiest substance to cling to and then other particles attach to it! This forms large solid clusters of solute called crystals. Hot liquids can fit more solute in than cold ones. The saturation point is raised when solutions are warmer. Overall, this means that more solute can be dissolved into hot solutions. When an over-saturated solution cools, it produces crystals! It is also quicker to cool a solution down than to evaporate it.

43
Q

Explain the steps to performing crystallization with an example.

A

To perform crystallisation, you need to perform the following basic steps:

  1. Heat your chosen salt solution.

2.Dissolve more of your chosen salt in the solution until it becomes saturated (no more salt will dissolve)

3.Cool the solution slowly. Salt crystals will slowly grow inside the container.

44
Q

What does Homogeneous mean?

A

Refers to a substance or mixture where every part of the substance or mixture is identical.

45
Q

What is a colloid?

A

A homogA homogeneous mixture of two insoluble substances, which does not settle over time.

46
Q

What is the dispersed phase?

A

The suspended particles in a colloid.

47
Q

What is the continuous phase?

A

The part of a colloid that suspended particles float in.

48
Q

What is Emulsion?

A

Type of colloid where a liquid is suspended in a liquid

49
Q

What is a centrifuge?

A

A device that rapidly spins so that the suspensions inside separate faster.

50
Q

NotAQuestion

Go onto EP, and do two minutes of the glossary - Definitions MSQ - under Gr7 mixtures.

A

Reward:

Grade 8 Science (2 decks)

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