Changes on heating chemicals Flashcards
What is a physical change?
A physical change is when a substance changes without forming new substances, like changing state or colour. This change is usually reversible
What is a chemical change?
A chemical change is when a substance changes completely, involving the creation of new substances. This change is usually irreversible.
What does wax look like before heating, during heating, and after heating?
White solid, colourless liquid, white solid
What does ice look like before heating, during heating, and after heating?
Colourless solid, colourless liquid, colourless liquid
What does sodium chloride look like before heating, during heating, and after heating?
White solid, white solid, white solid
What does Ammonium chloride look like before heating, during heating, and after heating?
White solid, white gas, white solid
What does zinc oxide look like before heating, during heating, and after heating?
White solid, yellow solid, white solid
What colour is zinc oxide when you heat it?
Yellow
How does wax change when you heat it?
It melts to become a colourless liquid
What is the transition from a liquid to a solid?
Freezing
What is the transition from a liquid to a gas?
Evaporating
What is the transition from a gas to a liquid?
condensation
What is the transition from a solid to a gas?
sublimation
How can you tell if something has chemically changed?
chemical changes can change colour, smell, releases light or gases, give off or take in heat
What is thermal decomposition?
the breaking down of a substance because of heat (in decomposition there is always more products than reactants)
What is synthesis?
when two substances are combined to form a new one (in synthesis there is always more reactants that products)
What are reactants?
the substances that you start with
What are products?
the substances that are made (produced) as a result of chemical change
What happens to the mass of a substance when it decomposes?
it loses mass
What happens to the mass of a substance when it synthesises?
it gains mass
What is the colour of Copper (ll) carbonate before heating?
green
What is the colour of the new solid created after Copper (ll) carbonate is heated?
black
How do we know if a substance has carbon dioxide in it?
it turns lime water milky white
What happened to the mass of copper (ll) carbonate when it was heated?
it decreased because carbon dioxide was released and it undergoes thermal decomposition
Why is carbon dioxide released from copper (ll) carbonate?
because it’s being heated
What is the word equation for the heating of copper (ll) carbonate?
copper (ll) carbonate→copper (ll) oxide + carbon dioxide
Does copper (ll) carbonate go through a physical or chemical change when heated?
chemical change because it undergoes thermal decomposition
What colour is copper (ll) sulphate before heating?
blue
what colour is copper (ll) sulphate after heating?
white
What happens as the copper (ll) sulphate crystals are being heated?
the water evaporates, the colour changed, and there was condensation
Is the heating of copper (ll) sulphate a physical or chemical change?
chemical change because it undergoes thermal decomposition (its mass decreases)
Is the heating of copper (ll) sulphate reversible or irreversible?
reversible, if you put water on a sample of anhydrous copper (ll) sulphate, it will turn from white to blue again
What is lost by the copper (ll) sulphate crystals as they are being heated?
water
what are crystals that contain water called?
hydrated
What is the solid called after the water has been lost by the crystals?
anhydrous
What is the word equation for the heating of copper (ll) sulphate?
hydrated copper (ll) sulphate ⇌ anhydrous copper (ll) sulphate + water
What does “⇌” mean?
that the process is reversible
What suggests that water is given out when copper (ll) sulphate is heated?
a colourless gas is given off, which condenses to a colourless liquid on the cooler parts of the tube
What is a reaction with oxygen called?
oxidation
