Many useful substances that we use every day, eg medicines, perfumes and paints, are mixtures of different chemical compounds.
What is meant if a chemical substance is described as 'pure'?
It is a solution of a single substance
It only contains a single substance
It contains only permitted additives
Which of the following is a property of a compound?
It has a constant composition
It can be separated easily
It contains substances that are not joined together
Air contains nitrogen, oxygen and argon gas. What term can be used to describe air?
How do the melting points of pure and impure substances differ?
Pure substances melt over a narrower temperature range than impure ones
Impure substances melt over a narrower temperature range than pure ones
Both substances melt over a narrow temperature range
Which piece of apparatus in a melting point experiment is most likely to cause skin burns if touched?
Clamp and stand
Tripod and gauze
A chemist is making a medicine. Why is it important to use a formulation?
So that the medicine tablets will be the right size
So that the medicine will be cheaper to make
So that the medicine will contain the correct amount of drug
Which of the following would you NOT find in the formulation for a processed food?
Which of the following is seawater?
A mixture of compounds
A mixture of elements
How many types of atom are present in a mixture of oxygen and carbon dioxide gases?
A student heats up solid X. It starts to melt at 35°C, and finishes melting at 40°C. What does this tell you about solid X?
Solid X is a pure compound
Solid X is a pure element
Solid X is an impure substance