Filtration and crystallisation

1. True or False? A heating curve with an upward sloping gradient during melting indi-cates a pure substance is present.

• False

• True

True or False? Pure substances only have one type of atom present.

• True

• False

What is a mixture?

• different elements and/or compounds that are not chemically joined together

• different elements that are chemically joined together

• Only made of one type of atom

Why can’t a pure substance be separated into other substances using physical means?

• Because it is only made up of one type of atom so cannot be broken into anything simpler

• It has no fixed composition so has to be broken down by chemical reactions

• it has the same fixed composition in all of its parts and so has to be broken down by using chemical reactions

Tags

NGSS.MS-PS1-5

Is melting a physical process or a chemical process?

• Chemical

• Physical

Name the two state changes involved in distillation.

• evaporating and condensing

• melting and evaporating

• Freezing and melting

Tags

NGSS.MS-PS1-4

Why does sand sink to the bottom of a bucket of water?

• water is heavier than sand

• the sand dissolves and is denser than water

• sand is denser than water and does not dissolve

Why do we need to add chlorine to water when cleaning it?

• to improve the taste

• to destroy microbes in the water

• to dissolve any dirt

Why is pure water used in chemical analysis?

• pure water contains nothing but water so nothing else can interfere with results

• it is very cheap to obtain

• there is lots of water so easily obtainable

What are the steps needed to make water potable?

• chlorination, filtration, sedimentation

• filtration, sedimentation, chlorination

• sedimentation, filtration, chlorination