1 The changes of matter

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3 Heating Curve  When we heat a solid, its temperature increases, the substance melts at the melting point and becomes a liquid  When we heat a liquid, its temperature increases, the substance boils at the boiling point and becomes a gas  Once the melting point and the boiling point are reached the temperature remains constant

4 Heating curve for iron Different substances have different melting points and different boiling points but the shapes of their heating curves are very similar this is the heating curve for iron. The melting point of iron is 1500 °C2750 °C The boiling point of iron is 1500 °C2750 °C

5 Cooling Curve  When we cool a gas, its temperature decreases, the substance condenses at the condensation point and becomes a liquid  When we cool a liquid, its temperature decreases, the substance freezes at the freezing point and becomes a solid  Once the condensation point and the freezing point are reached the temperature remains constant

6 Cooling curves for stearic acid and salol Cooling curve for salol Cooling curve for stearic acid freezing point Different substances have different condensation points and different freezing points but the shapes of their cooling curves are very similar

7 Changes of matter liquid Solid gas Getting hotter Getting colder boiling freezing melting condensing

8 Look at the table below and write sentences to describe the states of substances The substance will be a solid if the temperature is between above below the boiling point the melting point the melting point and the boiling point liquid gas

9 ANSWER THE QUESTIONS WHEN A LIQUID IS HEATED AND IT BOILS its particles lose their order and become completely free to form a gas or vapour Its particles gain energy and move faster Energy is needed to overcome the attractive forces in the liquid TRUE FALSE

10 ANSWER THE QUESTIONS WHEN A LIQUID IS COOLED AND IT FREEZES its particles lose energy and so become more tightly attracted to one other at the freezing point the forces of attraction are sufficient to remove any remaining freedom and the particles come together to form the ordered solid arrangement. TRUE FALSE

11  When we cool a gas, its temperature decreases, the substance condenses at the condensation point and becomes a liquid  When we cool a liquid, its temperature decreases, the substance freezes at the freezing point and becomes a solid  Once the condensation point and the freezing point are reached the temperature remains constant  For the same substance Tmelting equals Tfreezing and Tboiling equals Tcondensation   The Tc and Tf temperatures change for different substances (Tc of water is different from Tc of alcohol)