Science revision for spring term Flashcards
What is a pure substance?
A pure substance contains one substance only and all its particles are the same.
What is a mixture?
A mixture contains two or more substances that are not joined together.
What are some examples of mixtures?
- Orange juice
- Milk
- Honey
- Seawater
- Air
- Most rocks
What can be used to separate iron and sulfur in a mixture?
A magnet can be used to separate iron from sulfur.
What properties can be used to separate substances in a mixture?
- Melting points
- Boiling points
- Densities
How do chemists make mixtures?
Chemists determine the best amounts of each substance to add for a specific purpose.
What are the ingredients in toothpaste and their purposes?
- Hydrated silica - removes plaque
- Sodium fluoride - prevents cavities
- Sodium lauryl sulfate - makes foam
- Carrageenan - thickens the toothpaste
- Titanium oxide - makes it white
How can you identify pure substances?
A pure substance has a fixed melting point and a fixed boiling point.
What does it indicate if a sample melts between 70 °C and 80 °C?
It indicates that the sample is impure.
Fill in the blank: A pure substance has a fixed _______.
melting point
Fill in the blank: Most foods and drinks are _______.
mixtures
True or False: The particles of different substances in a mixture are joined together.
False
