Lesson · Grade 7 · Science
What Makes Each Pure Substance Different
- Grade 7
- Science
- 1 min 15 s
- British Columbia
- BC7-SC-15
Three test cards build up one at a time: water boils at 100 °C and ethanol at 78 °C, about 36 g of salt but about 200 g of sugar dissolve in 100 mL of water, and copper lights a bulb while sulfur leaves it dark. Every pure substance has its own boiling point, solubility and conductivity, so these properties help us identify it.
Concept: Boiling point, solubility and conductivity
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In one sentence
The question this lesson answers
How can we tell one pure substance from another?
We can test their properties, like boiling point, solubility and conductivity.
Transcript
What the lesson says
How can we tell one pure substance from another?
We can test their properties, like boiling point, solubility and conductivity.
Boiling point is the temperature at which a liquid boils.
At sea level, pure water boils at 100 degrees Celsius.
Ethanol, another pure substance, boils at 78 degrees Celsius.
Solubility is how much of a substance can dissolve in a liquid.
At room temperature, about 36 grams of salt dissolves in 100 millilitres of water.
In the same amount of water, about 200 grams of sugar dissolves.
Conductivity is how well electricity flows through a substance.
Copper in the gap lights the bulb, because copper conducts electricity.
Sulfur in the gap leaves the bulb dark, because sulfur does not conduct.
Every pure substance has its own set of properties.
So boiling point, solubility and conductivity help us identify a pure substance.
Curriculum
Where this fits
- British Columbia, Grade 7
Science, Chemistry: elements and compounds are pure substancesBC7-SC-15
Previous: Density: why some things floatNext: How Crystals Form
The outcomes and strands follow the British Columbia curriculum.
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