Chemical Reaction I
A process where substances change into new substances with different properties.
What is a chemical reaction?
Endothermic reactions absorb energy (feel cold); exothermic reactions release energy (feel hot).
What is the difference between an endothermic and an exothermic reaction?
Solid
Liquid
Gas
What are the three states for matter?
a substance that absorbs or releases heat during a change in its physical state, such as melting or freezing.
What is a PCM?
Color change, temperature change, gas production, formation of a precipitate, or light emission.
What are the signs that a chemical reaction has occurred?
To follow the Law of Conservation of Mass, showing that the same number of atoms are present before and after the reaction.
Why is it important to balance chemical equations?
Sunlight, carbon dioxide, and water
What do plants need for photosynthesis?
The temperature stays the same while the PCM is melting, even though it is absorbing heat.
What happens to the temperature of a PCM while it is melting?
Iron rusting
What is a sign of a chemical reaction?
It produces gas (carbon dioxide), which is a sign of a chemical reaction.
What is mixing vinegar and baking soda?
Gravity
What force pulls objects towards Earth?
The plateau
What happens to the temperature of a PCM while it is melting?
Burning wood
What is an example of a chemical change?
2H₂ + O₂ → 2H₂O
What is the chemical equation for the reaction of hydrogen and oxygen to form water?
To take in oxygen and remove carbon dioxide during breathing
What is the main function of the lungs in the human body?
Water (because it changes phase at 0°C and 100°C, storing or releasing energy)
an example of a PCM?
Atoms are rearranged to form new substances.
What happens to atoms during a chemical reaction?
Is baking a cake a chemical or physical change? Why?
Baking a cake is a chemical change because new substances are formed and it cannot be reversed.
Metal is a better conductor of heat than wood. It quickly transfers heat away from your hand, making it feel colder even though both are at the same temperature.
Why does a metal spoon feel colder than a wooden spoon when both are left in the same room?
They can store and release thermal energy, helping to keep temperatures steady.
Why are PCMs useful in temperature control?