Chemical Clues
What is one sign that a chemical reaction has occurred?
Color change, gas production, temperature change, or formation of a new substance
What happens to the number of atoms during a chemical reaction?
They stay the same
What does it mean when a device absorbs thermal energy?
It takes in heat from its surroundings
What is one way to minimize thermal energy transfer?
Use insulation
What happens to particle motion when thermal energy increases?
Particles move faster
If you mix vinegar and baking soda and see bubbles, what evidence tells you a chemical reaction happened?
Gas was produced
What law states that matter is not created or destroyed in a chemical reaction?
Law of Conservation of Mass
What is one thing you should test when building a device that releases or absorbs thermal energy?
How much the temperature changes
Why do metal spoons feel colder than plastic ones?
Metals conduct heat better/Metal has a lower specific heat capacity
What will heat up faster — 100g of water or 500g of water — with the same heat source?
100g of water
Write this as a chemical equation. Ammonia (NH₃) reacts with hydrochloric acid (HCl) to make ammonium chloride (NH₄Cl).
Underline the reactants and Circle the products
NH₃ + HCl -> NH₄Cl
If 10 grams of reactants go into a reaction, how many grams of products should be made?
10 grams
Give an example of a real-life device that releases thermal energy.
Hand warmer, heater, campfire, etc.
If you wanted to keep a drink cold, should you use a material that conducts or insulates heat?
Insulates heat
Why does metal heat up faster than wood?
Metal conducts energy better
If you measure the mass before and after a reaction in a sealed bag and it’s the same, what does that show?
Mass is conserved
In the reaction H₂ + O₂ → H₂O, why is this equation not balanced?
There are 2 oxygen atoms on the reactant side but only 1 on the product side
What could you change to improve a device that’s supposed to absorb heat energy?
Use darker colors, increase surface area, or use materials that conduct heat
Provide a definition for Conduction, Convection, and Radiation
Conduction is heat transfer through solids, Convection is heat transfer through liquids and solids, and Radiation is heat transfer through electromagnetic waves
If two substances absorb the same amount of energy, why might their temperatures change differently?
They have different masses or specific heats
A metal nail rusts after being left outside. Name two signs that a chemical reaction occurred.
Color change (rust), formation of a new substance (iron oxide)
How does a balanced equation show the Law of Conservation of Mass?
It has the same number of each type of atom before and after the reaction happens.
Does heat flow from hot to cold or cold to hot?
Heat only goes from hot to cold
Give one example of a device that maximizes heat transfer and one that minimizes it.
Maximizes: radiator; Minimizes: thermos
What variables should you keep constant to test how mass affects temperature change?
Type of material and energy input